Author Topic: Open Source Oscilloscope, can it be done?  (Read 35684 times)

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Offline garboui

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Open Source Oscilloscope, can it be done?
« on: February 01, 2017, 09:59:36 am »
The other day I went searching for an open source or extensible oscope available. PC based devices were the only things that came up. Why is there no bench scope that's open? Is it just not financially practical?
 
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Offline ataradov

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Re: Open Source Oscilloscope, can it be done?
« Reply #1 on: February 01, 2017, 10:19:58 am »
Well, a couple of ADCs + FPGA used even in entry level scope will cost you close to the price of the real scope. There is really no point.

Plus to debug and tune handmade scope, you need a scope an order of magnitude better, which defeats the point of making a worse one :)
Alex
 
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Offline garboui

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Re: Open Source Oscilloscope, can it be done?
« Reply #2 on: February 01, 2017, 11:44:05 am »
Granted, the FR and ADC will use u budget, but what if these were closesd blobs and the rest of the UI and processing were open (similar to raspi)?
 

Offline ataradov

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Re: Open Source Oscilloscope, can it be done?
« Reply #3 on: February 01, 2017, 11:47:59 am »
I think there is an effort to reverse-engineer firmware and hardware of the Rigol scopes. The problem is, people that want to use their equipment need it to work when needed, not tinker with it. You are already debugging a problem, do you also want to debug the scope?

There is very little to be gained. The UI is not perfect, but it is acceptable, way below the pain point to spend months of development time.
Alex
 
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Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #4 on: February 01, 2017, 12:24:49 pm »
I think one reason this hasn't really happened is that for the cost of the crucial parts, you can buy a used older model scope that will outperform the one you were going to build. Oscilloscopes have tended to be on the bleeding edge, a lot of fancy tricks were incorporated to get them to perform as well as possible, just look inside some of the older Tek scopes. They're an engineering masterpiece.
 

Offline JPortici

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Re: Open Source Oscilloscope, can it be done?
« Reply #5 on: February 01, 2017, 05:01:34 pm »
well there is the guy who hacked an owon scope..

http://blog.weinigel.se/2016/05/01/sds7102-hacking.html and following. nice reading
 

Offline Marco

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Re: Open Source Oscilloscope, can it be done?
« Reply #6 on: February 01, 2017, 09:43:54 pm »
Why is there no bench scope that's open? Is it just not financially practical?

Too much effort, too little pay off. Need to wait for the right crazy person to come along and make one.
 
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Online kripton2035

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Offline djnz

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Re: Open Source Oscilloscope, can it be done?
« Reply #8 on: February 06, 2017, 05:06:50 pm »
Have you seen this:

Texas Instruments - 50-Ohm 2-GHz Oscilloscope Front-end Reference Design  -> http://www.ti.com/tool/TIDA-00826

Not really open source, but very interesting. Of course, if you actually want to build it, the parts are very expensive.

 

Offline spanner888

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Re: Open Source Oscilloscope, can it be done?
« Reply #9 on: February 07, 2017, 10:37:36 am »
Well Bunnie has done one for the Novena laptop with "two 8-bit channels at 1GSPS or one 8-bit channel at 2GSPS with an analog bandwidth of up to 900MHz. As a side bonus we also wired in a set of 10 digital channels that can be used as a simple logic analyzer." Probably not directly what you want but food for thought, especially the front end.

http://www.bunniestudios.com/blog/?p=3957
 
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Offline ataradov

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Re: Open Source Oscilloscope, can it be done?
« Reply #10 on: February 07, 2017, 10:40:29 am »
ADC used in this design (ADC08D1020) costs ~$400 on DigiKey. I'm sure there are places to get it cheaper, but not much in low quantities.
Alex
 

Online tautech

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Re: Open Source Oscilloscope, can it be done?
« Reply #11 on: February 07, 2017, 11:38:52 am »
................... The problem is, people that want to use their equipment need it to work when needed, not tinker with it. You are already debugging a problem, do you also want to debug the scope?
Exactly and reliability was the primary reason years ago I ditched troublesome CRO's in favour of DSO's.

Quote
There is very little to be gained. The UI is not perfect, but it is acceptable, way below the pain point to spend months of development time.
:-+

I've seen a few threads like this over the years, all with members thinking they can build a better scope than the many that are currently available.  :-//
The functionality in basic entry level DSO's is no trivial task to implement, let alone in more advanced DSO's.

If we take a step back and look at the # of brands that are designing and building DSO's, there really are only a dozen or so which implies if it was easy everybody would be doing it.
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Offline garboui

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Re: Open Source Oscilloscope, can it be done?
« Reply #12 on: February 07, 2017, 12:16:42 pm »
................... The problem is, people that want to use their equipment need it to work when needed, not tinker with it. You are already debugging a problem, do you also want to debug the scope?
Exactly and reliability was the primary reason years ago I ditched troublesome CRO's in favour of DSO's.

Quote
There is very little to be gained. The UI is not perfect, but it is acceptable, way below the pain point to spend months of development time.
:-+

I've seen a few threads like this over the years, all with members thinking they can build a better scope than the many that are currently available.  :-//
The functionality in basic entry level DSO's is no trivial task to implement, let alone in more advanced DSO's.

If we take a step back and look at the # of brands that are designing and building DSO's, there really are only a dozen or so which implies if it was easy everybody would be doing it.

I understand this completely. I do design electronic goods for a living already and know the amount of work required to manufacture something, let alone design something with a degree of complexity to be manufactured reliably and economically.

Something I hinted at originally is working with a hybrid approach. Have a closed source blob, being a skeleton platform; ie. 1054z with basic functional interface (or the same). However the usb, Ethernet and UI will have end user accessible API's to customize UI looks, measurements, data displays etc... IO can be customized for automated tests etc, signal generation, decoding etc.

Doing something like this as a ground up effort would be a massive feat to be profitable/ feasible/ good. Finding a partner company that would allow a rebranding with the custom extensible interfaces may be feasible?
 

Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #13 on: February 07, 2017, 04:21:37 pm »
I don't know why a CRO would be any more troublesome than a DSO. I've been using my Tek 465B for 17 trouble-free years now, it's actually quite a lot more dependable than some of the (relatively cheap) DSO's I've dealt with. There are never firmware bugs or lockups with an analog CRO.
 

Offline ataradov

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Re: Open Source Oscilloscope, can it be done?
« Reply #14 on: February 07, 2017, 04:24:10 pm »
I don't know why a CRO would be any more troublesome than a DSO.
I like to capture signals and look at them in detail, for example. 24 Mpts of memory is pretty handy for that.  I also like to get things int a computer and do math om them from time to time.

If you only look at periodic signals, then may be CRO is good enough.
Alex
 

Online tautech

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Re: Open Source Oscilloscope, can it be done?
« Reply #15 on: February 07, 2017, 04:37:23 pm »
I don't know why a CRO would be any more troublesome than a DSO. I've been using my Tek 465B for 17 trouble-free years now, it's actually quite a lot more dependable than some of the (relatively cheap) DSO's I've dealt with. There are never firmware bugs or lockups with an analog CRO.
Some aren't, you're right.....when designed conservatively and to last like a good # of the classic Teks like yours.
However by virtue of the the high voltages in a CRO, several blocks of a CRO circuit are under some stress and with the now very common practice of using componentry close to limits, failures ensue.

With many CRO's as I'm on record having said before; you need another to keep the CRO you have in operational condition.
Fixed enough of them to know this for sure.  :rant:
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Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #16 on: February 08, 2017, 03:36:11 am »
I don't know why a CRO would be any more troublesome than a DSO.
I like to capture signals and look at them in detail, for example. 24 Mpts of memory is pretty handy for that.  I also like to get things int a computer and do math om them from time to time.

If you only look at periodic signals, then may be CRO is good enough.

I'm not debating the usefulness, there are indeed times when a DSO will do things that are simply not possible to do any other way. I was only speaking in terms of reliability to the comment about them being troublesome.
 

Offline ataradov

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Re: Open Source Oscilloscope, can it be done?
« Reply #17 on: February 08, 2017, 03:43:47 am »
I was only speaking in terms of reliability to the comment about them being troublesome.
Well, in my experience, old CROs almost always have issues with rotary switches. They oxidize, and fail in the most unpredictable way. This is solved with contact cleaner most of the time, but still annoying.

This will probably apply to DSOs as well, but given how cheap they are and improvements made over the years, I'd rather toss a scope after a few years of use anyway, so I'm unlikely to see them fail in any specific way.
Alex
 

Offline Cloud

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Re: Open Source Oscilloscope, can it be done?
« Reply #18 on: February 18, 2017, 08:43:35 pm »
What about this? http://www.scopefun.com/
 
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Offline ataradov

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Re: Open Source Oscilloscope, can it be done?
« Reply #19 on: February 19, 2017, 05:44:58 am »
What about this?
100 MHz Sampling rate is somewhat slow, memory depth is very low for a modern scope.

There are no hardware files in easily readable format, but I doubt it will be cheaper than $200-300, at which point it again does not make sense. Unless you actually want to have that open source stuff and may be use it in connection with scripting or something like that.

It seems like a nicely designed unit, but not a general use device.
Alex
 

Offline SaabFAN

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Re: Open Source Oscilloscope, can it be done?
« Reply #20 on: February 24, 2017, 02:57:03 pm »
Wasn't there a brand of Scopes that looked like HP-Scopes from the late 90s that were kind of open source?
I remember reading about the FPGA-Program and basically most of the firmware getting rewritten by hobby developers even before the manufacturer of the scopes went bankrupt and these scopes flooded ebay at suspiciously low prices (They're gone now on ebay, which I guess happened for a reason :) ).

Offline samofab

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Re: Open Source Oscilloscope, can it be done?
« Reply #21 on: February 25, 2017, 08:07:07 am »
Wasn't there a brand of Scopes that looked like HP-Scopes from the late 90s that were kind of open source?

You mean this one:
https://sourceforge.net/projects/welecw2000a/
 

Offline ohdsp

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Re: Open Source Oscilloscope, can it be done?
« Reply #22 on: March 07, 2017, 08:47:25 am »
Would love to build/design an open source oscilloscope. It has been another one of those projects I have had on my to do list for a long time (and no i'm not some delusional moron).

The front end would be my first concern (with a flat frequency/linear phase response and the voltage resolution).

Whilst you would need fast FPGAs to capture the data my thoughts where could you do something clever to interleave multiple channels in a slower device... No idea what it would end up like, and doubt you could beat a Chinese Siglent/Rigol initially with any design. Although most peoples expectations these days seem to be it's either everything you ever wanted and more or it shouldn't exist because why should it take time to develop and improve... Anyway I did have an FPGA dev kit somewhere....
Check out the Open Hardware DSP Platform:
http://www.ohdsp.org
http://github.com/ohdsp
 
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Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #23 on: March 07, 2017, 09:44:20 am »
I'm not an expert on oscilloscope design but I think the analog front end and the ADC is where most of the "magic" happens. Once you have the data in digital form that's relatively easy to manipulate. I seriously doubt you'd come close to the performance of a $400 Rigol for twice the price and many tens of hours invested but it could be a fun project none the less.
 

Offline SaabFAN

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Re: Open Source Oscilloscope, can it be done?
« Reply #24 on: March 08, 2017, 11:20:25 am »
I think for a bit more money and most likely not that much time to invest, it's possible to build the analog frontend out of ICs.
When looking at all the teardowns of new scopes, it is noteworthy that many manufacturers go the extra mile and build at least part of their frontends out of discrete components to save on the components.

As far as I know, at least TI and Analog Devices have ICs in their portfolio that are more or less specifically designed to be used in Scope frontends (variable gain amps good for frequencies in excess of 300MHz, very high speed single-ended to differential converters, etc.).
These chips aren't cheap though! Prices are about 5 to 9€ and they don't go down that much when bought in quantity, so I see why manufacturers shy away from them and go for a discrete solution that cost maybe 20 cents in components.

Offline JPortici

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Re: Open Source Oscilloscope, can it be done?
« Reply #25 on: March 08, 2017, 06:30:22 pm »
I think for a bit more money and most likely not that much time to invest, it's possible to build the analog frontend out of ICs.
When looking at all the teardowns of new scopes, it is noteworthy that many manufacturers go the extra mile and build at least part of their frontends out of discrete components to save on the components.

ehr... i believe it's few component -> less noise / more bandwidth
 

Offline paulcav

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Re: Open Source Oscilloscope, can it be done?
« Reply #26 on: March 09, 2017, 07:38:48 am »
ADC used in this design (ADC08D1020) costs ~$400 on DigiKey. I'm sure there are places to get it cheaper, but not much in low quantities.

on the ti site https://store.ti.com/ADC08D1020CIYB/NOPB.aspx
they can be purchased for US$345 for 100+

or could look at alternatives at a lower cost
https://store.ti.com/Search.aspx?e=High+Speed+ADCs+(%3E10MSPS)

 

Offline paulcav

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Re: Open Source Oscilloscope, can it be done?
« Reply #27 on: March 09, 2017, 02:18:23 pm »
I found this DIY DSO here
http://www.jyetech.com/Products/LcdScope/e150.php
that may be of interest


DSO Shell has similar bandwitch as DSO138 though it contains significant improvements in structure, mechanical, and operation.


Display and MCU are now mounted on the same board (mainboard) to avoid using inter-board pin-headers. Feedback from DSO138 usres have shown that soldering on the pin-headers are often problematic for many beginners. Analog channel is placed on a separated board which contains most user install parts. This brings in better separation between analog and digital circuits. Without the analog portion the mainboard is actually a general purpose control board that can be used in many other applications. The mainboard is fully installed (except a few through-hold components) and factory tested before packing.

And a viddeo of someone building it

 

Offline CCitizenTO

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Re: Open Source Oscilloscope, can it be done?
« Reply #28 on: March 10, 2017, 03:45:59 am »
I think the biggest hurdle in building an open source oscilloscope is running afoul of patents and patent lawyers at big name test gear manufacturers like Rigol and Tektronics. When you go from a one off build to production you start cutting into their marketshare and profits that's when you may start getting legalese nastygrams sent your way even if you just offered it up in kit form.

The other aspect that I see in most of Dave's teardowns is that to get high bandwidth oscilloscopes requires a good number of ADCs because it seems like most ADCs he finds in these oscilloscopes are 20-100MHz and they use like 5 or 6 of them to process the required bandwidth. I suspect they use the most reliable and cheapest chips they can source which is why on a 100MHz bandwidth scope you'll find 5x 20MHz chips as opposed to a single 100MHz chip. From a system engineering standpoint it would make sense if you could use 5x $0.20 part as opposed to a $3 part you'd improve your profit margin by $2.
 

Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #29 on: March 10, 2017, 07:06:47 am »
I don't see an open source scope being much of a threat to the big companies, although lawyers might see things differently. A company looking to purchase a DSO is not likely to even consider a hobbyist grade open source/DIY model. I still think that with current tech anyway no open source scope is going to come close to the price to performance ratio of something like the Rigols.
 

Offline paulcav

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Re: Open Source Oscilloscope, can it be done?
« Reply #30 on: March 10, 2017, 11:16:52 am »
I think this is an interesting topic however, i think we should define what is the goal of the project. Should it be a low cost item, what are the parameters such as speed, number of channels, screen size, screen resolution, touch screen, number of settings and many many more.

With regards to the legality side, if it was made as a NFP or even sponsored by a tech company then it would be considered legal and above board.

Consider this  if we would get sponsorship from Rigol and/or Tektronics or some other brand that could assist in some way then they could guide us away from the patented issues. They could provide support in finding or suggesting parts, testing solutions, issues to avoid that they have encountered, we could all learn from the big guys.

 
 

Offline CCitizenTO

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Re: Open Source Oscilloscope, can it be done?
« Reply #31 on: March 10, 2017, 12:04:28 pm »
I think this is an interesting topic however, i think we should define what is the goal of the project. Should it be a low cost item, what are the parameters such as speed, number of channels, screen size, screen resolution, touch screen, number of settings and many many more.

I think low cost is an important parameter if you are making an open source/hobby level oscilloscope. Or you could offer a range of options like the big guys offer.

Speed: I'm guessing you are referencing the bandwidth. 20MHz would be the bare minimum acceptable for hobby electronics use. 100MHz would be better if it doesn't cost much more.

Channels: Needs at least 2 channels, ideally 4 channels.

Screen Size: Likely the single most expensive component so cost is likely the biggest consideration in choice. A 5-7" LCD display would be like $50-100

Touch Screen: Not necessary, likely increases expense when you can just use knobs and buttons for adjusting settings for cheaper than buying a touchscreen.
 

Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #32 on: March 10, 2017, 12:43:59 pm »
Screens are dirt cheap, you can get 7" TFT monitors for under $30. Yeah they're not super high res but I bet the panel would be adequate for a scope. The most expensive part by far will be the capture hardware, ADC followed by the front end. I'd say 50MHz is about the minimum threshold between useful scope and toy, but yeah 100MHz would be better.
 

Offline ebclr

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Re: Open Source Oscilloscope, can it be done?
« Reply #33 on: March 10, 2017, 01:08:15 pm »
May be this one

https://redpitaya.com/
 

Offline Andrey_irk

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Re: Open Source Oscilloscope, can it be done?
« Reply #34 on: March 20, 2017, 07:46:07 pm »
There is another problem nobody noticed: US has export restrictions on some high speed ADCs. For example, you can't buy 8-bit 1GS/s ADC if it has more than 1 channel. And there are different speed limits for each resolution. The more resolution is the lower speed you can get.
I can be wrong, but I think Red Pitaya chose 125MHz 14-bit ADC for their board because it was the fastest 14-bit ADC they could get without licence and they didn't want to use multiple chips.
« Last Edit: March 20, 2017, 07:47:57 pm by Andrey_irk »
 

Offline ebclr

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Re: Open Source Oscilloscope, can it be done?
« Reply #35 on: March 20, 2017, 07:51:31 pm »
This export restriction apply only to what they call "hostile destinations", and is easily worked out with a form fill supposing you are not  on the target restrict area, also everything is easily available in China, where the unique restriction is to have money.

 

Offline paulcav

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Re: Open Source Oscilloscope, can it be done?
« Reply #36 on: March 20, 2017, 07:58:20 pm »
There are some chip manufactures like TI will sell 14 bit ADCs for a small fortune

http://www.ti.com/product/ADC32RF45/samplebuy
 

Offline Andrey_irk

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Re: Open Source Oscilloscope, can it be done?
« Reply #37 on: March 21, 2017, 11:41:35 am »
This export restriction apply only to what they call "hostile destinations", and is easily worked out with a form fill supposing you are not  on the target restrict area, also everything is easily available in China, where the unique restriction is to have money.

Maybe, but here in Russia, for example, its not that easy. And it was so even before sanctions. I was talking about buying a 250MS/s 14bit ADC with a local Analog distributor about a year ago and realized that it was possible to buy them one way or another if you were a company, but for a hobbyist it wasn't worth it.
So, you can't use such stuff in a real open source project because people won't be able to build the thing.
 
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Offline Andrey_irk

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Re: Open Source Oscilloscope, can it be done?
« Reply #38 on: March 21, 2017, 12:01:49 pm »
There are some chip manufactures like TI will sell 14 bit ADCs for a small fortune

http://www.ti.com/product/ADC32RF45/samplebuy

Then if you actually try to order samples of the "forbidden" stuff they will say that it is impossible to ship them to you.
 

Offline amspire

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Re: Open Source Oscilloscope, can it be done?
« Reply #39 on: March 21, 2017, 01:33:38 pm »
There are a few types of specialized scopes that I would be interested. One is a sampling scope, with perhaps a 10GHz analog bandwidth. The hardware for this can be very simple and cheap except for the sampling head and the trigger circuit. The A/D can be something like a cheap 1MS/s 16 bit - speed doesn't matter. One of the idea's I saw somewhere was a 50 ohm transmission line on the sampling board with, say, 20 sets of sampling diodes about every cm or so. All the diodes are hit with the sampling pulse at exactly the same time (pulse clock in the centre, transmission line circling around it so that all sampling pulse lines exactly the same length), so you end up with a sample consisting of 20 realtime samples with a 50ps spacing. You can still use it as a sampling scope, but you also have enough consecutive realtime samples to see an edge or a one time glitch. Wouldn't have a clue about doing this myself, but it would be great if a GHz guru did something brilliant.

The second one would be something extremely cheap, low featured box  (probably pretty slow speed) but with very smart triggering, big memory and continuous capturing ability. Something you could perhaps leave connected to the mains or anything you want to monitor and it can be set to catch any anomaly. Something with a parts cost of $10 to $40 that you control via PC, phone, etc.
 

Offline daybyter

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Offline Andrey_irk

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Re: Open Source Oscilloscope, can it be done?
« Reply #41 on: March 21, 2017, 03:25:33 pm »
The A/D can be something like a cheap 1MS/s 16 bit - speed doesn't matter. One of the idea's I saw somewhere was a 50 ohm transmission line on the sampling board with, say, 20 sets of sampling diodes about every cm or so. All the diodes are hit with the sampling pulse at exactly the same time (pulse clock in the centre, transmission line circling around it so that all sampling pulse lines exactly the same length), so you end up with a sample consisting of 20 realtime samples with a 50ps spacing. You can still use it as a sampling scope, but you also have enough consecutive realtime samples to see an edge or a one time glitch. Wouldn't have a clue about doing this myself, but it would be great if a GHz guru did something brilliant.

This is interesting. So the trick here seems to be in building these sample-and-hold circuits. And you'll need very high speed diodes or something like that.
 

Offline amspire

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Re: Open Source Oscilloscope, can it be done?
« Reply #42 on: March 21, 2017, 04:00:14 pm »
The A/D can be something like a cheap 1MS/s 16 bit - speed doesn't matter. One of the idea's I saw somewhere was a 50 ohm transmission line on the sampling board with, say, 20 sets of sampling diodes about every cm or so....

This is interesting. So the trick here seems to be in building these sample-and-hold circuits. And you'll need very high speed diodes or something like that.
I did mean 20 sets of sampling diodes - one every cm.

The sample and hold circuits are usually made from 2 or 4 high speed diodes.

There was an article that came out about 2000 with a simple scope circuit:

http://www.redrok.com/sampscope.htm

It has some nice ideas - like using the input capacitance of a common low frequency fet opamp as the first stage of a sub nanosecond aperture sample and hold.
 

Offline ebclr

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Re: Open Source Oscilloscope, can it be done?
« Reply #43 on: March 21, 2017, 07:33:39 pm »
Andrey_irk

Forget USA and Europe if you live in Russia

China, is Putins best friend, there is your place to buy, Near everything real and Fake can be found in China

www.taobao.com
www.aliespress.com

 

Offline ohdsp

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Re: Open Source Oscilloscope, can it be done?
« Reply #44 on: March 23, 2017, 10:28:19 am »
That STM32 $10 scope looks interesting.

Considering a faster design; if you could use some cheap fast 8 bit ADCs and interleave them with some clever manipulation on an FPGA interface that would seem the cheapest (although more complex to develop) option. If you can do this then maybe you could do things such as using some ADCs to do a rough scan of the waveform based on time base, but then use the extra ADCs to look at a much smaller ranges by adjusting reference voltages/sampling times based on the active user display.

If possible it would remove the need for an expensive single fast/high resolution ADC and allow for some neat features. Have found myself many times on scopes with the megazoom type functions where I can see the overall waveform but with not enough resolution to see the detail in the section I want; and where you can't set the trigger to capture that smaller section of data without seeing all the waveform. Would be nice if you could capture a waveform and then just point the scope to a timebase position and tell it "I want more detail here please!".

I like crazy ideas....
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Offline daybyter

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Re: Open Source Oscilloscope, can it be done?
« Reply #45 on: March 23, 2017, 12:19:28 pm »
I think the 10$ scope needs a simple ui. Then overclock the mcu maybe.

Another option could be one of those 13$ fpga boards + some old pc ram dimm?
 

Offline james_s

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Re: Open Source Oscilloscope, can it be done?
« Reply #46 on: March 24, 2017, 02:56:34 am »
The problem with the $13 FPGA boards (which I'm a big fan of) is the number of IO pins. Once you start trying to connect parallel memory you quickly go through a lot of IO pins. IIRC there are about 75 general purpose pins and that has to cover everything. Memory, display, ADC, user input, etc.
 

Offline Andrey_irk

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Re: Open Source Oscilloscope, can it be done?
« Reply #47 on: March 24, 2017, 04:49:26 pm »
Andrey_irk

Forget USA and Europe if you live in Russia

China, is Putins best friend, there is your place to buy, Near everything real and Fake can be found in China

www.taobao.com
www.aliespress.com

I was talking about availability of high speed ADCs for hobbyists around the world. Russia was just an example.
And I can't imagine a hobbyist buying 400$ worth IC at Aliexpress or Taobao.

 

Offline ebclr

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Re: Open Source Oscilloscope, can it be done?
« Reply #48 on: March 24, 2017, 05:29:20 pm »
In fact you can buy even a million USD of components specially from taobao,  As many you know , more you know what you don't know
 

Offline qu1ck

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Re: Open Source Oscilloscope, can it be done?
« Reply #49 on: April 30, 2017, 10:55:02 am »
This guy collected lots of opensource(ish) scope projects, starting from dumbest bare mcu variants to advanced ones with decent sampling rate external ADC, FPGA, waveform memory and the whole shebang.
http://stm32duino.com/viewtopic.php?f=45&t=1710

I particularly like the STM32F303 variants since it has better built-in ADC than most mainstream MCUs.
Check out GFXscope. The firmware for it isn't free though.
Also FusionScope, with free firmware. Author of that one is working on new version with external ADC and opamps.

An example of more advanced device is Neil Scope 3. 20 Mhz analog frontend, 100 msps ADC http://radiokot.ru/circuit/digital/measure/107/
Gotta learn Russian or suffer through google translate though :)
Nothing is true (as far as measurements go)
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Offline NiHaoMike

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Re: Open Source Oscilloscope, can it be done?
« Reply #50 on: April 30, 2017, 12:45:18 pm »
I can think of two approaches to a DIY scope that give capabilities no affordable scope on the market has.

First design is an ADC going directly into a FX2 or FX3 USB interface. Similar to the FX2-based logic analyzers supported by Sigrok, the record length is only limited by how much RAM your PC has. Or write a driver for GNUradio and have nearly limitless ways to do real time processing.

Second design uses a FPGA and RAM like a traditional digital scope does, but instead of a built in display, it uses an ESP8266 or similar to connect to a smartphone or tablet. Basically like the Mooshimeter but it's a scope.
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Offline abraxa

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Re: Open Source Oscilloscope, can it be done?
« Reply #51 on: April 30, 2017, 03:59:52 pm »
First design is an ADC going directly into a FX2 or FX3 USB interface. Similar to the FX2-based logic analyzers supported by Sigrok, the record length is only limited by how much RAM your PC has. Or write a driver for GNUradio and have nearly limitless ways to do real time processing.
There are already ADC+FX2 combos, for example the Hantek 6022BL or Hantek 6022BE. USB HS has too little bandwidth for a serious streaming scope, so USB SS it would need to be. However, the dumb people at Cypress apparently thought "Oh hey, the FX2 was such a major success, let's make everything 10x as complicated. Customers will love it!", which resulted in the FX3 now requiring an RTOS (ThreadX) with a proprietary license that does not allow redistribution of the code. That means a completely open source FX3 firmware isn't going to happen and I don't even know if it's allowed to redistribute the library binary. Way to go, Cypress! :palm:
Either way, I agree with you. I really, really, really want an open source USB3 streaming scope. Once someone makes it, though, it will be cloned 1000000x in China and sold for lowest prices, so there's no money to be made for the original developer(s). Not a strong motivator for anyone, I figure.

Quote
Second design uses a FPGA and RAM like a traditional digital scope does, but instead of a built in display, it uses an ESP8266 or similar to connect to a smartphone or tablet. Basically like the Mooshimeter but it's a scope.
Aside from perfect galvanic isolation, I never understood the point of wireless scopes. Why artificially limit your I/O bandwidth and add tons of latency for no other reason than "it can be done"? For examining mains circuits, those things could however be literal life savers indeed.
 

Offline Marco

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Re: Open Source Oscilloscope, can it be done?
« Reply #52 on: April 30, 2017, 06:37:29 pm »
I don't really need single digit msec latency, not trying to win a game of counterstrike on my scope.

Part of a frame's worth of extra input-output latency is hardly noticeable.
 

Offline NiHaoMike

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Re: Open Source Oscilloscope, can it be done?
« Reply #53 on: May 01, 2017, 02:44:51 am »
I'm thinking the wireless scope can be good for field use, as in make it a pen form factor.

Perhaps someone could reverse engineer what the ThreadX code does and then replace it with something open source like FreeRTOS?
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Offline branadic

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Re: Open Source Oscilloscope, can it be done?
« Reply #55 on: July 09, 2017, 08:14:49 pm »
Quote
Open Source Oscilloscope, can it be done?

Yes it can, unless you have enough people for the different sections of the scope:
- input stage and analog to digital conversion
- FPGA design, softcores, ...
- GUI
- ...

Once I developed a completely new input stage for the Welec DSO together with Walter M. This input stage design can be used, to design a complete oscilloscope.  We used the LMH6518 for the input stage. Later the LMH6518 was also used by Rigol.

http://welecw2000a.sourceforge.net/cgi-bin/trac.cgi/wiki/HardwareImprovement

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Offline neris.io

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Re: Open Source Oscilloscope, can it be done?
« Reply #56 on: July 18, 2017, 04:14:23 am »
may be a place to start ? https://www.kickstarter.com/projects/342199468/openscope-instrumentation-for-everyone/description

I started open scope and HTML5 frontend before Diligent (post processing data on the server before display if too much data for the browser to process etc)
https://hackaday.io/project/19374-ginscope-science-toolbox-oscilloscope
https://github.com/soholt/GinScope it was uploaded in November 2016 + spent much more time before that

Hoping to find help and advice, thanks

Offline slicendice

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Re: Open Source Oscilloscope, can it be done?
« Reply #57 on: July 20, 2017, 07:36:28 pm »
Finally an answer to the question that makes sense! Great job on the improvement project!
 

Offline zeqing

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Re: Open Source Oscilloscope, can it be done?
« Reply #58 on: August 07, 2017, 04:38:10 pm »
strange no one mentioned this: https://www.seeedstudio.com/DSO-nano-Pocket-size-digital-storage-oscilloscope-p-512.html a project more than 6 years...
 

Offline marcopolo

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Re: Open Source Oscilloscope, can it be done?
« Reply #59 on: September 20, 2017, 03:32:55 am »
https://www.arrow.com/en/products/bescope/arrow-development-tools

250Msps scope for $45 with FPGA and software sources included

Offline Marco

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Re: Open Source Oscilloscope, can it be done?
« Reply #60 on: September 20, 2017, 07:00:09 am »
250Msps scope for $45 with FPGA and software sources included
Only the Python GUI source code AFAICS and I don't think this includes the Bemicro CV board (which no longer seems available at all).
« Last Edit: September 20, 2017, 07:10:07 am by Marco »
 

Offline marcopolo

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Re: Open Source Oscilloscope, can it be done?
« Reply #61 on: September 21, 2017, 01:37:46 am »
I think you are right  :-//

Offline NiHaoMike

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Re: Open Source Oscilloscope, can it be done?
« Reply #62 on: September 24, 2017, 04:05:34 pm »
http://www.ftdichip.com/Products/ICs/FT600.html
Another apparently easy to use USB 3 chip for those who aren't against FTDI.
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Offline cdev

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Re: Open Source Oscilloscope, can it be done?
« Reply #63 on: September 29, 2017, 11:37:02 pm »
If existing computers and display hardware were available, then the cost of the scope can be much much lower..

For several years Ive wondered if the RTL2832 could be used to make a cheap 8 bit oscilloscope. The direct sampling input is better than people think for radio. Its clean. RTLSDR takes only around 170 ma and is tiny.

Really tiny. Imagine a really tiny, really cheap, high bandwidth USB scope//SDR.

People have synchronized them by running multiple RTLSDRs off the same clock.
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Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #64 on: October 03, 2017, 04:28:53 am »
For several years Ive wondered if the RTL2832 could be used to make a cheap 8 bit oscilloscope. The direct sampling input is better than people think for radio. Its clean.

RTL2832 is not capable to transfer whole ADC bandwidth over USB. Input shall be digitally downconverted (by RTL2832) to 2.4MSPS or below - to not lose samples. Who would want scope with 1MHz bandwidth?
« Last Edit: October 03, 2017, 04:30:30 am by ogden »
 

Offline cdev

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Re: Open Source Oscilloscope, can it be done?
« Reply #65 on: October 08, 2017, 09:48:31 am »
We have to remember how cheap they are- as little as $7 shipping included.
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Online JohnG

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Re: Open Source Oscilloscope, can it be done?
« Reply #66 on: October 09, 2017, 05:42:07 am »
Out of my expertise, but perhaps there is a way to make a sampling scope out of one? That way one could take advantage of the large bandwidth.

John
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #67 on: October 09, 2017, 11:10:35 pm »
Out of my expertise, but perhaps there is a way to make a sampling scope out of one? That way one could take advantage of the large bandwidth.

John

It *is* kind of sampling scope out of the box. You can tune DDC (digital downconverter) of the rtl chip to (close) frequency of your signal, for example 10MHz, then get frequency components in given (1-2 MHz) band around it. Thou you shall be knowing what are you looking at - because all other frequency components will not be there, including DC offset and so on. Very limited "scope" so to say :) Frequency domain information (FFT plot) is much more useful in such case.

Yes, mod your RTL to direct sampling and look at the signals using FFT plot of SDRsharp or similar software.
 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #68 on: October 15, 2017, 04:12:35 pm »
Hi. Been talking about this on the crowd funding category...
I'm about to launch a crowdsupply campaign for a new scope:
https://www.crowdsupply.com/andy-haas/haasoscope

It’s 4-channels, 125 MSPS, 8 bit, ~100 MHz BW.
The goal was to keep the cost as low as possible (with those specs). It should retail for < $100.
It's based on the ADC + FPGA principle, with a barebones front end and readout to a computer over serial.

It's completely open-hardware and open-source, including firmware and software. Hack away!

It's also designed to be expandable – just connect 2 (or more) of them together to get 8, 12, … channels, etc. A trigger in any channel can trigger the readout of all the boards, within ~1 clock tick (20 ns). I think that's actually a pretty unique feature.
 

Offline NiHaoMike

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Re: Open Source Oscilloscope, can it be done?
« Reply #69 on: October 16, 2017, 11:56:05 am »
Hi. Been talking about this on the crowd funding category...
I'm about to launch a crowdsupply campaign for a new scope:
https://www.crowdsupply.com/andy-haas/haasoscope

It’s 4-channels, 125 MSPS, 8 bit, ~100 MHz BW.
The goal was to keep the cost as low as possible (with those specs). It should retail for < $100.
It's based on the ADC + FPGA principle, with a barebones front end and readout to a computer over serial.

It's completely open-hardware and open-source, including firmware and software. Hack away!

It's also designed to be expandable – just connect 2 (or more) of them together to get 8, 12, … channels, etc. A trigger in any channel can trigger the readout of all the boards, within ~1 clock tick (20 ns). I think that's actually a pretty unique feature.

Really needs a USB 3.1 option for continuous streaming. Could make a great 4 stream SDR digitizer.
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Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #70 on: October 17, 2017, 01:01:10 pm »
It’s 4-channels, 125 MSPS, 8 bit, ~100 MHz BW.

Hate to disappoint, but does not look appealing. 4x100MHz scope channels hacked through USB-UART adapter sounds so wrong to me. I would live with just 2 channels, preferably 10-bit, but USB (at least 2.0) is a must requirement. Also PGA (programmable gain amplifiers) and AC/DC coupling for each channel are needed. Scope takes more than just bare ADC and FPGA on the board, sorry.

p.s. I am afraid that power budget is more than that little LDO w/o thermal pad can handle. What kind of ADCs do you use? How do you clock them? - Using PLL of the FPGA?
 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #71 on: October 18, 2017, 12:10:55 am »
Thanks for your feedback.
The serial output is very flexible, cheap, and easy to use, but yes many people want USB2 output in addition. I'm looking into it. There is adjustable gain and dc offset in the latest prototype: https://www.crowdsupply.com/andy-haas/haasoscope/updates/latest-prototype

10-bit is trivial to upgrade to (there's a pin-compatible ADC part), it's just another $10/board. I could eventually support a few board versions. (Or, since it's open-hardware, you could do it yourself!)

I personally never use AC coupling, but if people really want it, it would be trivial to add. In the meantime you just have to put a cap between your signal and the input.

The power drawn by the components on the board is about 0.3A @5V. The LDO supplies up to 1A, and it doesn't get too warm while the board is running. I don't see the issue. (There is thermal coupling to the ground plane.)

It's a Max19506 ADC. Yes, they're clocked from FPGA PLL outputs (on dedicated low-jitter clock outputs).
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #72 on: October 18, 2017, 03:22:00 pm »
The serial output is very flexible, cheap, and easy to use, but yes many people want USB2 output in addition.

Indeed flexibility is good thing but imagine useability and repeatability of instrument which shall be assembled from multiple boards using jumper cables. I would throw such away immediately. Leave UART as an option interface on GPIO connector for those who love to tinker, make USB primary one. Preferably USB socket shall reside on opposite to BNC connectors, board side. [edit] Obviously FPGA firmware software-loadable through USB, not JTAG.

Quote
10-bit is trivial to upgrade to (there's a pin-compatible ADC part), it's just another $10/board.

Right. Also consider board configuration with two channels unpopulated - to drive cost down a bit. Someone could appreciate such. [edit] I would prefer to have 2x100MSPS ADC channels with 2 x 200MHz DAC channels of signal gen output. Well, and level-translated digital I/os on front. You really shall think how your thing can be used if put in the box.

Quote
I personally never use AC coupling, but if people really want it, it would be trivial to add.

I am not representing all the people, but AC coupling is often needed, especially in the analog domain. For example how could you catch 1mV noise riding on the 5V rail with 8bit scope having DC-only input? Indeed AC coupling shall be software-switchable.

Quote
It's a Max19506 ADC. Yes, they're clocked from FPGA PLL outputs (on dedicated low-jitter clock outputs).

Punch in bandwidth and jitter numbers in this calculator: https://www.maximintegrated.com/en/app-notes/index.mvp/id/4466 Perhaps it is good idea to dedicate own 100MHz crystal oscillator for just ADC clock.

p.s. Having 100MHz clock, scope bandwidth shall be around 25 MHz or so. What opamps do you use? Why can't I find schematics for review?
« Last Edit: October 18, 2017, 05:45:38 pm by ogden »
 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #73 on: October 19, 2017, 12:11:37 am »
The USB-UART adapter plugs directly into the board. No jumper cables needed.

I'll put AC coupling on the list of things to add.

I'm using MAX4416 op-amps.

I'll be able to make schematics and all files available if/when the project is funded.

Thanks again for your interest / feedback!
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #74 on: October 20, 2017, 01:28:37 am »
The USB-UART adapter plugs directly into the board. No jumper cables needed.

Then your scope is not finished & ready to use product out of the box anyway. IMHO many could be discouraged because of that.

Did you check jitter calculator? PLL jitter of Altera Max 10 is 660ps. 8-bit resolution needs no more than 25ps for undistorted 25MHz sine. Don't use jittery PLL for hi-speed ADCs.

https://www.maximintegrated.com/en/design/tools/calculators/general-engineering/jitter.cfm
 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #75 on: October 20, 2017, 04:11:23 am »
I agree it's borderline, but the FPGA clock output is good enough in this case. The RMS jitter is 660ps / 14 = ~47ps.
The 660 ps is the peak-to-peak jitter, or bit error rate of 10^-12, as noted in footnote 31 of the datasheet: https://www.altera.com/en_US/pdfs/literature/hb/max-10/m10_datasheet.pdf

To convert to RMS jitter, you have to divide by the error function probability, which is about 14 for a 10^-12 BER. See:
http://pdfserv.maximintegrated.com/en/an/AN462.pdf

And this 660ps is when driven from a clock with jitter of up to 30ps. I'm using a low-jitter oscillator which has RMS jitter of ~3ps. This must reduce the output PLL jitter somewhat (not a factor of 10 though). With this, I'm within the 25 ps spec, or close enough that the additional noise/distortion is negligible.

Anyways, it works well, and a 25 MHz sine wave looks good. The FFT shows no signs of distortion.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #76 on: October 20, 2017, 12:11:55 pm »
I agree it's borderline, but the FPGA clock output is good enough in this case. The RMS jitter is 660ps / 14 = ~47ps.
The 660 ps is the peak-to-peak jitter, or bit error rate of 10^-12, as noted in footnote 31 of the datasheet: https://www.altera.com/en_US/pdfs/literature/hb/max-10/m10_datasheet.pdf

You are reading wrong book :) BER does relate to digital I/O, not analog signal sampling using ADC. You shall care not about BER but SNR and resulting ENOB degraded by ADC aperture jitter. For example this appnote says "At 100ps, the ADC SNR begins to degrade with input frequencies of only 200kHz!": http://cds.linear.com/docs/en/design-note/dn1013f.pdf

Quote
Anyways, it works well, and a 25 MHz sine wave looks good. The FFT shows no signs of distortion.

All the energy of 25MHz sine falls into single FFT bin, no "smearing" or PLL "spectrum skirts"? - No way for 660s p-p ADC clock jitter and 25MHz sine signal. What's order of FFT used?
« Last Edit: October 20, 2017, 12:30:09 pm by ogden »
 

Offline Marco

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Re: Open Source Oscilloscope, can it be done?
« Reply #77 on: October 21, 2017, 09:18:36 am »
Approximately the derivative times the jitter is the error range near 0 ... so 2*pi*25e6*47-12 ~= 8 mV RMS for a 1V amplitude 25 MHz sine. So you lose a bit or so.
« Last Edit: October 21, 2017, 09:21:15 am by Marco »
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #78 on: October 26, 2017, 02:30:39 am »
Have you guys seen this?

https://www.digikey.com/product-detail/en/analog-devices-inc/HMCAD1520TR/1127-1198-2-ND/3660273

It's ~$100 a chip, but I can imagine a multi-mode measurement device built around it.  Internal interleaving modes for 1,2 or 4 channels allow a range of speeds, multiple ADC precision levels are also switchable.  Four channel scope at 12 bits/160MSPS, two channels at 12/320MSPS, or one channel at 12/640MSPS.  You can also drop down to 8 bits for single channel rates up to 1GSPS, or engage "precision mode" for four channels at 14 bits/105MSPS.

Looks like it's designed to be used in portable devices too, with low power use and sleep modes.

The flexibility of the built-in interleaving plus the variable bit depth would seem to me to be a nice fit for a wide variety of uses... a portable cheap scope for field use, a first scope for hobby use, an "extra" scope for when you need just one more channel.  If it's cheap, you could even build the software to run multiple units as one... so you could run up to e.g. four of them as 1 GSPS scopes together.  You could also do tricks to save battery like sleep for an interval, wake up to sample, then trigger a reconfig to higher speed or precision, record data, then back to sleep.  Doing most of the processing in software on commodity PC hardware gives you lots of sample depth and open source allows for hardware/software upgrades and even a complete re-tasking of the hardware with a different program loaded.

Since I'm a noob at this though, I'm wondering what other components would be needed for such a critter?  The A/D has internal references, so it's a single chip solution for its function, but there would also have to be an op amp on the front end with wide bandwidth, a microcontroller running the show, and an interface chip for streaming the samples over USB 3.1.  Maybe local memory for buffering when not attached to a host PC, a watchdog, digital I/O for logic analysis and triggering, a dedicated SPI interface for target control that allows for a variety of control interfaces (SPI, I2C, RS-485, Ethernet, TTL, etc). 

Would it be possible to use a Beaglebone as the local controller, maybe using the PRUs to keep up with the data stream?

I'd guess overall it would be best to make the hardware acquire data and get it quickly to a computer, then make most of the functionality happen in software (basically a software defined 'scope).  A rough guess would be about $200-$300 or so in parts plus board fabrication and assembly cost... which is not nothing, but is still a lot cheaper than a Rigol DS1102, and it would have a much bigger screen :)

Anyone want to speculate on a cheap way to use this chip in a design for a software 'scope front end?

 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #79 on: October 26, 2017, 04:01:23 am »
Yeah, it's a nice chip! It's not so easy to make a board that uses such a chip however - there's huge data rates, lots to configure, noisy digital outputs, and you want super low noise! (Even just 12 bits means you want less than 0.2 mV of noise at your ADC inputs!)

You definitely need an FPGA to handle those data rates.

Take a look at their evaluation board:
https://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyEVAL01-HMCAD1520
and the linked datasheet there.
This is a reasonable start at what you'd have to do to have a working system. It's ~$500. You could probably design something more integrated and specialized and trim away the fat, so to speak, and get it down to ~$300. But not easy!
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #80 on: October 26, 2017, 06:13:17 am »
Yep, definitely not a board that would work if designed by a noob.

I'm sure I could do the software with more than a little effort, but hardware wise I basically can manage to understand why everything is where it is :)

So what criteria do you use to decide what's needed to handle the data rates?  Software wise, I'd expect something like a dedicated chip reading the data from the ADC and writing it to dual ported memory, and a dedicated USB processor reading it out the other end and transmitting it to a computer, with the computer doing all the hard work.

What does the FPGA do in this scenario?
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #81 on: October 27, 2017, 06:40:22 am »
I'm sure I could do the software with more than a little effort, but hardware wise I basically can manage to understand why everything is where it is :)

Yo mentioned 1GSPS at 8bits right? Most of modern CPU's will struggle to read data at 1GByte/s, not to mention doing something useful with it. For such a "beast chip" you don't even do a software but high speed logic using FPGA. https://en.wikipedia.org/wiki/Field-programmable_gate_array. Most likely digging into FPGA topic will answer your question:

What does the FPGA do in this scenario?

Hint: all the job.
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #82 on: October 27, 2017, 09:03:07 am »
I'm continuing with this thought experiment for learning purposes, thanks for reading and any replies you continue to provide. :)

So... getting that much data handled in real time would be nearly impossible to do over a USB link, ok.  Putting gigabytes of memory on the 'scope end for buffering is possible, but doing something with the data is the problem.  Even with data compression, something still has to scan through the data to e.g. trigger, and then whatever determines that the trigger conditions were met has to, well, trigger.

So that means a portable scope is difficult in general because of the hardware requirements for handling that much data.  An FPGA or an ASIC would be needed, and following that thought the FPGA has to be programmed with most of the functions of a 'scope, which would get expensive quickly, limit features, and in general not be significantly cheaper than a purchased scope.

It might be possible to use an FPGA with a simpler config to couple the ADC chip to a PCIe x8 slot on a PC motherboard, functioning as an LVDS receiver, buffer, and DMA engine?  That's more than enough speed to stream data to PC memory.  Lots of capture depth, and I could imagine streaming data to a ring buffer a few gig in size while the PC CPU scans through it looking for trigger conditions.  When triggered, data starts getting put somewhere else in memory for processing, possibly in compressed form. 

I'll start reading up on FPGAs.  I've wanted to learn about 'em anyway :)




 

Offline hermit

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Re: Open Source Oscilloscope, can it be done?
« Reply #83 on: October 27, 2017, 10:24:15 am »
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #84 on: October 27, 2017, 01:29:37 pm »
There is no way that an open source scope could be made cheaper than a low end Chinese unit.  If it could be done, the Chinese would.

What *could* be done is to reverse engineer something that uses a Linux distro and write custom firmware for it.  Unfortunately that is a good bit of work.  There is precedent though in the form of DD-WRT which leveraged the GPL to get enough information about the internals to write new firmware.

However, the easiest route to an open source oscilloscope is to write a portable PC UI for the SCPI LAN interface. The 2nd step would be to write a UI for specific hardware that transformed the button presses into SCPI commands sent via 127.0.0.1.

That might well tempt an OEM to build hardware for the UI.
 

Offline BradC

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Re: Open Source Oscilloscope, can it be done?
« Reply #85 on: October 27, 2017, 02:00:14 pm »
There is precedent though in the form of DD-WRT which leveraged the GPL to get enough information about the internals to write new firmware.

I think you need to re-check the history on that. DD-WRT started when they obtained a practically complete copy of a linksys firmware and effectively re-badged it. It has evolved significantly from there, however they started from a pretty-much complete working source.
That's more like Rigol giving you the V0.9 source in a buildable format and then you go and start enhancing it, and it's *considerably* different from reverse engineering from scratch.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #86 on: October 27, 2017, 02:51:25 pm »
There is no way that an open source scope could be made cheaper than a low end Chinese unit.

Agreed. Sure you can build low cost "toy scope" but again chinese are offering such all over the place  :)

DD-WRT started when they obtained a practically complete copy of a linksys firmware and effectively re-badged it.

Not the whole firmware, just source code of the kernel which have most of the router functionality in it. Kernel of the scope will contain just scope-specific I/O drivers which is close to nothing. All the scope magic is happening in the FPGA or ASIC. CPU is also doing some useful stuff, but in application code which again is unobtainable.
« Last Edit: October 27, 2017, 05:27:46 pm by ogden »
 

Offline hermit

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Re: Open Source Oscilloscope, can it be done?
« Reply #87 on: October 27, 2017, 03:16:50 pm »
There is no way that an open source scope could be made cheaper than a low end Chinese unit.  If it could be done, the Chinese would.

What *could* be done is to reverse engineer something that uses a Linux distro and write custom firmware for it.  Unfortunately that is a good bit of work.  There is precedent though in the form of DD-WRT which leveraged the GPL to get enough information about the internals to write new firmware.

However, the easiest route to an open source oscilloscope is to write a portable PC UI for the SCPI LAN interface. The 2nd step would be to write a UI for specific hardware that transformed the button presses into SCPI commands sent via 127.0.0.1.

That might well tempt an OEM to build hardware for the UI.
How far could you get with something like a Beagle Bone Black that has two real time units embedded?  They run at 200Mhz.  Someone did a cape with 16 logic analyzer channels running at 100Mhz.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #88 on: October 27, 2017, 03:17:14 pm »
It might be possible to use an FPGA with a simpler config to couple the ADC chip to a PCIe x8 slot on a PC motherboard, functioning as an LVDS receiver, buffer, and DMA engine?

Much more cheaper and simpler will be just to add external memory to the FPGA. Or maybe do not add too much memory to keep costs down ;) For example (now obsolete) 54855A Infiniium scope had PC inside, but it did not use RAM of embedded PC for sampling. Sorry, but it is stupid engineering to sample into PC RAM - of course if we talk about high speed (>= 1GSPS) scope. PC-based "open source" 1GSPS scope shall process waveform in the FPGA, draw video framebuffer there, transmit resulting video stream (containing just waveform picture, not even grid) over USB.
« Last Edit: October 27, 2017, 05:29:34 pm by ogden »
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #89 on: October 27, 2017, 07:10:16 pm »
I still believe that building DIY scope is like a building better mousetrap. Indeed it could be done as an challenge project "because I can", but economics is not worth it. There's lot of scopes which cannot be beat by DIY approach:

48MSPS/20MHz  Hantek 6022BE USB scope: ~60$, including two probes
100MSPS/25MHz OWON VDS1022 USB scope: ~80$, including two probes
100MSPS/25MHz isolated OWON VDS1022I USB scope: ~100$, including two probes
250MSPS/70MHz Hantek iDSO USB scope: ~170$, including two probes
1GSPS/100MHz Hantek DSO5102P (standalone!): ~225$, including two probes
« Last Edit: October 27, 2017, 07:39:54 pm by ogden »
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #90 on: October 28, 2017, 12:45:37 am »

However, the easiest route to an open source oscilloscope is to write a portable PC UI for the SCPI LAN interface. The 2nd step would be to write a UI for specific hardware that transformed the button presses into SCPI commands sent via 127.0.0.1.


It appears that a portable PC GUI already exists for some or all the GW Instek scopes in the form of:

https://github.com/OpenWave-GW/OpenWave-2KE

It's written in python, so I assume it's written on top of the SCPI interface, but I'll have to check that.

I don't see a lot of value in rewriting the FPGA software except for bug fixes.  The hardware choices pretty much control what can be done in terms of sampling, etc.   It might be possible to make minor improvements, but that depends upon whether there are any unallocated resources.

One can do all manner of interesting things with a Beaglebone or any other high power MCU dev board.  Lots of people are doing that and selling some version on eBay.  I had a project to do that, but dropped it when I realized that world + dog was doing the same thing.  Still a good project, I'd rather implement a VNA using a DSO and an add on board w/ DDS and directional couplers.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #91 on: October 28, 2017, 04:47:24 am »
I'd rather implement a VNA using a DSO and an add on board w/ DDS and directional couplers.

Great idea! -Especially if you could consider to add SCPI-capable waveform generator support. Then "VNA" electronics reduces to quite simple board (no DDS needed), all the magic is software. I think, Rigol 1000Z-S series scope owners/hobbyists would be especially happy with such.
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #92 on: October 28, 2017, 09:46:09 am »
>Sorry, but it is stupid engineering to sample into PC RAM

Why exactly is that?


>I still believe that building DIY scope is like a building better mousetrap. Indeed it could be done as an challenge project "because I can", but economics is not worth it. There's lot of scopes which cannot be beat by DIY approach

That's not the point, though.  The point of an open source scope is to have a working non toy Oscilloscope that's able to be modified and improved by anyone who wants to take the time, with those modifications able to be contributed back to the original design - everyone who's using it can benefit.  Since open source allows commercial use provided users can get schematics and are free to modify them (and any commercial mods are contributed back to the design) it's even possible for people to manufacture and sell open source hardware designs for profit.  Provided the design is somewhat modular, as new chips (like a new front end) come out, it can evolve and integrate new technology.

So... a DSO or MSO with complete schematics and source code that has reliable software, full documentation in a variety of languages, and isn't vulnerable to a single hardware manufacturer dropping support, getting sold, going out of business or otherwise sticking it to the buyer?  I'd buy two.  Even if they cost twice as much as the Chinese scopes.


 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #93 on: October 28, 2017, 12:52:30 pm »
>Sorry, but it is stupid engineering to sample into PC RAM

Why exactly is that?


Do I really need to explain that? Come on..

0) To reach 1Gbyte/s, scope shall be in form of some PCI express adapter for desktop PC. Scope "head" shall be connected to PCIe using hi-speed bus. It means quality hi-speed cable and connectors. Could add quite a lot of cost.
1) Because of point 0) laptop and miniPC users are out of luck of using such PCIe adapter scope. This is HUGE disadvantage.
2) PC is laggy and not "realtime" by definition. Do you really want to lose samples or trigger events when OS decides to flush some bigger data chunk on HDD?
3) Such "software" scopes cannot have trigger output hardware signal by definition - because PCs are laggy
4) Yes, PCIe can transfer data at 1GByte/s so what? - It shall be processed too. Even so simple operation as trigger event search requires quite lot of CPU cycles. No offense, but either you get it here or you are way too out of "1GSPS scope league".

As I said - all the job of such scope shall be done in the FPGA and PC shall act just as "I/O terminal" for it. Period. Then even USB2 is good enough BTW.

[edit] Owon VDS3104 have proper hi-speed USB scope architecture.

« Last Edit: October 28, 2017, 01:08:15 pm by ogden »
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #94 on: October 29, 2017, 12:59:20 pm »
>Do I really need to explain that? Come on..

Yes, because I'm trying to understand your point of view.  Replies below...

>0) To reach 1Gbyte/s, scope shall be in form of some PCI express adapter for desktop PC. Scope "head" shall be connected to PCIe using hi-speed bus. It means quality hi-speed cable and connectors. Could add quite a lot of cost.

PCIe slots just require the edge of the circuit board to be shaped for insertion... no cables required.  Not sure what you mean here?


>1) Because of point 0) laptop and miniPC users are out of luck of using such PCIe adapter scope. This is HUGE disadvantage.

It depends.  You can make it a half-height card suitable for mini PCs and full size.  Laptops are a miss, sure, but there's a limited amount you can do with them if you need more speed than USB can provide.

>2) PC is laggy and not "realtime" by definition. Do you really want to lose samples or trigger events when OS decides to flush some bigger data chunk on HDD?

Hard real time is difficult, but possible.  Look at the example of RTAI - https://www.rtai.org/.  Besides, we're talking about DMA over the PCIe bus, which doesn't require CPU intervention.  Unless there's a hardware fault holding the bus hostage, the 'scope card could write data whenever it needed to do so, right?

>3) Such "software" scopes cannot have trigger output hardware signal by definition - because PCs are laggy

Not true always, as mentioned above.  Even Windows 10 has a real time solution: http://www.intervalzero.com/

Besides, if you're using the PC's memory as a giant buffer, you don't need to trigger in real time, exactly.. you just record everything in a ring buffer a few GB in size and keep overwriting it with new data.  As long as the CPU gets around to examining the data before it gets overwritten so it can record the target data, it would work I think.

>4) Yes, PCIe can transfer data at 1GByte/s so what? - It shall be processed too. Even so simple operation as trigger event search requires quite lot of CPU cycles. No offense, but either you get it here or you are way too out of "1GSPS scope league".

See above, if you record all samples continually into memory it isn't necessary to trigger in real time... you just examine the recorded data often enough to ensure you don't miss something before it's overwritten.  Once the CPU finds the "trigger" condition, it just ceases overwriting data and records a sample for review instead.

I'm not sure how long a PC could sustain DMA at that speed, though.... from what I can tell, most of the high speed acquisition cards out there use local RAM and an FPGA like a Virtex-5 for sample capture, then transfer to the PC's memory for further processing.

Example: http://www.signatec.com/products/daq/high-speed-digitizers.html

>As I said - all the job of such scope shall be done in the FPGA and PC shall act just as "I/O terminal" for it. Period. Then even USB2 is good enough BTW.

Yes, but you're wasting all the PC's hardware (which is cheaper than oscilloscope hardware because it's commodity).  In particular, it would be good to use the memory space for sample depth and the ability to use multiple CPU cores and GPU cores for analysis. 

Thanks for replying, it's interesting.


 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #95 on: October 29, 2017, 03:49:10 pm »
>Not sure what you mean here?

Who wants scope BNC connectors on the back of desktop PC? Anywone?

>Laptops are a miss, sure, but there's a limited amount you can do with them

From which planet or century you just did arrive? ;)

>>Do you really want to lose samples or trigger events when OS decides to flush some bigger data chunk on HDD?
>Unless there's a hardware fault holding the bus hostage, the 'scope card could write data whenever it needed to do so, right?

Wrong. It does not require hardware fault for bus or RAM peripheral to become busy. Just as I said - it will happen "when OS decides to flush some bigger data chunk on HDD".

>3) Such "software" scopes cannot have trigger output hardware signal by definition - because PCs are laggy
>Not true always, as mentioned above.  Even Windows 10 has a real time solution:
>Besides, if you're using the PC's memory as a giant buffer, you don't need to trigger in real time, exactly..

It depends what you mean by real time. 1ms which for PC is quite "real time" on 100MHZ scope is "too late", not even yesterday. Don't tell now that hardware trigger output (connector) is not needed as someone told here about AC coupling.

>See above, if you record all samples continually into memory it isn't necessary to trigger in real time... you just examine the recorded data often enough to ensure you don't miss something before it's overwritten.

You say that CPU of average hobbyist PC can keep up analyzing & processing data which arrives at rate 1GBps?

>>As I said - all the job of such scope shall be done in the FPGA and PC shall act just as "I/O terminal" for it. Period. Then even USB2 is good enough BTW.
>Yes, but you're wasting all the PC's hardware (which is cheaper than oscilloscope hardware because it's commodity).

Exactly my point. RAM is commodity. 4GByte SODIMM DDR3 memory module costs 20$. 1Gbyte less than 10 bucks.

When you build PCIe-card scope, you are seemingly saving on PC computing and storage hardware (I disagree even here, but whatever). But you are losing huge on FPGA which shall be equipped with lot of GTX transceivers (for PCIe bus). So basically saving 7..20$ you will spend some 1000$ (wild guess) or so on FPGA alone. Monkey business I would say.

« Last Edit: October 30, 2017, 05:47:41 am by ogden »
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #96 on: October 31, 2017, 01:48:47 am »
>Wrong. It does not require hardware fault for bus or RAM peripheral to become busy. Just as I said - it will happen "when OS decides to flush some bigger data chunk on HDD".

Actually, this isn't possible with PCIe.  Due to the bus architecture, it supports multiple full duplex DMA transfers simultaneously, and in fact the CPU cores being busy would not delay or interrupt DMA transfers. 



I think you're probably misunderstanding what I'm saying for most of this post, but no worries.  Thanks for responding.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #97 on: October 31, 2017, 04:45:54 am »
>>Wrong. It does not require hardware fault for bus or RAM peripheral to become busy. Just as I said - it will happen "when OS decides to flush some bigger data chunk on HDD".

>Due to the bus architecture, it supports multiple full duplex DMA transfers simultaneously,

Well.. what a revelation :D

>in fact the CPU cores being busy would not delay or interrupt DMA transfers. 

I said "bus or RAM peripheral to become busy", did not even mention CPU. Well, ok - let's conclude that RAM will be no bottleneck at ANY of the moments. CPU searching for trigger events and processing waveforms - could be indeed. I am not ready to literally waste all the PC resources and performance just because you cannot comprehend that - if you have FPGA then best way is to use it, place RAM and processing where it supposed to be - at/in the FPGA :)

[edit] What we are talking here about? - That direct to PC RAM sampling at 1GBps is possible? Indeed it is. You did prove it by showing 10000$ sampler which is used by labs which can afford to buy as many rackmount PCs as samplers they have. And some more. Fact that it can be done does not help in discussion where we talk about  "hobby market" low cost, but hi-performance scope.

>I think you're probably misunderstanding what I'm saying for most of this post, but no worries.

No problem, no worries at all. Better show me where I did misunderstood you. BTW you did "skip" most of my arguments except one, which is not that important actually.
« Last Edit: October 31, 2017, 05:14:30 am by ogden »
 

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Re: Open Source Oscilloscope, can it be done?
« Reply #98 on: October 31, 2017, 08:41:03 am »
>1) Because of point 0) laptop and miniPC users are out of luck of using such PCIe adapter scope. This is HUGE disadvantage.

It depends.  You can make it a half-height card suitable for mini PCs and full size.  Laptops are a miss, sure, but there's a limited amount you can do with them if you need more speed than USB can provide.
More and more laptops are supporting eGPU nowadays. It's even possible to cobble together your own eGPU from under $20 in parts plus the GPU itself.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #99 on: October 31, 2017, 04:38:24 pm »
More and more laptops are supporting eGPU nowadays. It's even possible to cobble together your own eGPU from under $20 in parts plus the GPU itself.

Those who can afford such laptop and external PCIe cabinet most likely can afford and will be willing to get just proper standalone scope.
 

Offline BradC

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Re: Open Source Oscilloscope, can it be done?
« Reply #100 on: October 31, 2017, 07:25:32 pm »
More and more laptops are supporting eGPU nowadays. It's even possible to cobble together your own eGPU from under $20 in parts plus the GPU itself.

Those who can afford such laptop and external PCIe cabinet most likely can afford and will be willing to get just proper standalone scope.

Thunderbolt is just PCIe and I've had machines with those ports for 6ish years now. Laptop and Deskop, Mac & PC.
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #101 on: November 01, 2017, 03:21:36 am »
Quote
BTW you did "skip" most of my arguments except one, which is not that important actually.

Okay.  I'll go back and reply a bit more completely.

 
Quote
I am not ready to literally waste all the PC resources and performance just because you cannot comprehend that - if you have FPGA then best way is to use it, place RAM and processing where it supposed to be - at/in the FPGA :)

I actually comprehend this pretty well, and I think this is just a point where we have differing opinions.  Certainly FPGAs are excellent solutions and suitable for this task, but I think you're imagining the "right" way to design an Oscilloscope and I'm imagining an "unconventional" design that has other benefits.

Really, the differences in opinion in this thread and between us are based on different assumptions about what an open source Oscilloscope should be.  I can see four different points of view represented:

  • People who believe that an open source 'scope is only worth doing if it surpasses in price or performance what's available commercially, specifically the various Chinese import scopes.  Certainly it's hard to come up with a design that beats what already exists in both areas.
  • People who believe that an open source 'scope should be designed to cover the niche roles of a cheap/simple/portable/accessory scope, so it can be (for example) left in a field location to trigger on some very rare event, or used for tasks requiring dedication of a scope where someone would not want to tie up their main or preferred scope for a long time period.
  • People who believe that an open source scope is worth doing simply because of the benefits of having an open hardware design available to everyone.  Open Hardware is a concept that is in its infancy compared to open source software, but it's easy to see what benefits it could have if an open source scope project "takes off".  The most well known open source software project in the world has gone from being an academic curiosity to being the most used operating system in the world, period.  This is an extreme example, but if anything remotely similar to this were to happen for open hardware, the benefits would be obvious.
  • People who value the idea of designing an open hardware 'scope as a challenge for its own sake.

I tend to identify with the third point of view.  I believe that moving the main functionality of the scope into software would open the potential pool of developers for the project from the few that understand hardware and FPGAs enough to contribute to anyone with some device level programming experience in Linux.  The more people who are able to contribute, the better the project will become.  Certainly there are altruistic people all over the world, but most people with the skills to design or program something like an Oscilloscope choose their projects the same way most of the people posting in this thread do - based on how useful it would be for them personally.

So what I'm imagining isn't a traditional design for this reason.  Instead of a dedicated FPGA based scope which requires specialized hardware design knowledge I think it is possible to design what amounts to a digitizer card and add software to achieve the functions of an oscilloscope. 

If such a thing can be done within the constraints for a DIY project (cost, manufacturability) for a reasonable price and without design compromises turning the project into a toy rather than a tool, that is a much better route to go for an open hardware project because the success of open software and hardware projects depend heavily on popularity.  Just like a book, it will have little impact on people who can't read the language in which it is written, so it makes sense to design an open hardware project to appeal to the widest audience possible.  Putting the main functions of such a tool in software means that not only can it attract more developers for oscilloscope functionality, but since it can be reprogrammed for many more uses it gains an even wider audience.  It could be a high speed digitizer for software defined radio, or a processor for sonar data, or many other things.

If it is not technically and economically possible now, I think it will be in the next few years as technology advances.  It's even possible to see the day when an external peripheral with a wireless connection will perform all the functions of an oscilloscope, voltmeter, logic analyzer, vector network analyzer, spectrum analyzer, etc.  Essentially all these systems in their modern versions read data and provide it to a processor, and software does the rest.  Eventually, the hardware will merge into a single device class below a certain performance level simply because it's cheaper to make it that way.  All the various functions will be in software.  So I think an open hardware project could anticipate this.




 
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Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #102 on: November 01, 2017, 06:17:29 am »
Thank you for providing deep insight into your reasoning :) I appreciate that.

I agree that PCIe sampler architecture you propose is indeed possible. On the other hand you have only one single strong argument: community that knows PC-programming languages better than VHDL/Verilog. - True. But is it really showstopper?

Hi-performance 1Gsps sampler scope is not a kid's toy. Someone shall implement PCIe bus PHY with all the bells and whistles... and not only that. In my opinion/experience PCIe is not that easy task at all. Not to mention PCIe-capable FPGA price. Sample processing and storage is much more simpler task than PCIe PHY. Obviously couple of FPGA guru's needed as core of the project, but I believe - either it is done elegant way or there will be not enough enthusiasts ready to invest their time.

>I believe that moving the main functionality of the scope into software would open the potential pool of developers for the project from the few that understand hardware and FPGAs enough to contribute to anyone with some device level programming experience in Linux.

Well... huge pool of linux programmers is not enough. They shall be interested in the final product too.

> The more people who are able to contribute, the better the project will become.

The less people who could actually use product (laptop/minipc owners and those who do not like PC on the desk facing backwards) - the less support it will get.

> Certainly there are altruistic people all over the world, but most people with the skills to design or program something like an Oscilloscope choose their projects the same way most of the people posting in this thread do - based on how useful it would be for them personally.

Exactly. Personally I vote against PCIe sampler and do not participate. Why? - I have two computers, miniPC and desktop tower PC. None is suitable for PCIe sampler. MiniPC does not have PCIe slots nor Thunderbolt, but dekstop tower PC is standing on the floor too far away for scope leads to reach my table. I am not going to put that huge box on the table facing its back to me just because there is/could_be open source scope PCIe adapter which costs 2x my standalone 1Gsps scope, Sorry.
« Last Edit: November 01, 2017, 06:25:46 am by ogden »
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #103 on: November 01, 2017, 09:31:37 am »
Reality check: does anyone besides erikg want open source PC-based scope which costs more than "made in china" standalone? Please share your opinion.
« Last Edit: November 01, 2017, 09:35:13 am by ogden »
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #104 on: November 01, 2017, 10:06:54 am »
QEX came today with an article about a stand alone 100 MHz BW direct sampling SDR.  It uses a Zynq based Zedboard running Linux on a dual core ARM A9 and an AD 9467 eval board.  It takes a monitor, keyboard and mouse.

The web site is panoradio-sdr.de

This is everything for a single channel open source scope except the scope code. And it's all COTS.

AD9467 eval board $406 (Digikey)
Zedboard $495  (Digikey)

So approximately 1/2 a Rigol DS1102E for ~$1000.  However, it *is* 16 bit rather than 8.  So it's more Keysight and friends territory.

Using a desktop PC only makes things harder and more expensive.  There is no affordable way to get the BW required.

The real virtue of an open source scope is being able to fix bugs and add features.
 
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Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #105 on: November 01, 2017, 10:04:29 am »
QEX came today with an article about a stand alone 100 MHz BW direct sampling SDR.  It uses a Zynq based Zedboard running Linux on a dual core ARM A9 and an AD 9467 eval board.  It takes a monitor, keyboard and mouse.

The web site is panoradio-sdr.de

This is everything for a single channel open source scope except the scope code. And it's all COTS.

AD9467 eval board $406 (Digikey)
Zedboard $495  (Digikey)

So approximately 1/2 a Rigol DS1102E for ~$1000.  However, it *is* 16 bit rather than 8.  So it's more Keysight and friends territory.

Using a desktop PC only makes things harder and more expensive.  There is no affordable way to get the BW required.

The real virtue of an open source scope is being able to fix bugs and add features.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #106 on: November 01, 2017, 11:02:05 am »
This is everything for a single channel open source scope except the scope code. And it's all COTS.

AD9467 eval board $406 (Digikey)
Zedboard $495  (Digikey)

I rather have 8-bit 4 channel 1mV/div to 10V/div 50MHz 1GSPS scope for 400$ than 1-channel 500MSPS 16bit sampler without PGA and who knows when there will be scope software - for 1000$. Or am I missing something here?
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #107 on: November 01, 2017, 11:48:36 am »
I'd like to suggest looking at this thread:

http://www.eevblog.com/forum/testgear/agilent-54835a-scope-%284-channel-1ghz-4gss%29-repair-uphack/msg1251605/#msg1251605

which describes an early HP implementation of a PC based scope in considerable detail.

There's less to a scope than an SDR, but I don't particularly care either way.  I've got an Instek MSO in shipment to augment my DS1102E.  If someone makes an open source scope that is credible I'll probably get one and write things like VNA routines for it.  But I'm not going to design the hardware.  At least not any time soon.

BTW The Zedboard includes a Xilinx FPGA.  The ARM is just to run the user interface and other minor tasks.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #108 on: November 01, 2017, 10:40:04 pm »
If someone makes an open source scope that is credible I'll probably get one and write things like VNA routines for it.

VNA is closer to SDR than scope. Either it is low cost (more or less toy-) VNA add-on board with PC software for 4-channel <= 100MHz SCPI-capable scopes or it shall be built using SDR approach. How about 25 .. 1500 MHz VNA built out of four RTL2832U+R820T USB tuner dongles (8$ each, delivered)? Board with USB hub, programmable synth, couplers and clock fanout buffers for tuners needed and obviously PC software. Could be blockbuster in result. Tuners shall be freq/phase synced using following approach: https://www.rtl-sdr.com/a-multi-channel-coherent-rtl-sdr-product-for-passive-radardirection-finding-and-more/
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #109 on: November 02, 2017, 01:21:58 am »
[
VNA is closer to SDR than scope. Either it is low cost (more or less toy-) VNA add-on board with PC software for 4-channel <= 100MHz SCPI-capable scopes or it shall be built using SDR approach. How about 25 .. 1500 MHz VNA built out of four RTL2832U+R820T USB tuner dongles (8$ each, delivered)?


If you're doing HF design, a 100-200 MHz scope will work just fine.  Though, like the RTL-SDR it suffers from the 8 bit limitation.  As for using an SDR, that's the main reason I bought an SDRplay RSP2 and a LimeSDR.  The RTL-SDR is OK for VHF, but adding 4 downconverters makes it expensive for HF.  Buying a VNWA 3E is probably a cheaper option once you take into account directional couplers and the other bits an RTL-SDR setup would need.  But the RTL-SDR approach would be fine for someone using the sub GHz ISM bands.

There are a slew of VNA projects spawned by the cheap RF chipsets.
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #110 on: November 02, 2017, 02:35:34 am »
Quote
On the other hand you have only one single strong argument: community that knows PC-programming languages better than VHDL/Verilog. - True. But is it really showstopper?

I don't view it as a "showstopper" exactly.  Simply put, the more people an open source project appeals to the more likely it is to be successful.  You can argue that a software defined scope would be less attractive to EE types like yourself, and that could certainly be true, but the numbers are what matters.  The head count of people who know how to program in C or Python is a much bigger number than the head count people who know how to program an FPGA, so if only 1 in 1000 (0.01%) of C/Python people are interested, that's still far more individuals than if 1 in 20 FPGA programmers (5%) are interested.

Quote
Hi-performance 1Gsps sampler scope is not a kid's toy. Someone shall implement PCIe bus PHY with all the bells and whistles... and not only that. In my opinion/experience PCIe is not that easy task at all. Not to mention PCIe-capable FPGA price. Sample processing and storage is much more simpler task than PCIe PHY.

Probably not as expensive or hard as you think.  When I think of hardware to implement a PCIe capable scope, I'm thinking of something like an Artix-7, so between about $100-$200 US.  Xilinx has a PCIe "integrated block" supported on this series, so it's possible to just use that with supporting components for PCIe... basically a shrink wrapped solution.  An even quicker alternative would be to use an FPGA module like a Mars: https://www.enclustra.com/en/products/fpga-modules/mars-mx2/

... in which case only a carrier board needs to be designed with the supporting chips like the ADC and an SODIMM socket for the module.  Single unit price on these is more like $250-$300 US, so it's more expensive than a complete DIY, but it's also easier.

Probably the best way to go for a digitizing card is to specify hardware capabilities and interface methods for the software and permit multiple hardware implementations anyway :)  Kind of the path that Sigrok takes, being hardware agnostic.  That way is even better for a software defined project, because you can completely toss the previous generation of hardware if some great new technology comes out and keep most of your feature set.

Quote
Well... huge pool of linux programmers is not enough. They shall be interested in the final product too.

Yes, but if the project is defined mostly in software then the card will attract developers for applications other than oscilloscopes.

Quote
The less people who could actually use product (laptop/minipc owners and those who do not like PC on the desk facing backwards) - the less support it will get.

That's true if you assume that the card wouldn't be usable in a laptop or mini PC... if the card is low profile it probably would work in mini PCs, and even if it's not, then a solution like what gets used for GPU crypto coin mining could be used - essentially a flex based extension for the PCIe slot that runs to an add-on enclosure for the card, like this:

http://www.overclock.net/t/1427731/pci-express-extender-cables-benchmarked

As far as the PC facing backwards, it's not all that hard to get extra long probe cables (this is the solution HP used for their mainframe based Oscilloscopes) or a front facing breakout box could be designed to provide front BNC connectors.  It's extra cost, of course. 

Thinking about it, though, it probably makes sense instead of the above to use an external PCIe interface like Thunderbolt-3... it already exists on many systems, has plenty of speed, and if you use USB-C over TB3 you even get power delivery over the cable.  The scope digitizer "Card" would be a module in a box connected via thunderbolt to the PC.  One small box with BNC connectors and one cable to the PC up to 2 meters long.


Quote
None is suitable for PCIe sampler. MiniPC does not have PCIe slots nor Thunderbolt, but dekstop tower PC is standing on the floor too far away for scope leads to reach my table. I am not going to put that huge box on the table facing its back to me just because there is/could_be open source scope PCIe adapter which costs 2x my standalone 1Gsps scope, Sorry.


So you'd be unwilling to buy a $50 US PCIe card to put in your desktop tower PC to allow use of an external digitizer in a box on your table to which you attach leads, costing something like $400-$500?   Maybe you'd need to wait until the price comes down? :)



Quote
Reality check: does anyone besides erikg want open source PC-based scope which costs more than "made in china" standalone? Please share your opinion.

Opinion gathering is ok, but note that we're not really voting on something here.  I'm just writing this to learn about peoples' opinions and thoughts on this subject.  If I kick off a development project for a digitizer like this, you can be sure you'll see an announcement from me.  Right now I'm really only capable of writing the software for it, though.  Still learning hardware.

Thanks!

 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #111 on: November 02, 2017, 03:37:50 am »
So you'd be unwilling to buy a $50 US PCIe card to put in your desktop tower PC to allow use of an external digitizer in a box on your table to which you attach leads, costing something like $400-$500?   Maybe you'd need to wait until the price comes down? :)

I do not need such. After all I have standalone scope already. What I could consider to get: 400-500$ 200MHz 1Gsps USB/Ethernet mixed signal scope with deep & segmented memory. Ideally with optional 50ohm RF input channel - spectrum analyzer / RF-sampler. - Customizabe open source version of Tek MDO3000 :)

[edit] I'm afraid that you overestimate how much job is done in the FPGA of USB scope versus PCIe sampler scope. FPGA just do sampling, trigger, buffer management and interpolation (only samples going to be shown on display). All the measurements of resulting waveform is done by CPU in both cases anyway. Very good example is Infiniium early revision which has very dumb sampler with analog(?) trigger circuit, comparably slow CPU and slow bus between sampler and CPU, yet still it does lot of various signal measurements - obviously using CPU.

I'd like to suggest looking at this thread:

http://www.eevblog.com/forum/testgear/agilent-54835a-scope-%284-channel-1ghz-4gss%29-repair-uphack/msg1251605/#msg1251605

which describes an early HP implementation of a PC based scope in considerable detail.
« Last Edit: November 02, 2017, 04:40:50 am by ogden »
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #112 on: November 02, 2017, 05:51:36 am »
Quote
Very good example is Infiniium early revision which has very dumb sampler with analog(?) trigger circuit, comparably slow CPU and slow bus between sampler and CPU, yet still it does lot of various signal measurements - obviously using CPU.

That thread is an interesting read, but it's not really comparable to what we're talking about.  That's partly because that hardware is so incredibly old, but the important difference is the location of the sample buffer.  Essentially those Infinium scopes are PCs in the same box as a scope board, not a PC with a scope card.  If you took the internals of a stand alone DSO and found a way to interface them to a PC so it could be the UI, those scopes are what you would have.

By way of contrast, I've been talking about using modern components and a fast bus to add high speed data acquisition to a PC in such a way that it can be programmed to function as an Oscilloscope, with the sample buffer in main memory.  Ideally, the only components on the card would be those needed to acquire the data and get it into main memory.


 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #113 on: November 02, 2017, 06:37:11 am »
> That thread is an interesting read, but it's not really comparable to what we're talking about.

It is. - As an example that hi-end 5GSPS scope do not need direct to RAM sampling to do it's job very well. But whatever. You don't listen anyway so I am wrapping up this conversation.

> I've been talking about using modern components and a fast bus to add high speed data acquisition to a PC in such a way that it can be programmed to function as an Oscilloscope

I noticed. You have strong opinion about how to build hi-speed electronics but seems, do not have any experience in the field. So be it. Good luck building you sampler!
 

Offline erikg

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Re: Open Source Oscilloscope, can it be done?
« Reply #114 on: November 02, 2017, 08:46:59 am »
Well, there's a big difference between not listening and not agreeing, and we just don't agree.

I don't have any intention at this point of building this thing, as I've said repeatedly the whole thing is just a design exercise for me.

Who knows though, maybe sometime I will.

 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #115 on: November 15, 2017, 05:36:21 am »
FYI, the Haasoscope project is now live!
https://www.crowdsupply.com/andy-haas/haasoscope
I've really put some effort into it, and the specs have improved significantly.
Pick up a few!
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #116 on: November 15, 2017, 09:36:13 am »
FYI, the Haasoscope project is now live!
https://www.crowdsupply.com/andy-haas/haasoscope

Congrats and good luck!  :clap:
Hopefully you will meet your goal.

Quote
I've really put some effort into it, and the specs have improved significantly.

You also released new revision pretty fast. Respect! Noticed that you introduced AC/DC switching and 50 ohm input. -Very good. Thou I still believe that this is kind of "tinkerscope", due to external interface which I also consider as slow (for scope). In my humble opinion your product can become much more desirable if you put Cypress FX2LP or some USB-enabled ARM uC on-board - to achieve higher update speeds (20Hz is so slooooow). Then your product would be single-piece instrument which could have enclosure some day too. Just my 2 cents :)

I would like to see how test signals look not only on your scope but compared to at least one worthy competitor from Comparison Table, on both 5V and 500mV ranges. Especially want to see claimed bandwidth. Would be nice to see noise floor measurements - existing waveforms looks kinda noisy.
 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #117 on: November 15, 2017, 10:32:22 am »
Hi,
Thanks for the support!
20 Hz looks pretty fast on the screen - that's 20 _frames_ per second. It's hard to see more than that! However, for higher-speed data collection, I do offer a plug on FT232H board, which is supported by the firmware/software, and offers ~30x more bandwidth for the serial connection, and up to full USB2 speed (480MB/s) if someone writes a C++ interface using the FTDI drivers (wouldn't be too hard to do something simple).
I invested time in reducing noise last month - it's much better now - just about 1-2 mV in either range! I've moved to a 4-layer board with a full ground plane, and better dc offset control mechanism (DAC vs. PWM).
The bandwidth is as claimed. I've tested with an Agilent 80 MHz signal generator and see almost no degradation until 60 MHz. The 80 MHz sin wave is still very viewable in the 250 MS/s (2 channel) mode. (I've also implemented sinx/x filtering (in python), which cleans it up nicely!)
Best, Andy.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #118 on: November 15, 2017, 12:07:16 pm »
Thanks for the support!

You are welcome :)

Quote
20 Hz looks pretty fast on the screen - that's 20 _frames_ per second. It's hard to see more than that!

Well.. Even for movies 20Hz is not enough :) When you are trying to catch various irregularities of the signal - then you need to get on the screen as many waveforms per second as possible, preferably intensity-graded way. The more - the better. You want to minimize blind time of the scope to maximize your chances of seeing something that does not happen too often.

Further reading: https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/application_notes/1er02/1ER02_1e.pdf
EEVblog discussion: http://www.eevblog.com/forum/testgear/some-important-points-to-remember-when-evaluating-waveform-update-rates/msg205797/#msg205797
There also was some oscilloscope review by Dave where he was measuring, comparing and commenting update rate of some scopes. Unfortunately I struggle to find it at the moment.

Quote
However, for higher-speed data collection, I do offer a plug on FT232H board, which is supported by the firmware/software, and offers ~30x more bandwidth for the serial connection, and up to full USB2 speed (480MB/s)

Good news then! Why don't you put it on the board? After all it is "just" ~3.1$/piece @100qty.

Quote
I invested time in reducing noise last month - it's much better now - just about 1-2 mV in either range!

Seems like 1..2 counts of ADC which is completely OK for any digital scope. I just wondered why this particular screen seems so "noisy":
https://www.crowdsupply.com/img/efc5/8chan_png_project-body.jpg
One more reason to show "side by side" comparison of the same test signal to some competitor scope, like Rigol DS1104Z.

Quote
The bandwidth is as claimed. I've tested with an Agilent 80 MHz signal generator and see almost no degradation until 60 MHz. The 80 MHz sin wave is still very viewable in the 250 MS/s (2 channel) mode.

Good. Then you shall demonstrate it too - so potential buyers see true performance of this thing.
 

Offline ez24

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YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Offline haastyle

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Re: Open Source Oscilloscope, can it be done?
« Reply #120 on: November 15, 2017, 12:31:22 pm »
Ah, I agree that "blurry super fast update" mode is cool. I'll have to work on that. I think it's fair to say that's rarely available for $99 though.
With the USB2 output it should be doable.

Yes, some of those screenshots are with an older, noisy, prototype. Here is a more recent pic from yesterday:
https://www.dropbox.com/s/a3ox94f5zdex4d9/low%20noise%20sin.png?dl=0

As for bandwidth, I do have that shot in the video of scrolling up to 40 MHz in the FFT plot. You can see the amplitude is unchanged up to 40 MHz at least. It's also here:
https://www.dropbox.com/s/nmfw128er7p4hfu/scope%20fft.mp4?dl=0

Get one and test it out for me! OR maybe Dave can review?!  :o :-[

 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #121 on: November 15, 2017, 01:09:15 pm »
Ah, I agree that "blurry super fast update" mode is cool. I'll have to work on that. I think it's fair to say that's rarely available for $99 though.

Indeed. On the other hand, hopefully you are not building "just yet another low cost scope", right? Having some unique feature will add to the value of your product.

Quote
As for bandwidth, I do have that shot in the video of scrolling up to 40 MHz in the FFT plot. You can see the amplitude is unchanged up to 40 MHz at least.

Well... at least amplitude does not steadily go down :) However to be honest - does not look smooth to me at all. Amplitude jumps around and what's worse - bounds of vertical scale too. Can't you make it fixed? Maybe you can make separate video just with smooth and slow sweep 0..60MHz during 1minute as (IMHO) elegant demonstration of bandwidth and FFT function?

Quote
Get one and test it out for me! OR maybe Dave can review?!  :o :-[

Sorry, I have scope already, not a blogger/vlogger too. Maximum I can offer - share some thoughts about your hardware/software. You make some promotional doc/pic/video for new features of you product, put preliminary versions somewhere, PM me. I will look and tell what I think. Disclaimer: I just represent my view, better you doublecheck everything with couple of other people too, before implementing something I suggested to you :)
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #122 on: November 15, 2017, 01:21:03 pm »
 

Offline seaCAT

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Re: Open Source Oscilloscope, can it be done?
« Reply #123 on: November 22, 2017, 05:59:11 pm »
As a person learning hardware engineering from a software engineering background i can confirm that the prospect of an open source, PC based scope is exactly what i want.
I would be willing to pay much more for it than a proprietary device of a similar specification as it would both allow me to operate natively in an environment that i am accustomed to and to deploy any modifications to the functionality of the scope with a few commands.

I feel like we must not be alone either as this exists(for a hefty 10k price tag):
http://www.wuntronic.de/files/wuntronic-theme-2016/Downloads/Thunderbolt-3-PCIe-Gen3-Digitizers-Overview.pdf

 

Offline hv222

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Re: Open Source Oscilloscope, can it be done?
« Reply #124 on: December 02, 2017, 09:58:40 am »
I have an idea to design new main board for Keysight 1000 x-series scope, to make it 800MHz bandwidth.  It have ADC, FPGA and processor on separated board, so I will be much easier then design all oscilloscope hardware and software for processor and FGPA. Do you have some schematics, application notes, literature and other resources, which can be helpful? I want to base on http://www.ti.com/lit/ug/tiduba4/tiduba4.pdf and on photos from Dave teardown - https://www.flickr.com/photos/eevblog/albums/72157657671196148 . I have complete schematic of Keysight main board from reverse engineering.
 

Offline axitece

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Re: Open Source Oscilloscope, can it be done?
« Reply #125 on: December 13, 2017, 12:24:28 am »
I have an idea to design new main board for Keysight 1000 x-series scope, to make it 800MHz bandwidth.  It have ADC, FPGA and processor on separated board, so I will be much easier then design all oscilloscope hardware and software for processor and FGPA. Do you have some schematics, application notes, literature and other resources, which can be helpful? I want to base on http://www.ti.com/lit/ug/tiduba4/tiduba4.pdf and on photos from Dave teardown - https://www.flickr.com/photos/eevblog/albums/72157657671196148 . I have complete schematic of Keysight main board from reverse engineering.

Would you mind sharing the schematics that you have reverse engineered? I would be very interested in seeing how the Keysight design compares to the already available schematics from Rigol and other vendors. Thanks a lot in advance!
 

Offline slicendice

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Re: Open Source Oscilloscope, can it be done?
« Reply #126 on: December 14, 2017, 08:35:46 pm »
Since opinions here seems to be very divided, I decided to contribute.

Looks like many here wants something like a high end oscilloscope with high bandwidth and multiple channels.

Let us take one commercial oscilloscope as a reference point:

Rigol DS6104
Bandwidth: 1GHz
Channels: 4
Price: > $10.000

Now let us compare this to OpenHarware/Software, by answering a few question:

Q: Would it be possible to develop such scope as OHW/SW?
A: Absolutely

Q: Will developing such scope cost more than $10.000?
A: Most likely

Q: Will the completed product, assembled and ready for use, cost more than $10.000?
A: Most definitely NOT!

Q: Who would benefit from such OHW/SW project?
A: Everybody who value OHW/SW.

Q: Would such scope be competitive/comparable in performance with commercial scopes?
A: Most definitely YES.
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #127 on: December 15, 2017, 02:33:34 am »
We already have open source scopes on the market.  We just don't have the source code even when it falls under the GPL.

A number of OEMs produce instruments using embedded Linux.  Anything using the Zynq FPGA line is almost certainly using the Xilinx embedded Linux package.  The Arago/Yocto projects are also in use in T&M kit.  I know this from personal observation as do quite a few other people.

It seems to me far more effective to get the GPL code released and fix the bugs than it does to engineer a new instrument from scratch.  Even if a new Open Source design were made, someone would still need to manufacture it.  This is certainly not toaster oven reflow territory. Just tooling up to do the production QC is a major investment.

There is no evidence of Linux in the Rigol DS1102E, however, there's also unusually little text in the FW updates.  It does not take a rocket scientist to strip all the tell tale text from the source code.  But a port scanning tool designed to identify TCP/IP stacks should be able to tell quite easily for more recent models.  It seems highly unlikely that Rigol went to the expense of writing their own stack.  They could be using BSD licensed code, but if they are, the requisite copyright notice should be present in a FW update package for the DS1xxxZ.  Whatever instruments you have,  run strings(1) on a FW update package and grep(1) for a copy right notice.  Post what you find to the thread.

The best  way to proceed is to politely request the source code for any instrument you own using an embedded Linux distro. In the request make the point that whichever OEM provides good support for open source instruments will get your business.  They don't have to release the device drivers, but that's not that big a deal.  How many people worry about the nVidia drivers being closed source?  Most of the issues are UI bugs.

As a reminder, only people who own an instrument can make a valid request for the source code.  Only the copyright holder can take an enforcement action.  There will be a great deal of stalling by the Chinese OEMs. Rohde & Schwartz already supply the GPL source for their instruments on request by instrument owners.  Lots of polite requests for source sent to the marketing departments at the OEMs will make them realize that there is a marketing edge to be gained by complying voluntarily.  Unless the new "forgiveness" clause in GPL 2 is retroactive, failing to comply would force an OEM to take the product off the market.

I've got to take a long trip today, so I'll work on a draft source code request as I'm not driving.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #128 on: December 15, 2017, 08:05:13 am »
The best  way to proceed is to politely request the source code for any instrument you own using an embedded Linux distro.

"Running Linux" does not universally mean "I can get source code for it". You cannot request source code of application that does not contain (or link to) GPL'ed software or parts of it. Even drivers can be proprietary, thus "closed source", if developed correctly from licensing point of view - as you correctly mention nVidia example. Those companies can afford to invest into development that does not rely on open source components, thus have no obligation to give away their intellectual property. All you can get - some irrelevant kernel code modifications that maybe show how to I/O hardware of instrument, but basically that's it. In case of scope it is even worse - because most of "business" happens not in the Linux "user land" application, but FPGA. You definitely can cool down on your idea :)
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #129 on: December 15, 2017, 12:56:02 pm »
The best  way to proceed is to politely request the source code for any instrument you own using an embedded Linux distro.

"Running Linux" does not universally mean "I can get source code for it". You cannot request source code of application that does not contain (or link to) GPL'ed software or parts of it. Even drivers can be proprietary, thus "closed source", if developed correctly from licensing point of view - as you correctly mention nVidia example. Those companies can afford to invest into development that does not rely on open source components, thus have no obligation to give away their intellectual property. All you can get - some irrelevant kernel code modifications that maybe show how to I/O hardware of instrument, but basically that's it. In case of scope it is even worse - because most of "business" happens not in the Linux "user land" application, but FPGA. You definitely can cool down on your idea :)


Duh.  Yeah, entirely true.  Aside from a lack of attention to grammar, what is your point? The serious problems are in the UI, not the FPGA code.  What the FPGA does is so tightly controlled by mathematical physics that it's pretty trivial to recreate if there is a problem.  Apparently you think it's a big deal.  I don't know VHDL, but I know the math.  After a dozen or so programming languages, I don't see a new one as much of an obstacle.  Aside from that, there are plenty of people who already  know VHDL.  I'm sure some of them are interested.

I've had to maintain over 2 million lines of other people's code.  At *least* 500,000 lines of it had no comments other than the author's name. And the range of calculations being done in that stuff makes an oscilloscope look trivial.  I could do it because I knew "if it's Tuesday we must be in Rome".

My point is simply this.

If we can read the data from the input channels and write data to the display, the rest is easy to do.  It does *not* require doing something difficult like designing a broadband front end or manufacturing it. Writing a new UI is not a big deal.  And using what exists as a base is a waste of time it's so bad.

If you think the GPL code is irrelevant, you have no clue about the subject.  While it is not necessary, it is highly useful to have the source code for the GPL parts.  This is why Stallman created the Gnu license.  It doesn't solve all the problems, but it makes things a lot easier.



 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #130 on: December 15, 2017, 08:15:35 pm »
Duh.  Yeah, entirely true.  Aside from a lack of attention to grammar, what is your point?

I find your public comment about my grammar as rude. If you want to improve my English which is no my native language - send PM instead.

My point is: "You cannot request source code of application that does not contain (or link to) GPL'ed software or parts of it.".

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The serious problems are in the UI, not the FPGA code.

So what? How does it help if you cannot get source code of it? For example try to get source code of those products to improve them yourself:

https://en.wikipedia.org/wiki/List_of_proprietary_software_for_Linux

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If you think the GPL code is irrelevant, you have no clue about the subject.

Don't put words in my mouth. Where did you read "irrelevant"?

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I've had to maintain over 2 million lines of other people's code.

Well.. Seems, your experience is not enough to comprehend simple thing - Linux-based device can be designed such a way that you gain absolutely nothing by getting GPL-relevant source code of it. Most reputable manufacturers are careful enough so their intellectual property is safe from individuals like you and most importantly - from competitors.

For example check this thread where guys tear down one Linux instrument, see how this product is made from software point of view:

http://www.eevblog.com/forum/testgear/agilent-e7495-linux-root-account/


Quote
If we can read the data from the input channels and write data to the display, the rest is easy to do.  It does *not* require doing something difficult like designing a broadband front end or manufacturing it. Writing a new UI is not a big deal.

Sorry, but seems you have no idea how scope actually works and what is actual complexity of firmware parts that are not UI. FPGA firmware is much more complex part of whole thing. As frontend you simply can use reference design mentioned in this thread.

Do you really suggest that anybody would want to buy 10k$ scope, throw away it's original software including warranty and use "open source firmware" that is developed by unknown guys who most likely will not support "product" in time when it is needed?
« Last Edit: December 15, 2017, 11:19:15 pm by ogden »
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #131 on: December 16, 2017, 01:48:27 am »
I was deliberately rude because your sole interest is trumpeting that you are right and everyone else is wrong.   That may make you feel good, but it does not accomplish anything useful. You're also sloppy in reviewing what you write for errors.  I suggest you read your own post.  I did *not* put words in your mouth.

You have no way of knowing what I do or do not know.  Fact is I have repaired several analog scopes including a Tek 465.  I also have over 30 years of DSP experience.  There are lots of things I don't know.  But I do know how to learn.  If you actually knew what a DSO is doing, you would not consider it very complex.  It's not.  There are some significant timing challenges, but that and broadband circuit design are the only hard parts.  The timing constraints pretty much dictate everything about the VHDL code for the FPGA.  There's just not much wiggle room in how the logic is laid out on the device.

As regards the Agilent thread,  I'd seen it, but never bothered to read it.  As I suspected, it's almost entirely about enabling license options.  I would not,  and do not advocate hacking a $10k instrument.

The primary purpose of having people ask for the source is to make clear to the the low end Chinese T & M OEMs  that there is a marketing advantage to making their products "open source" and allowing the user community to write apps for the instruments.

Substantial parts of the UIs are written in a scripting language. Once one has the ability to run a script that reads button presses and sends commands to the FPGA and the ARM host, pretty much all the functionality of the unit becomes accessible.  That's not a very high bar.  The T & M OEMs are using the dev tools provided by the chip makers.  They are not developing all this stuff from scratch the way Keysight does.

If you're not interested in having an open source instrument, that's fine with me. I and other people are.  Unfortunately, you seem to have driven them away.

Your assertions amount to saying that the Chinese are able to clone competitor's instruments but no one else can even grasp how they work.  I don't recall that the Chinese invented the stuff they're making.  They just copied American products using American parts.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #132 on: December 16, 2017, 06:21:16 am »
I was deliberately rude because your sole interest is trumpeting that you are right and everyone else is wrong.

Everyone else? I did not notice that somebody else is "trumpeting" getting GPL source code of instrument, just you.

What did you expect? - That everybody here will applaud "yes you are so right!" and that's it? Whole purpose of discussion is to discuss :)

Obviously I do not share naive optimism of yours: "It seems to me far more effective to get the GPL code released and fix the bugs", so I tell you that source code you can get such way (if any) will have just some irrelevant (to instrument function) code.

Quote
I suggest you read your own post.  I did *not* put words in your mouth.

I said "some irrelevant kernel code modifications", you read "GPL code is irrelevant".  What a stretch.  :palm:

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You have no way of knowing what I do or do not know.

Obviously I can comment only about what you said here. And you were mistaken about many things.

Quote
Fact is I have repaired several analog scopes including a Tek 465.  I also have over 30 years of DSP experience.

What can I say - respect!

Regarding mine experience: while ago I was involved in design decision making of Linux-based device (not test instrument obviously) and can assure that Linksys router "incident" was isolated one. Other companies do not make such a stupid mistakes and oscilloscopes are not routers as well.

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If you actually knew what a DSO is doing, you would not consider it very complex.  It's not.

Right.  :-DD

Quote
There are some significant timing challenges, but that and broadband circuit design are the only hard parts.  The timing constraints pretty much dictate everything about the VHDL code for the FPGA.  There's just not much wiggle room in how the logic is laid out on the device.

So you just explained what DSO is doing, right?

Quote
As regards the Agilent thread,  I'd seen it, but never bothered to read it.  As I suspected, it's almost entirely about enabling license options.

Sure it talks about enabling licenses, but this is not why I mentioned that thread. You missed that all the application code of particular instrument is binary Java code which do not fall under GPL. By requesting source code you would get tiny part, close to nothing of what you need to fix bugs.

Quote
The primary purpose of having people ask for the source is to make clear to the the low end Chinese T & M OEMs  that there is a marketing advantage to making their products "open source" and allowing the user community to write apps for the instruments.

Initially you said something completely different: "It seems to me far more effective to get the GPL code released and fix the bugs than it does to engineer a new instrument from scratch."

Quote
Substantial parts of the UIs are written in a scripting language. Once one has the ability to run a script that reads button presses and sends commands to the FPGA and the ARM host, pretty much all the functionality of the unit becomes accessible. That's not a very high bar.

What's the point of changing buttons if you cannot add or modify functions of instrument?

Quote
The T & M OEMs are using the dev tools provided by the chip makers.

Indeed they use dev tools provided by chip makers! If they use Xilinx FPGA - they for sure use Vivado suite. So what?

Quote
If you're not interested in having an open source instrument, that's fine with me. I and other people are.

This is good one  :popcorn:

I just say that asking source code of Linux based devices is dead end. You shall re-read thread to see that I am not against open source instrument/scope, also I have my own idea what open source scope shall look like.

Quote
Unfortunately, you seem to have driven them away.

Wow this is something. You blame me that others do not stand on your side. How convenient.

Quote
Your assertions amount to saying that the Chinese are able to clone competitor's instruments but no one else can even grasp how they work.

It's just you who do not know which functions of DSO is handled by FPGA and which - by CPU or scripting language :)

Quote
I don't recall that the Chinese invented the stuff they're making.  They just copied American products using American parts.

Seriously?  :-DD

With the same success we can say that Americans also did not invent stuff they are making. Stuff was invented by German inventor.
 

Offline zeqing

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Re: Open Source Oscilloscope, can it be done?
« Reply #133 on: December 16, 2017, 01:16:43 pm »
i have used the seeed DSO nan0https://www.seeedstudio.com/DSO-Nano-v3-p-1358.html for 4 years, and studied it's hardware and firmware(seems not designed by the seeed official but some pressional firmware engineers), almost meet my daily requests , with only about 60$(purchased in their special sales.)
 

Offline ez24

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Re: Open Source Oscilloscope, can it be done?
« Reply #134 on: December 16, 2017, 02:05:27 pm »
i have used the seeed DSO nan0https://www.seeedstudio.com/DSO-Nano-v3-p-1358.html for 4 years, and studied it's hardware and firmware(seems not designed by the seeed official but some pressional firmware engineers), almost meet my daily requests , with only about 60$(purchased in their special sales.)

Funny a lot cheaper on Amazon

https://www.amazon.com/seeed-studio-TOL01241P-Nano-Oscilloscope/dp/B00BB4ETJW/ref=sr_1_1?ie=UTF8&qid=1513393398&sr=8-1&keywords=dso+nano+v3

YouTube and Website Electronic Resources ------>  http://www.eevblog.com/forum/other-blog-specific/a/msg1341166/#msg1341166
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #135 on: December 18, 2017, 01:00:19 am »
Funny a lot cheaper on Amazon

https://www.amazon.com/seeed-studio-TOL01241P-Nano-Oscilloscope/dp/B00BB4ETJW/ref=sr_1_1?ie=UTF8&qid=1513393398&sr=8-1&keywords=dso+nano+v3

Funny that for same money you can get decent 2-channel 100MSPS/25MHz USB scope:

https://www.amazon.com/Owon-VDS1022-USB-Oscilloscope-100MS/dp/B00HC4KY2G

By adding 20$ you get isolated VDS1022I model.

Actually this scope is good candidate for hardware platform of "open source scope" we are talking about here in this thread. Thou I still believe that hardware shall be open source as well because nobody can tell how long any particular scope will be available.
 

Online David Hess

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Re: Open Source Oscilloscope, can it be done?
« Reply #136 on: December 18, 2017, 07:43:46 am »
The problem with the proposals I have read here is that they duplicate functionality which is already available in low cost budget DSOs.  What about designing something which does what they cannot?

1. Include a simple function generator so the relatively low performance DSO may be used as a low frequency network analyser.  Keysight has taken a minor step in this direction but the performance of their solution is terrible; is this to prevent competition with their low frequency network analyzers?  There are a couple of USB DSOs which support this but not very well.

2. Include the noise marker function in the FFT capability.  I am tired of DSOs which cannot do this simple thing making them useless without a PC to do it for them and in that case, why is the DSO needed at all?

3. Design a real digital *sampling* oscilloscope for high bandwidth.  Yea, a simple design will *only* be 100 MSamples/second and perhaps slower but greater than 4 GHz of bandwidth with 10ps (100 GSamples/second) timing resolution is feasible.  Picotech makes some expensive USB oscilloscopes like this.
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #137 on: December 18, 2017, 09:33:44 am »
I had mentioned the idea of implementing a VNA on an Instek MSO-2204EA when I was doing pre-purchase research.  I *think* they are pursuing the idea.  The marketing guy seemed quite interested.  It's easily doable for HF by dumping the data to a CSV file and using Octave.  When I saw that their PC scope software used Python I thought it would be easily scriptable.  Then I tried the software :-(  All it does is retrieve a screen dump.

However, if the SCPI facility works it's still scriptable, just more work.

My view is that what's needed most is the ability to fix the shortcomings of existing products.  I don't care if the HW is "open source" or not so long as it is documented and usable.  I want the ability to fix bugs and implement new features at will.  There's a nice SA facility in the Instek MDO line.  It works on all the GDS-2000E line, but is crippled by design so it only works on the MDO line.  However, it *does* work on the MSO2204EA with some clumsiness.

Take a look at the article in QEX #305 (Nov/Dec 2017) by DC9ST implementing an SDR using COTS eval boards.  At 250 MSa/s and 16 bits, the combination of a Zedboard and an AD9467-250 eval board is pretty potent. It  is most of the hardware for the sampling scope you mentioned for about $1k. For a 1920 point screen that would be 4000 wfms/s for a 4 GHz signal.

I plan to get a miniZed to play with, but I'm more interested in hacking a commercial DSO for the simple reason the hardware is cheaper and it's already in a convenient package.
 

Offline 2N3055

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Re: Open Source Oscilloscope, can it be done?
« Reply #138 on: December 18, 2017, 10:28:21 am »
Sampling scope is already done....
http://www.fastsampling.com/PHP/products.php

4 GHz for 300+ USD, 11 GHZ for a 1000 USD... Members of the forum here tested it and said it worked quite well..

I will probably spring for a 4GHz one in months to come.. I have  some work for it...


Also  @rhb , you should check Picoscopes... Full API and lots of examples...

Regards,

Sinisa



 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #139 on: December 18, 2017, 10:59:13 am »
@2N3055

Quite a deal.  I'd never heard of them.  I don't happen to need one at the moment though.

I looked at the PicoTech scopes quite closely, but decided on the Instek MSO-2204EA instead.  Crappy FW, but the HW is quite good from what I can tell without a cal lab.  It *should* do everything I want via SCPI commands, but I've not gotten started on that yet.  I'm hoping I can find a way to modify the FW so I can write user apps for it.  Lots of stuff to learn about the Zynq platform.  But I'm an old hand at Unix and already know a fair bit about how the Instek works.

I've got some serious work setting up the development tools for the project.  I've got  disks on the way to run a RAID 0 mirror.  But I may bump up to a 5 disk RAIDZ2 (double parity ZFS) on OI Hipster.  I need to have a couple of VirtualBox  VMs running to access software.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #140 on: December 18, 2017, 09:53:59 pm »
1. Include a simple function generator so the relatively low performance DSO may be used as a low frequency network analyser.  Keysight has taken a minor step in this direction but the performance of their solution is terrible; is this to prevent competition with their low frequency network analyzers?  There are a couple of USB DSOs which support this but not very well.

Rigol 1000Z series and Instek MSO-2000EA scopes are doing what you ask for, they both have 2-channel 25MHz AWG. Just add PC software and directional coupler(s).

Quote
2. Include the noise marker function in the FFT capability.  I am tired of DSOs which cannot do this simple thing making them useless without a PC to do it for them and in that case, why is the DSO needed at all?

Even more annoying is that FFT of all scopes (that I know) have fixed start frequency of the span: 0Hz.

All what's needed for scopes to be much more useful in frequency domain - DDC (Digital Down Converter) between ADC and FFT which is quite straightforward software function (numerical oscillator + mixer + decimating filter). Instead of having ultra slow 1 zillion points FFT handled by CPU, I would love to "zoom" into spectrum using 512 or 1024-point FFT which can be run in the FPGA having fast display update rate as spectrum analyzer shall do.
« Last Edit: December 18, 2017, 09:58:38 pm by ogden »
 

Online David Hess

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Re: Open Source Oscilloscope, can it be done?
« Reply #141 on: December 19, 2017, 02:09:12 am »
Sampling scope is already done....
http://www.fastsampling.com/PHP/products.php

4 GHz for 300+ USD, 11 GHZ for a 1000 USD... Members of the forum here tested it and said it worked quite well..

I will probably spring for a 4GHz one in months to come.. I have  some work for it...

I saw some details on these and while they operate like sampling oscilloscopes, they are not.  I kept things simple in my description but what I have in mind is a little more complex and does away with all of those trigger connections and difficulties on the Fastsampling products.

1. Include a simple function generator so the relatively low performance DSO may be used as a low frequency network analyser.  Keysight has taken a minor step in this direction but the performance of their solution is terrible; is this to prevent competition with their low frequency network analyzers?  There are a couple of USB DSOs which support this but not very well.

Rigol 1000Z series and Instek MSO-2000EA scopes are doing what you ask for, they both have 2-channel 25MHz AWG. Just add PC software and directional coupler(s).

That is the maddening thing about it.  These DSOs have all of the necessary hardware but the firmware lacks these features.  In some cases like FFTs, the firmware deliberately prevents it from being used this way by for instance discarding the phase results.

If the firmware could be rewritten this could be solved but that is never going to happen.

« Last Edit: December 19, 2017, 07:18:03 am by David Hess »
 

Offline xani

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Re: Open Source Oscilloscope, can it be done?
« Reply #142 on: December 19, 2017, 04:30:42 am »

That is the maddening thing about it.  These DSOs have all of the necessary hardware but the firmware lacks these features.  In some cases like FFTs, the firmware deliberately prevents it from being used this way but for instance discarding the phase results.

If the firmware could be rewritten this could be solved but that is never going to happen.

Isn't most of the low end scopes just an FPGA(s) + some ARM CPU to do display/buttons/communication ? Writing oscilloscope software from scratch shouldn't be much harder than writing it for "fully open sourced" scope hardware (that would probably also end up being some FPGA + CPU or zynq).

I dont think rewriting it is the biggest problem, the problem is what if vendors says "fuck you" and blocks ability to flash custom firmware in new version/model and that would waste a ton of work even if hardware-independent parts could be salvaged to another project
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #143 on: December 19, 2017, 05:09:50 am »
@ David Hess

Look at these and the following figures I posted.

http://www.eevblog.com/forum/testgear/feeltech-fy6600-60mhz-2-ch-vco-function-arbitrary-waveform-signal-generator/msg1360021/#msg1360021

@xani

The vendors are using the development tools provided by the FPGA OEMs. Yes, they *can* make life tedious, but I can't see anything they can do to stop people from loading custom FW.

A FW update consists of a pair of images, one of the filesystem for the ARM and one for the FPGA plus a few other odd bits.  These get copied to the appropriate places and the system reboots.  The programs to do the copying get copied to RAM disk for execution during the update.  The various OEMs have their own version of this, but the basic principle is the same.  It's what you *have* to do if you're using an embedded Unix based OS to run the instrument and you're going to provide FW updates.

At present the updates are not encrypted.  They *could*, but there is not a lot of CPU available.  So doing that would make updates *really* slow.  Moreover, the relative speed of a desktop machine with a GPU makes brute forcing the encryption key very simple, albeit perhaps slow.  But so what?  Let's say it takes a week to brute force the FW update key.  The OEM simply cannot use a key that is unique to each scope unless it's a hash of something like the serial number.  So once the key is cracked it does not need to be done again.

Which goes back to what I said some days back.  We *already* have open source scopes.  We just don't have the source.  But with the GPL part in hand from the instrument OEM, the rest is pretty straight forward.  A lot of the code can be used as is with or without the source.  There is no need to rewrite all the scope code before gaining control of the instrument.

If there are a large number of people who buy a scope *because* it is fully open source, the OEM is not going to should themselves in the head to prevent it.   My theory is that at least one of the OEMs will decide to exploit the marketing advantage.



 

Offline xani

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Re: Open Source Oscilloscope, can it be done?
« Reply #144 on: December 20, 2017, 02:24:13 am »

At present the updates are not encrypted.  They *could*, but there is not a lot of CPU available.  So doing that would make updates *really* slow.  Moreover, the relative speed of a desktop machine with a GPU makes brute forcing the encryption key very simple, albeit perhaps slow.  But so what?  Let's say it takes a week to brute force the FW update key.
Nowadays even tiny micros get hardware AES acceleration and you ain't bruteforcing AES128 anytime soon. So getting code out isn't that easy, if vendor really wanted to.

If you want to see some raw numbers here is some router chips vs SSL https://wiki.openwrt.org/doc/howto/benchmark.openssl but short version is that anything bigger than say Cortex M3 will probably get at least 1MB/s

Preventing getting code in is much harder (as if all things fail you can go to JTAG) so I doubt any would bother doing that as that would also make life harder for them.
Quote
The OEM simply cannot use a key that is unique to each scope unless it's a hash of something like the serial number.  So once the key is cracked it does not need to be done again.
Actually, they can generate firmware update per-device, pretty easily. What you do is.

* have a x509 certificate loaded on the scope
* manufacturer has a key for that certificate
* manufacturer makes a firmware image that has device's serial number embedded
* manufacturer signs it using his private key
* firmware updater checks for the signature and compares image's serial with device's
* if all matches, it proceeds with update.

even few hundred MHz ARM can do that verification in few seconds or less.

IIRC similiar method is used for license keys for switches (the ethernet kind)

Quote
If there are a large number of people who buy a scope *because* it is fully open source, the OEM is not going to should themselves in the head to prevent it.   My theory is that at least one of the OEMs will decide to exploit the marketing advantage.

That's probably the closest we're gonna get, the problem is that there would have to be "the first" fully hacked scope with fully open-source software that also is significantly better than base software. Which is a LOT of work. Also that cuts into their profits of selling software-unlocked features for way too much...

But having something like Digilent's Waveforms 2015 equivalent but on beefy hardware would be amazing
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #145 on: December 20, 2017, 03:08:27 am »
It's not really necessary for it to be "fully open".  It just needs to be sufficiently open that it can be modified to add features and fix bugs.  Doing that *is* a good bit of work, but not as difficult as it might seem. If the FPGA bitstream is working properly it doesn't matter if the source is not available at the moment.

Take a look at FW update files for a few instruments. They're pretty simple and do the obvious thing.  Better yet, get a Zedboard and implement a FW updater.  The minZed is about $100.

I agree with your comments about encryption, but I stand by my original comment.  I am not an expert, but I learned the rudiments of cryptanalysis 50 years ago.  The principles have not changed.  But the nVidia and Radeon GPUs have radically changed how large a problem you can solve by brute force.  Bitcoin miners are doing this at large scale.

Rigol has sold a lot of DS1054Zs by allowing the license keys to be hacked.  Another OEM would get a lot of that market share if their scope were open.  I don't think they would be so stupid as to fight it.  Linksys restarted production of the WRT54G in response to the popularity of that device.

As I have commented previously, an important first step is to get the GPL'd  source code so we can build the infrastructure from source.  The OEMs are using one of several embedded Linux distros.  I *very* much doubt that any of the Zynq based scopes use anything other than the Xilinx tool chain.  Try selling "We're going to use a Zynq, but we don't want to use the Xilinx supported Linux distro for the Zynq." to your boss.
 

Offline xani

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Re: Open Source Oscilloscope, can it be done?
« Reply #146 on: December 20, 2017, 04:47:18 am »
It's not really necessary for it to be "fully open".  It just needs to be sufficiently open that it can be modified to add features and fix bugs.  Doing that *is* a good bit of work, but not as difficult as it might seem. If the FPGA bitstream is working properly it doesn't matter if the source is not available at the moment.

Take a look at FW update files for a few instruments. They're pretty simple and do the obvious thing.  Better yet, get a Zedboard and implement a FW updater.  The minZed is about $100.

Well unless you need FPGA to implement something extra (and you probably would want that pretty soon, like extra trigger modes or hardware-accelerated FFT). But yes, even having a fpga blob with documented communication would be a big step.

I was wondering about getting one of them, but while I have decent amount of Linux experience (I've built few Linux images from scratch incl. compiling all apps in system), I have absolutely no FPGA experience.

I agree with your comments about encryption, but I stand by my original comment.  I am not an expert, but I learned the rudiments of cryptanalysis 50 years ago.  The principles have not changed.  But the nVidia and Radeon GPUs have radically changed how large a problem you can solve by brute force.  Bitcoin miners are doing this at large scale.
That's not the same level. Unless there is a bug in AES, it would take a lot of time. Here is someone's that did actual math on it: https://www.reddit.com/r/theydidthemath/comments/1x50xl/time_and_energy_required_to_bruteforce_a_aes256/

TL;DR: if it's encrypted "correctly not happening. Even AES128 would take bilion years, assuming crypto itself wouldn't be broken

Quote
Rigol has sold a lot of DS1054Zs by allowing the license keys to be hacked.  Another OEM would get a lot of that market share if their scope were open.  I don't think they would be so stupid as to fight it.  Linksys restarted production of the WRT54G in response to the popularity of that device.

Yes, if we had OS software at that level, I wouldn't be even suprised if vendors customized and installed it on their own scopes, as that would basically be free R&D for them and advertisement.

As for Rigol I do not think they "allowed" it to be cracked, rather saw  it and said"oh, they are cracking them! But hey, actually that's not bad, people buy us over competition now".

I have noticed that in many fields there is a lot of fear for open-sourcing things(latest example: Dave's new multimeter ), companies being afraid that it would "aid their competition" or some other bogus reason, even tho 95% of the code is just repeating what someone's else invented decades ago but with different bugs.

Quote
As I have commented previously, an important first step is to get the GPL'd  source code so we can build the infrastructure from source.  The OEMs are using one of several embedded Linux distros.  I *very* much doubt that any of the Zynq based scopes use anything other than the Xilinx tool chain.  Try selling "We're going to use a Zynq, but we don't want to use the Xilinx supported Linux distro for the Zynq." to your boss.

The problem is that selling "hey, you know that code we put 10 man-years into ? Let's give it away for free" to your boss is even harder. Even if long term option would be "customers buy our scopes instead of 5x as expensive LeCroys because our software capabilities are same".

Because now mid-high end scopes seem to be more about software than actual hardware. Sure you still need to get that part right, but no technology gonna save scope with bad firmware.
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #147 on: December 20, 2017, 07:42:22 am »
I've got lots of Unix experience, though relatively little of it with Linux.  And *no* FPGA experience.  But being an old R&D rat, that's not much concern.  In fact it's an attraction.  I haven't done that.  The things I dislike are the ones I've done 3-4 times already.  These days I only do those for money or necessity.

There's brute force and there's brute force.  Don't underestimate the impact of known plaintext.   More interestingly, David Donoho proved that L1 == L0 under certain rather general and highly probable conditions.  That's *extremely* important.  It's a proof that linear programming can solve an NP-Hard problem in tractable time.  I don't know how to apply it to a cryptanalysis problem at the moment, but one might be able to. The only thing that makes *any* modern crypto system secure is that the problem of finding the key is NP-Hard.  I'm rather amazed that this was done in 2004 and I did not learn of it until 2013. And I've still never seen mention of it in a CS & crypto context.

Vendors like R&S raised the bar to unauthorized licenses.  Rigol and apparently also Siglent have elected not to.  They could *very* easily change the algorithm for the license keys.

I'm *not* and never have suggested the OEMs should give away their proprietary code.  I am simply saying that the first step to an open source instrument is to get the GPL'd code from the scopes on the market already.  To paraphrase Lao Tsu, the journey from Shenzen to Santa Clara begins with a single step.

I'm also saying that analyzing FW updates will provide a lot of information needed to build an open source alternative.  I am working on collecting some of that information.  It will go faster if other people also work on the problem.  Arguing about whether it is possible is useless.  It's obviously possible.  It just takes sufficient resources.
 

Offline Marco

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Re: Open Source Oscilloscope, can it be done?
« Reply #148 on: December 23, 2017, 12:08:16 am »
Reverse engineering the software on an oscilloscope to improve it is obviously possible, it's been done. But it takes someone very far out on the spectrum donating 10s to 100s of thousands worth of his time. Stuff like this is never a team effort at the start, it's one lone mad man getting something to a workable level.

The source code of the OS doesn't really help, because with GPL V2 they don't have to provide you the tools and means to get it running. You can generally hack shell access, which is infinitely more useful than the source code of the OS ... the OS doesn't need to be improved after all, you can leave it entirely alone. All the important functionality is in the drivers and applications.
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #149 on: December 23, 2017, 02:03:19 am »
Actually writing code is probably largely a solo effort at the start.  However, there is the ARM code and the FPGA code, so two people is probably ideal. But there is a lot of information to be gathered.  For example:

Block diagrams and major components
Existing menu structure and modules
Datasheets for key components
Chip vendor code examples and libraries

All of that takes time.  Right now all of my time is being consumed by trying to get guest OSes to load on VirtualBox which is throwing a hissy fit for no obvious reason.  Once that is done I can get back to the task of peeling apart update images to see how the updates are handled and identify the components of the scope application.  For me the first task is to reenable ssh.

Your estimate of the cost in labor is pretty accurate, but there is no work for old oil & gas R&D types, and I'm *really* annoyed by the UIs.

There is also the not small matter of conveying to the OEMs that an open source instrument is desired by many people.

I started a job once and discovered I had 1.25 million lines of code to support, 500,000 lines of which the only comment was the author's name.  It took 6 weeks to sort out the system so it would compile.  The authors still worked there, but they had no real idea how to compile the mess.  Before I could fix *any* bugs I had to be able to compile and link everything.

The first major step is to be able to build a working image from the available source.  That will not be everything.  Some pieces will just be binary blobs that have to be put in the right places.  But that *is* a major milestone for which the GPLd parts are essential.  One might or might not be able to do that using the chip OEM distro.  A few changes by the instrument OEM can translate into many hours of work.  Once one has a buildable code base, then one can start the task of replacing the binary only parts.  But until you have the GPL'd code base in buildable form you cannot do *any* work on the FPGA and UI code.

How do you swallow an elephant?  One mouthful at a time.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #150 on: December 23, 2017, 08:06:49 pm »
There's brute force and there's brute force.  Don't underestimate the impact of known plaintext.

Firmware that may have large blocks of 0's or 1's or any other known plaintext shall be (and usually are) encrypted using AES-CTR (counter mode) which is safe against known plaintext brute force attack.
 

Offline jebivetar

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Re: Open Source Oscilloscope, can it be done?
« Reply #151 on: September 27, 2018, 02:17:42 am »
Someone out there does seem to be working on an open source scope.

The (wonderful) Interactive HTML BOM Kicad plug-in https://github.com/openscopeproject/InteractiveHtmlBom has a couple of interactive demos "of (soon to be published) in house designs" one of which OSPx201 which looks like a pretty-far-along oscilloscope.

https://openscopeproject.org/InteractiveHtmlBomDemo/OSPx201/ibom.html

A two-sided <10x10cm open source oscilloscope (cheaply fabbed) with a ~$100 BOM capable of 10Mhz or so would be revolutionary. 

 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #152 on: September 27, 2018, 03:11:31 am »
Someone out there does seem to be working on an open source scope.

https://openscopeproject.org/InteractiveHtmlBomDemo/OSPx201/ibom.html
A two-sided <10x10cm open source oscilloscope (cheaply fabbed) with a ~$100 BOM capable of 10Mhz or so would be revolutionary.

I struggle to find ADC on board. If built-in 5Msps ADC's of stm32f303 are used, then that thing does not seem very appealing, especially knowing that ADC's of stm32 shall be run from PLL which have inherent jitter. I found 12MHz ceramic resonator for stm32 instead [facepalm].
 

Offline 2N3055

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Re: Open Source Oscilloscope, can it be done?
« Reply #153 on: September 27, 2018, 06:54:40 am »
LOL jebivetar....
 

Offline bloguetronica

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Re: Open Source Oscilloscope, can it be done?
« Reply #154 on: September 27, 2018, 07:22:38 am »
Hi,

I found this open source scope design that looks serious: https://www.scopefun.com/. Although it is PC based, it seems to have a decent analog front-end and ADC. The layout is very well designed and the hardware very professionally made. This is way above the average DIY kit, IMHO.

They will launch a second version, but I don't know how soon. Kudos for who developed this amazing project that, IMO, should be in the spotlight.

Kind regards, Samuel Lourenço
 

Online janoc

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Re: Open Source Oscilloscope, can it be done?
« Reply #155 on: September 27, 2018, 07:38:03 am »
A two-sided <10x10cm open source oscilloscope (cheaply fabbed) with a ~$100 BOM capable of 10Mhz or so would be revolutionary.

What would be revolutionary on it, exactly?

E.g. this Owon is more capable and for less than your $100 BOM.
https://www.sainsmart.com/products/owon-vds1022-25mhz-2-1-channel-pc-usb-oscilloscope

Or get one of the Bitscopes, those have open source software support, I believe:
http://my.bitscope.com/store/

Or just get a used analog scope which will likely be still much more capable than anything you can build for $100. And those tend to be as "open source" as it gets, especially if you get a classic scope with no fancy digital stuff.

It is not two sides board and certainly not 10x10cm, but that is a totally unrealistic requirement for a 10MHz scope. Keep in mind that you need at least ~100Msps to actually see a 10MHz square wave as a square wave - that's not going to work on a tiny two sided board. Four layers would be a minimum.

Open source is cool, but seriously, what do you exactly want to hack on a device like this? No matter how clever software you design, you will be always limited by the necessarily crappy/low cost hardware. And if you think it will be somehow cheaper than the "regular" options, then you are completely wrong, as shown above.


 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #156 on: September 27, 2018, 07:51:23 am »
Keep in mind that you need at least ~100Msps to actually see a 10MHz square wave as a square wave - that's not going to work on a tiny two sided board. Four layers would be a minimum.

To avoid any confusion here - scope bandwidth does not mean that you will be able to see square wave of particular frequency on it:

https://www.tek.com/support/faqs/how-bandwidth-defined-oscilloscope-0

On the bright side, manufacturers try to put significant margins here. It is reported that some quite popular entry-level Rigol 100MHz scope have actual 150MHz bandwidth or so. I may stand corrected. If interested - seek EEVblog forums threads about Rigol scopes.
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #157 on: September 27, 2018, 10:43:58 am »
In the end it comes down to what's your  budget and what's your skill level.  There is no way to beat the price-performance of COTS DSOs.

If what you want is a FOSS FW DSO, then get a Zynq based DSO (non-Instek. I have that already) and send me a PM. Also if you are interested in sub $1K 3 GHz DSOs.  There's a LeCroy DDA-120 HW modification that would give 3 GHz on a single channel.  A lot more could be done if one replaced the PowerPC board with an FPGA/ARM board.
 

Online ogden

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Re: Open Source Oscilloscope, can it be done?
« Reply #158 on: September 27, 2018, 05:05:27 pm »
In the end it comes down to what's your  budget and what's your skill level.  There is no way to beat the price-performance of COTS DSOs.

It's already discussed earlier in this thread - that building oscilloscope for purpose is not feasible. Only reason some shall consider building scope - 1) just education/fun 2) specific, custom DSP function which is available only in hi-end scopes or not available at all. Example: hopeless FFT implementation in nearly all the scopes except R&S RTO series.

 

Online janoc

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Re: Open Source Oscilloscope, can it be done?
« Reply #159 on: September 28, 2018, 02:09:29 am »
To avoid any confusion here - scope bandwidth does not mean that you will be able to see square wave of particular frequency on it:

https://www.tek.com/support/faqs/how-bandwidth-defined-oscilloscope-0

Of course, I do know that. However, he wasn't speaking about bandwidth but about it being "10MHz capable" (whatever that means).

From a practical point of view, being able to display a 10MHz square wave signal today is pretty much at the low end of what one should ask from an oscilloscope (even Arduinos run at higher clocks).

If someone wants to only do audio, then a regular sound card will do a better job than such gizmo anyway.
 

Offline bloguetronica

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Re: Open Source Oscilloscope, can it be done?
« Reply #160 on: September 28, 2018, 06:37:58 am »
...
From a practical point of view, being able to display a 10MHz square wave signal today is pretty much at the low end of what one should ask from an oscilloscope (even Arduinos run at higher clocks).
...
If you want to see a 10MHz square wave, you should use a 100MHz oscilloscope, or, at least, a 50MHz one. Now, let me tell you that designing a 50MHz oscilloscope is not easy. The "50MHz" only refers to the cutt-off frequency of the steep low pass filter that you'll have to employ in your AFE. Plus, it has to be a Bessel aligned one, to avoid ringing. That means you will have to use a DAC capable of, at least 500MSa/s of sampling (because Bessel filters may be steep, but are not very selective by any standards, even very high order ones - and you will have to avoid aliasing, hence the extra sampling rate). Although that is low end from a professional standpoint, and I agree on that part, it is not easy to design. No DIY kit scope will do, sorry.

But that is just my two cents.

Kind regards, Samuel Lourenço
 

Offline rhb

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Re: Open Source Oscilloscope, can it be done?
« Reply #161 on: September 28, 2018, 11:55:05 am »
Amazingly, if you want >10 GSa/S  it's a COTS dev board build.  The 1 GSa/S DSO is where it gets really hard.  But hijacking a COTS DSO is so much easier than designing and building one there is no comparison.

The Zynq based scopes are generally more money, but it gives a well defined infrastructure imposed by the low parts count.
 

Online janoc

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Re: Open Source Oscilloscope, can it be done?
« Reply #162 on: October 01, 2018, 06:39:57 pm »
Dave has just tweeted this:

https://www.crowdsupply.com/andy-haas/haasoscope

That should pretty much satisfy the OPs needs - small, $99, 4 channels, reasonable specs and open source. However, it is not two sided board (that's just not realistic) and you better do read the manual, there are plenty of gotchas for the unwary (like the bandwidth/sensitivity and voltage limits).

If you need a general purpose oscilloscope you would do better buying a normal desktop instrument than this (even used analog one). However, this gadget can be very useful for some specific applications.
« Last Edit: October 01, 2018, 06:44:25 pm by janoc »
 

Online mbest

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Re: Open Source Oscilloscope, can it be done?
« Reply #163 on: October 02, 2018, 01:34:23 am »
Dave has just tweeted this:

https://www.crowdsupply.com/andy-haas/haasoscope

That should pretty much satisfy the OPs needs - small, $99, 4 channels, reasonable specs and open source. However, it is not two sided board (that's just not realistic) and you better do read the manual, there are plenty of gotchas for the unwary (like the bandwidth/sensitivity and voltage limits).

Only if you don't watch the mailbag video or previous mention in the live stream.

Quote
If you need a general purpose oscilloscope you would do better buying a normal desktop instrument than this (even used analog one). However, this gadget can be very useful for some specific applications.

As a newbie, I'm convinced to stay away from USB scopes :)

-Mike
 

Online janoc

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Re: Open Source Oscilloscope, can it be done?
« Reply #164 on: October 02, 2018, 06:10:45 am »

Only if you don't watch the mailbag video or previous mention in the live stream.


Yeah, I have watched the video afterwards. However, the most of the problem seems to be a really crappy software - that's fixable. The rest is kinda par for the course, with pennies being pinched everywhere. Except maybe for the ridiculous issue with the BNC connectors being too close to each other.

However, if the OP wants an open source scope, it is probably the best contender available. Which doesn't mean it is any good only that there aren't really any other open source scopes around.
 

Offline abraxa

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Re: Open Source Oscilloscope, can it be done?
« Reply #165 on: October 02, 2018, 04:15:34 pm »
Yeah, I have watched the video afterwards. However, the most of the problem seems to be a really crappy software - that's fixable. The rest is kinda par for the course, with pennies being pinched everywhere. Except maybe for the ridiculous issue with the BNC connectors being too close to each other.

However, if the OP wants an open source scope, it is probably the best contender available. Which doesn't mean it is any good only that there aren't really any other open source scopes around.

I'll bite and politely disagree - 8k sample buffer/channel is a joke. I know why that limitation exists but that doesn't change the fact that it makes it a bad device to do actual work with. The Scopefun project is not much better: 10k sample buffer per channel. From my point of view, that makes both really only suitable for basic signal analysis, unfortunately.

However, since both are open, it's possible to extend them and add DDR RAM support. If someone would do that with the Scopefun and make actual kits to buy, I'd bite.
 

Offline bloguetronica

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Re: Open Source Oscilloscope, can it be done?
« Reply #166 on: October 03, 2018, 12:47:38 am »
Yeah, I have watched the video afterwards. However, the most of the problem seems to be a really crappy software - that's fixable. The rest is kinda par for the course, with pennies being pinched everywhere. Except maybe for the ridiculous issue with the BNC connectors being too close to each other.

However, if the OP wants an open source scope, it is probably the best contender available. Which doesn't mean it is any good only that there aren't really any other open source scopes around.

I'll bite and politely disagree - 8k sample buffer/channel is a joke. I know why that limitation exists but that doesn't change the fact that it makes it a bad device to do actual work with. The Scopefun project is not much better: 10k sample buffer per channel. From my point of view, that makes both really only suitable for basic signal analysis, unfortunately.

However, since both are open, it's possible to extend them and add DDR RAM support. If someone would do that with the Scopefun and make actual kits to buy, I'd bite.
I don't consider a 8KSa buffer a joke. It is quite useful, and pretty standard (actually, 10KSa is more standard). If you said that 1KSa or 2KSa was a joke, I would agree. Anyway, you can't expect to pay less for an advanced scope, even if it is OSH (if that exists).

How do you expect to raise the buffer limit? I'm just curious. By the way, if I recall correctly, there will be a new version of the ScopeFun oscilloscope.

Kind regards, Samuel Lourenço
 

Online janoc

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Re: Open Source Oscilloscope, can it be done?
« Reply #167 on: October 03, 2018, 02:54:02 am »
I'll bite and politely disagree - 8k sample buffer/channel is a joke. I know why that limitation exists but that doesn't change the fact that it makes it a bad device to do actual work with. The Scopefun project is not much better: 10k sample buffer per channel. From my point of view, that makes both really only suitable for basic signal analysis, unfortunately.

DDR3 support likely wouldn't fit on that size of the board.

And re 8k - well, I guess the Tektronix TDS2024C bench (!) scopes with 2.5kB are also a joke then? A $2700 joke, btw (https://www.newark.com/tektronix/tds2024c/oscilloscope-digital-storage-4/dp/86R8482 )

The small sample memory is really the least of the problem with this device.

From my point of view, that makes both really only suitable for basic signal analysis, unfortunately.

And what exactly did you expect to use a $100 devboard for? If you need more than the basics, you probably would buy a proper scope anyway.

I don't think that anyone (except maybe the author of the gadget) thinks this is a viable general purpose instrument. What this "Haasoscope" could be useful for is data acquisition where you need many channels and similar jobs (that's why I was talking about specific niche uses), where you will likely write your own software to go with it too. That's where it being open source is actually the most valuable.
« Last Edit: October 03, 2018, 02:56:11 am by janoc »
 


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