Low Cost PCB's Low Cost Components

Author Topic: Open Source Oscilloscope, can it be done?  (Read 15010 times)

0 Members and 3 Guests are viewing this topic.

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 3380
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
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.
Cryptocurrency has taught me to love math and at the same time be baffled by it.
 

Offline abraxa

  • Regular Contributor
  • *
  • Posts: 165
  • Country: de
  • Sigrok associate
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

  • Super Contributor
  • ***
  • Posts: 2916
  • Country: nl
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

  • Super Contributor
  • ***
  • Posts: 3380
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
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?
Cryptocurrency has taught me to love math and at the same time be baffled by it.
 

Offline Tom10000

  • Contributor
  • Posts: 12
  • Country: au
I Think its a good idea you could go off a design one yourself
« Reply #54 on: May 03, 2017, 04:52:53 PM »
great idea
 

Online JPortici

  • Super Contributor
  • ***
  • Posts: 1808
  • Country: it
 

Offline branadic

  • Frequent Contributor
  • **
  • Posts: 710
  • Country: de
Re: Open Source Oscilloscope, can it be done?
« Reply #56 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

-branadic-
Prema 5000 | Prema 5017 SC | Keithley 181 | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Prema 5017 SC, 34401A, 34410A, HDO6054, Keysight 53230A and other goodies at work
 

Offline neris.io

  • Contributor
  • Posts: 5
  • Country: gb
  • To change the world
    • Public Projects
Re: Open Source Oscilloscope, can it be done?
« Reply #57 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

  • Frequent Contributor
  • **
  • Posts: 362
  • Country: fi
Re: Open Source Oscilloscope, can it be done?
« Reply #58 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

  • Regular Contributor
  • *
  • Posts: 63
  • Country: de
Re: Open Source Oscilloscope, can it be done?
« Reply #59 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

  • Contributor
  • Posts: 43
  • Country: fr
    • Retronik
Re: Open Source Oscilloscope, can it be done?
« Reply #60 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

  • Super Contributor
  • ***
  • Posts: 2916
  • Country: nl
Re: Open Source Oscilloscope, can it be done?
« Reply #61 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

  • Contributor
  • Posts: 43
  • Country: fr
    • Retronik
Re: Open Source Oscilloscope, can it be done?
« Reply #62 on: September 21, 2017, 01:37:46 AM »
I think you are right  :-//
 

Offline NiHaoMike

  • Super Contributor
  • ***
  • Posts: 3380
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: Open Source Oscilloscope, can it be done?
« Reply #63 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.
Cryptocurrency has taught me to love math and at the same time be baffled by it.
 

Online cdev

  • Super Contributor
  • ***
  • Posts: 2554
  • Country: aq
  • [Personal Text]
Re: Open Source Oscilloscope, can it be done?
« Reply #64 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.
"What the large print giveth, the small print taketh away."
 

Offline ogden

  • Regular Contributor
  • *
  • Posts: 110
Re: Open Source Oscilloscope, can it be done?
« Reply #65 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 »
 

Online cdev

  • Super Contributor
  • ***
  • Posts: 2554
  • Country: aq
  • [Personal Text]
Re: Open Source Oscilloscope, can it be done?
« Reply #66 on: October 08, 2017, 09:48:31 AM »
We have to remember how cheap they are- as little as $7 shipping included.
"What the large print giveth, the small print taketh away."
 

Offline JohnG

  • Regular Contributor
  • *
  • Posts: 66
  • Country: us
Re: Open Source Oscilloscope, can it be done?
« Reply #67 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
 

Offline ogden

  • Regular Contributor
  • *
  • Posts: 110
Re: Open Source Oscilloscope, can it be done?
« Reply #68 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

  • Contributor
  • Posts: 15
  • Country: us
Re: Open Source Oscilloscope, can it be done?
« Reply #69 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

  • Super Contributor
  • ***
  • Posts: 3380
  • Country: us
  • "Don't turn it on - Take it apart!"
    • Facebook Page
Re: Open Source Oscilloscope, can it be done?
« Reply #70 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.
Cryptocurrency has taught me to love math and at the same time be baffled by it.
 

Offline ogden

  • Regular Contributor
  • *
  • Posts: 110
Re: Open Source Oscilloscope, can it be done?
« Reply #71 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

  • Contributor
  • Posts: 15
  • Country: us
Re: Open Source Oscilloscope, can it be done?
« Reply #72 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).
 

Offline ogden

  • Regular Contributor
  • *
  • Posts: 110
Re: Open Source Oscilloscope, can it be done?
« Reply #73 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

  • Contributor
  • Posts: 15
  • Country: us
Re: Open Source Oscilloscope, can it be done?
« Reply #74 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!
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf