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Author Topic: 4-channel 100 MHz 8-bit Open-everything Scope Project  (Read 669 times)

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Offline haastyle

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4-channel 100 MHz 8-bit Open-everything Scope Project
« on: October 12, 2017, 08:19:36 AM »
Hi all,
Wanted to spread the word and get some feedback on my new project, 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 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.

Comments / questions please!
 
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Online ataradov

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #1 on: October 12, 2017, 09:17:14 AM »
Is there a schematic? There does not seem to be any front end. What are input capabilities of this device?
Alex
 

Offline haastyle

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #2 on: October 12, 2017, 09:24:58 AM »
Check out the latest update:
https://www.crowdsupply.com/andy-haas/haasoscope/updates/latest-prototype

There's more of a front-end now. One op-amp and 2 gains per channel, with somewhat adjustable DC-offset.
 

Online JPortici

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #3 on: October 13, 2017, 02:14:32 AM »
It's still not very clear of what you want to accomplish :)
being an academic, is see why you think that a 100 MHz DSO is still 800$
nobody buys tek anymore ;)

stupid jokes aside, what do you want to do to make this better than say a picoscope? have you ever seen their software? it's amazing!
your onboard digital channels and separate slow-but-high res channels are an intriguing addition but there is still a lot to do..
looks promising though, i subscribed :)
 

Offline haastyle

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #4 on: October 13, 2017, 02:37:36 AM »
OK, maybe you can get a Rigol for $400. :)

I checked out picoscope: https://www.picotech.com/oscilloscope/2000/picoscope-2000-overview
They're not too cheap either. For _2_ channels, 25 MHz bandwidth, 200 MSPS, it's $199.
I'm shooting for $99 for _4_ channels, 100 MHz bandwidth, 125 MSPS.

Also, the main point is that mine is totally open-source (including firmware!). Picoscope and others I'm aware of don't let you easily play with the firmware. Why's that important? Access to the firmware gives you amazing flexibility. You can code up your own custom trigger, for instance. Make some custom combination of external input and some combination of ADC inputs, etc. It's also a great learning platform for students, etc.
Plus it's open hardware. People can adjust the board design, using a different ADC, or more powerful FPGA, or add RAM, more or fewer channels, add a DAC for waveform generation, whatever.

I think the ability to plug mine together for many channels is also a killer feature I haven't seen elsewhere. I have 3 plugged together on my desk right now, giving me 12 channels at 125 MSPS! :)

Thanks for subscribing!
 

Online ataradov

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #5 on: October 13, 2017, 03:24:44 AM »
What's the point of 125 MSPS and 100 MHz bandwidth?

Openness for a tool in a non-academic setting is mostly irrelevant. I want to use the tool, not dick around, and potentially introduce an error on a tool side, while simultaneously debugging my project.

I've seen some pen-style scopes that can be plugged together, but I would not call it a huge selling point.

The main thing I don't like here is a lack of a real frontend. It is not a scope, it is a data logger at best. And given its memory and bandwidth limitations, not even a good data logger.
Alex
 

Offline ebclr

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #6 on: October 13, 2017, 03:34:20 AM »
As a reference here a picture of the bescope, as you can see a lot of things are missing on your board, and this one is just USD 45 AT 250 MSPS

https://www.arrow.com/en/products/bescope/arrow-development-tools

« Last Edit: October 13, 2017, 03:44:59 AM by ebclr »
 

Offline haastyle

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #7 on: October 13, 2017, 03:38:21 AM »
By 100 MHz bandwidth I mean the "average" bandwidth. It depends on the op-amp output signal size, so depends on the signal you're looking at. Designing for 100 MHz gave me some margin of safety, so even if you are looking at +-4 V, you still have ~40 MHz bandwidth in the worst case and can make use of the 125 MSPS.

I disagree that openness is not useful to people outside academics. Look at the raspberry pi, arduino, Linux, etc. They're not just used at Universities.

To me the ability to get lots of channels does fill a niche. How else can you capture data from >4 inputs simultaneously?

I agree my front-end is bare-bones. But the point is to keep the cost minimal, while still having something usable.
 

Online ataradov

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #8 on: October 13, 2017, 03:41:52 AM »
so depends on the signal you're looking at.
What? That's some innovation right there. How on earth then you will know if signal is limited by your scope, or it is actually low, if scope BW depends on the signal level?

Designing for 100 MHz gave me some margin of safety, so even if you are looking at +-4 V, you still have ~40 MHz bandwidth in the worst case and can make use of the 125 MSPS.
Do you know how Nyquist theorem works?

Alex
 


Online ataradov

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #10 on: October 13, 2017, 03:45:17 AM »
It's quite hard to reinvent the wheel

2.4MSa/s, not even close to the goal of this project.

But I still don't know why I would need 8 channels of really chopped up signal.
Alex
 

Offline haastyle

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #11 on: October 13, 2017, 03:52:45 AM »
That BeScope board (thanks for the pointer!) is actually pretty close to the front-end I have now, as you can see here:
https://www.crowdsupply.com/andy-haas/haasoscope/updates/latest-prototype

They 3 gains, I have 2, but the design is pretty close.

Their board has only 2 channels, and no FPGA - that would be a separate board.

I'm amazed they can sell that board for $45 though... the ADC they use goes for ~$50 by itself!
http://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyAD9286BCPZ-500


 

Online JPortici

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #12 on: October 13, 2017, 04:57:40 AM »
OK, maybe you can get a Rigol for $400. :)

I checked out picoscope: https://www.picotech.com/oscilloscope/2000/picoscope-2000-overview
They're not too cheap either. For _2_ channels, 25 MHz bandwidth, 200 MSPS, it's $199.
I'm shooting for $99 for _4_ channels, 100 MHz bandwidth, 125 MSPS.

there is much more than just the hardware. i don't give a damn if i have more bandwidth but all i can do is look at the waveform ;) and software costs money too..

Quote
Also, the main point is that mine is totally open-source (including firmware!).
while this is good and everything you'll soon find out that giving something away won't automatically make a community grow around it.
How many users are there of open source projects and how many developers?
 

Online JPortici

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #13 on: October 13, 2017, 05:01:13 AM »
Openness for a tool in a non-academic setting is mostly irrelevant. I want to use the tool, not dick around, and potentially introduce an error on a tool side, while simultaneously debugging my project.

my thoughts exactly

But I still don't know why I would need 8 channels of really chopped up signal.

well, i usually have to look at slow signals (BW up to the 10-100 Hz) and i prefer to have resolution and accuracy over bandwidth. If a thing like this work and can be bought for less than what NI asks for...
 

Offline KNSSoftware

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #14 on: October 13, 2017, 05:08:45 AM »

I disagree that openness is not useful to people outside academics. Look at the raspberry pi, arduino, Linux, etc. They're not just used at Universities.


They are not test gear, they are development boards.  ataradov has a good point; the last thing you need on a project is wondering whether an issue is with your test gear, or the DUT.  That is why people spend large money, on having as much high end kit as possible.  It frees you to add as many known trusted constants as possible, leaving just the suspect variable.
 

Offline KNSSoftware

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #15 on: October 13, 2017, 05:14:02 AM »
Not only that, but Dave has done video before pointing out how devices should remain constant within themselves, and just characterized.  I recall one where he mentions calibration doesn't always mean adjusting the device, but adjusting your understanding of what reading you are getting.  If you keep playing with how your device is even producing a result, how can you compare previous and future readings?
 

Offline haastyle

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #16 on: October 13, 2017, 05:34:36 AM »
I'm not suggesting that people change the firmware every 30 minutes. But once you've modified it and tested/calibrated that it does what you want, it's stable.
I'm not trying to compete with a pro piece of gear. This is for the student / hobbyist market. Actually, it's also useful for scientific research, which tends to take place on a tight budget these days, but where people like to customize the hardware/firmware to do what they want.
 

Offline Mukrakiish

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #17 on: October 13, 2017, 07:06:02 AM »
I'm not suggesting that people change the firmware every 30 minutes. But once you've modified it and tested/calibrated that it does what you want, it's stable.
I'm not trying to compete with a pro piece of gear. This is for the student / hobbyist market. Actually, it's also useful for scientific research, which tends to take place on a tight budget these days, but where people like to customize the hardware/firmware to do what they want.

I think part of the types of responses you are getting are also akin to the forum you're posting this in. This is the EEVblog...mostly "get things done" type people who want the proven bit for extra cash than the starving student/academia who like to fiddle. You may just need to seek out a different crowd of peers better suited to what your developing. It somewhat reminds me of ExpEyes (www.expeyes.in).
 

Offline Bassman59

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Re: 4-channel 100 MHz 8-bit Open-everything Scope Project
« Reply #18 on: October 13, 2017, 07:17:19 AM »
stupid jokes aside, what do you want to do to make this better than say a picoscope? have you ever seen their software? it's amazing!

This.
 


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