Products > Test Equipment
Building my own scope
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pcprogrammer:
Here are some threads on this forum

https://www.eevblog.com/forum/testgear/a-high-performance-open-source-oscilloscope-development-log-future-ideas/
https://www.eevblog.com/forum/chat/500-mhz-8b-2gss-oscilloscope/

The first one shows what it takes and it was never finished due to not having the time to work on it anymore.

This kind of development takes a lot of time and money for something better than store bought.

As a learning project I would suggest cheaper modules that do at max 100MSa/s and a simple FPGA connected to a simple MCU.

I started a project to make both a scope and a function generator. Due to shifting interests I left it as is, after finishing the FPGA part for the function generator. Might continue with it someday. https://github.com/pecostm32/Lichee_Nano
ledtester:
Saw this listing on ebay:

https://www.ebay.com/itm/114051630870

Probably doesn't have the specs you want but still could be interesting because there seems to be rather extensive documentation about how it works here:

https://earthpeopletechnology.com/digital_storage_oscilloscope_dso_100m
balnazzar:

--- Quote from: nctnico on October 20, 2022, 12:05:23 pm ---You might want to start with something that already works and go from there. Maybe the AD2 is suitable. An alternative is to use your existing oscilloscope as an acquisition device and do data processing on a PC.

--- End quote ---

You mean for building the custom scope?
balnazzar:
Yours was quite an informative reply, thanks.


--- Quote from: pcprogrammer on October 20, 2022, 12:09:52 pm ---
For that kind of money there are acceptable scopes to be bought, but it depends on your demands on it if you can like it.


--- End quote ---

Uh, I wrote extensively about that in other threads, for example the one baout bode plotting on a MSO5K. Essentially, I'm bothered by acoustical noise (1104x-e) and front end noise (MSO5000). USB scopes starting with 100 MHz and 1 GSa/s are expensive (the pico is near 1500 eur).


--- Quote from: pcprogrammer on October 20, 2022, 12:09:52 pm ---On the other hand, sticking modules together and throwing some open source software in it, will not be much of a learning experience in my eyes. Writing your own FPGA code for the acquisition bit and the software to process the samples will, but it involves a lot of knowledge.


--- End quote ---

That's the problem. I don't even know where to start. I don't have any experience with the FPGAs, and the discussions here are generally between people who already have a lot of expertise about them.


--- Quote from: pcprogrammer on October 20, 2022, 12:09:52 pm ---
This also depends on what you need. If 1 GSa/s and 8 bit is enough then there are more then enough ADC's out there, but getting a module to stick it to a zynq board becomes much harder.


--- End quote ---

Mh, can you give me some links to shops where I can buy the ADCs? TBH, I was hoping to get something a bit better than 8 bit.
Also, what do you mean by saying that it will be hard to stick them to the FPGA board? Aren't there some standards for connection? Pardon my ignorance!


--- Quote from: pcprogrammer on October 20, 2022, 12:09:52 pm ---
A four channel ADC board for in the PC with high speed will be expensive too.


--- End quote ---

I see. But expensive like how much? Consider that in going along that way I'll spare the money for the FPGA board...


--- Quote from: pcprogrammer on October 20, 2022, 12:09:52 pm ---
I dabble with this kind of things for fun

--- End quote ---

Maybe you can point me towards some learning resources. It's true that there are plenty of threads about such stuff here, but they are a bit over my current level of competence...

Thanks!
balnazzar:

--- Quote from: 2N3055 on October 20, 2022, 12:13:38 pm ---
Of course you need FPGA. It's hosting triggering, data transfers from ADCs, memory transfers etc. It guarantees scope will sample at regular intervals and will have enough data BW to do so. ADC is only a dummy device doing conversions. Scope is in a FPGA...
And then there is a matter of scope front end before ADC.
Scope is much different than sound card..

Read on the subject first.
And soon enough you will start to realize that even cheapest scopes are marvel of engineering and very sophisticated devices..

--- End quote ---

As a matter of fact, I'd like to build one precisely because they are fascinating pieces of engineering.

Anyway.. It's a bit difficult to find the information I need. I'm delving into the forum, but like I said to the other user above, the discussions are a bit over my current level of knowledge.

You said that the heavy lifting is done by the FPGA. Ok, I have two questions then:

1. If I stick a PCIe frontend/ADC card into a desktop computer, can the computer do what the FPGA does in commercial scopes?

2. Do USB scopes have a FPGA board inside??

Thanks.
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