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Joined: Fri Jan 27, 2023 3:52 pm

External ADC (PIO i think?)

Fri Jan 27, 2023 3:58 pm

Hi guys. I've purchased an external ADC (iCE40-ADC) to try and make a high-frequency oscilloscope. I do have some experience with arduinos, and a bit of experience with the Pi Pico but nowhere near enough for this. I saw a guy who did it but his explanation was very superficial. Below are links to the ADC and the schematic, which makes zero sense to me. I also linked the place i saw someone do this. Any advice on how to wire this thing would be much appreciated. ... DC/6580751 ... _Rev_A.pdf ... ython/5669


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Joined: Tue Jun 30, 2015 1:35 pm

Re: External ADC (PIO i think?)

Sat Jan 28, 2023 8:18 am

You should ask that question to OLIMEX!

Posts: 501
Joined: Mon Aug 19, 2019 9:56 pm

Re: External ADC (PIO i think?)

Sat Jan 28, 2023 12:19 pm

This is a parallel ADC, so its data output is on 8 lines, that you need to connect to inputs on the Pico. You also need to wire up a clock signal that triggers the conversions, that must be between 20 and 100 MHz, and ground gpio pin 23 (see the circuit diagram) to select the device.

As to which Pico pins to use, the best option is to ask the person who posted that project for a wiring diagram, or just a list of point-to-point connections.

You need to be aware of some limitations of the resulting 'oscilloscope'. Most importantly, the ADC input on that board is low impedance (50 ohms) so you can't just connect up a high-impedance scope probe and expect it to work - you'll see nothing. Secondly, the input is AC-coupled, so lower frequencies (and DC) will be filtered out, which could be a real nuisance. Thirdly, the minimum ADC capture rate is 20 MHz, so it'll fill up the available Pico RAM really quickly.

However, if you can cope with these limitations, it looks like an interesting project.

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