ADC problem

Question

ADC problem

georgestheking opened this issue 2 years ago · comments

The PICO is buggy and has limitation following PICO HARDWARE DATASHEET.
One idea will be to use an external ADC like the MCP3204.

Best regards

Georges

redoxcode · Answer 1 · Thu Jan 12 2023 05:03:52 GMT+0800 (China Standard Time)

Can you elaborate on how 'the PICO is buggy'?

georgestheking · Answer 2 · Thu Jan 12 2023 05:41:42 GMT+0800 (China Standard Time)

Hi, A small problem for the ADC : https://www.hackster.io/news/raspberry-pi-confirms-it-is-investigating-a-flaw-in-the-raspberry-pi-pico-rp2040-adc-95c393b55dfb Best regards Georges Le mer. 11 janv. 2023 à 22:04, redoxcode ***@***.***> a écrit :

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Can you elaborate on how 'the PICO is buggy'? — Reply to this email directly, view it on GitHub <#214 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEWZCAJTZUZQIOPQ6M7WPX3WR4N4HANCNFSM6AAAAAATQA4VUE> . You are receiving this because you authored the thread.Message ID: ***@***.***>

redoxcode · Answer 3 · Thu Jan 12 2023 17:05:46 GMT+0800 (China Standard Time)

I am not sure if I understand this correctly, but from my calculations the ADC makes an error of +- 5.64 mV (measuring 0-3.3V) at it's worst.
So if the EuroPi hardware would map 10V to that range in a perfect way, that would be +- 17.09 mV.
I would not say it makes the PICO buggy. It just isn't able to reach it's full potential.
But since the behavior is systematic and understood there should be ways to compensate for that at least partially, if needed.
I think the PICOs ADC with the bug compares to a 11.99 bit ADC. So an external 12 bit ADC isn't that much of an improvement for a lot of added hardware complexity.

Rory Allen · Answer 4 · Sun Feb 12 2023 20:48:53 GMT+0800 (China Standard Time)

I understand the limitations with the inbuilt ADC of the Pico, but it is really too late to fix this now with the current hardware! Future hardware will almost certainly have external ADCs to allow there to be more of them as well, so I'll mark this as closed but know that it's on the list for future hardware improvements!