3 ms·

The ESP32 ADC is a dumpster fire. I used one to sample an analog signal at 8Khz, looking for 400uS wide pulses (pacemaker capture pulses.) I originally started

The ESP32 ADC is a dumpster fire. I used one to sample an analog signal at 8Khz, looking for 400uS wide pulses (pacemaker capture pulses.) I originally started with an interrupt that triggered conversion from software. It would completely miss pulses 10-20% of the time and instead drift around, as if the ADC was floating rather than connected to anything. I finally got it to work reliably by switching to DMA through the I2S peripheral. Pretty much every hobby project I look at, people complain about how bad the ADC is, and then just proceed to take N samples and average them. It's not that the ADC is bad, it's that the underlying firmware is buggy. I suspect there's a race condition with the main CPU and a coprocessor that's using the ADC for some internal wifi stuff.

rkagerer 4y ago
Yeah I felt that pain :-). On the ESP32-S3 ADC2 is shared with Wifi, but I don't think that's the case for ADC1. I made headway by throwing away all their boilerplate code and setting up the raw peripheral registers myself. I actually prefer it that way without all the abstraction underneath. Was getting nice results at 80kHz sample rate. Would love to turn it into a write-up as I'm not sure anyone has done this before with that chip (at least I couldn't find any sample code around). It's actually all in MicroPython at the moment to boot... but wouldn't be hard to convert to C (and might even clean things up due to the more natural fit of that language working with bitfields). What I'd really like is to make it into a DMA-based ADC module for MicroPython but I'm not familiar enough with compiling that platform from scratch, particularly on Windows.
- matthewfcarlson 4y ago
  If you do end up writing it up, consider dropping it in the hackaday tip line (https://hackaday.com/submit-a-tip/ https://hackaday.com/submit-a-tip/). It sounds incredibly useful.

rkagerer 4y ago

Yeah I felt that pain :-). On the ESP32-S3 ADC2 is shared with Wifi, but I don't think that's the case for ADC1. I made headway by throwing away all their boilerplate code and setting up the raw peripheral registers myself. I actually prefer it that way without all the abstraction underneath. Was getting nice results at 80kHz sample rate. Would love to turn it into a write-up as I'm not sure anyone has done this before with that chip (at least I couldn't find any sample code around). It's actually all in MicroPython at the moment to boot... but wouldn't be hard to convert to C (and might even clean things up due to the more natural fit of that language working with bitfields). What I'd really like is to make it into a DMA-based ADC module for MicroPython but I'm not familiar enough with compiling that platform from scratch, particularly on Windows.

matthewfcarlson 4y ago
If you do end up writing it up, consider dropping it in the hackaday tip line (https://hackaday.com/submit-a-tip/ https://hackaday.com/submit-a-tip/). It sounds incredibly useful.