I was expecting results to be noisy but around the same baseline. And I get that, both on the RP2040 and RP2350B, but only if I read the ADC at an interval shorter than 13 minutes.So, you are basically measuring a floating analog input, expecting consistent results.Open circuit, though the Pimoroni Pico Plus 2W I am using has an on-board in-line 1K between the pad and the GPIO40/ADC0 on the RP2350B.
This is the mystery; it all works as would be expected when reading the ADC at intervals shorter than 13 minutes but not with longer intervals.
I am not convinced it's related to the inputs floating because why would a floating input behave significantly differently depending on ADC read interval, giving consistently similar good readings with intervals under 13 seconds, but consistently escalating readings when the interval is greater than 13 minutes ?
The characteristics of the effect seen on the RP2350B appears exactly the same as on the RP2040, and it manifests itself on that when reading the temperature sensor. It reads perfectly fine, gives consistent readings, but leave it longer than 13 or so minutes and the first reading is significantly higher, a second and subsequent reading is back to what it was before that interval.
I am not sure if it's the same on the RP2350B, not sure if the MicroPython bug which prevented it being read has been fixed or not. I'll give it a go when I get the time.
Statistics: Posted by hippy — Wed Nov 20, 2024 9:25 pm