SAADC on NRF52832 returns strange values intermittent

[Mike]

Hi,

I see intermittent incorrect values from the saadc. The code is described here.

The graf shows battery voltage in mV over about 4 days with one sample per minute. Note the 3 samples that are off. I'm aware that there's no calibration done in the code, but I suspect that has nothing to do with this (the periodic fluctuations are well correlated to the temperature).

Am I doing something wrong?

Thanks, Mike

[Jørgen Holmefjord]

It might be caused by ground bounce internally on the nRF52832, which would not be picked up by the other ADC. Could you try measuring differentially, by connecting GND to one of the AIN pins and set:

ch.pin_n = NRF_SAADC_INPUT_AINx;

Where x is the Analog input number.