I am working on a capacitive sensing application using the SAADC module and csense code on the nRF52 DK (SDK v14.2). I use the recommended hardware configuration, with a charging output P0.26 connected to each pad through 100k resistors, and each pad wired to an ADC input (please see setup below).
I have all eight ADC pins responding to touch correctly when the board is powered via USB connection. However, when I switch to battery using the same hardware configuration (coin cell on DK, also LiPo on a custom board I am testing), I am unable to get a consistent (or barely any) response on any of the pins.
It appears that the change in capacitance from touch is dramatically reduced when on battery, and setting the threshold to lower values does not help to fix. Is there any workaround for this? Any information on running csense code from CR2032/LiPo instead of USB power? I found this thread that seemed to reference the same issue but no solution was provided: https://devzone.nordicsemi.com/f/nordic-q-a/31114/problem-of-capacitive-sensor-output-on-nrf52-dk-board
Thank you
