We have a device that is using the nrf_drv_csense module to measure a capacitive touch via the event_handler passed to nrf_drv_csense_init(). Unfortunately, due to various limitations and miscommunications, the signal we are detecting is somewhat small. I was able to create a solution that works for us, but I did notice a strange interaction between the USB and this csense module.
Namely, when the USB would reset, I would see a drop in the read values, which would eventually equalize back to their original values after the USB had fully enumerated.
This drop wasn't very large. Maybe 10-15 units. However, since the signal we were detecting was relatively small, this did require us to discard measure values during a USB re-enumeration.
At first, we thought this may be a hardware issue. Perhaps there was some crosstalk between the USB lines and the capacitive sensor. However, after investigating, this seemed unlikely. And I removed the capacitive touch plate from our board, isolated it as best I could, and still observed a distinct drop is measured values after a USB reset, even though I could not visually see any change to the signal from an oscilloscope.
Does anyone know of any potential cause for this behavior?
Thanks.
