Capacitive Touch on the nRF52 series

RE: Capacitive Touch on the nRF52 series

user79998 — Wed, 25 Aug 2021 12:47:39 GMT

Hello

I think the "Important updates" on top of this article sends a mixed message.

- The first bullet says that we should not use the COMP/Isource/relaxation oscillator method due to error in the Isource / comp.

- The second bullet says that we should use the new capacitive sensor driver and capacitive sensor library.

However, according to the errata for nrf52832 Rev 2, it looks like the Isource / comp issue is still active. At the same time, the new capacitive sensor driver looks like it is relying on COMP/Isource/relaxation.

We want to equip an nRF52832 with a capacitive sensors (that also should work outside of room temperature). Is the correct way forward to ignore the new capacitive sensor driver and instead do a custom RC charge time implementation?

RE: Capacitive Touch on the nRF52 series

user91813 — Thu, 09 Jul 2020 17:10:43 GMT

Here's the source file from the last comment.[View:/cfs-file/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0de7b43c-db1f-4b2a-964d-dffe3daee0af/nrf_5F00_drv_5F00_csense.c.txt:320:240]

RE: Capacitive Touch on the nRF52 series

user91813 — Thu, 09 Jul 2020 17:08:59 GMT

Given that COMP: ISOURCE is not functional. I was able to add a separate GPIO with series 1M resistor to stimulate the pad with the newer capacitor sensor driver. This is the case where you set USE_COMP to 1. I like this method because it uses MCU peripheral hardware to offload the CPU the most and can handle the complex timing. I've attached the driver file from SDK16.0 with modifications to get the same ISOURCE functionality with a relaxation oscillator.