SAADC VDD Measurement with nRF52833

RE: SAADC VDD Measurement with nRF52833

Dominic — Thu, 03 Mar 2022 18:44:29 GMT

Thanks Jorgen, I tested this out before the network stack was initialized and the peripheral works as expected. The ticket can be closed.

RE: SAADC VDD Measurement with nRF52833

Jørgen Holmefjord — Fri, 25 Feb 2022 09:39:22 GMT

Hi,

I tested the above code in a standalone application on a nRF52833 DK, and it seems to be working as expected.

Did you test it on your end, without initializing the "network stack"? If it works without the stack, you should contact the developers of the stack to get help regarding how they use the SAADC peripheral.

You may also test the workaround from Errata 212, which will reset the whole SAADC peripheral, but I'm not sure how well the network stack will react if you mess with its configuration.

Best regards,
Jørgen

RE: SAADC VDD Measurement with nRF52833

Dominic — Fri, 25 Feb 2022 04:29:27 GMT

I think the issue is that on the nRF52833, the network stack is using a different SAADC channel to perform voltage measurement (Wirepas closed-source stack).

When I use SAADC channel 1 instead of channel 0 on the nRF52833, the code works as expected.

To test the theory I un-set the PSELP register on all channels to disable them before calling the above function.

Per the documentation: An analog input is selected as a positive converter input if CH[n].PSELP is set, setting CH[n].PSELP also enables the particular channel.

for(uint8_t i=0; i<8; i++)
{
    NRF_SAADC->CH[i].PSELP = 0;
}

But still, it only works on channel 1. Is there something else that needs to be done to load the register configuration?