saadc oversampling

RE: saadc oversampling

JONATHAN LL — Tue, 05 Oct 2021 08:17:38 GMT

[quote user="sabsari"]Values fluctuate within a single digit range[/quote]

measured in mV this is a good result.

[quote user="sabsari"]BUT There are times when the value fluctuates significantly.[/quote]

how much is significantly ?

If the value fluctuation that is significant occurs as the same time that the CPU, Radio or some peripheral is doing something then there will be peaks and valleys on the VDD. So you will have to figure out if something else is going on during those significant fluctuations periods.

In addition you will also have to use the discharge curve of the battery that you are using. We only have it for CR2032.

You can also average with oversampling, by having buffer size 1 and oversampling 16, then only one value will be written to the buffer anyways.

Regards,
Jonathan

RE: saadc oversampling

sabsari — Tue, 05 Oct 2021 04:35:20 GMT

Values fluctuate within a single digit range.BUT There are times when the value fluctuates significantly.

I also tried to derive the remaining battery capacity through the average value by setting the buffer to 1.However, the remaining battery capacity is not constant due to the large splashing values.

Should we process additional signals?

RE: saadc oversampling

JONATHAN LL — Mon, 04 Oct 2021 14:28:46 GMT

Hello,

How much does the values fluctuate ?

Maybe consider adding in some signal processing in addition.

Oversampling is good at reducing white noise, but there are other factors that contribute to fluctuations. Like for example if the radio is used while the SAADC is taking samples, it will lower the voltage a bit.

We do have some older cases here on Devzone that you can look at also:
nRF52832 SAADC sampling - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)
SAADC oversampling sampling interval? - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com)

Regards,
Jonathan