How to Calibrate SAADC for temperature compensation Example code

[adnan arshad]

Hi,

I want to calibrate SAADC for temperature compensation please guide me with example.

[adnan arshad]

I have used the following example and the issue is that after calibration done the first sample of saadc read is in -ive value or some thing 1,2,3,5,6 etc which is for more away from the actual value 1622-1630.

https://github.com/NordicPlayground/nRF52-ADC-examples/blob/master/saadc_low_power/main.c

[Kenneth]

Can it be related to this?
https://infocenter.nordicsemi.com/topic/errata_nRF52832_Rev2/ERR/nRF52832/Rev2/latest/anomaly_832_86.html#anomaly_832_86 

I think the example I linked already handle this as described.

[adnan arshad]

Thanks Kenneth,

Please refer to some example code of doing this remedy.

[Kenneth]

The first link I shared contain an example that does this. Check out directly link (answer to question 5):
https://devzone.nordicsemi.com/f/nordic-q-a/39454/calibrating-saadc-on-nrf52832/152901#152901 

Kenneth

[adnan arshad]

Dear Kenneth,

I have followed this 

https://devzone.nordicsemi.com/f/nordic-q-a/34785/saadc---calibration

and my code snipped is 

if(saadc_calibrate == true)
{
while(nrf_drv_saadc_calibrate_offset() != NRF_SUCCESS); //Trigger calibration task
nrf_saadc_disable();
while(NRF_SAADC->STATUS == (SAADC_STATUS_STATUS_Busy << SAADC_STATUS_STATUS_Pos));
nrf_saadc_enable();
while(NRF_SAADC->STATUS == (SAADC_STATUS_STATUS_Busy << SAADC_STATUS_STATUS_Pos));

SEGGER_RTT_printf(0, "Calibration Done\n\r");
saadc_calibrate = false;
}

But still the first wrong sample issue persists.

[adnan arshad]

I have also followed the following example

https://devzone.nordicsemi.com/f/nordic-q-a/32982/can-t-stop-saadc/127645#127645

it causes all the 5 samples to be corrupted after calibration.

[adnan arshad]

I have tried this link and found the issue of my problem.

https://devzone.nordicsemi.com/f/nordic-q-a/48462/questions-on-saadc-calibration-gain-best-use