How to read the same ADC channel multiple times in a very short time in the app timer timeout callback function?

RE: How to read the same ADC channel multiple times in a very short time in the app timer timeout callback function?

run_ar — Mon, 06 Jan 2020 09:01:41 GMT

Glad to hear that solved your problem, and yes, it was much likely a interrupt priority issue.

The recommendation to use app scheduler was meant for the whole application. Please be aware there is a known limitation with the app timer, see here: https://devzone.nordicsemi.com/f/nordic-q-a/34155/what-are-sdk-15-x-0-known-issues

Linking to the overview for reference, search for app_timer to fine the limitation.

RE: How to read the same ADC channel multiple times in a very short time in the app timer timeout callback function?

w52918 — Fri, 03 Jan 2020 22:21:36 GMT

Hi,

I used the scheduler to do it, and everything works fine! Thanks!

I think it's priority problem that app timer has higher priority than ADC. That's why adc callback function only called one time.

RE: How to read the same ADC channel multiple times in a very short time in the app timer timeout callback function?

w52918 — Fri, 03 Jan 2020 19:28:16 GMT

Hi,

When you say app scheduler, you mean I can use it for all tasks or just for reading the 4 pressure sensors.

And u_adc_start_sampling() does nothing but just calls nrf_drv_saadc_sample().

void u_adc_start_sampling(void) {
    nrf_drv_saadc_sample();
}

Should I manually clear the ADC busy flag or something?

RE: How to read the same ADC channel multiple times in a very short time in the app timer timeout callback function?

run_ar — Fri, 03 Jan 2020 13:21:54 GMT

Hi,

Have you considered using the app scheduler instead? i.e. this way you can keep your interrupt routines short and do the work in main context after you exit the interrupt?

Also not sure what you do in µ_adc_start_sampling();