SAADC callback never called.

RE: SAADC callback never called.

Edvin — Thu, 07 Jun 2018 08:23:35 GMT

Hello,

I agree that it is not very intuitive. But it says on infocenter, and in nrf_drv_saadc.h (line 140) that the NRF_DRV_SAADC_EVT_DONE event is generated when the buffer is filled with samples. But to stumble upon that description is rather random 🙂

Best regards,

Edvin

RE: SAADC callback never called.

fab — Wed, 06 Jun 2018 13:30:36 GMT

Hi Edvi,

Thank you.

If SAMPLES_IN_BUFFER is equal to n, I have to call nrf_drv_saadc_sample() n times to get the callback been called.

I usually use a fast timer and ppi to start the saadc and so far I haven't realized that n saadc external activations are required to fill the buffer.

Changing the timer interval to 2000ms in the saadc sample, the callback is called about every 10s (2000ms x 5). I simply thought that a sigle saadc activation was enough to automatically fill the buffer up.

I think this behavior should be better documented in the SDK.

Regards,

Fab.

RE: SAADC callback never called.

Edvin — Wed, 06 Jun 2018 12:04:33 GMT

Hello,

What is your SAMPLES_IN_BUFFER size?

If this is greater than 1, and you only call nrf_drv_saadc_sample() once, it will not trigger the event. If you look in the saadc example in the SDK, you will see that it sets up a timer with the saadc to call the sampling function on regular intervals in the function saadc_sampling_event_init(). It uses the ppi, so it is a bit cryptic to read.

Try to change your SAMPLES_IN BUFFER to 1, and you should see the event.

Best regards,

Edvi