nRF52 SAADC burst sampling

RE: nRF52 SAADC burst sampling

Kenneth — Thu, 11 Mar 2021 11:54:42 GMT

You can read of the different modes of operation here:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/saadc.html#saadc_operationmodes

There is no automatic retrigger no, but I assume you can setup a timer to trigger the sample task for instance every 100us using ppi from a timer compare event -> sample task, and then if the saadc buffer is for instance 100bytes, you only need to handle the data every 100us * 50 = 5ms in the saadc callback handler (every sample take up 2bytes of the buffer). You should get 100kHz this way.

Figure 4 should show how this can be done, only thing missing from that figure is the ppi channel is triggering the sample task from a timer. The end event can trigger the saadc callback so you may handle the data and prepare a new pointer to next buffer that should be used by the saadc.

Kenneth

RE: nRF52 SAADC burst sampling

Andreas52 — Thu, 11 Mar 2021 10:39:25 GMT

Thanks for clarification. So, there is no automatic retrigger of a next sample task with a DONE event. Is there an example sketch available to see the maximum sample rate for one input channel? Do I need to wait for the DONE event before calling SAMPLE task again?

RE: nRF52 SAADC burst sampling

Kenneth — Mon, 08 Mar 2021 14:57:57 GMT

Hi,

If you set MAXCNT to 2, then you need to call SAMPLE task two times before END event will trigger. You may get DONE events for each sample.

Kenneth