RE: NRF51 PPI: ADC event NRF_DRV_ADC_EVT_DONE not working?

Spritkopf — Tue, 25 Feb 2020 08:21:08 GMT

Hi. This confirms my suspicion. I will then stick to my current solution of stopping the timer in the ADC callback handler.

Thanks for the answer!

Cheers.

RE: NRF51 PPI: ADC event NRF_DRV_ADC_EVT_DONE not working?

Jørgen Holmefjord — Thu, 20 Feb 2020 15:13:17 GMT

Hi,

Your assumption is correct, NRF_DRV_ADC_EVT_DONE is an application event, only available in the driver/application. It cannot be used with PPI, which is a hardware peripheral.

The ADC in nRF51 does not support EasyDMA like SAADC in the nRF52 series, the buffer feature is a driver-feature. The hardware ADC peripheral will not generate any event when the buffer is filled, it will only generate the END event after each sample conversion.

You have two possible options:

Stop the timer in the ADC driver callback handler, when you receive the DONE event.
Use a third timer in count-mode, counting the number of END events from the ADC peripheral. Set the compare register to the desired number of samples, and configure PPI to stop the second timer when compare the event from the third timer is generated.

Best regards,
Jørgen