Running SAADC in continuous mode without timer/ppi trigger

[pamo]

Hi All,

I have problem running nRF5340 in continuous mode without any external trigger (timer/ppi). I would like to setup SAADC so that last conversion triggered new set of conversions.

I'm using nrfx_saadc_advanced_mode_set function with internal_timer_cc set to 0 and start_on_end to true. Then I setup two buffers (primary and secondary) and then call nrfx_saadc_mode_trigger.

With that configuration I get irq handler called with NRF_SAADC_EVENT_STARTED, but not get NRF_SAADC_EVENT_END which I believe should restart conversion with provided configuration.

Can you point me what I'm doing wrong?

[Jørgen Holmefjord]

Hi,

It would help to determine exactly what the problem if you could post the exact code you used for configuring the SAADC, but it sounds like you are missing a trigger of the sampling.

The advanced mode is mainly intended for use with PPI and external triggering of the sampling. Setting internal_timer_cc to 0 will disable continuous mode (the internal sampling timer in the SAADC peripheral).In the interrupt handler, the SAMPLE task is only triggered on STARTED event if continuous mode is enabled (in advanced mode). 

Setting start_on_end will only cause the driver to trigger the START task in the interrupt handler when the END event is received, if this is not set, you need to do this in the application through PPI (this is done to mitigate this issue). 

The SAMPLE task is triggered in the driver in simple mode, right away if no event handler is provided, or in the interrupt handler when the STARTED event is received. The SAMPLE task is also triggered in nrfx_saadc_mode_trigger() in advanced mode if no event handler is provided.

Do you require to use the advanced mode? Sounds like the simple mode may suit your requirements better.

Best regards,
Jørgen

[pamo]

I'm using advanced mode because I need to fill buffer with couple of samples from each channel. As I understand in simple mode I'm going to get only one sample per each channel.

I'm using nrfx_saadc_mode_trigger to trigger conversion, I forgot to mention that in previous post. Attaching code snippet might be hard as I'm doing stuff in different places of code.