Buffer order swap of SAADC used with NRF Mesh

RE: Buffer order swap of SAADC used with NRF Mesh

bivay — Fri, 03 Jul 2020 03:55:41 GMT

Sorry for late response, We are testing your solution again, and we found that node SAADC buffer not swapped since 2 days, may this work, we are observing this and let you know result.

RE: Buffer order swap of SAADC used with NRF Mesh

Jørgen Holmefjord — Wed, 01 Jul 2020 13:28:14 GMT

Can you post your project for a review and for me to reproduce the issue? There should not be any way (at least that I'm aware of) for a buffer swap to happen if this workaround is used, but it could be something else in your application that causes this.

RE: Buffer order swap of SAADC used with NRF Mesh

bivay — Wed, 01 Jul 2020 07:56:31 GMT

I have tried your solution, initially works well, but after few hours buffer get swapped.

I have tested with below conditions:

1) Used SAADC example of SDK with 1ms Interval of 5 adc, and sample buffer of 5

2) Used SAADC example of SDK with 1ms Interval of 5 adc, and sample buffer of 100

3) Added Brust On and oversampling to 4x with 1ms Interval of 5 adc, and sample buffer of 100

4) Your Solution Of START_EVENT with PPI (added on 3rd condition) with 1ms Interval of 5 adc, and sample buffer of 100

In all cases buffer get swapped after 5-6 hours of average.

Please help me to solve this issue.

RE: Buffer order swap of SAADC used with NRF Mesh

bivay — Wed, 01 Jul 2020 04:14:07 GMT

Thanks Your this solution, I have a doubt about this that I only have to change on nrfx_saadc.c to comment the line 128 ,

nrf_saadc_task_trigger(NRF_SAADC_TASK_START);

and add above solution in my application code.

Thank you

RE: Buffer order swap of SAADC used with NRF Mesh

Jørgen Holmefjord — Mon, 29 Jun 2020 09:43:14 GMT

Hi,

If you are referring to this solution with connecting END event to START task using PPI, this is not used in any SDK examples as far as I know.

The SDK SAADC example uses PPI to trigger the SAMPLE task, but this is what's causing the issue in the first place. You need to setup an additional PPI channel to trigger the START task on END event. Something like this should work:

nrf_ppi_channel_t saadc_buffer_swap_ppi_channel;
nrf_drv_ppi_channel_alloc(&saadc_buffer_swap_ppi_channel);
nrf_drv_ppi_channel_assign(saadc_buffer_swap_ppi_channel,
                           (uint32_t)&NRF_SAADC->EVENTS_END,
                           (uint32_t)&NRF_SAADC->TASKS_START);
nrf_drv_ppi_channel_enable(saadc_buffer_swap_ppi_channel);

When adding this to the application, you may also need to remove the triggering of the START task in the interrupt handler (nrfx_saadc.c:128 in SDK 16.0.0).

Best regards,
Jørgen