nrfx_saadc_sample_convert

[Juniorprogrammer]

Hi,

I was using the nrfx_saadc_buffer_convert to make everytime a single sample.

void saadc_init(void)
{
  ret_code_t  err_code;
   
  nrf_saadc_channel_config_t channel_config = NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN2);

  err_code = nrf_drv_saadc_init(NULL, saadc_callback_handler);
  APP_ERROR_CHECK(err_code);

  err_code = nrfx_saadc_channel_init(0, &channel_config);
  APP_ERROR_CHECK(err_code);

  err_code = nrfx_saadc_buffer_convert(m_buffer_pool[0], SAMPLE_BUFFER_LEN);
  APP_ERROR_CHECK(err_code);

  err_code = nrfx_saadc_buffer_convert(m_buffer_pool[1], SAMPLE_BUFFER_LEN);
  APP_ERROR_CHECK(err_code);
}

Now I did find out there is also nrfx_saadc_sample_convert. How do I initialize this?

And do I get my val then by val = p_event->data.done.p_value instead of val = p_event->data.done.p_buffer[i]

[Juniorprogrammer]

void saadc_callback_handler(nrf_drv_saadc_evt_t const * p_event)
{
  float val;

  if(p_event -> type == NRFX_SAADC_EVT_DONE)
  {
    ret_code_t err_code;
    uint8_t data[20];

    err_code = nrfx_saadc_sample_convert(0, &m_sample);
    APP_ERROR_CHECK(err_code);
  
    val = m_sample * 3.3 / 4096;
    
    sprintf((char*)data, "ADC: %.2f", val);
    uint16_t d_len   = strlen(data);
    err_code = ble_nus_data_send(&m_nus, data, &d_len, m_conn_handle); 
    APP_ERROR_CHECK(err_code);

  }
}

void saadc_init(void)
{
  ret_code_t  err_code;
   
  nrf_saadc_channel_config_t channel_config = NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_SE(NRF_SAADC_INPUT_AIN2);

  err_code = nrf_drv_saadc_init(NULL, saadc_callback_handler);
  APP_ERROR_CHECK(err_code);

  err_code = nrfx_saadc_channel_init(0, &channel_config);
  APP_ERROR_CHECK(err_code);

  err_code = nrfx_saadc_sample_convert(0, &m_sample);
  APP_ERROR_CHECK(err_code);

  //err_code = nrfx_saadc_buffer_convert(m_buffer_pool[0], SAMPLE_BUFFER_LEN);
  //APP_ERROR_CHECK(err_code);

  //err_code = nrfx_saadc_buffer_convert(m_buffer_pool[1], SAMPLE_BUFFER_LEN);
  //APP_ERROR_CHECK(err_code);
}

I tried this but don't get any value.

[Vidar Berg]

Have you verified that the calback is invoked with the NRFX_SAADC_EVT_DONE? Also, you should read the sample result from the event pointer as shown in the ble_app_proximity example.

[Juniorprogrammer]

Yes, I think that was the matter. I did make it an empty handler and call the function in my application timer. It works now. 

What is the difference between blocking and non-blocking mode? Does it have effect on the bluetooth functionality? 

[Vidar Berg]

The blocking call will return the sampled SAADC reading and not trigger any SAADC interrupts. Unlike the non-blocking call which will only trigger the sampling task and return immediately (competition of this task is notified through the interrupt handler).

And no, it will not affect Bluetooth. But try to avoid using it from an interrupt context.

[Juniorprogrammer]

I'm now using an application timer (every 1 second) to call the nrfx_saadc_sample_convert() and get my sample value. Is this a way to do it?

[Vidar Berg]

Yes, I think this is an OK way to do it.

[Juniorprogrammer]

Thanks Vidar!