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]

Vidar Berg said:

Also, you should read the sample result from the event pointer as shown in the ble_app_proximity example

In the ble_app_proximity they are also using nrf_drv_saadc_buffer_convert().

That also worked for me, but I don't need a buffer. I tried to figure out how nrfx_saadc_sample_convert() works, but it works different.

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 think I'm doing something wrong here:

val = m_sample * 3.3 / 4096;

Is there any example of using nrfx_saadc_sample_convert()?

[Vidar Berg]

Sorry, I read nrfx_saadc_sample_convert() as nrf_drv_saadc_buffer_convert(). But nrfx_saadc_sample_convert() is blocking and it does not make sense to call from the saadc handler. You can try to call nrfx_saadc_sample_convert() from main() after configuring the SAADC and see if that works.

[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.