SAADC calibration doesn't generate DONE events consistently

[Andy]

Hi,

I'm working with the SAADC on an NRF52832. I'm using the SAADC driver from SDK15.2.

I have a problem with the calibration routine because it's generating DONE events inconsistently. Every time I get a done event, I queue a new buffer for conversion. The problem happens because I have an APP_ERROR_CHECK after the nrf_drv_saadc_buffer_convert call and this fails sometimes due to the done event generated by the calibration.

In my current implementation, this would consistently crash my application if the calibration triggered done events all the time, but it doesn't.

I "worked around" the problem by just removing the APP_ERROR_CHECK and allowing this call to fail sometimes due to random done events triggered by the calibration procedure.

My question is: Is there an actual pattern in which the calibration procedures triggers DONE events?

The documentation just states the following:

/**
 * @brief Function for triggering the ADC offset calibration.
 *
 * This function is non-blocking. The application is notified about completion by the event handler.
 * Calibration will also trigger DONE and RESULTDONE events.
 *
 * The function will fail if ADC is busy or calibration is already in progress.
 *
 * @retval NRFX_SUCCESS    If calibration was started successfully.
 * @retval NRFX_ERROR_BUSY If the ADC driver is busy.
 */

The sentence "Calibration will also trigger DONE and RESULTDONE events" to me sounds like it should ALWAYS trigger the events.

[Jørgen Holmefjord]

Hi,

The SAADC driver should not generate a DONE event to the application during offset calibration, the completion of the calibration is indicated by the CALIBRATEDONE event. The comment for the function refers to the HW events DONE and RESULTDONE, which are not used at all by the SAADC driver. The driver should only generate a DONE event to the application when an END event is generated by the SAADC peripheral HW.

Best regards,
Jørgen