30.3.1 Initialization

The following steps are recommended to initialize the ADC operation:
  1. Configure the resolution by writing to the Resolution Selection (RESSEL) bit in the Control A (ADCn.CTRLA) register.
  2. Optional: Enable the Free-Running mode by writing a ‘1’ to the Free-Running (FREERUN) bit in ADCn.CTRLA.
  3. Optional: Configure the number of samples to be accumulated per conversion by writing the Sample Accumulation Number Select (SAMPNUM) bits in the Control B (ADCn.CTRLB) register.
  4. Configure a voltage reference by writing to the Reference Selection (REFSEL) bit in the Control C (ADCn.CTRLC) register. The default is the internal voltage reference of the device (VREF, as configured there).
  5. Configure the CLK_ADC by writing to the Prescaler (PRESC) bit field in the Control C (ADCn.CTRLC) register.
  6. Configure an input by writing to the MUXPOS bit field in the MUXPOS (ADCn.MUXPOS) register.
  7. Optional: Enable Start Event input by writing a ‘1’ to the Start Event Input (STARTEI) bit in the Event Control (ADCn.EVCTRL) register. Configure the Event System accordingly.
  8. Enable the ADC by writing a ‘1’ to the ENABLE bit in ADCn.CTRLA.

Following these steps will initialize the ADC for basic measurements, which can be triggered by an event (if configured) or by writing a ‘1’ to the Start Conversion (STCONV) bit in the Command (ADCn.COMMAND) register.