33.6.5 Differential and Single-Ended Conversions

The ADC has two conversion options: differential and single-ended:
  • If the positive input may go below the negative input, the differential mode should be used in order to get correct results.
  • If the positive input is always positive, the single-ended conversion should be used in order to have full 12-bit resolution in the conversion.

The negative input must be connected to ground. This ground could be the internal GND, IOGND or an external ground connected to a pin. Refer to the Control B (CTRLB) register for selection details.

If the positive input may go below the negative input, creating some negative results, the differential mode should be used in order to get correct results. The differential mode is enabled by setting DIFFMODE bit in the Control B register (CTRLB.DIFFMODE). Both conversion types could be run in single mode or in free-running mode. When the free-running mode is selected, an ADC input will continuously sample the input and performs a new conversion. The INTFLAG.RESRDY bit will be set at the end of each conversion.