Overview

The SAADC peripheral supports up to eight external analog inputs. It can be operated in one-shot mode with sampling under software control, or continuous mode with a programmable sampling rate.

The analog inputs can be configured as eight single-ended inputs, four differential inputs, or a combination of these. Each channel can be configured to select the following:

GPIO pins with names starting with AIN which have analog input function, see Pin assignments. Input range is 0 V to VDD.
VDD (divided down to a valid range using the programmable gain stage)
DVDD
AVDD

Channels can be sampled individually in one-shot or continuous sampling modes, or multiple channels can be sampled in sequence using scan mode. To improve noise performance, channels can be oversampled.

Oversampling can be done with either noise shaping or by accumulation and averaging.

Internally, the ADC is always a differential analog-to-digital converter. By default, it is configured with single-ended input in the register CH[n].CONFIG using the MODE field. In single-ended mode, the negative input will be shorted to ground internally.

In single-ended mode, the ADC internal ground is the same as the external ground that is used for measuring the reference voltage. Because of this, the ADC is sensitive to ground bounce on the PCB in single-ended mode. Differential measurement is recommended if this is of concern.