Purpose: ADC channels, multiplexer selections, references and modes.

Namespace: atmega2560::adc.

The ATmega2560 has a 10-bit ADC with 16 single-ended external inputs. ADC0–ADC7 map to PF0–PF7; ADC8–ADC15 map to PK0–PK7. MuxSelection contains every valid MUX5:0 encoding from datasheet Table 26-4.

#include <atmega2560/ADC.h>
 
namespace mcu = atmega2560;
 
static_assert(mcu::adc::external_channel_count == 16, "ATmega2560 ADC definition");
static_assert(static_cast<unsigned>(mcu::adc::MuxSelection::SingleEndedADC15) == 0x27, "ADC MUX definition");
static_assert(static_cast<unsigned>(mcu::adc::MuxSelection::DifferentialADC13_ADC10_Gain1) == 0x3D, "ADC differential MUX definition");

External channels and references

Channels	MCU pins
ADC0–ADC7	PF0–PF7
ADC8–ADC15	PK0–PK7

Reference encodings are AREF = 0, AVCC = 1, internal 1.1 V = 2, and internal 2.56 V = 3.

Multiplexer selections

MUX5:0	Selection
0x00–0x07	Single-ended ADC0–ADC7
0x08–0x0F	Differential ADC0/1 and ADC2/3 pairs, gain 10x or 200x
0x10–0x1D	Differential ADC0–ADC7 inputs, gain 1x, against ADC1 or ADC2
0x1E	Internal 1.1 V bandgap
0x1F	Ground
0x20–0x27	Single-ended ADC8–ADC15
0x28–0x2F	Differential ADC8/9 and ADC10/11 pairs, gain 10x or 200x
0x30–0x3D	Differential ADC8–ADC15 inputs, gain 1x, against ADC9 or ADC10
0x3E–0x3F	Reserved; not exposed as enum values

The datasheet gives expected resolutions of 8 bits at 1x and 10x, and 7 bits at 200x. The 10x and 200x differential gain settings should not be used below 2.7 V when the specified accuracy is required.

TriggerSource encodings map to ADTS2:0. MuxSelection encodings map to MUX5:0, with MUX5 located in ADCSRB and MUX4:0 in ADMUX.

These are hardware definitions, not runtime register access or initialization.

Source: ATmega2560 datasheet (DS40002211A), Sections 26.7–26.8, Table 26-4.