The ATmega328P ADC input pins are available in the J203 header.
AREF is available in J200 pin 8.
| J203 Pin | ATmega328P Pin | Function |
|---|---|---|
| 1 | PC0 | ADC Input Channel 0 |
| 2 | PC1 | ADC Input Channel 1 |
| 3 | PC2 | ADC Input Channel 2 |
| 4 | PC3 | ADC Input Channel 3 |
| 5 | PC4 | ADC Input Channel 4 |
| 6 | PC5 | ADC Input Channel 5 |