In addition to the Xplained Pro Standard Extension Header, XMEGA A1U Xplained Pro has one additional header with spare signals that offers access to the I/O of the microcontroller which are otherwise not easily available elsewhere or might be favorable to have collected together. The header has a pitch of 2.54mm.
| Pin on header | XMEGA pin | Function | Shared functionality |
|---|---|---|---|
| 1 | PA0 | AREFA | EXT1 |
| 2 | PB0 | AREFB | |
| 3 | PB2 | DACB0 | |
| 4 | PB3 | DACB1 | |
| 5 | PA7 | ACA0OUT | EXT3 |
| 6 | PA6 | ACA1OUT | EXT2 |
| 7 | PB7 | ACB0OUT | EXT2 |
| 8 | PB6 | ACB1OUT | EXT2 |
| 9 | PC6 | CLOCKOUT (src) | EXT1, EXT2, EXT3, and LCD Connector |
| 10 | PC7 | CLOCKOUT (per) | EXT1, EXT2, EXT3, and LCD Connector |
| 11 | PE7 | EVOUT | EXT1 |
| 12 | - | - | GND |