| ピン番 | 機能 | AVRポート | 全AVRポート機能 | 備考 |
| 1 | RESETn | RESETn | PC6 / PCINT14 / RESETn | ハマルと厄介なのでI/Oポートにはしない |
| 2 | MIDI IN | RXD | PD0 / PCINT16 / RXD | |
| 3 | MIDI OUT | TXD | PD1 / PCINT17 / TXD | |
| 4 | PD2 / PCINT18 / INT0 | |||
| 5 | PD3 / PCINT19 / OC2B / INT1 | |||
| 6 | PD4 / PCINT20 / XCK / T0 | |||
| 7 | +5V | VCC | VCC | |
| 8 | GND | GND | GND | |
| 9 | 20MHz | XTAL1 | PB6 / PCINT6 / XTAL1 / TOSC1 | |
| 10 | 20MHz | XTAL2 | PB7 / PCINT7 / XTAL2 / TOSC2 | |
| 11 | PD5 / PCINT21 / OC0B / T1 | |||
| 12 | PD6 / PCINT22 / OC0A / AIN0 | |||
| 13 | PD7 / PCINT23 / AIN1 | |||
| 14 | PB0 / PCINT0 / CLKO / ICP1 | |||
| 15 | PB1 / PCINT1 / OC1A | |||
| 16 | PB2 / PCINT2 / SS / OC1B | |||
| 17 | PB3 / PCINT3 / MOSI / OC2A | |||
| 18 | PB4 / PCINT4 / MISO | |||
| 19 | PB5 / PCINT5 / SCK | |||
| 20 | +5Va | AVCC | AVCC | |
| 21 | (+5Va) | AREF | AREF | |
| 22 | AGND | AGND | AGND | |
| 23 | PC0 / PCINT8 / ADC0 | |||
| 24 | PC1 / PCINT9 / ADC1 | |||
| 25 | PC2 / PCINT10 / ADC2 | |||
| 26 | PC3 / PCINT11 / ADC3 | |||
| 27 | PC4 / PCINT12 / ADC4 / SDA | |||
| 28 | PC5 / PCINT13 / ADC5 / SCL |
