| 1 | CDC_TX | CDC UART transmit |
| 2 | CDC_RX | CDC UART receive |
| 3 | Power supply adjust | Analog output for power supply adjustment |
| 4 | VTG_ADC | Analog input for target voltage measurement |
| 5 | DBG0_RX | Receive signal for debug interface data |
| 6 | Reserved | Do not connect |
| 7 | DBG0_TX | Transmit signal for debug interface data |
| 8 | DBG1 | Debug interface clock |
| 9 | VDDANA | Analog voltage supply for SAMD21 |
| 10 | GNDANA | Analog ground for SAMD21 |
| 11 | DBG2_CTRL | Level shifter direction for DBG2 (DGI GPIO) |
| 12 | DBG2 | Data for DBG2 (DGI GPIO) |
| 13 | Power supply enable | Enable signal for power supply switch |
| 14 | VBUS_ADC | Analog input for USB VBUS measurement |
| 15 | DBG0_CTRL | Level shifter direction for DBG0 (debug data) |
| 16 | DBG1_CTRL | Level shifter direction for DBG1 (debug clock) |
| 17 | DBG3 RESET MCLR | Open-drain control for DBG3 (RESET ,MCLR ) |
| 18 | VTG_EN | Enable switch for target voltage |
| 19 | CDC_RX_CTRL | Level shifter direction for CDC RX |
| 20 | VOFF | External voltage detection |
| 21 | CDC_TX_CTRL | Level shifter direction for CDC TX |
| 22 | ID_SYS | ID system |
| 23 | USB_DM | USB data |
| 24 | USB_DP | USB data |
| 25 | BOOT | Force bootloader entry |
| 26 | RESET | Nano Debugger reset |
| 27 | LED | Status LED |
| 28 | GND | Ground |
| 29 | VDDCORE | SAMD21 core decoupling |
| 30 | VDDIN | SAMD21 VDD |
| 31 | SWCLK | SWCLK for debugging the Nano Debugger |
| 32 | SWDIO | SWDIO for debugging the Nano Debugger |
