You can connect the headers for I2C, UART, SPI connections. The 5V and 3.3 V power output are also available here. Meanwhile, there are several pins free for GPIO pins for your specific usage.
| CON3 | Pin Name | Multiplex Function Select | GPIO |
|---|---|---|---|
| Multi 1 | Multi 2 | ||
| Pin 1 | 3.3V1 | VCC-3V3 | |
| Pin 2* | 5.0V1 | VCC-5V | |
| Pin 3 | SDA | TWI2-SDA | PB21 |
| Pin 4* | 5.0V2 | VCC-5V | |
| Pin 5 | SCL | TWI2-SCK | PB20 |
| Pin 6 | GND3 | GND | |
| Pin 7 | IO-GCLK | GPCLK | PI3 |
| Pin 8 | TXD0 | UART3-TX | PH0 |
| Pin 9 | GND1 | GND | |
| Pin10 | RXD0 | UART3-RX | PH1 |
| Pin11 | IO-0 | IO-0(UART2-RX) | PI19 |
| Pin12 | IO-1 | IO-1 | PH2 |
| Pin13 | IO-2 | IO-2(UART2-TX) | PI18 |
| Pin14 | GND4 | GND | |
| Pin15 | IO-3 | IO-3(UART2-CTS) | PI17 |
| Pin16 | IO-4 | IO-4(CAN_TX) | PH20 |
| Pin17 | 3.3V2 | VCC-3V3 | |
| Pin18 | IO-5 | IO-5(CAN_RX) | PH21 |
| Pin19 | SPI-MOSI | SPI0_MOSI | PI12 |
| Pin20 | GND5 | SPI0_GND | |
| Pin21 | SPI-MISO | SPI0-MISO | PI13 |
| Pin22 | IO-6 | IO-6(UART2_RTS) | PI16 |
| Pin23 | SPI-CLK | SPI0_CLK | PI11 |
| Pin24 | SPI-CE0 | SPI0_CS0 | PI10 |
| Pin25 | GND2 | GND | |
| Pin26 | SPI-CE1 | SPI0_CS1 | PI14 |