3.2 I/O Expansion Headers
The Atmel AVR XMEGA-E5 Xplained headers J1, J2, J3, and J4 offer access to the I/Os of the microcontroller in order to expand the board, for example by mounting a top module onto the board.
The header J1 offers digital communication interfaces like UART, TWI, and SPI. The table below shows how the Atmel AVR XMEGA is connected to the header.
Note that when using TWI no pull-ups are mounted on the board from the factory, so it is required to enable the internal pull-ups of the device.
| Pin on J1 | Name on J1 | XMEGA pin | Shared with on-board functionality |
|---|---|---|---|
| 1 | SDA | PC0 | Connected to the Board Controller 1 |
| 2 | SCL | PC1 | Connected to the Board Controller 1 |
| 3 | RXD | PC2 | - |
| 4 | TXD | PC3 | - |
| 5 | SS | PC4 | Connected to the Board Controller 2 |
| 6 | MOSI | PC7 | Connected to the Board Controller 2 |
| 7 | MISO | PC6 | Connected to the Board Controller 2 |
| 8 | SCK | PC5 | Connected to the Board Controller 2 |
| 9 | GND | - | - |
| 10 | VCC_P3V3 | - | - |
Header J2 is connected to analog ports of the XMEGA as shown in the table below.
| Pin on J2 | Name on J2 | XMEGA pin | Shared with on-board functionality |
|---|---|---|---|
| 1 | ADC0 | PA0 | - |
| 2 | ADC1 | PA1 | - |
| 3 | ADC2 | PA2 | - |
| 4 | ADC3 | PA3 | - |
| 5 | ADC4 | PA4 | - |
| 6 | ADC5 | PA5 | Quadrature Encoder Button 3 |
| 7 | ADC6 | PA6 | Quadrature Encoder Output 4 |
| 8 | ADC7 | PA7 | Quadrature Encoder Output 4 |
| 9 | GND | - | - |
| 10 | VCC_P3V3 | - | - |
Header J3 is connected to digital ports of XMEGA. The table below shows the mapping of the XMEGA I/O to J3.
| Pin on J3 | Name on J3 | XMEGA pin | Shared with on-board functionality |
|---|---|---|---|
| 1 | GPIO0 | PR0 | Shared with OLED display: data/cmd function |
| 2 | GPIO1 | PR1 | Shared with OLED display: CS function |
| 3 | GPIO2 | QENC_A | Quadrature Encoder Output 5 |
| 4 | GPIO3 | QENC_B | Quadrature Encoder Output 5 |
| 5 | GPIO4 | PC4/ SS | |
| 6 | GPIO5 | PC7/MOSI | |
| 7 | GPIO6 | PC6/MISO | |
| 8 | GPIO7 | PC5/SCK | |
| 9 | GND | - | - |
| 10 | VCC_P5V0 | - | - |
Header J4 offers digital communication interfaces such as UART and TWI, but care must be taken because some pins are also connected to on-board peripherals.
| Pin on J4 | Name on J4 | XMEGA pin | Shared with on-board functionality |
|---|---|---|---|
| 1 | SDA | PD0 | Shared with button SW100 (silkscreen SW0) |
| 2 | SCL | PD1 | Shared with Light sensor 6 |
| 3 | RXD | PD2 | Shared with button SW101(silkscreen SW1) |
| 4 | TXD | PD3 | Shared with OLED display: reset function |
| 5 | SS | PD4 | Shared with LED D100 (silkscreen LED0) |
| 6 | MOSI | PD7 | Connected to the Board Controller 7 |
| 7 | MISO | PD6 | Connected to the Board Controller 7 |
| 8 | SCK | PD5 | Shared with LED D101 (silkscreen LED1) |
| 9 | GND | - | - |
| 10 | VCC_P3V3 | - | - |
Need to mount R408/R409 to connect TWI lines to Board Controller.
Need to mount R410/R411/R412/R413 to connect SPI lines to Board Controller.
Can be disconnected from on-board functionality by cut-straps.
Can be disconnected using SW103 mechanical switch.
Quadrature encoder outputs can be accessible on this header when SW103 mechanical switch is pushed up.
Can be disconnected from on-board functionality by cut-strap J100.
RXD and TXD lines swapped from PD3 and PD4 and used for communication with board controller.