Atmel AVR XMEGA-A3BU, Application Note

Atmel AVR1923

7

8394B-AVR-02/12 

This however will disable the JTAG interface until the connection is reestablished by, 
for example soldering a bridge on the cut-strap. 

4.2 I/O expansion headers 

The Atmel AVR XMEGA-A3BU Xplained headers J1, J2, J3, and J4 offer access to 
the I/O 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. 

Table 

4-2

 shows how the Atmel AVR XMEGA is connected to the header. 

NOTE 

When using TWI please note that no pull-ups are mounted on the board from the 
factory, so it is required to either enable the internal pull-ups of the device or to mount 
the external pull-ups on the available footprints (R200 and R201). Please refer to the 
assembly drawing in the design documentation for the location of these footprints. 

Table 4-2. 

Expansion header J1. 

Pin on J1 

Name on J1 

XMEGA pin 

Shared with onboard functionality 

1 SDA 

PC0 

- 

2 

SCL PC1 - 

3 RXD 

PC2 

- 

4 TXD 

PC3 

- 

5 SS 

PC4 

- 

6 MOSI 

PC5 

- 

7 MISO 

PC6 

- 

8 SCK 

PC7 

- 

9 GND 

-  - 

10 VCC_P3V3 

-  - 

The header J2 is connected to analog ports of the XMEGA as shown in 

Table 4-3

. 

Table 4-3. 

Expansion header J2. 

Pin on J2 

Name on J2 

XMEGA pin 

Shared with onboard functionality 

1 ADC0 

PB0 

- 

2 ADC1 

PB1 

- 

3 ADC2 

PB2 

- 

4 ADC3 

PB3 

- 

5 ADC4 

PA4 

- 

6 ADC5 

PA5 

- 

7 ADC6 

PA6 

- 

8 ADC7 

PA7 

- 

9 GND 

-  - 

10 VCC_P3V3 

-  - 

The I/O connected to the expansion header J3 is shared with on-board features as 
sensors and JTAG interface. Therefore care must be taken when J3 is used for 
expansions. 

Table 4-4

 shows the mapping of the XMEGA I/O to J3.