User manual

Atmel AVR1923

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 sho

ws 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 sho

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