4.1.3 Other Headers

In addition to the Xplained Pro extension headers, ATmega324PB Xplained Pro has additional headers with signals that offers access to the I/O of the microcontroller which are otherwise not easily available elsewhere or might be favorable to have collected together. All headers have a pitch of 2.54mm.

The J305 header enables easy connection to the ATmega324PB comparator function.

Table 4-4. Analog Comparator Header (J305)
Pin on header	ATmega324PB pin	Function	Shared functionality
1	PB2	AIN0	EXT4.9
2	PB3	AIN1	EXT4.7
3	PC5	ACO	EXT3 via J200 and EDBG JTAG TDI
4		VCC Target
5		GND

Tip: Disable JTAG interface to get access to ACO. Set the JTD bit in MCUCR to disable the JTAG interface.

Warning: Use of the JTAG signals might cause conflict when using the debugger/programmer.

The J200 header enables use of the ATmega324PB JTAG signals for EXT3.

Table 4-5. JTAG to EXT3 Strap Header (J200)
Pin on header	ATmega324PB pin	EXT3 pin	Shared functionality
1	PC5_JTAG_TDI		EDBG via R404
2		EXT3.3
3	PC2_JTAG_TCK		EDBG via R401
4		EXT3.6
5	PC4_JTAG_TDO		EDBG via R402
6		EXT3.7
7	PC3_JTAG_TMS		EDBG via R403
8		EXT3.8

Tip: Disable JTAG interface to get access to PC2 to PC5. Set the JTD bit in MCUCR to disable the JTAG interface.

Warning: Use of the JTAG signals might cause conflict when using the debugger/programmer.

Tip: Assemble strap in the J200 header and remove strap when using the JTAG interface.

The J201 strap enables use of the ATmega324PB PA7 for both the EXT4 and EDBG SPI-SS.

Table 4-6. PA7 to EXT4 strap (J201)
Pin on header	ATmega324PB pin	EXT4 pin	Shared functionality
1	PA7		EDBG SPI- SS
2		EXT4.6

Remember: Remove the strap if the EDBG SPI bus is to be used.

The DGI GPIO signals are available on a separate header J303.

Table 4-7. DGI GPIO Header (J303)
Pin on header	ATmega324PB pin	EDBG pin	Extension pin
1	PB4	GPIO0	EXT1.15
2	PB2	GPIO1	EXT4.9
3	PC1	GPIO2	EXT1.9
4	PC6	GPIO3	EXT3.9
5	GND	GND	GND

Tip: The GPIO signals can be disconnected from the ATmega324PB by removing R215, R216, R217, and R218. The header can be used to monitor any signal on the board with the EDBG.