I have two atmega boards, and one atmega board - A can be directly connected to the UART. The other board- B has only extension pins and I connect its UART pins to DUE's UART pin as in the picture(UPLOAD). Both the boards are connected through zigbee and i want to test. The A displays menu as like in figure 2 but B does not display as like in figure 3. It can take the inputs like 't' transmission and 'r' reception. But cannot display the sub-menu . I flashed both the boards with same software. How can B display same like A ? the baud rate is proper. What changes to be done in UART setings ? I checked for baud rate and clock. The arduino DUE clock is 4mhz . My atmega board works with internal RC and then at the beginning of the program I added # define F_CPU 4000000 . Is there anything whic´h can be done ?