The MEGA-1284P Xplained kit has five 10-pin 100mill headers. Two headers have a fixed communication interface (J1 & J4). One header has analog functionality (J2) and the last header (J3) has general purpose digital IO.

The 90° angled header is the JTAG programming and debugging header for the Atmel ATmega1284P.

For the location of the respective headers, refer to Figure 1.