Finally, clear explanation of TinyOS 2.x serial packet structure
TinyOS 2.x A message sent through serial ports from motes to PC will typically look like this: 00 FF FF 00 00 08 00 09 19 77 02 07 00 13 00 00 The first byte 00 is the leading zero. After that, the whole packet is of the type " serial_packet_t ", defined in tinyos-2.x/tos/lib/serial/Serial.h . Inside the serial_packet_t structure, the first 7 bytes are of the type " serial_header_t" , which is also defined in tinyos-2.x/tos/lib/serial/Serial.h . In the case above, it would be FF FF 00 00 08 00 09 . Within the "serial_header_t", the following structure takes place: nx_am_addr_t dest // Destination (2 bytes) nx_am_addr_t src // Source (2 bytes) nx_uint8_t length // Payload Length (1 byte) nx_am_group_t group // Group ID (1 byte) nx_am_id_t type // Active Message Handler Type (1 byte), some enum value that you can def