AB Protocol
Communicate to a RFID Module and a LCD display through Arduino via USB (Serial 9600 bauds)

1.Message format

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------+---------------+---------------+--------...----------------+
|     0xAB      | MESSAGE TYPE  |   DATA SIZE   |       DATA IF ANY         |
+---------------+---------------+---------------+--------...----------------+

2.Message Type

0x00 : Ping request
0x01 : Ping response
0x02 : RFID Request
0x03 : RFID Response
0x04 : LCD Request
0x07 : ACK
0x08 : ERR (negative ACK)

3. Description
Every message starts with 0xAB
If the message has no data then DATA SIZE must be set
to 0x00 and ends the message else DATA SIZE is the DATA lenght in byte
(Equals to message size - 3)

4. RFID Request
A RFID Request contains the RFID message (using ISO/IEC 14443 protocol) the RFID datas received are in the data of the RFID Response.

5. LCD Request
If LCD Request content is 1 byte set to 0xAB then the screen shut down.