Rainbow Electronics MG260 - Manual (Page 240)

FLYFOT-MG260-MODULE
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B7 B6 B5 B4 B3 B2 B1 B0
Start pattern → 0xAA
AT command length LSB
AT command pattern → 0x1D
AT command
length MSB
AT command
Checksum
The 3 bytes of the header are:
Î the first byte (0xAA) is used to identify the packet,
Î the second byte represents the 8 LSB (Low Significant Bits) bits of the length of the AT command,
Î the third byte is made of 2 parts :
- the 3 LSB bits are the 3 MSB (Most Significant Bits) bits of the length of the AT command,
- the 5 MSB bits (0x1D which equals to 0xE8 with the 3 bits offset) are used to identify an AT
command.
The maximum length of an AT command could be 2047 bytes which is greater than all the existing AT
commands.
The checksum is the addition (modulo 256) of all the transmitted bytes (header bytes and AT command
bytes).
Data packets
Like for AT commands, DATA are encapsulated into packets. These packets are composed of a header
(3 bytes), the data bytes and the checksum (1 byte) :
B7 B6 B5 B4 B3 B2 B1 B0
Start pattern → 0xDD
Data packet length LSB
Data packet type
Data packet length
MSB
Data bytes
Checksum
The 3 bytes of the header are:
Î the first byte (0xDD) used to identify the packet,
Î the second byte represents the 8 LSB bits of the length of the data field,
Î the last byte is made of 2 parts :
- the 3 LSB bits represent the 3 MSB bits of the length of the data field,
- the 5 MSB bits represent the packet type.
Data packets can have different values according to the type of packet:
Î 0 . DATA packet : the packet contains the data to transmit on the radio link or received from the radio
link,
Î 1 . STATUS packet: the packet contains the status of SA, SB, X bits (1) and the break condition
coding as follow :
SA SB X BRK RI Spare Spare Spare