XBee® Wi-Fi RF Modules
© 2013 Digi International, Inc. 67
interfering data byte, insert 0x7D and follow it with the byte to be escaped XOR’d with
0x20.
Data bytes that need to be escaped:
• 0x7E – Frame Delimiter
• 0x7D – Escape
• 0x11 – XON
• 0x13 – XOFF
Example - Raw UART Data Frame (before escaping interfering bytes):
0x7E 0x00 0x02 0x23 0x11 0xCB
0x11 needs to be escaped which results in the following frame:
0x7E 0x00 0x02 0x23 0x7D 0x31 0xCB
Note: In the above example, the length of the raw data (excluding the checksum) is
0x0002 and the checksum of the non-escaped data (excluding frame delimiter and
length) is calculated as: 0xFF - (0x23 + 0x11) = (0xFF - 0x34) = 0xCB.
Length
The length field has a two-byte value that specifies the number of bytes that will be
contained in the frame data field. It does not include the checksum field.
Framed Data
Frame data of the UART or SPI data frame forms an API-specific structure as follows:
UART or SPI Data Frame & API-specific Structure:
The cmdID frame (API-identifier) indicates which API messages will be contained in the
cmdData frame (Identifier-specific data). Note that multi-byte values are sent big
endian. The XBee modules support the following API frames:
API Frame Names and Values
Tx64 Request 0x00
Remote Command Request 0x07
AT Command - Queue Parameter Value 0x09
ZigBee Transmit Packet 0x10
ZigBee Explicit Transmit Packet 0x11
ZigBee Remote AT Command 0x17
Put Request 0x28
Device Response 0x2A
Remote Command Response 0x87
AT Command Response 0x88
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