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XBee Series 2 OEM RF Modules ‐ ZigBee ‐ v1.x2x [2007.07.019]
2.2.3. Receive Mode
2.2.4. Command Mode
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If a valid RF packet is received, the data is transferred to the serial transmit buffer
To modify or read RF Module parameters, the module must first enter into Command Mode - a
state in which incoming serial characters are interpreted as commands. Refer to the API Mode
section for an alternate means of configuring modules.
AT Command Mode
To Enter AT Command Mode:
Send the 3-character command sequence "+++" and observe guard times before and after the
command characters. [Refer to the "Default AT Command Mode Sequence" below.]
Default AT Command Mode Sequence (for transition to Command Mode):
• No characters sent for one second [GT (Guard Times) parameter = 0x3E8]
• Input three plus characters ("+++") within one second [CC (Command Sequence Character)
parameter = 0x2B.]
• No characters sent for one second [GT (Guard Times) parameter = 0x3E8]
All of the parameter values in the sequence can be modified to reflect user preferences.
NOTE: Failure to enter AT Command Mode is most commonly due to baud rate mismatch. Ensure the
'Baud' setting on the "PC Settings" tab matches the interface data rate of the RF module. By default,
the BD parameter = 3 (9600 bps).
To Send AT Commands:
Send AT commands and parameters using the syntax shown below.
Figure 2‐05. Syntax for sending AT Commands
To read a parameter value stored in the RF module's register, omit the parameter field.
The preceding example would change the RF module Destination Address (Low) to "0x1F". To store
the new value to non-volatile (long term) memory, subsequently send the WR (Write) command.
For modified parameter values to persist in the module's registry after a reset, changes must be
saved to non-volatile memory using the WR (Write) Command. Otherwise, parameters are
restored to previously saved values after the module is reset.
System Response. When a command is sent to the module, the module will parse and execute
the command. Upon successful execution of a command, the module returns an "OK" message. If
execution of a command results in an error, the module returns an "ERROR" message.
To Exit AT Command Mode:
1.
Send the ATCN (Exit Command Mode) command (followed by a carriage return).
[OR]
2.
If no valid AT Commands are received within the time specified by CT (Command Mode
Timeout) Command, the RF module automatically returns to Idle Mode.
For an example of programming the RF module using AT Commands and descriptions of each
configurable parameter, refer to the "Examples" and "XBee Series 2 Command Reference Tables"
chapters.
© 2007 Digi International, Inc.
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Chapter 2 ‐ RF Module Operation
14
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