Digi International Inc XBEEPRO2 Manuel D’Utilisation

When data is transmitted from one node to another, a network-level acknowledgement is transmitted back 
across the established route to the source node. This acknowledgement packet indicates to the source node that 
the data packet was received by the destination node. If a network acknowledgement is not received, the 
source node will re-transmit the data. 

It is possible in rare circumstances for the destination to receive a data packet, but for the source to not receive 
the network acknowledgment. In this case, the source will retransmit the data, which could cause the 
destination to receive the same data packet multiple times. The XBee modules do not filter out duplicate 
packets. The application should include provisions to address this potential issue

See Data Transmission and Routing in chapter 4 for more information. 

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 in chapter 9 for an 
alternate means of configuring modules.

Send the 3-character command sequence “+++” and observe guard times before and after the com-
mand 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) parame-

ter = 0x2B.]
•No characters sent for one second [GT (Guard Times) parameter = 0x3E8]

Once the AT command mode sequence has been issued, the module sends an "OK\r" out the DOUT pin. The 
"OK\r" characters can be delayed if the module has not finished transmitting received serial data.

When command mode has been entered, the command mode timer is started (CT command), and the 
module is able to receive AT commands on the DIN pin. 

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. By default, 

the BD (Baud Rate) parameter = 3 (9600 bps).

Send AT commands and parameters using the syntax shown below.

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.

Command Response