Xbee Guide - arthurbenemann/ardupilot GitHub Wiki

APM defaults to sending telemetry data over port 3 ("!TelemPort" on the IMU shield) at 57k baud. If you want to change that, you can do so via the APM_Config.h file, and then compile and load the code via Arduino.

The hardware installation guide is here.

1) Speed selection

//                      *EXPLAINED*  
//                           Telemetry is information that is sent over a wireless link between the UAV and your laptop, this is used when a GCS(Ground Control Station) like HK*GCS or QGCS is 
//                           used and it sends that information through "Telemport" on your APM through a Xbee module(wireless module see link above)
//                           
//                      *INSTRUCTIONS*
//                          Because telemetry is a additional add on you need to tell APM that you are using one, 
//                          if you followed the instructions in the link above exactly then you need to do the following.
//                          The Xbee modules has different speed settings (Baudrates) the default baud rate for telemetry is 57600, if you do not have enough knowledge yet we 
//                          Suggest you use the default baud. simply change the statement "#define SERIAL3_BAUD   57600"to whatever speed you would like if you chose to change it.
//                          
//                      *AVAILABLE SPEED OPTIONS*                                             NOTE: WHEN CHOSING A BUAD SPEED FOR YOUR TELEMETRY YOU NEED TO SET UP YOUR 
//                          #define SERIAL3_BAUD   9600                                              XBEE TO THE SAME SPEED AS WELL AS YOUR GCS(gound control station)
//                          #define SERIAL3_BAUD   19200                                             INSTRUCTIONS CAN BE FOUND IN LINK ABOVE
//                          #define SERIAL3_BAUD   38400
//                          #define SERIAL3_BAUD   57600
//                          #define SERIAL3_BAUD   115200
//            ******************
//            *SELECTED OPPTION*
                #define SERIAL3_BAUD   57600            
//            ******************              

2) Port selection

{{{
// EXPLAINED // The telemetry can be set up to exit the APM board through 2 ports "0" and "3" // "0" being your USB and "3" being your TelemPort because of this you need to tell APM through wich port // you want the Telemetry(information) to go. //
// INSTRUCTIONS // Simple change the following statement from"#define GCS_PORT 0" to "#define GCS_PORT 3" //
// AVAILABLE OPPTIONS // # define GCS_PORT 0 (APM will send information through the mini usb port) // # define GCS_PORT 3 (APM will send information through the Telemport to be sent wirelessly by Xbee module) // ****************** // SELECTED OPPTION #define GCS_PORT 3 // ******************
}}}