© 2014 Digi International Inc. 69
XBee/XBee-PRO
®
DigiMesh 2.4 User Manual
XBee/XBee-PRO DigiMesh 2.4 API Operation
As an alternative to Transparent Operation, API (Application Programming Interface) Operations
are available. API operation requires that communication with the module be done through a
structured interface (data is communicated in frames in a defined order). The API specifies how
commands, command responses and module status messages are sent and received from the
module using a UART Data Frame.
Please note that Digi may add new frame types to future versions of firmware, so please build
into your software interface the ability to filter out additional API frames with unknown Frame
Types.
XBee API Frame Specifications
Two API modes are supported and both can be enabled using the AP (API Enable) command.
Use the following AP parameter values to configure the module to operate in a particular mode:
• AP = 1: API Operation
• AP = 2: API Operation (with escaped characters)
XBee API Operation (AP parameter = 1)
When this API mode is enabled (AP = 1), the UART data frame structure is defined as follows:
UART Data Frame Structure:
1 MSB = Most Significant Byte, LSB = Least Significant Byte
Any data received prior to the start delimiter is silently discarded. If the frame is not received
correctly or if the checksum fails, the module will reply with a module status frame indicating the
nature of the failure.
XBee API Operation-with Escape Characters (AP parameter =
2)
When this API mode is enabled (AP = 2), the UART data frame structure is defined as follows:
UART Data Frame Structure - with escape control characters:
Length
(Bytes 2-3)
Checksum
(Byte n + 1)
MSB LSB 1 Byte
Start Delimiter
(Byte 1)
0x7E
Frame Data
(Bytes 4-n)
API-specific Structure
Start Delimiter
(Byte 1)
Length
(Bytes 2-3)
Frame Data
(Bytes 4-n)
Checksum
(Byte n + 1)
0x7E MSB LSB API-specific Structure 1 Byte
Characters Escaped If Needed
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