XLR PRO Radio Frequency (RF) Modem User Guide
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XLR PRO API operation
As an alternative to Transparent Operation, API (Application Programming Interface) Operations are available. API
operation requires that communication with the XLR PRO be done through a structured interface (data is
communicated in frames in a defined order). The API specifies how commands, command responses, and XLR PRO
status messages are sent and received from the XLR PRO using a serial 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.
API frame format
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 XLR PRO to operate in a particular mode:
•
AP = 1: API Operation
•
AP = 2: API Operation (with escaped characters)
API operation (AP parameter = 1)
When this API mode is enabled (AP = 1), the serial data frame structure is defined as follows:
Any data received prior to the start delimiter is silently discarded. If the frame is not received correctly or if the
checksum fails, the XLR PRO will reply with a radio status frame indicating the nature of the failure.
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
MSB = Most Significant Byte, LSB = Least Significant Byte