Api Frame Specifications; Api Operation (Ap Parameter = 1); Api Operation-With Escaped Characters (Ap Parameter = 2) - Digi XBee User Manual

API operation

API frame specifications

The firmware supports two API operating modes: without escaped characters and with escaped
characters. Use the AP command to enable either mode. To configure a device to one of these modes,
set the following AP parameter values:
AP command
setting
AP = 0
AP = 1
AP = 2
The API data frame structure differs depending on what mode you choose.
The firmware silently discards any data it receives prior to the start delimiter. If the device does not
receive the frame correctly or if the checksum fails, the device discards the frame.

API operation (AP parameter = 1)

We recommend this API mode for most applications. The following table shows the data frame
structure when you enable this mode:
Frame fields
Start delimiter
Length
Frame data
Checksum

API operation-with escaped characters (AP parameter = 2)

Set API to 2 to allow escaped control characters in the API frame. Due to its increased complexity, we
only recommend this API mode in specific circumstances. API 2 may help improve reliability if the
serial interface to the device is unstable or malformed frames are frequently being generated.
When operating in API 2, if an unescaped 0x7E byte is observed, it is treated as the start of a new API
frame and all data received prior to this delimiter is silently discarded. For more information on using
this API mode, refer to the following knowledge base article:
http://knowledge.digi.com/articles/Knowledge_Base_Article/Escaped-Characters-and-API-Mode-2
The following table shows the structure of an API frame with escaped characters:
Frame fields
Start delimiter 1
XBee/XBee-PRO S1 802.15.4 (Legacy) User Guide
Description
Transparent operating mode, UART serial line replacement with API modes
disabled. This is the default option.
API operation.
API operation with escaped characters (only possible on UART).
Byte Description
1 0x7E
2 - 3 Most Significant Byte, Least Significant Byte
4 - n API-specific structure
n + 1 1 byte
Byte Description
0x7E
API frame specifications
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