User's Manual

Enhanced Class 1 Bluetooth v2.1 Module
User’s Guide
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CONN-GUIDE-BT740_v0.2
14.7.6 Enhanced Inquiry Responses
Bluetooth 2.1 specification allows up to 240 bytes of extended inquiry data. On BT740-Sx modules, this
data is limited to a maximum length based on firmware builds due to internal memory restrictions.
Extended inquiry data transmits e.g. the friendly name, UUIDs of supported profiles, or user defined data
within the inquiry process and without a Bluetooth connection.
The architecture for managing EIR data is composed of a BLOB buffer, a set of AT commands around
them, and:
 Baseband (EIR data visible to inquiring devices)
 RAM buffer (allows accumulation of data)
 EIR persistent store (non-volatile buffer, copied to baseband at boot time)
As the input buffer length for one AT command is limited, there is a RAM buffer to accumulate several
short data packets. The accumulated data of the RAM buffer can be copied to the baseband where it
becomes visible to other inquiring devices immediately.
The content of the RAM buffer can copy to the EIR persistent store. If the EIR persistent store contains
data, it copies to the baseband automatically at boot time. This allows a flexible usage of extended inquiry
data. For example, data with a low data rate (e.g. temperature) can transmit without creating a connection
between Bluetooth devices, however without the benefits of encryption and authentication.
The command AT+BTB is provided to manage EIR data in AT mode.
14.7.6.1 EIR Data Format
When passing EIR data (“<data>”) to AT commands (AT+BTB=”<data>” / AT+BTB+”<data>”), each byte
should be presented by its ASCII representation whenever it is a printable character.
Each non-printable ASCII character must be presented as 2 hex digits with a preceding ‘\’. For example, a
byte of decimal value 5 is presented as “\05” because the ASCII character of 05d is not printable.
A decimal value of 43 should be presented as ‘+’ because ‘+’ is the ASCII character representing 43d.
The module also accepts “\2B” (the hexadecimal presentation of 43d) but at the price of two redundant
characters.
Exceptions:
‘“’ (quotation mark) must be presented as \22
‘\’ (backslash) must be presented as \5C
When querying the content of the BLOB, non-printable ASCII characters are presented by 2 hex digits
with preceding ‘\’.
Exceptions:
‘“’ (quotation mark) is presented as \22
‘\’ (backslash) is presented as \5C
‘,’ (comma) is presented as \2C
Any data passed to the baseband must match the format defined in the Bluetooth Specification Version
2.1 + EDR [1], vol3, Part C – Generic Access Profile, 8 Extended Inquiry Response Data Format (page
1305 in the *.pdf file).
The AT command interpreter does not perform any checks on the baseband data format.