User's Manual

Enhanced Class 1 Bluetooth v2.1 Module
User’s Guide
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www.lairdtech.com/wireless
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CONN-GUIDE-BT740_v0.2
The claim made for this device is that it has a protocol similar to an AT modem. In fact, the protocol is
similar enough so that existing source code written for modems can be used with very little modification
with a Laird device.
Therefore the following assumptions are made:
 All commands terminate by the carriage return character 0x0D, represented by the string <cr> in
subsequent sections. It cannot be changed at runtime.
 All responses from the Laird device have carriage return and linefeed characters preceding and
appending the response. These dual character sequences have the values 0x0D and 0x0A
respectively and are represented by the string <cr,lf>.
 All Bluetooth addresses are represented by a fixed 12 digit case insensitive hexadecimal string.
 All Bluetooth Device Class codes are represented by a fixed 6 digit case insensitive hexadecimal
string.
 Most new Bluetooth specific commands are identified by the string +BTx, where x is generally a
mnemonic of the intended functionality.
5.2.2 Protocol Activation
Depending on the variant of the module, the AT protocol needs to activate so that on power up it presents
this protocol interface instead of the alternate multipoint protocol.
The method that is always available and works is activation via S Register 255 in multipoint mode (and
mapped to 9255 in AT mode), where setting a value of 1 selects multipoint packet protocol and a value of
2 selects AT protocol.
Note: Changes to this S register store in non-volatile memory at time of change and does not require
the AT&W command (or the equivalent in multipoint mode CMD_STORE_REG) to commit to
non-volatile memory.
Optionally, some firmware variants allow a value of 0 in this S Register and in this case on power up the
protocol selection depends on the state of one of the GPIO pins (user settable) so that one state forces
AT and the other forces multipoint.
5.3 AT Commands and Responses
This section describes all available AT commands. Many commands require mandatory parameters and
some take optional parameters. These parameters are integer values, strings, Bluetooth addresses or
device classes. The following convention is used when describing the various AT commands, and the
response to a command is also stated.
<bd_addr>
A 12 character Bluetooth address consisting of ASCII characters ‘0’ to ‘9’, ‘A’ to ‘F’
and ‘a’ to ‘f’.
<devclass>
A 6 character Bluetooth device class consisting of ASCII characters ‘0’ to ‘9’, ‘A’ to
‘F’ and ‘a’ to ‘f’.
N
A positive integer value.
M
An integer value which could be positive or negative, which can be entered as a
decimal value or in hexadecimal if preceded by the ‘$’ character.
E.g. the value 1234 can also be entered as $4D2
<string>
A string delimited by double quotes. E.g. "Hello World". The " character MUST be
supplied as delimiters.