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www.lairdtech.com
Laird Technologies
BTM520/521
Bluetooth
®
Multimedia Plus Module
CONFIGURING
THE BTM520/521
INTRODUCTION
This document describes the protocol used to control and configure the BT-MM+ Bluetooth device.
The AT commands described in the document apply to firmware releases from V14.0.9 onwards.
The protocol is similar to the industry standard Hayes AT protocol used in telephony modems which is
appropriate for cable replacement scenarios, as both types of devices are connection oriented.
Just like telephony modems, Laird Technologies’ devices powers up in an unconnected state and will only
respond via the serial interface. In this state the device will not even respond to Bluetooth Inquiries. Then,
just like controlling a modem, the host can issue AT commands which map to various Bluetooth activities.
The command set is extensive enough to allow a host to make connections which are authenticated and/or
encrypted or not authenticated and/or encrypted or any combination of these. Commands can be saved,
so that on a subsequent power up the device is discoverable or automatically connects.
The device has a serial interface which can be configured for baud rates from 1200 up to 921600 (default
setting is 9600) and an RF communications end point. The latter has a concept of connected and unconnected
modes and the former will have a concept of command and data modes. This leads to the matrix of states
shown below.
RF UNCONNECTED
RF CONNECTED
Local Command Mode
OK
OK
Remote Command Mode
ILLEGAL
OK
Data Mode
ILLEGAL
OK
The combinations, ‘Data and RF Unconnected Mode’ and ‘Remote Command and RF Unconnected Mode’ do
not make sense and will be ignored.
Navigation between these states is done using the AT commands which are described in detail in subsequent
sections.
REFERENCES
[1] “AT Command Set”
[2] “BlueLab_v4.0_Release_Note.pdf”
[3] “Audio/Video Distribution Transport Protocol Specification” Rev.V12, 16/04/2007
[4] “Advanced Audio Distribution Profile Specification” Rev. V12, 16/04/2007
[5] “Audio/Video Remote Control Profile” Revision V14r00, 26/06/2008
[6] “Software Release Note Stereo Headset SDK Q3 2007 RC3.1” CS-117522-RNP1, CSR
[7] “Stereo Headset SDK Q3 2007 User Guide” CSR, CS-116451-UGP1, CSR, December2007
[8] “Bluetooth Specification Version 2.1 + EDR [vol3]”, 26 July 2007
