Laird BTM510 User manual

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BTM510/511 Development Kit –A2DP and AVRCP
Quick Start Guide v1.0
A2DP SINK AVRCP CONTROL EXAMPLE
Introduction
This example will demonstrate how to use the BTM511 as an A2DP stereo audio sink and AVRCP controller.
An A2DP source is required. Most smartphones are able to act as a source but please check with your device
manufacturer for information on your specific device.
Requirements
BTM511 development board
USB cable (A-B)
Windows computer
Terminal software such as Ezurio Terminal
Bluetooth A2DP source (such as a Bluetooth mobile phone or PC with media player software)
Speakers or headphones with 3.5 mm jack
FTDI VCP driver
BTM51x firmware 18.1.3.0 or above
Note: Not all phones and computers support Bluetooth A2DP. Check with the manufacturer for A2DP
support.
The development board USB connector provides both power to and serial communications with the module.
You can use the Laird-provided terminal program (Ezurio Terminal) or your own preferred terminal program.
A set of stereo speakers or headphones should be plugged into the stereo out socket on the development
board using a 3.5 mm audio jack.

BTM510/511 Development Kit –A2DP and AVRCP
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Device Setup
To set up the device, follow these steps:
1. Install the FTDI VCP drivers on your PC.
2. If not already installed, install your preferred terminal program.
3. Connect the USB cable to the computer and development board. Ensure that the development
board switch is set to USB. Windows should find and install the development board as new
hardware.
4. Identify the virtual com port used by the development board using the device manager on a
Windows computer.
5. Connect the speakers to the development board 3.5 mm Stereo Out socket.
6. Open the terminal program and select the virtual com port (9600 8N1) identified earlier.
7. Check to be sure you can communicate by sending “at”. Once you press Enter, you should see OK.
8. Send the commands as shown in Figure 1 to configure the BTM511. Refer to the user manual for
detailed command explanations.
Notes: Commands are shown in lower case, responses from the BTM511 in upper case.
If you power cycle the BTM511, the at+btp command must be resent. All other settings are stored
in non-volatile memory.
Figure 1: BTM511 Configuration Commands
You may need to experiment with the ats515 setting depending on the device acting as a source; this is the
Bluetooth Class of Device (COD) which describes the general characteristics and capabilities of a device. The
COD does not reliably indicate which profiles or services are actually available. There are numerous possible
combinations but typical values of ats515 could include $200400 (generic audio), $200414 (loudspeaker),
and $200418 (headphones).
Discovery and Pairing
The BTM511 is now ready to be discovered by your Bluetooth A2DP source device.

BTM510/511 Development Kit –A2DP and AVRCP
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Because different devices handle pairing in different ways, it is not possible to provide step-by-step
instructions for a specific device. Typically, you need to go to the device’s settings screen and select
Bluetooth; this should allow you to search for and pair with the module.
If your source device uses legacy pairing, you must enter the pairing PIN as 1234 on your source device when
prompted. This PIN was previously setup on the BTM511 with the at+btk=<PIN> command.
Source devices that support Bluetooth 2.1 (most recent smartphones do) use simple secure pairing (SSP). For
these devices, you receive a prompt on both the source device and from the BTM511 as shown in Figure 2:
Figure 2: SSP Prompts
PAIR ?
Indicates an incoming pair request
BCB1F3781D4F
BT address of the source device
Galaxy Nexus
Its ‘friendly name’
056029
A random six-digit number displayed on both devices
Accept the pairing request on the source device and then accept the pairing request on the BTM511 by
sending at+btby, if required. Some devices may pair automatically without prompting depending on their
security settings. The BTM511 pairing settings can be configured with various levels of security and user
interaction. Please refer to the user manual for more details.
A successful pairing is indicated by a PAIR 0 <remote device address> message.
Connecting
At this point you may see two connect messages: one for A2DP (UUID:0x110D) and one for AVRCP
(UUID:0x110E). If the connect messages do not appear, you must manually connect from your source device;
please refer to the manufacturer’s instructions if this issue occurs. Most smartphones will automatically
connect.
From your source device, begin audio streaming by opening the media player and playing a music track. You
should hear the track from the speakers/headphones connected to the development board rather than from
the source devices own internal speaker.
Once the audio is streaming you will receive a message indicating the current sampling frequency (Figure 3).

BTM510/511 Development Kit –A2DP and AVRCP
Application Note
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Figure 3: Current sampling frequency
In this example:
44100
Refers to 44100 khz
INT
Indicates that an internal codec is being used
Figure 4: Audio output gain and connection status
at+god
at+gou
Control the audio output gain
ati61
Sent to determine the status of the connection
1
Indicates that A2DP is connected
Remote Control
AVRCP can be used to control the source device media player from the BTM511. See Figure 5.

BTM510/511 Development Kit –A2DP and AVRCP
Application Note
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Figure 5: AVRCP Commands
at+avc45
Stop media playback
at+avc44
Start playback
Figure 6: Skip back and playback commands
at+avc4c
Skip back
at+avc46
Pause playback
Note: Not all commands may be supported by all devices.
Disconnecting
The command ath* can be used to drop the all current Bluetooth connections. As each connection drops, a
corresponding No Carrier message displays (Figure 7).

BTM510/511 Development Kit –A2DP and AVRCP
Application Note
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Figure 7: Disconnection commands
Resources
FTDI Driver: http://www.ftdichip.com/Drivers/VCP.htm
Ezurio terminal: http://www.lairdtech.com/zips/Bluetooth%20Terminal%20Download.zip
Support: http://www.lairdtech.com/Products/Wireless-M2M-and-Telematics-Solutions/Bluetooth-Module/
BTM511 User Manual: http://www.lairdtech.com/WorkArea/linkit.aspx?LinkIdentifier=id&ItemID=5114
REVISION HISTORY
Revision
Date
Description
Initiated By
1.0
20 June 2013
Initial Release
Jonathan Kaye