Headset Profile
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8/28/2008
The Bluetooth Headset Profile (HSP) depends on the Serial Port Profile (SPP), and defines procedures to support interoperability between a headset and a mobile device. The mobile device is the audio gateway (AG) that provides both input and output audio to the headset. The headset acts as an audio input and output mechanism for the AG, and controls the mobile device through AT commands.
Windows Embedded CE supports HSP by providing the Audio Gateway Service that links Bluetooth devices by using the Winsock interface to the Bluetooth Protocol Architecture. This service also interfaces with the TAPI to control a cellular phone.
The headset sends AT commands to the AG, in response to user-initiated events. The following table shows the AT commands supported in Windows Embedded CE.
| AT command | Description |
|---|---|
AT+CKPD=200 |
Notifies the AG service when a button on the headset is pressed. |
AT+VGM=<gain> |
Notifies the AG service when the microphone volume on the headset is changed to the specified gain value. |
AT+VGS=<gain> |
Notifies the AG service when the speaker volume on the headset is changed to the specified gain value. |
When the AG receives an AT command, it processes the command and controls the headset by returning an unsolicited result code. The following table shows the result codes supported in Windows Embedded CE.
| Result code | Description |
|---|---|
+VGM=<gain> |
Sets the microphone volume on the headset. |
+VGS=<gain> |
Sets the speaker volume on the headset. |
RING |
Rings the headset. |
The procedures specified by the HSP define the set of features that the headset supports. The following table shows the features supported by Windows Embedded CE.
| Feature | Procedure |
|---|---|
Incoming connection from the Headset |
The AG can receive an incoming ACL connection from a headset. Upon receiving the connection, the headset will send the AT+CKPD command. The AG will not establish an audio connection upon receiving this initial AT+CKPD command. |
Outgoing connection to the Headset |
The AG can create an outgoing connecting to the headset. |
Audio connection transfer |
The AG may transfer audio to the headset by initiating an SCO connection. The headset does not have the ability to initiate an audio transfer in Headset Profile. |
Remote audio volume control |
To set the volume of the microphone or of the speaker on the headset, there must be an active connection between the AG and the headset. To change the microphone or speaker volume, the AG sends the +VGM or +VGS result code, respectively, to the headset and specifies the gain as a parameter of the result code. |
The following list shows the user interface requirements for the headset profile to work:
- The user interface must toggle audio output between the headset and the mobile device.
- The user interface must allow the user to choose between the headset and the phone to receive or place a call.
For more information about the procedures related to these features, see the Headset Profile Specification at the Official Bluetooth Wireless Info Web site.
See Also
Concepts
Bluetooth Profiles
Audio Gateway Service