The Hands-Free Profile (HFP) defines the minimum set of functions such that a mobile phone can be used in conjunction with a Hands-Free device, with a Bluetooth link providing a wireless means for both remote control of the mobile phone by the Hands-Free device and voice connection between the mobile phone and the Hands-Free device. More...

Overview

The Hands-Free Profile (HFP) defines the minimum set of functions such that a mobile phone can be used in conjunction with a Hands-Free device, with a Bluetooth link providing a wireless means for both remote control of the mobile phone by the Hands-Free device and voice connection between the mobile phone and the Hands-Free device.

The following roles are defined for this profile. Audio Gateway (AG). A device that acts as a gateway of the audio, both for input and output. Typical devices acting as AGs are cellular phones. Hands-Free unit (HF). A device that acts as the AG's remote audio input and output. It also provides remote control means.

Supported profile version. 1.6
Supported role. Hands-free unit.
Supported features:
- Call waiting and 3-way calling.
- CLI presentation capability.
- Voice recognition activation.
- Remote volume control.
- Enhanced call status.
- Enhanced call control.
- Codec negotiation.

Terms and Acronyms

Terms	Details
BATTCHG	Battery Charge indicator of AG to provide the battery level.
BRSF	Bluetooth Retrieve Supported Features.
SYNC	Synchronization.
MIC	Microphone.
DTMF	Dual Tone Multi-Frequency, is an in-band telecommunication signaling system using the voice-frequency band over telephone lines. For more information, please refer to Dual tone multi-frequency signaling in Wikipedia.
AG	Audio Gateway, the remote device.
NREC	Noise Reduction and Echo Canceling, the feature to disable or enable in AG.
WBS	Wide Band Speech.
CLI	Calling Line Identification, the feature to disable or enable in AG.
DIR	Director, the call's director, an attribute of a call.
HFP	Hands-Free Profile. For more information, please refer to Hands-free profile in Wikipedia.
CVSD	Continuously Variable Slope Delta modulation, a codec of audio. For more information, please refer to Continuously variable slope delta modulation in Wikipedia.
MSBC	Modified Sub Band Codec, a codec of audio.
CHLD	Call Hold, the 3-way call action in AG.
ISDN	Integrated Services Digital Network. For more information, please refer to Integrated services digital network in Wikipedia.
FAX	Facsimile.
SLC	Service Level Connection, the HFP connection with status negotiation.

How to use this module

This section presents the HFP connection handle and the method to send the command to dial a number.

1. Mandatory, implement bt_app_event_callback() to handle the HFP events, such as connect, disconnect, indication and more.
- Sample code:
  void bt_app_event_callback(bt_msg_type_t mgs, bt_status_t status, void *buff)
  {
  switch (event_id)
  {
  case BT_HFP_CONNECT_REQUEST_IND:
  {
  bt_hfp_connect_request_ind_t *re_ind =
  (bt_hfp_connect_request_ind_t *)buff;
  bt_hfp_connect_response(re_ind->handle,true);
  break;
  }
  default:
  {
  break;
  }
  }
  }
2. Mandatory, implement the initialization callback bt_hfp_get_init_params().
- Sample code:
  bt_status_t bt_hfp_get_init_params(bt_hfp_init_param_t *init_params)
  {
  init_params->supported_codecs = BT_HFP_CODEC_TYPE_MSBC;
  init_params->indicators.battery = BT_HFP_INDICATOR_ON;
  init_params->indicators.roaming = BT_HFP_INDICATOR_ON;
  init_params->indicators.signal = BT_HFP_INDICATOR_ON;
  init_params->indicators.service = BT_HFP_INDICATOR_ON;
  init_params->support_features = BT_HFP_INIT_SUPPORT_ALL;
  init_params->disable_nrec = true;
  init_params->enable_call_waiting = true;
  init_params->enable_cli = true;
  return BT_STATUS_SUCCESS;
  }
3. Mandatory, connect to the remote device, as shown in figure titled as "HFP connection establishment message sequence" in the Bluetooth developer's guide under the [sdk_root]/doc folder.
- Sample code: Connect to a remote device by passing the remote address and get the connection handle. The event BT_HFP_SLC_CONNECTING_IND captured by bt_app_event_callback() indicates the RFCOMM is connected and SLC is to be created. The event BT_HFP_SLC_CONNECTED_IND captured by bt_app_event_callback() indicates the SLC is connected.
  ret = bt_hfp_connect(&handle, &addr);
4. Optional, after receiving the event BT_HFP_SLC_CONNECTED_IND, call the API bt_hfp_send_command() to send a command to dial a number, such as 'ATDXXXX', 'ATD>XXX', 'AT+BLDN', as shown in figure titled as "Initiate an outgoing voice call message sequence" in the Bluetooth developer's guide under the [sdk_root]/doc folder.
- Sample code:
  uint8_t hfp_cmd[7] = "ATD114";
  ret = bt_hfp_send_command(handle, hfp_cmd, strlen(hfp_cmd));
5. Mandatory, activate the audio link after the BT_HFP_AUDIO_CONNECT_IND event is received. The application needs to activate the audio link status, as shown in figure titled as "HFP connection release message sequence" in the Bluetooth developer's guide under the [sdk_root]/doc folder.
- Sample code: The event BT_HFP_AUDIO_STATUS_CHANGE_IND captured by bt_app_event_callback() indicates the audio link status has changed.
  ret = bt_hfp_set_audio_status(handle, BT_HFP_AUDIO_STATUS_ACTIVE);
6. Mandatory, disconnect the remote device, as shown in figure titled as "HFP connection release message sequence" in the Bluetooth developer's guide under the [sdk_root]/doc folder.
- Sample code: Disconnect the remote device by passing the connection handle. The event BT_HFP_DISCONNECT_IND captured by bt_app_event_callback() indicates the RFCOMM channel has disconnected.
  ret = bt_hfp_disconnect(handle);

Functions
bt_status_t	bt_hfp_connect (uint32_t handle, bt_bd_addr_t address)
	This function sends a HFP connect request to the AG. More...

bt_status_t	bt_hfp_connect_response (uint32_t handle, bool accept)
	This function responds to a connection request from AG. More...

bt_status_t	bt_hfp_disconnect (uint32_t handle)
	This function sends a HFP disconnect request to AG. More...

bt_status_t	bt_hfp_audio_transfer (uint32_t handle, bt_hfp_audio_direction_t audio_dir)
	This function transfers the audio direction to AG or to HF. More...

bt_status_t	bt_hfp_set_audio_status (uint32_t handle, bt_hfp_audio_status_t status)
	This function sets the current audio connection status. More...

bt_status_t	bt_hfp_send_command (uint32_t handle, uint8_t *command, uint16_t command_length)
	This function sends an HFP command to the AG. More...

bt_bd_addr_t *	bt_hfp_get_bd_addr_by_handle (uint32_t handle)
	This function gets the remote device's Bluetooth address of current connection. More...

bt_status_t	bt_hfp_get_init_params (bt_hfp_init_param_t *init_params)
	This function gets the initialization settings. More...

Modules
	Define
	This section defines the HFP events and error codes.

	Struct
	This section defines data structures for the HFP.

Function Documentation

bt_status_t bt_hfp_audio_transfer	(	uint32_t	handle,
		bt_hfp_audio_direction_t	audio_dir
	)

This function transfers the audio direction to AG or to HF.

Parameters

[in]	handle	is the handle of the current connection.
[in]	audio_dir	is the switch direction, either to AG or HF, please refer to bt_hfp_audio_direction_t.

Returns: BT_STATUS_SUCCESS, the operation completed successfully. BT_STATUS_FAIL, the operation has failed.

bt_status_t bt_hfp_connect	(	uint32_t *	handle,
		bt_bd_addr_t *	address
	)

This function sends a HFP connect request to the AG.

The event BT_HFP_SLC_CONNECTING_IND returns when the SLC is connecting. The event BT_HFP_SLC_CONNECTED_IND returns when HFP negotiation is complete.

Parameters

[out]	handle	is the channel handle returned.
[in]	address	is the Bluetooth address of the AG.

Returns: BT_STATUS_SUCCESS, the operation completed successfully. BT_STATUS_FAIL, the operation has failed. BT_STATUS_OUT_OF_MEMORY, out of memory.

bt_status_t bt_hfp_connect_response	(	uint32_t	handle,
		bool	accept
	)

This function responds to a connection request from AG.

Calll this API to accept or reject the connection, when BT_HFP_CONNECT_REQUEST_IND is received.

Parameters

[in]	handle	is the handle of the current connection.
[in]	accept	is the operation of accepting or rejecting the current connection request.

Returns: BT_STATUS_SUCCESS, the operation completed successfully. BT_STATUS_FAIL, the operation has failed.

bt_status_t bt_hfp_disconnect ( uint32_t handle )

This function sends a HFP disconnect request to AG.

The event BT_HFP_DISCONNECT_IND returns the current request’s result.

Parameters

[in] handle is the handle of the current connection.

Returns: BT_STATUS_SUCCESS, the operation completed successfully. BT_STATUS_FAIL, the operation has failed.

bt_bd_addr_t* bt_hfp_get_bd_addr_by_handle ( uint32_t handle )

This function gets the remote device's Bluetooth address of current connection.

Parameters

[in] handle is the handle of the current connection.

Returns: The Bluetooth address.

bt_status_t bt_hfp_get_init_params ( bt_hfp_init_param_t * init_params )

This function gets the initialization settings.

This API invoked by the SDP process should be implemented by the application.

Parameters

[out] init_params is the settings to initialize.

Returns: BT_STATUS_SUCCESS, the operation completed successfully, otherwise it failed.

bt_status_t bt_hfp_send_command	(	uint32_t	handle,
		uint8_t *	command,
		uint16_t	command_length
	)

This function sends an HFP command to the AG.

The event BT_HFP_ACTION_CMD_CNF returns when the remote device responds.

Parameters

[in]	handle	is the handle of the current connection.
[in]	command	is the command to send.
[in]	command_length	is the command's length.

Returns: BT_STATUS_SUCCESS, the operation completed successfully. BT_STATUS_FAIL, the operation has failed. BT_STATUS_OUT_OF_MEMORY, out of memory.

bt_status_t bt_hfp_set_audio_status	(	uint32_t	handle,
		bt_hfp_audio_status_t	status
	)

This function sets the current audio connection status.

Parameters

[in]	handle	is the handle of the current connection.
[in]	status	is the audio status to set.

Returns: BT_STATUS_SUCCESS, the operation completed successfully. BT_STATUS_FAIL, the operation has failed.

Overview

Terms and Acronyms

How to use this module

Functions

Modules

Function Documentation