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Supported Targets ESP32

Hands-Free Client

This example is to show how to use the APIs of Hands-Free Client Component and the effects of them by providing a set of commands. You can use this example to communicate with a device that implements Hands-Free Audio Gateway (HF-AG) (e.g. a smartphone).

This demo sends back the audio data back to the HFP AG device, so you can hear your own voice when you link this demo with your HFP-AG device.

How to use example

Hardware Required

This example is designed to run on commonly available ESP32 development board, e.g. ESP32-DevKitC. To operate it should be connected to an AG running on a smartphone or on another ESP32 development board loaded with Hands Free Audio Gateway (hfp_ag) example from ESP-IDF.

Configure the project

Open the project configuration menu:

idf.py menuconfig

Special Configurations for HFP

Data Path

ESP32 HFP supports two types of audio datapath: PCM and HCI.

The default configuration is PCM, if you want to use vHCI you should configure the data path before building and downloading the binary.

  • PCM: To use PCM, audio stream is directed from Bluetooth controller to the specific GPIO pins you set in the demo, and you should link these GPIO pins to a speaker via I2S port. The audio data will not go through the Bluedroid. In menuconfig, you should choose PCM in menuconfig:

    Component config --> Bluetooth controller --> BR/EDR Sync(SCO/eSCO) default data path --> PCM

    and also

    Component config --> Bluetooth --> Bluedroid Options --> Hands Free/Handset Profile --> audio(SCO) data path --> PCM.

  • vHCI: To use vHCI, audio data stream will be directed from Bluetooth Controller through vHCI on ESP32 and go through the Bluedroid to the Application layer. In menuconfig, you should choose vHCI in menuconfig:

    Component config --> Bluetooth controller --> BR/EDR Sync(SCO/eSCO) default data path --> HCI

    and also

    Component config --> Bluetooth --> Bluedroid Options --> Hands Free/Handset Profile --> audio(SCO) data path --> HCI.

PCM Signal Configurations

PCM Signal supports three configurations in menuconfig: PCM Role, PCM Polar and Channel Mode(Stereo/Mono).

  • PCM Role: PCM role can be configured as PCM master or PCM slave. The default configuration is Master, you can change the PCM role in menuconfig path: Component config --> Bluetooth --> Controller Options --> PCM Signal Configurations --> PCM Signal Configurations: Role, Polar and Channel Mode(Stereo/Mono) --> PCM Role

  • PCM Polar: PCM polarity can be configured as Falling Edge or Rising Edge. The default configuration is Falling Edge, you can change the PCM polar in menuconfig path: Component config --> Bluetooth --> Controller Options --> PCM Signal Configurations --> PCM Signal Configurations: Role, Polar and Channel Mode(Stereo/Mono) --> PCM Polar

  • Channel Mode(Stereo/Mono): PCM frame synchronization signal can be configured as Stereo mode or Mono mode, where the Mono mode can be configured in two different forms(Mono mode 1 and Mono mode 2). As is shown in the figure Stereo/Mono

    • Stereo Mode(Dual channel): FSYNC and DOUT signals both change simultaneously on the edge of CLK. The FSYNC signal continues until the end of the current channel-data transmission.
    • Mono Mode 1(Single channel): FSYNC signal starts to change a CLK clock cycle earlier than the DOUT signal, which means that the FSYNC signal takes effect a clock cycle earlier than the first bit of the current channel-data transmission. The FSYNC signal continues for one extra CLK clock cycle.
    • Mono Mode 2(Single channel): FSYNC and DOUT signals both change simultaneously on the edge of CLK. The FSYNC signal continues for one extra CLK clock cycle.

  • The default configuration is Stereo Mode, you can change the PCM Channel mode in menuconfig path: Component config --> Bluetooth --> Controller Options --> PCM Signal Configurations --> PCM Signal Configurations: Role, Polar and Channel Mode(Stereo/Mono) --> Channel Mode(Stereo/Mono)

Codec Choice

ESP32 supports two types of codec for HFP audio data: CVSD and mSBC.

CVSD is the default setting and is also the widely used codec for voice audio. But, mSBC is designed to have a better voice quality through HFP. To select which one is in use, we provide Wide Band Speech item in the menuconfig path:

Component config --> Bluetooth --> Bluedroid Options --> Wide Band Speech.

Switching on the Wide Band Speech means that the preferred codec is mSBC, but which one is actually being used also depends on the Data Path configuration.

  • If you choose PCM for datapath, you can only use CVSD and hardware is responsible for the codec job. In the meanwhile, you cannot use mSBC by switching Wide Band Speech on, because the mSBC is implemented in the Bluedroid (Bluetooth Host Stack) by software.

  • If you choose vHCI for datapath with Wide Band Speech on, codec job is done in the Bluedroid and mSBC is being used.

  • If you choose vHCI for datapath with Wide Band Speech off, hardware is responsible for the codec job and CVSD is in use.

Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

idf.py -p PORT flash monitor

(Replace PORT with the name of the serial port to use.)

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example Output

When you run this example, the explain prints the following at the very beginning:

Type 'help' to get the list of commands.
Use UP/DOWN arrows to navigate through command history.
Press TAB when typing command name to auto-complete.

 ==================================================
 |       Steps to test hfp_hf                     |
 |                                                |
 |  1. Print 'help' to gain overview of commands  |
 |  2. Setup a service level connection           |
 |  3. Run hfp_hf to test                         |
 |                                                |
 =================================================

Service Level Connection and Disconnection

You can type con to establish a service level connection with AG device and log prints such as:

connect
W (79632) BT_APPL: new conn_srvc id:27, app_id:1
I (79642) BT_HF: APP HFP event: CONNECTION_STATE_EVT
I (79642) BT_HF: --connection state connected, peer feats 0x0, chld_feats 0x0
I (79792) BT_HF: APP HFP event: CALL_IND_EVT
I (79792) BT_HF: --Call indicator NO call in progress
I (79792) BT_HF: APP HFP event: CALL_SETUP_IND_EVT
I (79802) BT_HF: --Call setup indicator NONE
I (79802) BT_HF: APP HFP event: NETWORK_STATE_EVT
I (79812) BT_HF: --NETWORK STATE available
I (79812) BT_HF: APP HFP event: SIGNAL_STRENGTH_IND_EVT
I (79822) BT_HF: -- signal strength: 4
I (79822) BT_HF: APP HFP event: ROAMING_STATUS_IND_EVT
I (79832) BT_HF: --ROAMING: inactive
I (79832) BT_HF: APP HFP event: BATTERY_LEVEL_IND_EVT
I (79842) BT_HF: --battery level 3
I (79842) BT_HF: APP HFP event: CALL_HELD_IND_EVT
I (79852) BT_HF: --Call held indicator NONE held
I (79852) BT_HF: APP HFP event: CONNECTION_STATE_EVT
I (79862) BT_HF: --connection state slc_connected, peer feats 0x16e, chld_feats 0x0
I (79872) BT_HF: APP HFP event: INBAND_RING_TONE_EVT
I (79872) BT_HF: --inband ring state Provided

Note: Only after Hands-Free Profile(HFP) service is initialized and a service level connection exists between an HF Unit and an AG device, could other commands be available.

You can type dis to disconnect with the connected AG device, and log prints such as:

disconnect
W (93702) BT_RFCOMM: port_rfc_closed RFCOMM connection in state 3 closed: Closed (res: 19)
W (93712) BT_APPL: BTA_HF_CLIENT_SCO_SHUTDOWN_ST: Ignoring event 3
I (93712) BT_HF: APP HFP event: CONNECTION_STATE_EVT
I (93712) BT_HF: --connection state disconnected, peer feats 0x0, chld_feats 0x0

Audio Connection and Disconnection

You can type cona to establish the audio connection between HF Unit and AG device. Log prints such as:

connect audio
I (117232) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (117232) BT_HF: --audio state connecting
E (117262) BT_BTM: btm_sco_connected, handle 181
I (117262) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (117262) BT_HF: --audio state connected

Also, you can type disa to close the audio data stream. Log prints such as:

disconnect audio
I (133262) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (133262) BT_HF: --audio state disconnected

Scenarios for Audio Connection

  • Answer an incoming call
  • Enable voice recognition
  • Dial an outgoing call

Scenarios for Audio Disconnection

  • Reject an incoming call
  • Disable the voice recognition

Choice of Codec

ESP32 supports both CVSD and mSBC codec. HF Unit and AG device determine which codec to use by exchanging features during service level connection. The choice of codec also depends on the your configuration in menuconfig.

Since CVSD is the default codec in HFP, we just show the scenarios using mSBC:

  • If you enable BT_HFP_WBS_ENABLE in menuconfig, mSBC will be available.
  • If both HF Unit and AG support mSBC and BT_HFP_WBS_ENABLE is enabled, ESP32 chooses mSBC.
  • If you use PCM data path, mSBC is not available.

Answer or Reject an incoming call

Answer an incoming call

You can type ac to answer an incoming call and log prints such as:

Answer call
I (197102) BT_HF: APP HFP event: AT_RESPONSE
I (197102) BT_HF: --AT response event, code 0, cme 0
E (197232) BT_BTM: btm_sco_connected, handle 181
I (197232) BT_HF: APP HFP event: CALL_IND_EVT
I (197232) BT_HF: --Call indicator call in progress
I (197232) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (197242) BT_HF: --audio state connected

Reject an incoming call

You can type rc to reject an incoming call and log prints such as:

Reject call
I (210822) BT_HF: APP HFP event: AT_RESPONSE
I (210822) BT_HF: --AT response event, code 0, cme 0
I (210842) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (210842) BT_HF: --audio state disconnected
I (210902) BT_HF: APP HFP event: CALL_IND_EVT
I (210902) BT_HF: --Call indicator NO call in progress

Dial Number

This example supports three dialing commands:

  • d <num> Dial the specific number.
  • rd Redial the last number.
  • dm <index> Dial the specific indexed number in the AG memory.

For example, type d 186xxxx5549 to make an outgoing call to 186xxxx5549 and log prints such as:

Dial number 186xxxx5549
E (229702) BT_BTM: btm_sco_connected, handle 181
I (229712) BT_HF: APP HFP event: CALL_SETUP_IND_EVT
I (229712) BT_HF: --Call setup indicator OUTGOING_DIALING
I (229712) BT_HF: APP HFP event: CALL_IND_EVT
I (229712) BT_HF: --Call indicator call in progress
I (229722) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (229722) BT_HF: --audio state connected
I (229732) BT_HF: APP HFP event: CALL_SETUP_IND_EVT
I (229732) BT_HF: --Call setup indicator NONE

Respond and Hold

You can type rh <btrh> to respond or hold the current call. The parameter should be set as follows:

  • <btrh> : 0 - hold current call, 1 - answer held call, 2 - end held call.

Volume Control

You can type vu <tgt> <vol> to update volume gain of speaker or microphone. The parameter should be set as follows:

  • <tgt> : 0 - speaker, 1 - microphone.
  • <vol> : Integer among 0 - 15.

For example, type vu 0 9 to update the volume of speaker and log on AG prints:

I (43684) BT_APP_HF: APP HFP event: VOLUME_CONTROL_EVT
I (43684) BT_APP_HF: --Volume Target: SPEAKER, Volume 9

And also, vu 1 9 update the volume gain of microphone and log on AG prints:

I (177254) BT_APP_HF: APP HFP event: VOLUME_CONTROL_EVT
I (177254) BT_APP_HF: --Volume Target: MICROPHONE, Volume 9

Voice Recognition

You can type vron to start the voice recognition of AG and type vroff to terminate this function. For example, type vron and log prints such as:

Start voice recognition
I (293172) BT_HF: APP HFP event: AT_RESPONSE
I (293172) BT_HF: --AT response event, code 0, cme 0
E (293702) BT_BTM: btm_sco_connected, handle 181
I (293702) BT_HF: APP HFP event: AUDIO_STATE_EVT
I (293702) BT_HF: --audio state connected

Query Current Operator Name

You can type qop to query the current operator name and log prints like:

Query operator
I (339202) BT_HF: APP HFP event: CURRENT_OPERATOR_EVT
I (339202) BT_HF: --operator name: 中国联通
I (339202) BT_HF: APP HFP event: AT_RESPONSE
I (339202) BT_HF: --AT response event, code 0, cme 0

Retrieve Subscriber Information

You can type rs to retrieve subscriber information and log prints such as:

Retrieve subscriber information
I (353702) BT_HF: APP HFP event: SUBSCRIBER_INFO_EVT
I (353702) BT_HF: --subscriber type unknown, number 186xxxx5549
I (353702) BT_HF: APP HFP event: AT_RESPONSE
I (353702) BT_HF: --AT response event, code 0, cme 0

Query Current Call Status

You can type qc to query current call status and log prints like:

Query current call status
I (354582) BT_HF: APP HFP event: CLCC_EVT
I (354582) BT_HF: --Current call: idx 1, dir incoming, state active, mpty single, number 186xxxx5549
I (354582) BT_HF: APP HFP event: AT_RESPONSE
I (354592) BT_HF: --AT response event, code 0, cme 0

Transport DTMF Code

You can type k <dtmf> to transport a DTMF code to AG. Log on HF unit side prints like:send dtmf code: 9 and log on AG side prints such as:

I (196284) BT_APP_HF: APP HFP event: DTMF_RESPONSE_EVT
I (196284) BT_APP_HF: --DTMF code is: 9.

Troubleshooting

If you encounter any problems, please check if the following rules are followed:

  • You should type the command in the terminal according to the format described in the commands help table.
  • Not all commands in the table are supported by AG device like Hands Free Audio Gateway (hfp_ag) example from ESP-IDF.
  • If you want to use con to establish a service level connection with specific AG device, you should add the MAC address of the AG device in bt_app.c, for example: esp_bd_addr_t peer_addr = {0xb4, 0xe6, 0x2d, 0xeb, 0x09, 0x93};
  • Use esp_hf_client_register_callback() and esp_hf_client_init(); before establishing a service level connection.

Example Breakdown

Due to the complexity of HFP, this example has more source files than other bluetooth examples. To show functions of HFP in a simple way, we use the Commands and Effects scheme to illustrate APIs of HFP in ESP-IDF.

  • The example will respond to user command through UART console. Please go to console_uart.c for the configuration details.
  • For voice interface, ESP32 has provided PCM input/output signals which can be mapped to GPIO pins. So, please go to gpio_pcm_config.c for the configuration details.
  • If you want to update the command table, please refer to app_hf_msg_set.c.
  • If you want to update the responses of HF Unit or want to update the log, please refer to bt_app_hf.c.
  • Task configuration part is in bt_app_core.c.