This example is to show how to use the APIs of Hands-Free (HF) Unit Component and the effects of them by providing a set of commands. You can use this example to communicate with an Audio Gateway (AG) device (e.g. a smart phone). This example uses UART for user commands.
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.
ESP32 supports two types of audio data path: PCM() and HCI(Host-Controller Interface) but the default sdkconfig of this example does not config the data path in a specific way. You should config the data path you want:
- PCM : When using PCM, audio data stream is mapped to GPIO pins and you should link these GPIO pins to a speaker via I2S port. And you should choose PCM in `menuconfig` path: `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`.
- HCI : When using HCI, audio data stream will be transport to HF unit app via HCI. And you should choose HCI in `menuconfig` path: `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`.
**Note: Wide Band Speech is disabled by default, if you want to use it please select it in menuconfig path: `Component config --> Bluetooth --> Bluedroid Options --> Wide Band Speech`.**
See the [Getting Started Guide](https://docs.espressif.com/projects/esp-idf/en/latest/get-started/index.html) for full steps to configure and use ESP-IDF to build projects.
- This command help table will print out in monitor whenever you type `hf h;` or if you input a command that is not required by the command parse rule.
- The command you type will not echo in monitor and your command should always start with `hf` and end with `;` or the example will not responds.
**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.**
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`.
You can type `hf vron;` to start the voice recognition of AG and type `hf vroff;` to terminate this function. For example, type `hf vron;` and log prints such as:
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 `hf 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.
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 command parse rules, please refer to `app_hf_msg_prs.c`.
- If you want to update the responses of HF Unit or want to update the log, please refer to `bt_app_hf.c`.
