AIROC™ BTSTACK: Bluetooth® headset for Linux host

This code example demonstrates the implementation of a Bluetooth® headset with the AIROC™ Wi-Fi & Bluetooth® combo chip using Embedded Linux platforms (Arm® Cortex®-A Class processors).

View this README on GitHub.

Provide feedback on this code example.

Requirements

Programming language: C
Embedded Linux Host platforms (Arm® Cortex®-A Class processors). Supported Embedded Linux host platforms:
1. RPI CM4-lite with custom HW base board from Infineon
2. IMX8 nano uCOM board from Embedded Artists
AIROC™ BTSTACK library and Linux porting layer source code
AIROC™ Wi-Fi & Bluetooth® combo chip Bluetooth® Firmware file (.hcd).
Linux Host PC with Ubuntu 20.04

Supported toolchains (make variable 'TOOLCHAIN')

GNU Arm® GCC AArch64 v9.3.0 (GCC_ARM)

Supported AIROC™ Wi-Fi & Bluetooth® combo chip

Hardware setup

Set up the hardware according to the following diagram:

Figure 1. Block diagram: Hardware setup

Software setup

Set up a cross compiler according to the target platform along with CMake on the host PC based on Ubuntu 20.04.

These steps are for arm64 based target platform. Please review these steps before adding support for any other target

Open a terminal on the Ubuntu host PC.
Use the following command to install the cross compiler, build tools, and dependencies:
```
sudo apt-get install git cmake gcc-aarch64-linux-gnu build-essential -y
```

Using the code example

Do the following on the Linux host PC to compile the code example:

Create a directory under $HOME on the host PC and switch to the created directory. Use the following commands, for example:
```
mkdir $HOME/Linux_CE
cd $HOME/Linux_CE
```
Note: Replace Linux_CE with a directory of your choice.

Fetch the code example source code using the following command:

git clone https://github.com/Infineon/linux-example-btstack-headset

Clone the code example dependencies (BTSTACK library and Linux porting layer source code) using the following commands:

git clone https://github.com/Infineon/btstack --branch release-v3.6.1
git clone https://github.com/Infineon/bt-audio-profiles --branch release-v1.0.0
git clone https://github.com/Infineon/bluetooth-linux --branch release-v2.0.0
git clone https://github.com/Infineon/btsdk-gfps --branch release-v3.3.0

Four different directories are created after cloning the code example and its dependencies - see the following example:

Figure 2. Code example directory structure

Clone the Bluetooth® firmware using following command.
```
git clone https://github.com/Infineon/combo-bluetooth-firmware.git
```
User can choose appropriate Bluetooth® firmware for particular AIROC™ Wi-Fi & Bluetooth® combo chip from cloned "combo-bluetooth-firmware" directory.
Use the following command to patch btsdk-gfps:
```
cd btsdk-gfps/
git am ../linux-example-btstack-headset/btsdk-gfps-patch/*
cd ..
```
If you see the message Applying: linuxCe porting layer include, it means successful patch
Use the following command to patch bt-audio-profiles:
```
cd bt-audio-profiles/
git am ../linux-example-btstack-headset/bt-audio-patch/*
cd ..
```
If you see the message Applying: fix wiced_bt_get_buffer twice issue, it means successful patch
Create the build folder under the code example source folder and build the code example using the following commands:
```
cd $HOME/Linux_CE/linux-example-btstack-headset
mkdir build && cd build
cmake -DCMAKE_C_COMPILER:PATH=<GCC_CROSS_COMPILER> ../ && make
```
Where,
- GCC_CROSS_COMPILER is the target cross compiler for GCC (generally /usr/bin/aarch64-linux-gnu-gcc for ARM64-based targets)
The code example executable is generated under the build folder with the same name of code example.

For example, in this project, the "linux-example-btstack-headset" executable is generated at /home/$USER/Linux_CE/linux-example-btstack-headset/build.

Operation

This code example acts as a Headset. The remote device will be a mobile or laptop for Audio streaming or calling functionality.

Two devices are required to demonstrate this application: One hardware platform (Linux host platform + AIROC™ Wi-Fi & combo chip, i.e., the device running the Headset application) and a mobile or laptop.

Take SSH console of target platform.

ssh <TARGET_DEVICE_USER_NAME>@<TARGET_DEVICE_IP_ADDRESS>

Copy the code example executable and AIROC™ BTSTACK library from the host PC to the target platform using SCP. For example, use the following commands:

cd $HOME/Linux_CE/linux-example-btstack-headset/build
scp linux-example-btstack-headset <TARGET_USER>@<TARGET_IP>:<TARGET_PATH>/.
cd $HOME/Linux_CE/btstack/stack/COMPONENT_WICED_DUALMODE/COMPONENT_ARMv8_LINUX/COMPONENT_GCC
scp libbtstack.so <TARGET_USER>@<TARGET_IP>:<TARGET_PATH>/.
cd $HOME/Linux_CE/bt-audio-profiles/sbc/COMPONENT_ARMv8_LINUX/COMPONENT_GCC
scp libsbc.so <TARGET_USER>@<TARGET_IP>:<TARGET_PATH>/.
scp <FW_FILE.hcd> <TARGET_USER>@<TARGET_IP>:<TARGET_PATH>/.

Where,

TARGET_USER is the user name of the target platform
TARGET_IP is the IP address of the target platform
TARGET_PATH is the path of the target platform
FW_FILE.hcd file is Bluetooth® Firmware file cloned in Using the code example section.

Add the udev rule in the target host board for HCI UART and GPIO to bypass root access. Use the following steps to create and set up a udev rule.

Note: If you have root access, the following udev rules are not required; you can execute the code example with sudo permissions or by switching to the root user.
1. Create a new .rules (for example, combo-chip-uart-port.rules) file under /etc/udev/rules.d/ directory for HCI UART. Use the following commands:
  
  IMX8Nano:
```
echo "KERNEL==\"ttymxc0\"d,SYMLINK+=\"combo_chip_uart\",MODE=\"0666\"" | sudo tee /etc/udev/rules.d/combo-chip-uart-port.rules
```
  RPICM4:
```
echo "KERNEL==\"ttyAMA0\",SYMLINK+=\"combo_chip_uart\",MODE=\"0666\"" | sudo tee /etc/udev/rules.d/combo-chip-uart-port.rules
```
2. Create new .rules (for example, combo-chip-gpio-port.rules) for BT_REG_ON GPIO under /etc/udev/rules.d/. Use the following commands:
  
  IMX8Nano & RPICM4:
  1. Create a rule file using the following command.
```
sudo vim /etc/udev/rules.d/combo-chip-gpio-port.rules.rules
```
  2. Add the following rules in created files:
```
SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R $user:$group /sys/class/gpio/export /sys/class/gpio/unexport;'"
SUBSYSTEM=="gpio*", PROGRAM="/bin/sh -c 'chown -R $user:$group /sys%p/direction /sys%p/value; chmod 660 /sys%p/direction /sys%p/value;'"
```
3. Reboot the target device:
```
sudo reboot
```
  Where,
  - ttymxc0, and ttyAMA0 are HCI UART ports for IMX8Nano and RPICM4 respectively
  - combo_chip_uart is a friendly name for the HCI UART port
  - 0666 is the permission mask to bypass the root access for HCI UART
Check and configure the ALSA playback sound card and record sound card settings.
1. Use aplay -l to check which card you need to be used for audio playback.
  
  For an example, if user want to choose card 2 device 0, User should set pcm hw:2,0
2. Use arecord -l to which card need to be used for audio record.
  
  For an example, if user want to choose card 2 device 0, User should set ctl hw:2,0
3. Modify or add an ALSA setting file ~/.asoundrc and add the below setting, the number of pcm hw:X,X and ctl hw:Y,Y should refer above sound card information.
```
pcm.!default {
   type plug
   slave {
      pcm "hw:3,0"
   }
}
ctl.!default {
   type plug
   slave {
      ctl "hw:3,0"
   }
}
```
  Where,
  - pcm "hw:3,0" is your card number check use the aplay -l cmd
  - ctl "hw:3,0" is your card number checked using the record -l cmd
4. Use following commands to test card configurations done using above steps. If the card set-up is successful, User can record and playback the audio file successfully.
```
arecord -f S16_LE -r 8000 -c 2 -d 3 mic_test.raw
aplay mic_test.raw
```
  Note: use the same user to set up the ALSA setting and launch the code example, ex: don't use sudo to set-up ALSA setting and launch code example without sudo
Execute the application with setting the paths of the AIROC™ BTSTACK library using the following command on the target platform:
```
cd <TARGET_PATH>
chmod +x <APP_NAME>
LD_LIBRARY_PATH=$LD_LIBRARY_PATH:<BTSTACK_LIB_PATH>
./<APP_NAME> -c <COM_PORT> -b <HCI_BAUDRATE> -f <FW_DL_BAUDRATE> -r <GPIOCHIPx> <REGONPIN> -n -p <FW_FILE_NAME>.hcd -d 112233221144
```
Where,
- TARGET_PATH is the path of the target platform where the code example application copied to
- BTSTACK_LIB_PATH is the path of the AIROC™ BTSTACK library. Skip this if the AIROC™ BTSTACK library and code example application executable are in the same folder
- COM_PORT is the HCI communication port.
  - /dev/ttymxc0 for IMX8Nano
  - /dev/ttyAMA0 for RPICM4
- HCI_BAUDRATE is the baud rate to be used for HCI communication.
  - 3000000 is the HCI baud rate
- 112233221133 is a device BD address
- -r <GPIOCHIPx> <REGONPIN> -n is setting the GPIO control to program the Bluetooth® Firmware for AIROC™ Wi-Fi + Bluetooth® combo chip
  - -r gpiochip5 0 -n For IMX8Nano
  - -r gpiochip0 3 -n For RPICM4
- FW_DL_BAUDRATE is the baud rate to be used for patch download; default value is 115200 if not specified. Different chips support different maximum download speed.
  - 921600 for AIROC™ CYW5557x Wi-Fi & Bluetooth® combo chip
  - 115200 for AIROC™ CYW54591 Wi-Fi & Bluetooth® combo chip
  - 115200 for AIROC™ CYW43439 Wi-Fi & Bluetooth® combo chip
  - 115200 for AIROC™ CYW43012 Wi-Fi & Bluetooth® combo chip
- <FW_FILE_NAME>.hcd is the firmware patch to download (make sure to validate this firmware patch file path)
  
  Note 1: If you haven't set up a udev rule mentioned in Step 4, execute the command with sudo permissions.
  
  Note 2: Currently, random BD addresses are used for testing.

When the code example is launched, a menu appears on the terminal as follows:

------------Headset MENU-----------------------
0.  Exit
1.  Print Menu
2.  Set Visibility
3.  Set Pairing Mode
4.  Set Inquiry and Connect Device
5.  BR/EDR ReConnect Paired Device
6.  BR/EDR Disconnect
7.  Get Current Statuses
8.  [HFP] Print Connection Details
9.  [HFP] Answer Call
10. [HFP] Hangup Call
11. [HFP] Dial Number
12. [HFP] Redial
13. [HFP] Query Current Calls
14. [HFP] Set Speaker Volume
15. [HFP] Set Microphone Volume
16. [HFP] Get Subscriber Info
17. [AVRCP] AVRCP_ACTION_VOLUME_UP
18. [AVRCP] AVRCP_ACTION_VOLUME_DOWN
19. [AVRCP] ACTION_PAUSE_PLAY
20. [AVRCP] AVRCP_ACTION_FORWARD
21. [AVRCP] AVRCP_ACTION_BACKWARD
22. [AVRCP] AVRCP_ACTION_STOP
23. [AVRCP] AVRCP_ACTION_FAST_FORWARD
24. [AVRCP] AVRCP_ACTION_FAST_REWIND
25. [AVRCP] AVRCP_ACTION_UNIT_INFO
26. [GFPS] Enable GFPS Discoverable
Choose option ->

Connect a mobile phone with headset code example.

User can connect the headset application and mobile phone in one of the two ways: using BR/EDR or using Google Fast Pair (through Bluetooth® LE).

Using BR/EDR
1. Select Option 3: Set Pairing Mode and select 1 to enable Pairing Mode.
2. Enter Option 2: Set Visibility -> select 1 then select 1 to set visibility and connectable.
3. Use a mobile phone to scan for Bluetooth® devices. When the "Headset CE" device appears, tap on headset code example to pair and connect.
PS: option 4. Set Inquiry and Connect Device can scan the nearby Bluetooth devices and show their Address and RSSI. after the scan finish, you can choose 1 to directly connect the device. before using this function, please first enable pairing mode and visibility by options 2 and 3.

Using Google Fast Pair
1. Install the Fast Pair Validator app on an Android mobile phone.
2. Enter option 3: Set Pairing Mode -> and select 1 to enable Pairing Mode.
3. Enter option 26: [GFPS] Enable GFPS Discoverable -> select 1 to enable Google Fast Pair advertising.
4. On your Android mobile phone, close the DUT device. You will be notified that a device capable of Google Fast Pair is available. Tap the button to connect.
Play some music from Mobile phone and verify it is playing on speaker connected to headset application setup. Also place a call to/from Mobile phone connected to headset application setup and verify headset functionality.
Get and check status of headset application connection with mobile phone.
- Enter Option 7: Get Current Statuses to display the connected state, call active state and sink player state.
- Enter Option 8: [HFP] Print Connection Details to display the connected state and pairing key.
Use following options to control HFP functionality.

Enter options 9 ~ 16 for hands-free operations.
Option 13. [HFP] Query Current Calls: get current active call information.
Option 14. [HFP] Set Speaker Volume: set the speaker Volume for 1 ~ 15,
Option 15. [HFP] Set Microphone Volume: set the speaker Volume for 1 ~ 15.
Option 16. [HFP] Get Subscriber Info: get the phone number that connected with Headset device.

Use following options to control music functionality.

Enter options 17 ~ 25 for Audio/Video Remote Control Profile (AVRCP) operations, including volume up/down, play, pause, stop, forward, backward, fast forward, and fast rewind.
Option 25. [AVRCP] AVRCP_ACTION_UNIT_INFO: get the information of title, Artist and album of current song, the sound of playback will pause 1 second.

Use following options to disconnect and reconnect mobile phone with headset application.

Enter Option 6: BR/EDR Disconnect to disconnect BR/EDR.
Enter Option 5: BR/EDR ReConnect Paired Device to re-pair the device. Note that the device should be already paired before, and the code example should be running.

Please ignore the all zero message of Link Key, ex: LinkKey: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Debugging

You can debug the example using a generic Linux debugging mechanism such as the following:

Debugging by logging: You can add prints in the application and check them during execution.
Debugging using GDB: See GDB man page for more details.

Design and implementation

This code example demonstrates the headset use case. It supports the following profiles and features:

A2DP Sink
Audio/Video Remote Control Profile (AVRCP)
Hands Free Unit (HFU)
Google Fast Pair

Figure 3. Headset code example architecture

This code example does the following:

Parses the command-line arguments
Initializes the AIROC™ BTSTACK library for the combo chips device
Waits until interrupted or closed

Note: Run the application without any arguments to get details of command-line arguments.

Resources and settings

Table 1. Application resources

Resource	Alias/object	Purpose
UART	HCI	UART is used for HCI communication with host system

Related resources

Resources	Links
Device documentation	AIROC™ CYW5557x Wi-Fi 6E tri-band Wi-Fi and Bluetooth® 5.2 SoC AIROC™ CYW54591 Wi-Fi & Bluetooth® combo chip AIROC™ CYW43439 Wi-Fi & Bluetooth® combo chip AIROC™ CYW43012 Wi-Fi & Bluetooth® combo chip
Libraries and middleware	AIROC™ BTSTACK library BT Audio profile layer btsdk-gfps Linux porting layer source code

Other resources

Infineon provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.

Document history

Document title: CE237648 – AIROC™ BTSTACK: Bluetooth® headset for Linux host

Version	Description of change
1.0.0	New code example

---------------------------------------------------------

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Name		Name	Last commit message	Last commit date
Latest commit History 1 Commits
app		app
app_bt_config		app_bt_config
app_bt_utils		app_bt_utils
audiomanager		audiomanager
bt-audio-patch		bt-audio-patch
bt_hs_spk_lib		bt_hs_spk_lib
btsdk-gfps-patch		btsdk-gfps-patch
ce_internal		ce_internal
deps		deps
docs		docs
images		images
include		include
linux_platform		linux_platform
CMakeLists.txt		CMakeLists.txt
LICENSE.txt		LICENSE.txt
README.md		README.md
RELEASE.md		RELEASE.md
version.xml		version.xml

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AIROC™ BTSTACK: Bluetooth® headset for Linux host

Requirements

Supported toolchains (make variable 'TOOLCHAIN')

Supported AIROC™ Wi-Fi & Bluetooth® combo chip

Hardware setup

Software setup

Using the code example

Operation

Using BR/EDR

Using Google Fast Pair

Debugging

Design and implementation

Resources and settings

Related resources

Other resources

Document history

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