AIROC™ BTSTACK: Bluetooth® SPP server for Linux host

This code example demonstrates Bluetooth® SPP server using AIROC™ Wi-Fi & Bluetooth® combo chip.

Requirements

• Programming language: C
• Embedded Linux platforms (Arm® Cortex®-A Class processors) for host communications. Supported Embedded Linux host platforms:
  1. RPI CM4-lite IFX custom HW 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

• AIROC™ CYW5557x Wi-Fi & Bluetooth® combo chip

Hardware setup

Set up the hardware required for this code example as follows:

Figure 1. Hardware setup block diagram

Software setup

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

Note: These steps are for Arm® 64-based target platform. Review these steps before adding support for any other target.

1. Open a terminal on the Linux host PC.

2. 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

This section describes the steps to be executed on the Linux host PC for compiling the code example.

1. Create a directory under $HOME on the Linux host PC and switch to the created directory. Use the following commands for reference:

   mkdir $HOME/Linux_CE
   cd $HOME/Linux_CE

2. Fetch the code example source code using the following command:

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

3. Clone the code example dependencies (BTSTACK library, Linux porting layer source code, and audio profiles) using the following commands:

   git clone https://github.com/Infineon/btstack --branch release-v3.6.0
   git clone https://github.com/Infineon/bluetooth-linux.git --branch release-v1.0.0
   git clone https://github.com/Infineon/bt-audio-profiles.git --branch release-v1.0.0

   Creates four different directories after cloning the code example and its dependencies with the directory structure as follows:

   Figure 2. Code example directory structure

   

4. 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.

5. 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-spp
   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 Arm® 64-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-spp" executable is generated at /home/$USER/Linux_CE/linux-example-btstack-spp/build.

Operation

Using one hardware platform (Linux host platform and AIROC™ Wi-Fi & Bluetooth® combo chip)

This code example acts as a SPP server.

Devices used:

• Device Under Test (DUT): One hardware platform (Linux host platform and AIROC™ Wi-Fi & Bluetooth® combo chip) are required that runs the SPP code example. Role: "SPP Server"

• Testing Device: Windows 10 Machine with a terminal emulator application such as Tera Term for creating SPP connection. Role: "SPP Client"

Operation procedure:

1. Copy the code example executable, AIROC™ BTSTACK libraries and Bluetooth® Firmware file from the Linux host PC to the target platform using SCP. For example, use the following commands:

   cd $HOME/Linux_CE/linux-example-btstack-spp/build
   scp linux-example-btstack-spp <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>/.
   scp <FW_FILE.hcd> <TARGET_USER>@<TARGET_IP>:<TARGET_PATH>/.
   

   Where,

   • TARGET_USER is user name of the target platform
   • TARGET_IP is the IP address of the target platform
   • TARGET_PATH is the path of target platform
   • FW_FILE.hcd file is the Bluetooth® Firmware file cloned in step-4 of Using the code example section.

2. Take SSH console of target platform.

   ssh <TARGET_DEVICE_USER_NAME>@<TARGET_DEVICE_IP_ADDRESS>

3. 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

4. Execute the application by 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 3000000 -f 921600 -r <GPIOCHIPx> <REGONPIN> -n -p <FW_FILE_NAME>.hcd -d 112233221133

   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 executable are in the same folder
   • /dev/ttymxc0 is the COM_PORT for IMX8Nano
   • /dev/ttyAMA0 is the COM_PORT for RPICM4
   • 3000000 is the HCI baud rate
   • 112233221133 is a device BD address
   • -r <GPIOCHIPx> <REGONPIN> -n is setting the GPIO control to enable autobaud for AIROC™ Wi-Fi & Bluetooth® combo chip
     • -r gpiochip5 0 -n For IMX8Nano
     • -r gpiochip0 3 -n For RPICM4
   • 921600 is the firmware download baud rate
   • .hcd is the firmware to download (make sure to validate this firmware file path)

   Note: Currently, random BD addresses are used for testing.

5. On Windows 10 PCs, right click on the Bluetooth® icon in the system tray and select 'Show Bluetooth® Devices'. In the Settings menu that opens for 'Bluetooth® & Other Devices', Select 'Add a Bluetooth® Device'. Find and pair with the SPP Server.

6. In the Settings menu that opens for 'Bluetooth® & Other Devices', scroll down and select "More Bluetooth® options" and then select the 'COM Ports' tab. You can see an incoming and an outgoing COM port on your computer.

Figure 3. SPP Server Connection with Windows 10 PC

7. Use serial port application such as Tera Term to open the outgoing COM port with 115200 baud rate (115200-8-N-1 serial configuration). Opening the port will create the SPP connection(see Figure 4).

Figure 4. Opening COM port in Tera Term

     ---------------------SPP MENU-----------------------

     0.  Exit
     1.  Print Menu
     2.  Send Large Sample Data
     3.  Send Data
     Choose option -> 3
     Enter the Data to be Sent :
     Hello

8. Press any key (a-z or 0-9) on terminal of the outgoing COM port, the spp application will receive the key that was pressed from the outgoing COM port.

9. On the SPP Server CE, select option 2, "Send Large Sample Data", to send large size data to the SPP client. Repeated continuous numbers from 0 to max payload size will be sent and the corresponding printable ascii characters will be visible on the terminal emulator such as Tera Term of the Windows 10 machine(see Figure 5).

Figure 5. Sending large sample data

You can also use option 3, "Send Data", to send the user-entered characters to the SPP Client. The same will be visible on the Windows 10 machine's terminal emulator, such as Tera Term (see Figure 6).

Figure 6. Sending user's data

Debugging

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

1. Debugging by logging: Add required prints in the application and check them during execution.

2. Debugging using GDB: See the GDB man page for more details.

Design and implementation

This code example does the following:

The SPP server CE initializes the stack, opens the RFCOMM channel, and waits for the SPP connection from the client. Once SPP is connected, users can send data to the SPP client via the user menu. Data sent from the SPP client is printed on the SPP Server CE console.

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

Source file details

Files	Description of files
app/main.c	Implements the main function which takes the user command line inputs.
app/spp.c	Implements SPP Server functionalities
include/spp.h	Header file for SPP server functionality.
app_bt_config/wiced_bt_config.c	This file contains configurations related to BT settings, GAP and HF.

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	CYW5557x
AIROC™ BTSTACK library	AIROC™ BTSTACK library
Linux porting layer source code	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: CE237175 - AIROC™ BTSTACK: Bluetooth® SPP server for Linux host

Version	Description of change
1.0.0	New code example

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