br2-external-bluetooth

br2-external-bluetooth

Overview

External layer for experimenting with Linux BlueZ bluetooth software.

Major purposes:

• integrate BlueZ components into systemd to enable seamless Linux bluetooth bring-up on boot
• experiment with Linux CAN software

Supported board configurations:

• RFCOMM serial access to Raspberry Pi Zero W board

$ make BR2_EXTERNAL=/path/to/br2-external-bluetooth connect_rpi0w_rfcomm_defconfig

• TODO: ELM237 CAN logger using Raspberry Pi Zero W board

$ make BR2_EXTERNAL=/path/to/br2-external-bluetooth connect_rpi0w_can_defconfig

Build and flash image

$ time make

Follow Buildroot instructions and write image to SDcard. Before booting device, mount SDcard and edit several files to customize WiFi and Bluetooth settings:

• /var/lib/connman/wifi_test1.config: edit to configure AP name and password for wireless access
• /var/lib/bluetooth/XX:XX:XX:XX:XX:XX:rename directory to MAC address of rpi0w board under test

Access rpi0w serial console using Bluetooth rfcomm

Serial access to rpi0w board via Bluetooth rfcomm should be available right out of the box:

• bluetooth enablement is handled by systemd: see rfcomm and btattach services
• discovery and pairing is enabled by bluetooth configuration files:
  • see /etc/bluetooth/main.conf and /var/lib/bluetooth/XX:XX:XX:XX:XX:XX/settings

Execute the following steps on host:

• Configure bluetooth on host: Use bluetoothctl tool to bring-up controller on host, then to scan and to pair with rpi0w:

$ sudo systemctl start bluetooth
$ bluetoothctl
[bluetooth]# power on
[bluetooth]# scan on
[bluetooth]# pair XX:XX:XX:XX:XX:XX
[bluetooth]# quit

• Configure rfcomm on host: Setup rfcomm and connect to rpi0w after pairing is successfully completed:

$ sudo rfcomm bind 0 XX:XX:XX:XX:XX:XX
$ sudo minicom -D /dev/rfcomm0

Here replace XX:XX:XX:XX:XX:XX by bluetooth MAC address of rpi0w board under test.