7.2.9 Bluetooth Initialization Guide

This chapter describes the initialization process and usage of the Bluetooth feature on the development board.

Overview

The development board supports connecting Bluetooth modules through USB or UART interfaces. At system startup, the hobot-bluetooth service automatically detects and initializes Bluetooth devices.

Supported Bluetooth Types

Type	Interface	Description
USB Bluetooth	USB interface	Bluetooth adapter connected through a USB interface
UART Bluetooth	UART serial port	Bluetooth module connected through a UART serial port (such as CYW55560)

System Services

hobot-bluetooth Service

Bluetooth initialization is managed by the hobot-bluetooth.service system service, which runs automatically at system startup.

Service configuration file location: /lib/systemd/system/hobot-bluetooth.service

[Unit]
Description=Hobot init Bluetooth
Before=getty.target system-getty.slice
After=hobot-loadko.service
StartLimitIntervalSec=60
StartLimitBurst=5

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/etc/init.d/hobot-bluetooth start
ExecStop=/usr/bin/hciconfig hci0 down > /dev/null 2>&1
TimeoutStartSec=1min
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Service Management Commands

# Check service status
systemctl status hobot-bluetooth

# Start service manually
sudo systemctl start hobot-bluetooth

# Stop service manually
sudo systemctl stop hobot-bluetooth

# Enable auto-start at boot
sudo systemctl enable hobot-bluetooth

# Disable auto-start at boot
sudo systemctl disable hobot-bluetooth

Initialization Script Description

Initialization Flow

The Bluetooth initialization script /usr/bin/startbt.sh detects and initializes Bluetooth devices in the following order:

┌─────────────────────────────┐
│    Bluetooth init start     │
└──────────────┬──────────────┘
               │
               ▼
┌─────────────────────────────┐
│    Detect USB Bluetooth     │
│    (lsusb -t | grep btusb)   │
└──────────────┬──────────────┘
               │
       ┌───────┴───────┐
       │               │
       ▼               ▼
   USB detected    USB not detected
       │               │
       ▼               ▼
┌──────────────┐  ┌──────────────────┐
│ Load btusb   │  │ Detect UART BT    │
│ driver module│  │ (/dev/ttyS1)      │
└──────┬───────┘  └────────┬─────────┘
       │                   │
       │           ┌───────┴───────┐
       │           │               │
       │           ▼               ▼
       │       UART detected  UART not detected
       │           │               │
       │           ▼               ▼
       │    ┌──────────────┐  ┌──────────────┐
       │    │ GPIO control │  │  Exit with   │
       │    │ FW download  │  │    error     │
       │    │ hciattach    │  │              │
       │    └──────┬───────┘  └──────────────┘
       │           │
       └─────┬─────┘
             │
             ▼
    ┌──────────────────┐
    │ hciconfig hci0 up │
    │ hciconfig piscan  │
    └────────┬─────────┘
             │
             ▼
    ┌──────────────────┐
    │  Init complete   │
    └──────────────────┘

USB Bluetooth Initialization

When a USB Bluetooth device is detected, the initialization flow is as follows:

# 1. Load the btusb driver module
modprobe btusb

# 2. Wait for firmware loading to complete
sleep 3

# 3. Enable the Bluetooth device
hciconfig hci0 up
sleep 2
hciconfig hci0 piscan

UART Bluetooth Initialization

When a UART Bluetooth device is detected, the initialization flow is as follows (using XM612 as an example; if you use a different Bluetooth module, contact the module vendor for details):

# Configuration parameters
BT_REG_GPIO=427              # Bluetooth enable GPIO
UART_PORT="/dev/ttyS1"       # UART port
UART_BAUD=921600             # Baud rate
FW="/lib/firmware/cypress/CYW55560A1.hcd"  # Firmware path

# 1. Export and configure GPIO
echo 427 > /sys/class/gpio/export
echo out > /sys/class/gpio/gpio427/direction

# 2. Reset the Bluetooth module
echo 0 > /sys/class/gpio/gpio427/value
sleep 1
echo 1 > /sys/class/gpio/gpio427/value
sleep 2

# 3. Download firmware
mbt download /lib/firmware/cypress/CYW55560A1.hcd --autobaud3M
mbt update_baudrate 921600

# 4. Start HCI attach
hciattach -s 921600 /dev/ttyS1 any 921600 &

# 5. Enable the Bluetooth device
hciconfig hci0 up
hciconfig hci0 piscan

Bluetooth Firmware

Firmware Storage Paths

Bluetooth firmware is stored in the following directories:

Chip Model	Firmware Path
Realtek RTL8852BTU	`/lib/firmware/rtl_bt/rtl8852btu_fw.bin`
Realtek RTL8723BS	`/lib/firmware/rtl_bt/rtl8723bs_fw.bin`
Cypress CYW55560	`/lib/firmware/cypress/CYW55560A1.hcd`

View Loaded Firmware

# View rtl_bt firmware
ls -la /lib/firmware/rtl_bt/

# View cypress firmware
ls -la /lib/firmware/cypress/

Bluetooth Status Query

View Bluetooth Devices

# List Bluetooth devices
hciconfig

# View detailed Bluetooth device information
hciconfig hci0

Example output:

hci0:   Type: Primary  Bus: USB
        BD Address: 00:11:22:33:44:55  ACL MTU: 1021:8  SCO MTU: 64:1
        UP RUNNING PSCAN ISCAN
        RX bytes:1234 acl:0 sco:0 events:456 bytes:789
        TX bytes:987 acl:0 sco:0 commands:123 errors:0

View Bluetooth Device Properties

# View Bluetooth device status
hciconfig hci0 status

# View Bluetooth device address
hciconfig hci0 | grep "BD Address"

Bluetooth Operation Commands

Enable/Disable Bluetooth

# Enable Bluetooth device
sudo hciconfig hci0 up

# Disable Bluetooth device
sudo hciconfig hci0 down

# Enable scan mode
sudo hciconfig hci0 piscan

# Disable scan mode
sudo hciconfig hci0 noscan

Bluetooth Scanning

# Scan nearby Bluetooth devices
hcitool scan

# Scan BLE devices
hcitool lescan

Bluetooth Pairing

# Pair using bluetoothctl
bluetoothctl

# In the bluetoothctl interactive interface:
[bluetooth]# power on
[bluetooth]# agent on
[bluetooth]# default-agent
[bluetooth]# scan on
[bluetooth]# pair XX:XX:XX:XX:XX:XX
[bluetooth]# trust XX:XX:XX:XX:XX:XX
[bluetooth]# connect XX:XX:XX:XX:XX:XX

FAQ

Bluetooth Device Not Recognized

If the Bluetooth device is not recognized, check the following:

Check service status
```
systemctl status hobot-bluetooth
```

Check device connection

# USB Bluetooth
lsusb

# UART devices
ls -la /dev/ttyS*

Check driver modules
```
lsmod | grep bt
```

Firmware Loading Failed

If firmware loading fails:

Check whether firmware files exist

ls -la /lib/firmware/rtl_bt/
ls -la /lib/firmware/cypress/

Check kernel logs

dmesg | grep -i bluetooth
dmesg | grep -i firmware

UART Bluetooth Initialization Failed

If UART Bluetooth initialization fails:

Check GPIO status
```
cat /sys/class/gpio/gpio427/value
```
Check UART port permissions
```
ls -la /dev/ttyS1
```

Manually test UART

stty -F /dev/ttyS1 921600
cat /dev/ttyS1 &
echo "test" > /dev/ttyS1

Manually Reinitialize Bluetooth

If you need to manually reinitialize Bluetooth:

# Stop the Bluetooth service
sudo systemctl stop hobot-bluetooth

# Disable the Bluetooth device
sudo hciconfig hci0 down

# Unload the driver module
sudo rmmod btusb

# Reload the driver
sudo modprobe btusb

# Start the Bluetooth service
sudo systemctl start hobot-bluetooth

Overview​

Supported Bluetooth Types​

System Services​

hobot-bluetooth Service​

Service Management Commands​

Initialization Script Description​

Initialization Flow​

USB Bluetooth Initialization​

UART Bluetooth Initialization​

Bluetooth Firmware​

Firmware Storage Paths​

View Loaded Firmware​

Bluetooth Status Query​

View Bluetooth Devices​

View Bluetooth Device Properties​

Bluetooth Operation Commands​

Enable/Disable Bluetooth​

Bluetooth Scanning​

Bluetooth Pairing​

FAQ​

Bluetooth Device Not Recognized​

Firmware Loading Failed​

UART Bluetooth Initialization Failed​

Manually Reinitialize Bluetooth​