How to scan BLE devices

Applicable for

STM32MP13x lines, STM32MP15x lines

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This page lists the different operations needed to scan, connect and display BLE device information. BLE stands for Bluetooth Low Energy

1 Packages needed

• bluez5
• bluez5-noinst-tools (if you need gatttool)

2 Configuration

Init file modification for automatic Bluetooth start
/etc/udev/rules.d/10-local.rules:

# Set bluetooth power up
ACTION=="add", KERNEL=="hci0", RUN+="/usr/bin/hciconfig hci0 up"

3 Existing tool selection

Bluez provides some tools, by default, to analyze Bluetooth networks.
hciconfig to configure hci connections
hcitool to scan, find a device, connect to a device, manage a device list.. deviceS may be normal or low energy
gatttool for BLE device management

3.1 BLE device connection step-by-step

Command to scan all low-energy Bluetooth hardware:

 hciconfig hci0 up
 hcitool lescan

To scan available BLE devices:

 hcitool lewladd <BLE_MAC_ADDRRESS>

To add BLE device in the white list (optional):

 hcitool lecc <BLE_MAC_ADDRESS>

To connect a BLE device:

Once a BLE device is identified, its characteristics (attibutes) can be discovered, read and modified using GATTTOOL.
GATTTOOL offers two working modes: interractive and non-interractive

3.1.1 Gatttool Interractive mode

 gatttool -b <MAC Address> --interactive

In interractive mode, a new prompt is available to perform BLE commands.
connect: to connect to a specified device
primary: to disable all primary attributes
char-read-hnd <handle> to read specified handle/attribute values
char-write-cmd <handle> <value> to modify handle values

3.1.2 Gatttool Non-interractive mode:

In non-interractive mode, commands are issued one by one. At each command, GATTTOOL performs device connection, action and disconnection.
Few a few examples are given below:

 gatttool -b <Mac Address> --primary 
 gatttool -b <MAC Address> --characteristics 
 gatttool -b <MAC Address> --char-read 
 gatttool -b <MAC Address> --char-desc