Test Bluetooth in Yocto-based Linux Distributions

Introduction

This article discusses some ways to test Bluetooth radios in TechNexion Yocto-based distributions.

Yocto 2.5 and 3.0

Beginning with Yocto 2.5 and 3.0 distributions, systemd will automatically start up the Bluetooth interface. You can check the status of the service as follows:

# systemctl status serial-qcabtfw@*
    ● serial-qcabtfw@ttymxc0.service - QCA Bluetooth firmware service on ttymxc0
       Loaded: loaded (/lib/systemd/system/serial-qcabtfw@.service; indirect; vendo>
       Active: active (exited) since Tue 2019-07-02 05:30:49 UTC; 3h 33min ago
      Process: 3167 ExecStart=/usr/bin/hciattach -t 30 /dev/ttymxc0 qca 3000000 flo>
     Main PID: 3167 (code=exited, status=0/SUCCESS)
        Tasks: 1 (limit: 1623)
       CGroup: /system.slice/system-serial\x2dqcabtfw.slice/serial-qcabtfw@ttymxc0.>
               mq3174 /usr/bin/hciattach -t 30 /dev/ttymxc0 qca 3000000 flow -

    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: get_vs_hci_event: Response type   >
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: read_vs_hci_event: Wait for HCI-Ve>
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: rome_set_baudrate_req: Received HC>
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: rome_set_baudrate_req
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: rome_hci_reset_req: HCI RESET
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: rome_hci_reset_req: HCI CMD: 0x1 0>
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: ## userial_vendor_set_baud: 14
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: HCI Reset is done
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: Setting TTY to N_HCI line discipli>
    Jul 02 05:30:50 pico-imx8mm hciattach[3167]: Device setup complete

Check if interface hci0 device node exists:

    ~# hciconfig -a
    hci0:   Type: Primary  Bus: UART
            BD Address: 00:1F:7B:31:1F:1B  ACL MTU: 1024:7  SCO MTU: 60:8
            UP RUNNING
            RX bytes:713 acl:0 sco:0 events:42 errors:0
            TX bytes:1015 acl:0 sco:0 commands:42 errors:0
            Features: 0xff 0xfe 0x8f 0xfe 0xd8 0x3f 0x5b 0x87
            Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
            Link policy: RSWITCH HOLD SNIFF
            Link mode: SLAVE ACCEPT
            Name: 'pico-imx8mm'
            Class: 0x200000
            Service Classes: Audio
            Device Class: Miscellaneous,
            HCI Version: 5.0 (0x9)  Revision: 0x0
            LMP Version: 5.0 (0x9)  Subversion: 0x25a
            Manufacturer: Qualcomm (29)

Scan the local environment for Bluetooth devices:

    ~# hcitool -i hci0 scan
    Scanning ...
            20:74:CF:27:82:56       TREKZ Titanium by AfterShokz

Check Bluetooth boot messages

# dmesg | grep Bluetooth
[    0.089295] Bluetooth: Core ver 2.22
[    0.089322] Bluetooth: HCI device and connection manager initialized
[    0.089329] Bluetooth: HCI socket layer initialized
[    0.089337] Bluetooth: L2CAP socket layer initialized
[    0.089350] Bluetooth: SCO socket layer initialized
[    1.383864] Bluetooth: HCI UART driver ver 2.3
[    1.388323] Bluetooth: HCI UART protocol H4 registered
[    1.393471] Bluetooth: HCI UART protocol BCSP registered
[    1.398809] Bluetooth: HCI UART protocol LL registered
[    1.403953] Bluetooth: HCI UART protocol ATH3K registered
[    1.409375] Bluetooth: HCI UART protocol Three-wire (H5) registered
[    1.415733] Bluetooth: HCI UART protocol Broadcom registered
[    1.421417] Bluetooth: HCI UART protocol QCA registered
[    1.953694] Bluetooth: RFCOMM TTY layer initialized
[    1.958590] Bluetooth: RFCOMM socket layer initialized
[    1.963753] Bluetooth: RFCOMM ver 1.11
[    1.967511] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    1.972828] Bluetooth: BNEP filters: protocol multicast
[    1.978075] Bluetooth: BNEP socket layer initialized
[    1.983046] Bluetooth: HIDP (Human Interface Emulation) ver 1.2
[    1.988973] Bluetooth: HIDP socket layer initialized

Identify the Device

# hciconfig -a
hci0:   Type: Primary  Bus: UART
        BD Address: 00:1F:7B:31:EE:4B  ACL MTU: 1024:7  SCO MTU: 60:8
        UP RUNNING 
        RX bytes:777 acl:0 sco:0 events:51 errors:0
        TX bytes:2269 acl:0 sco:0 commands:51 errors:0
        Features: 0xff 0xfe 0x8f 0xfe 0xd8 0x3f 0x5b 0x87
        Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3 
        Link policy: RSWITCH HOLD SNIFF 
        Link mode: SLAVE ACCEPT 
        Name: 'edm-g-imx8mp'
        Class: 0x2c0000
        Service Classes: Rendering, Capturing, Audio
        Device Class: Miscellaneous, 
        HCI Version: 5.0 (0x9)  Revision: 0x0
        LMP Version: 5.0 (0x9)  Subversion: 0x25a
        Manufacturer: Qualcomm (29)

Run hcitool to get the Bluetooth MAC address:

# hcitool dev
Devices:
        hci0    00:1F:7B:31:EE:4B

Pairing a device

You can pair a device using bluetoothctl:

# bluetoothctl
[bluetooth]# agent on
Agent registered
[bluetooth]# agent off
Agent unregistered
[bluetooth]# pairable on
Changing pairable on succeeded

Ensure that your device (the device you wish to connect) is also pairable (e.g. by pressing a button, setting it on in a settings menu).

[bluetooth]# scan on

A number of pairable BT devices may then be scanned. Copy the MAC address of the device to which you wish to pair.

[bluetooth]# scan off
[bluetooth]# pair <MAC address of device>

At this point you may be prompted to approve pairing of the device. After doing so, you can then trust the device:

[bluetooth]# trust <MAC address of device>

Connect to the paired device:

[bluetooth]# connect <MAC address of device>

For example, here is the process to connect a Creative T30 Wireless speaker:

[bluetooth]# scan on
Discovery started
[CHG] Controller 00:1F:7B:31:EE:4B Discovering: yes
[NEW] Device 27:83:92:E7:A9:3E 27-83-92-E7-A9-3E
[NEW] Device 44:92:A2:00:2B:72 44-92-A2-00-2B-72
[CHG] Device 60:F8:1D:C1:D6:B3 RSSI: -51
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Key: 0x004c
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Value:
  0c 0e 08 37 6c 93 5e b0 a3 61 83 07 28 fa 36 6f  ...7l.^..a..(.6o
[NEW] Device 4E:62:E1:5F:95:7E 4E-62-E1-5F-95-7E
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Key: 0x004c
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Value:
  10 05 49 1c f6 e5 2e                             ..I....         
[NEW] Device 68:64:4B:26:91:2C 68-64-4B-26-91-2C
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Key: 0x004c
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Value:
  0c 0e 08 37 6c 93 5e b0 a3 61 83 07 28 fa 36 6f  ...7l.^..a..(.6o
[NEW] Device D0:D2:B0:A0:8A:D6 D0-D2-B0-A0-8A-D6
[NEW] Device 2C:AB:D4:A2:B0:9C 2C-AB-D4-A2-B0-9C
[CHG] Device 4E:62:E1:5F:95:7E RSSI: -72
[NEW] Device 00:02:3C:49:FE:6D Creative T30 Wireless

[Creative T30 Wireless]# scan off
[CHG] Device 00:02:3C:49:FE:6D TxPower is nil
[CHG] Device 00:02:3C:49:FE:6D RSSI is nil
[CHG] Device 2C:AB:D4:A2:B0:9C RSSI is nil
[CHG] Device D0:D2:B0:A0:8A:D6 TxPower is nil
[CHG] Device D0:D2:B0:A0:8A:D6 RSSI is nil
[CHG] Device 68:64:4B:26:91:2C RSSI is nil
[CHG] Device 4E:62:E1:5F:95:7E TxPower is nil
[CHG] Device 4E:62:E1:5F:95:7E RSSI is nil
[CHG] Device 60:F8:1D:C1:D6:B3 RSSI is nil
[CHG] Device 44:92:A2:00:2B:72 TxPower is nil
[CHG] Device 44:92:A2:00:2B:72 RSSI is nil
[CHG] Device 27:83:92:E7:A9:3E RSSI is nil
[CHG] Controller 00:1F:7B:31:EE:4B Discovering: no
Discovery stopped

[bluetooth]# pair 00:02:3C:49:FE:6D
Attempting to pair with 00:02:3C:49:FE:6D
[CHG] Device 00:02:3C:49:FE:6D Connected: yes
[CHG] Device 00:02:3C:49:FE:6D UUIDs: 0000110b-0000-1000-8000-00805f9b34fb
[CHG] Device 00:02:3C:49:FE:6D UUIDs: 0000110c-0000-1000-8000-00805f9b34fb
[CHG] Device 00:02:3C:49:FE:6D UUIDs: 0000110e-0000-1000-8000-00805f9b34fb
[CHG] Device 00:02:3C:49:FE:6D ServicesResolved: yes
[CHG] Device 00:02:3C:49:FE:6D Paired: yes
Pairing successful
[CHG] Device 00:02:3C:49:FE:6D ServicesResolved: no
[CHG] Device 00:02:3C:49:FE:6D Connected: no

[bluetooth]# trust 00:02:3C:49:FE:6D
[CHG] Device 00:02:3C:49:FE:6D Trusted: yes
Changing 00:02:3C:49:FE:6D trust succeeded

[bluetooth]# connect 00:02:3C:49:FE:6D
Attempting to connect to 00:02:3C:49:FE:6D
[CHG] Device 00:02:3C:49:FE:6D Connected: yes
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Key: 0x004c
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Value:
  0c 0e 08 3a 6c 47 9c 59 cb 52 2a b7 6f 7d 12 dd  ...:lG.Y.R*.o}..
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Key: 0x004c
[CHG] Device 60:F8:1D:C1:D6:B3 ManufacturerData Value:
  10 05 49 1c f6 e5 2e                             ..I....         
[CHG] Device 4E:62:E1:5F:95:7E RSSI: -56
[CHG] Device 44:92:A2:00:2B:72 ManufacturerData Key: 0x004c
[CHG] Device 44:92:A2:00:2B:72 ManufacturerData Value:
  10 07 13 1f ad 66 62 81 28                       .....fb.(       
Connection successful
[CHG] Device 00:02:3C:49:FE:6D ServicesResolved: yes
[Creative T30 Wireless]# quit

For additional information regarding playing audio to attached Bluetooth speakers, please see Playing Audio to Bluetooth Speaker using Pulseaudio and Bluez (Yocto).