Having difficulty pairing with a bluetooth OBDII device on Ubuntu

Question

I'm attempting to pair with a automotive OBDII bluetooth device from a Beaglebone Black running Ubuntu Linux, and not having a ton of luck.

I was able, initially to set up hci0 using bluez-simple-agent, although it never asked me for a PIN. The PIN for this device is supposed to be "1234". Now, when I run bluez-simple-agent, I get this:

ubuntu@ubuntu-armhf:/etc/bluetooth$ sudo bluez-simple-agent hci0 00:0D:18:A0:4E:35
Creating device failed: org.bluez.Error.AlreadyExists: Already Exists

Which would be fine if it was working, but when I try to bind using rfcomm, I repeatedly get either "Can't connect RFCOMM socket: Invalid exchange" (first time after restarting the device) and then "Can't connect RFCOMM socket: Connection refused" every time thereafter.

This is my /etc/bluetooth/rfcomm.conf file:

rfcomm0 {
    # Automatically bind the device at startup
    bind no;

    # Bluetooth address of the device
    device 00:0D:18:A0:4E:35;

    # RFCOMM channel for the connection
    channel 16;

    # Description of the connection
    comment "OBDII";
}

And running "rfcomm bind 0" does successfully create a device at /dev/rfcomm0:

rfcomm0: 00:0D:18:A0:4E:35 channel 16 clean

However, trying to read from /dev/rfcomm0, gives me this:

ubuntu@ubuntu-armhf:/etc/bluetooth$ sudo cat /dev/rfcomm0
cat: /dev/rfcomm0: Invalid exchange
ubuntu@ubuntu-armhf:/etc/bluetooth$ sudo cat /dev/rfcomm0
cat: /dev/rfcomm0: Connection refused
ubuntu@ubuntu-armhf:/etc/bluetooth$

And thereafter, rfcomm returns this:

ubuntu@ubuntu-armhf:/etc/bluetooth$ rfcomm
rfcomm0: 00:0D:18:A0:4E:35 channel 16 closed

I think I am using the correct channel (16) based on the result of "sdptool records"

ubuntu@ubuntu-armhf:/etc/bluetooth$ sudo sdptool records 00:0D:18:A0:4E:35 
...
Protocol Descriptor List:
  "L2CAP" (0x0100)
  "RFCOMM" (0x0003)
    Channel: 16
Profile Descriptor List:
  "Serial Port" (0x1101)
    Version: 0x0100

Any help would be greatly appreciated, because I'm pretty well out of ideas at this point.

Refs:

rfcomm
Manually Using Bluetooth RFCOMM
How to Set Up Bluetooth Serial connection over Bluetooth
The device

Regarding error found as "Creating device failed: org.bluez.Error.AlreadyExists: Already Exists", its because device is already created, try with these dbus commands to remove that device 1. dbus-send --system --type=method_call --print-reply --dest=org.bluez "/org/bluez/bluetooth_PID/hci0"org.bluez.Adapter.GetProperties 2. dbus-send --system --type=method_call --print-reply --dest=org.bluez "/org/bluez/3858/hci0" org.bluez.Adapter.RemoveDevice objpath:"/org/bluez/3858/hci0/dev_00_0D_18_A0_4E_35" , after this try pairing again with agent utility . — ashish, Oct 10 '13 at 08:57

score 4 · Answer 1 · edited Apr 25 '14 at 07:01

4

Remove the paired device from bluetooth settings and add it again

edited Apr 25 '14 at 07:01

Uri Agassi

36,848
14
76
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answered Apr 25 '14 at 05:49

Joseph Thomas

484
1
5
11

score 1 · Answer 2 · edited Apr 29 '22 at 10:59

I know this is a little bit late but since I got here may be there is some other people struggling with it so I will post what worked for me, using what I suppose is the same device (OBDII ELM327 Blue Connector).

[USING BBB WITH DEBIAN WHEEZY]

I have the following rfcomm.conf file under /etc/bluetooth/

rfcomm0 {
    bind yes;
    device AA:BB:CC:DD:EE:FF; # Remote device's MAC
    channel 16;
    comment "OBDII";
}

# rfcomm connect rfcomm0

Each time the BBB is connected to a device, it seems it saves its configuration under /var/lib/bluetooth/XX:XX:XX:XX:XX:XX (MAC Address of the Bluetooth dongle gotten with hcitool dev)

What Im doing to make sure it gets connected next time, I'm deleting all of the contents of the /var/lib/bluetooth/XX:XX:XX:XX:XX:XX folder with a cron job at boot, adding the following line to cron, using "crontrab -e" command on console

$ @reboot rm /var/lib/bluetooth/*

So each time it boots up again, I'm able to re-establish the connection using Linux commands when necesary.

I know this is little bit tricky and I don't know how good or bad is removing the bluetooth folder but it works for me, if you have any other comment or suggestion please let me know.

Having difficulty pairing with a bluetooth OBDII device on Ubuntu

2 Answers2