Ubuntu – Having difficulty pairing with a bluetooth OBDII device on Ubuntu

If you can provide the name / link to the medical device (if it is a commercial device) it might help to read up its guide to guess more on what might be going on. Here are a few suggestions :

1. In addition to the Serial Port UUID , each service over the SPP can have a custom specific UUID - example the medical device could look for the service with which it is compatible using this custom-specific UUID.
   If the medical device currently connects to a PC or some other access point successfully and transfers data , the you could try read the SDP record of that device and determine what specific UUID in addition to the SPP UUID is in use if any, and use the same in your application also.

2. If the medical device is not able to find your phone / application it could be because it is not discoverable. Android device by default is not discoverable even when you are a server, it will be only connectable and not discoverable, you can try to make it discoverable programetically or through the settings and see if the medical device can find your device. See here - Enabling Discoverability in Android

3. For PIN pairing , The android device should start the pairing process when a non paired device tries to connect to it, you can try it after getting through the recommendations (1) and (2), PIN pairing is used if one of the devices are prior to version Bluetooth 2.1 , Even with newer devices a 6-digit passkey with some user intervention / confirmation will be required at the phone to allow for the pairing (its is just a good security policy to not allow this to just happen automatically without user intervention) , hopefully pairing will only be require the first time a connection happens, later it will not require any user intervention for subsequent connections.

OK, it took a bit of playing around to get the MindSet connected reliably.

The command-line bluetooth tools are more or less useless. The only repeatable way to read off the Mindset (once paired via BlueMan) was to do this:

  bash$ sudo /etc/init.d/bluetooth stop
  bash$ sudo /etc/init.d/bluetooth start
  bash$ sudo rfcomm connect /dev/rfcomm0 00:13:##:##:##:## 1
  bash$ ./mindset_capture.rb

...but this reaches EOF before a valid ThinkGear packet has been received.

Instead, pair using Blueman.

Setup:

1. bash$ blueman-manager &
2. enable pairing on MindSet
3. Click Search in BlueMan
4. Select MindSet device
5. Click on Pair
6. Enter PIN (0000)

Connect:

1. bash$ blueman-manager &
2. Right-click on MindSet and select "Connect To: Dev B" (serial connector icon)
3. Run capture utility (e.g. bash$ ./mindset_capture.rb)
4. Right-click on MindSet and select "Disconnect: Dev B"
5. Quit Blueman

6. Restart bluetooth to release rfcomm0 (thanks, BlueMan!)

   bash$ sudo /etc/init.d/bluetooth stop; sudo /etc/init.d/bluetooth start

Wouldn't it be better to have a completely command-line driven solution? Yes, yes it would. Unfortunately, the Bluetooth stack on Linux seems to be in a state where the GUI tools and the command line tools do not cooperate -- and the command-line tools do not support pairing (* UPDATE - see comments).

Reading from the device is straightforward. It continuously transmits bytes, so read from it until you encounter two SYNC bytes (0xAA), which mark the beginning of a packet. The structure of the packet is described in mindset_communications_protocol.pdf, which is supplied in the MDT.

Ruby code for reading from the MindSet:

  require 'rubygems'      # gem install serialport
  require 'serialport' 
  conn = SerialPort.new "/dev/rfcomm0", 57600
  while true
    next if conn.readbyte != 0xAA
    next if conn.readbyte != 0xAA
    while true
      c = conn.readbyte
      break if c == 0xAA
      puts "%02X" % c
    end
  end 

It's not perfect as it does no real parsing, but that's how bytes are read from the device.