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I've been working on making my RPi 2 function like a car bluetooth receiver and all is well, except I have no idea how I could automate the pairing of bluetooth devices in Bluez5. In the past I would've used the bluetooth agent and a simple script, but that seems to have gone out the window with the move from 4 -> 5. The nature of the setup means I have no kb/mouse on the RPi once its in the car, so it needs to be a fully automated setup where anyone can scan for the RPi, and if the probably hard-coded PIN is correct, the trusting of the device needs to be automatically done, no cli input.

I've searched all over the web but everyone seems to say that using bluetoothctl works for them, but in this particular setup where I'd like to be able to have friends pair their own phones, having to trust devices with the RPi out of the car isn't ideal.

szeater
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2 Answers2

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I'm not sure why you say using a simple script is not possible with bluez5. I think you can do it. Below is one example how.

Download the bluez5 source and edit test/simple-agent. Comment out the lines of code as shown below:

def RequestAuthorization(self, device):
        print("RequestAuthorization (%s)" % (device))
        #auth = ask("Authorize? (yes/no): ")
        #if (auth == "yes"):
        return
        #raise Rejected("Pairing rejected")

What that does it remove the prompt for authorisation and always accepts the pairing request.

Can now start the simple-agent with the NoInputNoOutput capability so that it uses simple pairing and will go through the above code path:

./simple-agent -c NoInputNoOutput

After that you should be able to pair with the RPi without any user prompt or PIN.

Note that this is just one example of what you can do. If say you wanted to have a hard coded PIN instead of simple pairing then edit the appropriate section of the same simple-agent code to do that. I'll leave that as an exercise for you.

kaylum
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  • I probably should've mentioned it, but in my rush I didn't. I tried doing something similar to this, and it worked mostly well, except it won't 'trust' the device it pairs with, which means the device can't actually connect. I'll keep having a play around, but if you have any suggestions I'd greatly appreciate them. – szeater May 14 '15 at 14:32
  • Just call `set_trusted(device)` before the `return` in the above code. – kaylum May 14 '15 at 23:04
  • I've tried this and it didn't work. There's quite a few calls to set_trusted in the simple-agent, but it doesn't seem to function correctly. – szeater May 15 '15 at 09:56
  • It works. But somehow it needs quite a few of deps, like python, dbus, python-gi. – aGuegu Aug 02 '17 at 03:45
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I already had bluez-5.43 installed. This is how to automate the pairing process on a raspberry pi.

(1) First test a line like this out to make sure bluetooth agent works:

 bluez-5.43/test/simple-agent -c NoInputNoOutput

(2) To automate pairing, put this code into a shell file (I named mine pairbot.sh): 

if [ "$(id -un)" != "pi" ]; then
        exec sudo -u pi $0 "$@"
    fi

    export XAUTHORITY=/home/pi/.Xauthority
    export DISPLAY=:0

     lxterminal --command="/bin/bash -c '/home/pi/bluez-5.43/test/simple-agent -c NoInputNoOutput &; read'"

(3) Go to crontab:

sudo cronetab -e

(4) At the bottom add: 

@reboot sleep 20 &&  /home/pi/pairbot.sh > /home/pi/blelog.txt 2>&1

(5) Reboot and test if it works.

My recommendation for others facing the same issue would be to look into your bluez folder (or if you don't have one install the latest version of bluez) and search for the folder that says "test" for "simple agent" to locate the file path. From here, you should be able to construct the command line shown above (1). Hopefully it will work for you too.

Ion Flare
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