Holux Bluetooth GPS Module And The Raspberry Pi

Back in the old days I had an Acer N50 Premium PDA. For the youngsters out there it was like a Smart Phone but without the phone bit, the capacitive touch-screen, memory, apps, GPS or battery life. I mainly used it as a TomTom based sat-nav device connected to a Holux GPSlim236 Bluetooth module.

The module had been sat in a drawer for at least five years and I decided to see if I could get it working with the Raspberry Pi. Surprisingly I didn’t need to charge it as five years later it still powered up fine. It uses what at the time was a standard Nokia phone battery.

This is the hardware I used :

• Holux GPSlim236 Bluetooth GPS Module
• PoundWorld Bluetooth module
• Raspberry Pi Model B (Rev 2)
• Power supply
• Fresh Raspbian SD card
  (2013-09-25-wheezy-raspbian)

This was one of those experiments where Google gave me all the answers once I had pieced together fragments from many different blogs and forums.

Although I’m using a specific GPS device I don’t see why it wouldn’t work with any Bluetooth GPS module given they will all be sending serial data in standard NMEA format. Let me know if it works for other units.

Step 1 – Initial Setup

Start with a fresh Raspbian image on your SD card and plug it into the Pi along with the Bluetooth dongle. Power up the Pi with it connected to a network as we will need access to the internet.

As this is a fresh SD card start by running :

sudo raspi-config

and expand the SD card partition to fill the spare card space. Then run :

sudo apt-get update
sudo apt-get upgrade

to ensure everything was up to date. This will take a while (5-10 minutes) so it is a good opportunity to grab a coffee. In order to form the link between the Pi and the device we will need to install a few extra packages :

sudo apt-get -y install bluez-utils gpsd-clients

Answer “Y” when prompted. “bluez-utils” provides some Bluetooth tools and “gpsd-clients” is a collection of tools for processing and displaying data.

As we’ve installed so many new files it is a good idea to reboot :

sudo reboot

Step 3 – Get MAC Address

With the Pi powered up switch on the Holux module and give it 60 seconds to look for satellites. We need to know the MAC address of the module so run :

hcitool scan

After a few seconds you should get a response :

Scanning ...
        00:0B:0D:6F:B5:D4       HOLUX GPSlim236

This will give you the MAC address of your device. In my case it is “00:0B:0D:6F:B5:D4” which I took a note of.

Step 4 – Connect To The GPS Module

Next we need to run the following command to connect the Pi to the remote Bluetooth device :

rfcomm connect 0 00:0B:0D:6F:B5:D4 &

The & at the end tells the command to run in the background and return to the command prompt. Remeber to use your MAC address! When it runs it echoes a process ID to the screen. A few seconds later it will display some text :

Connected /dev/rfcomm0 to 00:0B:0D:6F:B5:D4 on channel 1
Press CTRL-C for hangup

You may need to press the Enter key to return to the command prompt. Do not press “CTRL-C”!

To test the connection we can run :

cat /dev/rfcomm0

If the connection is working you should see some GPS data (NMEA format) being streamed from the GPS module. Press CTRL-C to return to the command prompt.

Step 5 – GPSD Daemon

Next is the “gpsd” daemon. This is a process that runs in the background and translates the NMEA messages for use by the clients.

gpsd -b /dev/rfcomm0

The b switch tells it to only read messages and not attempt to send anything back to the GPS receiver.

Step 6 – Terminal Client

At this stage your GPS module should be streaming data to the Pi over Bluetooth. To present this data in a more readable way we can use one of the clients that comes with the gpsd package. Try :

cgps -s

If everything has gone to plan you should see something a bit think this :

To return to the command prompt you can press CTRL-C.

Step 7 – GUI Client

Once you’ve got cgps working you can try the GUI client xgps. Fire up the GUI by typing :

startx

Open a LXTerminal window by clicking the desktop icon. Then run the client by using :

xgps

You should see something like :

If it’s all working and you are still reading this then congratulations!

Step 8 – Reconnecting After Reboot

When you reboot you will lose the Bluetooth link and will have to repeat the process from Step 4. That’s boring. By editing a system file we can get the Pi to reconnect on start-up.

sudo nano /etc/bluetooth/rfcomm.conf

Remove the # characters in front of the rfcomm0 {} block and edit the settings so you end up with something like this :

rfcomm0 {
        # Automatically bind the device at startup
        bind yes;

        # Bluetooth address of the device
        device YOUR_DEVICE_MAC_ADDRESS;

        # RFCOMM channel for the connection
        channel 1;

        # Description of the connection
        comment "My GPS Module";
}

Remember to set bind to “yes” and replace “YOUR_DEVICE_MAC_ADDRESS” with the MAC address of your device.

Use CTRL-X, Y and then enter to save and exit from the nano text editor. On reboot you will now be able to start at Step 5 (running gpsd).

To take it a step further you can get gpsd to run at boot automatically. To do that run :

sudo dpkg-reconfigure gpsd

This will bring up a wizard which configures gpsd to start automatically. You will need to enter a few details such as the serial port location (/dev/rfcomm0) and the command line switches (-b). I wasn’t interested in USB devices so I told it to ignore those.

When you restart your Pi it should connect to the GPS device and allow you to launch the clients straight away.

Step 9 – Other Clients

Once you’ve got the basics working you can start exploring all the other applications that are happy to read data from the gpsd process. One application worth trying is FoxtrotGPS. It can be installed using :

sudo apt-get -y install foxtrotgps

and then run using :

foxtrotgps

It loads maps from OpenStreetMap and will show your current position as well as speed and altitude.

Final Thoughts

There are plenty of other GPS clients that will probably run on the Pi. What you do with them is just down to your imagination.

Updates

I have seen messages that the following devices work using this tutorial :

• Dell BT-309 GPS
• Emtac D1598 Bluetooth GPS
• Holux GPSlim236 GPS
• Holux GR-230
• Holux M-241 GPS Data Logger
• Navicore SiRF III Bluetooth GPS
• RoyalTek RBT-2300 GPS
• QStarz BT-Q816 GPS

If you’ve tried it and it works for your device let me know and I will update this list.