Saturday 29 June 2019

Bluefly_GPS_AddOn_v12 Released

I am pleased to be able to release the Bluefly_GPS_AddOn_v12 board today. Adding a GPS to the Bluefly has been possible for many years (see this post for an example This new board is designed especially for the Bluefly and uses the XA1110 module which offers a range of premium features.

Before reading on, why would you want to add a GPS to the Bluetooth model of the Bluefly? For many pilots the answer is you probably do not. If you are using the Bluefly in stand alone mode (just using it's audio), or if you are connecting to almost any Android or iOS device, then that device probably already has a GPS. However, there are a few Android devices that do not have GPS such as Android based eReaders that some pilots are now using with XCSoar. The Bluetooth model of the Bluefly with this new GPS board can provide the location input you need for XCSoar or other apps.


The image below shows the layout of the board.

Features of the board are:

  • The XA1110 Mulit-GNSS module from Sierra Wireless
  • It's own 3.0v Voltage Regulator and conditioning components for optimal performance. 
  • The blue LED flashes once per second when the GPS has a fix. 
  • The main connectors are:
    • The U1 connections to the Bluefly for Ground, Tx, Rx and 3.3v input. 
    • RA7 enables the voltage regulator (you need the most recent version of the firmware for the Bluetooth model of the Bluefly for this to work). 
    • VBAT connects to the GPS VBACKUP for fast time-to-first-fix (about 5 seconds) and maintains other configuration settings on the GPS. You need to close the solder jumper for this to work. 
  • There are pads for a U.Fl connector for those that want to experiment with an external antenna. 


Assembly is pretty easy if you have basic soldering skills. Before you begin read through all of these steps. If you are really uncomfortable doing this yourself then I am also able to offer an assembly service (but note that this makes the size of the package greater than can be shipped with free shipping).

Step 1 - Checking your Bluefly 

To complete your the assembly process your Bluefly will need to be removed from the case. Do this carefully by first removing the battery and any packing holding the vario in position. Next use a small flat screwdriver and gently twist between the end of the PCB and the end of the case with the USB hole. The aim is to release the end tabs of the USB connector from the hole, then press on the button to push the PCB free from the case. If you are gentle the PCB should come out easily, and you will not damage the button or the USB connector.

Next, plug the battery back in and connect to the BFVDesktop application on a windows PC. Send the 'BTN' command a few times just to make sure you have a good connection to the vario.  You need firmware version 12.423 or later for this to work.

Step 2 - Attaching the GPS_AddOn

Begin by soldering headers to U1, RA7 and VBAT as shown below (I will include a strip of 6 or more headers in the package with the AddOn board). Note that I have used right angled headers in this image, but you can also use straight headers. I strongly suggest that you trim the pin of the headers flush with the board before you solder it (not shown in this image). This will help prevent the LiPo battery from damage. Also note that the secret of all good soldering is lots of flux, a clean hot soldering iron with quality solder, and good cleaning with isopropyl alcohol after soldering.

Next, attach the AddOn board. Note that it sits flush on top of the bluetooth module shield, and slightly squishes the neoprene. Again, trim the headers before soldering. 

This final image shows the required pins soldered. Also, note that the VBAT solder jumper has been closed.

Step 3 - Configuration

At this point, before putting it in the case, it is a good idea to test to make sure it is working. Follow these steps:

  • Connect the vario to the BFVDesktop application and start it up. You should see the vario data streaming in. 
  • Adjust uart1BRG from the default of 207 to 16. That changes the U1 baud rate (the rate between the vario microcontroller and the GPS module) from 9600 to 115200. 
  • You should now see data from the GPS streaming in. Change the outputMode to 4 to disable the Bluefly sentences and you will be left with just the GPS information. 
  • Shut down and restart the Bluefly. After a few minutes, if the antenna is pointing to the sky, you should get your first fix (and the blue light on the under side of the GPS board will start to blink). 
  • Shut down and restart the Bluefly again. If you have VBAT connected correctly and the solder jumper has been closed then the time-to-first-fix should be no more than 5 to 10 seconds. 
  • Make sure to set the outputMode and outputFrequency back to whatever you want for connecting to your app.

Step 4 - Prepare the case

The Bluefly with GPS_AddOn fits in the Sky Blue or new Translucent Blue case provided you cut out a hole for the GPS.

Begin by downloading the pdf template to use to cut the hole in the right spot. The only really tricky part is to make sure you print the template at the right scale. The images below show the template and final cutout.

This final image shows the vario assembled into the older Sky Blue case.

Next Steps

Now you have a vario with working XA1110 you may want to experiment with the capabilities of that GPS module. There are many configuration options which you might find useful.

At some stage I will be blogging about configuring and using the onboard memory of the XA1110 GPS module. With a little effort the GPS can be made to continuously record the last 8186 track points (including height) in its 128k memory. This can provide a backup GPS track for the last 11 hours of GPS on time at 5 second intervals. It is not super awesome, and takes some effort to configure and download the memory, but as a backup track could make the difference for many pilots.