Wednesday 6 April 2016

BlueFlyVario_TTL_GPSv11 released

In November 2015 I released the v11 version of the Bluetooth model. Today I am pleased to announce the release of the BlueFlyVario_TTL_GPS_v11 model. I have actually been shipping this model for a few weeks now to fulfill v10 orders, but only just got around to posting the details. Out of almost 4000 BlueFly's of various types and versions, we now have over 1500 TTL_GPS model BlueFlyVario's around the world, most of which are probably installed on Kobo eReaders running xcsoar to make pretty fully featured flight instruments.

I was not really sure that a new version of the TTL_GPS was needed. However, in the end a few factors which drove the decision included:
  • Keeping consistency in firmware and features moving forward by having a common processor type as the Bluetooth model.
  • Allowing intrepid hardware hackers the ability to add an airspeed indicator
  • Some design layout changes to help with my new production system. 
What is in the bag?

With the v11 model you get a very similar set of parts as the v10 model:
  • The main module. The PCB size is 50mm x 17 mm which is the same as the v10 and the v9. The speaker, GPS, button and header locations are in the same spot as the v10. 
  • A small piece of neoprene. This is really important. It must be placed over the pressure sensor if the sensor is exposed to any light (even light through a translucent case). The neoprene allows the air pressure through, but stops the light. Light makes the pressure sensor go crazy. It is really important to place it on the pressure sensor with the black foam side down - do not stick it to the pressure sensor - you will block the hole and it will not work! It is shown in the image below in the correct spot. 
  • Some blue PVC heat shrink cut to size. It is fine to install the module without a case if you use the heatshink.
    • Poke a small hole through one side of the heatshrink just big enough for the button.
    • Put the neoprene on the pressure sensor, and the heatshrink evenly over the module.
    • Use a heat gun, or a hairdryer on hot setting to carefully shrink the plastic around the module.
[Edit: The header and dupont connector are no longer included in the package. They have been replaced by a small piece of 4 core flat telephone cable. See this update for more information]
  • A 4x1P right angled header. Some people solder the wires directly to the module, others use the header so it is easy to remove for testing. If you use the header I suggest you trim the through-hole pins to the thickness of the PCB so they are flush with the bottom of the board. See the range of other Kobo install related blog posts so see different examples of how you might use the header. 
  • A 4x1P DuPont connector with 20 cm wires. This will fit in the header, and the wires connect to the serial port of the Kobo. You should trim the wires to be as short as possible so you minimize stray voltages.

Hardware changes

There have been a few hardware changes from the v10. Refer to the circuit diagram, pcb layout and image below. Also refer to the Bluetooth model release blog post for more information:
  • I have changed to the microprocessor to the PIC24F32KA302 and am now using the QFN package instead of SSOP. Even though it is smaller it is actually easier to solder without jumping leads, and most importantly, I have a bunch of extra IO lines to add new features. 
  • The TC1015 regulator has been upgraded to the TC2185 (3.0V for the TTL_GPS). This provides a higher max current to allow for the add-ons and has slightly better power supply noise performance. 
  • Some of the IO lines are exposed in a new way (see the image below of the bottom of the PCB): 
    • The I2C lines V+, SCL, SDA and Gnd can be used by hardware hackers for connecting the MS4525DO pressure sensor. 
    • RB10 and RB11 can used for extra buttons and LED. 
  • The solder jumpers are on the bottom of the board. In the image below SJ1 is shown closed. The jumpers have the following functions:
    • SJ1 is used to bypass the button function for turning on the module as soon as power is supplied to Vin. 
    • SJ2 is used to keep the VBACKUP power tied to Vin. I found VBACKUP was normally more pain than it was worth so I removed the extra pin. 
  • There is now a 10k pull-up resistor on the BlueFly-Tx line (which will be connected to the Kobo Rx line). This keeps the voltage high rather than floating, which in turns allows the newer Kobo Touch 2.0 and the Kobo Glo HD to proceed through the boot sequence without hanging up. 
  • I added a couple of holes to the bottom of the board to make soldering an external speaker easier, although it is still pretty tricky unless you are good at soldering.  

Firmware Changes

New features of the v11 firmware include:
  • Boot up shorts for entering the bootloader and resetting all of the hardware settings:
    • Previously to enter bootloader mode you shorted programming pads 2 and 5. Now you short SDA to ground (see the picture above). 
    • Previously to reset all the default hardware settings you shorted programming pads 2 and 4. Now you short SCL to ground. 
  • An updated ds30bootloader. This was required for the new microprocessor and to support the new boot up short mechanisms. 
  • A new hardware setting for supporting the airspeed sensor. 
Adding an airspeed sensor

An airspeed sensor shield is available separately for the Blutooth module. If you are a confident hardware hacker, and can read and understand the circuit diagrams, and want to experiment, then the connections are the same as described in the blog post about the shields.


The image below shows a simple installation on the Kobo Glo HD (without the really important neoprene and heatshrink). I hope to find some time soon to provide a more comprehensive post about the simple installation on the Glo HD. In the meantime some tips for all installs:

  • Use the neoprene, but do not use the sticky side which would block the holes in the pressure sensor.
  • Read an earlier blog post about using xci files. That is currently the easiest way to send commands to the vario (you also need to read the hardware settings manual on the support page of the website). 
  • If you get 'Waiting for GPS fix' and after 20 minutes of the vario being on, outside, and with the antenna having a clear view of the sky, the do the following debugging:

    • Check in the Devices Monitor for incoming data from the vario. 
    • Record a NMEA log and look for $GPGSV messages to assess what is going on with the satellites. 
    • Check your wires to ensure the solder quality is good, and that the wires are not routed next to other components on the Kobo circuit board which might pick up stray power. I like to keep the wire length less than 5cm. 
    • Send the command $PMTK104*37<CR><LF> to the BlueFly module a couple of times by connecting to it with a USB-Serial converter and the BlueFlyVario desktop application (<CR> and <LF> are replaced by the BlueFlyVario desktop application by the \r and \n characters respectively). This command is passed from U2, through the processor, and out from U1 to the GPS. This asks the GPS to do a full cold start and get rid of any stored Time, Position, Almanacs and Ephemeris data which might be corrupting a fix.
    • If that fails, send me an email with some images of your installation, and a NMEA log.