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Version1
Version2
Waveform
PacketDesc.txt
readme.md

readme.md

Garmin HUD interface in C++

Because I was unable to disassemble the Navigon application for locating the code implementing the communication with Garmin HUD, I decided to open the gadget, identify the internal connection between ST32F100 microcomputer and bluetooth module. Then attaching the oscilloscope to proper pins and they were damn small, so I had to use needle, I sniffed some packets. The internal UART decoder in oscilloscope gave some nonsense characters while I was expecting ASCII commands in human readable format. I took snapshots of the signals (Waveform/.SVG) and analysed them manually (Waveform/decoder.html). The communication between bluetooth module and microcomputer is regular UART with 10 bit frames (1 startbit, 8 data bits, 1 stopbit). Then I realized that the oscilloscope gave exactly the same results as manual decoding. After enabling logging the frames into text file (Logs/.txt) I tried sending each of these frames to the bluetooth serial port through FAR manager and watched what was displayed on the hud. Then I was able to identify various commands and their description is in PacketDesc.txt. Code in C++ implementing this protocol is in HudInterface.h. If you don't know how to connect to bluetooth device, maybe the bluetooth library (Bluetooth.h, Main.cpp) will came in handy. I tried to convert the library also for WindowsCE, but without success :(

Description of garmin protocol, stuffing and crc can be found here: http://www8.garmin.com/support/commProtocol.html

And here is a video of Sygic Navigation working with Garmin HUD, I am proud to say that all this took about 24 hours to get it working: http://www.youtube.com/watch?v=WK9IV0syupE

In folder Version1 you will find my initial code. Frank Huebenthal has made some improvements and was kind enough to share his code, you will find his work in folder Version2.

Contributors:

  • Gabriel Valky - initial research
  • Frank Huebenthal - some improvements, added roundabouts, removed MFC dependency
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