Friday, January 15, 2016

More Yaesu VX-8 GPS implementation details.

4Z7DTF left a comment on my post "Another Yaesu VX-8DR external GPS with an Arduino/..." to let me know about his VX-8 Arduino GPS project on github.

There have been a number of projects that use either an Arduino or bare ATtmega microcontroller to turn the GPS module's NMEA sentences back into the a format the brain dead parser built into the VX-8's firmware can handle.

He has done some additional testing, actually fuzzing, showing the VX-8's parser does no error checking what so ever. 

Also, another interesting bit, in his work, he noted there is no need for the communication to be bi-directional. I don't know what, if anything the VX-8 tries to send to the GPS module, but it appears to be unnecessary. 

What is interesting about that is the microcontroller then really only needs a single serial port.  Most of the other projects are bi-directional using a software UART emulation for the second port.   So it might be possible to implement this project with something much smaller and even lower power.   It would be interesting to see if this can be done with the ATTiny85, using something like the Adafruit 3.3V trinket.  That is supposed to draw around 9 milliAmps at 8 Mhz, but 3 mA of that is just for the green power LED!  The ATTiny has no built in UART, so it would be all software serial. 

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