Friday, August 14, 2015

Another Yaesu VX-8DR external GPS with an Arduino/ATmega328 translator.

I've collected links for a few of these projects to add a better external GPS to the Yaesu VX-8DR, instead of the somewhat proprietary Yaesu option.

Here's another one from VK3YY that got posted recently:

Here's code from DFannin on github:
Update 2016-01-15, 4Z7DTF notified me about his project, which includes more additional analysis of how poor the VX-8's parsing and error handling is.

Background Info:

Good detailed blog post Reverse Engineering the Yaesu VX-8DR GPS Interface. From Feb. 2013. He didn't arrive at the solution, which I believe F4FXL and at least one other have. But I think he's got most of the relevant details for the padding differences listed as well as some other very useful info including details on the GPS chips used in VX-8 and VX-8G.

We now know how to connect to and send a properly formatted GPS NMEA message to the Yaesu VX-8DR. Here's the summary:
  • 9600baud TTL 3.3V serial signalling, 8/N/1
    • NOT RS232 -5 to +5V signalling -- you need a level converter if that's all you have
  • 3-wire physical interface to the following pins:
    Pin GPS Side Purpose Yaesu Side Purpose
    4 GPS RX Yaesu TX
    5 GPS TX Yaesu RX
    6 GPS GND Yaesu GND
  • According to 4Z7DTF (2016-01-15), there is no need for the communication to be bidirectional. Only the TX Data from the GPS to the VX-8 is required.

The messages need to be formatted exactly as follows:

Message Type Source Sentence
$GPGGA Sample $GPGGA,123223.000,4131.2334,N,00021.1216,E,1,04,02.7,00123.4,M,0051.7,M,000.0,0000*41

Syntax $GPGGA,hhmmss.sss,llll.llll,a,yyyyy.yyyy,a,x,xx,xx.x,xxxxx.x,M,xxxx.x,M,xxx.x,xxxx*hh
$GPRMC Sample $GPRMC,123223.000,A,4131.2334,N,00021.1216,E,0000.00,291.33,301011,,*3E

Syntax $GPRMC,hhmmss.sss,A,llll.llll,a,yyyyy.yyyy,a,xxxx.xx,xxx.xx,xxxxxx,,*hh
$GPZDA Sample $GPZDA,123223.000,30,10,2011,,*55

Syntax $GPZDA,hhmmss.sss,xx,xx,xxxx,,*hh


iosaaris said...
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iosaaris said...

Here is my project with some more research: