[time-nuts] TruePosition on an Arduino

Ben Hall kd5byb at gmail.com
Sat May 13 15:15:31 EDT 2017

Good afternoon all,

I've not had any luck getting the Arduino source code and libraries from 
the PackRat guys.  Another listmember reported to me this morning that 
he'd tried loading the hex file, but had no luck getting it to work.

I've been wanting to dive more into Arduino...so I figured I'd write my 
own interface program.  The last software class I took was FORTRAN...and 
then I did a little BASIC, so this C code stuff is all new to me and 
it's been a real learning experience.

And I'm sure that a real program would probably look at my code and just 
shake his or her head.  :(

Thankfully...I've found some really good example code on the web.  The 
serial input engine is lifted from here pretty much intact:


And is working perfectly as best I can tell.  The serial port on the 
TruePosition is going right into the serial port (pins 1 and 2) on the 
Uno thru a resistor level-shifter on the TX port (because the arduino is 
5 volts...the trueposition is 3.3v...but the 3.3V TX is being read by 
the 5V arduino w/o any problems.)  Using the hardware port is non-ideal, 
as I've got to remove the jumpers to the TruePosition in order to upload 
code to the Arduino, which also means that I can't use the built-in 
Serial Monitor to view what my code is doing.

Thankfully...the software serial library allows you to create serial 
ports on other pins...so while the True Position is on the hardware 
serial, pin 11 is providing the debugging output.

(I may flip this around where SoftwareSerial is talking to the 
TruePositon, and the hardware serial pins get freed up)

The parsing engine is also based on JHaskell's work here:


But is heavily modified with if-then-else string compares as the parsing 
depends on what sort of message has been received.  This took a bit of 
brain work, as I couldn't get the compare function to work right at first.

Next up...I've got to figure out how to convert GPS seconds into date 
and time...then I'll move along to the display and a rudimentary menu 
system as I think one part will be time/date/status...and another page 
will be GPS satellites...

thanks much and 73,
ben, kd5byb

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