Which GPS simulator?

[MFB]

Please can anyone recommend a GPS simulator like the PC based examples below…?

www.sailsoft.nl/gpssimul.htm

www.gpslab.us/index1.htm


I am working on a 28X1 based data logger and think the simulator requirements are pretty simple. Just need stable data via the serial port of a PC, rather than sticking a GPS receiver out the window.

 

[hippy]

Why not just generate 'fake GPS' strings from another PICAXE ? A single SEROUT/SERTXD should be all that you need.

 

[MFB]

It would certainly take up less bench space than a PC. A forum search did not show up any examples. Please does anyone already have code for simulating GPS data with a PICAXE or will I have to roll my own?

 

[RexLan]

Why not just generate 'fake GPS' strings from another PICAXE ? A single SEROUT/SERTXD should be all that you need.

That's a clever idea Hippy.

If you want it quite precise you could put it in a timed loop and output the message at precisely the same interval as the module you intend to use .. 1 Hz, 2 Hz, 5 Hz, etc. This would also facilitate any timing issues you might have with writing to your EEPROM and receiving the data from the selected GPS module.

 

[hippy]

@ MFB : Yes, you'd have to roll your own, but it won't be that hard ...

Do
SerTxd( "$GPRMC,040302.663,A,3939.7,N,10506.6,W,0.27,358.86,200804,,*1A" )
Pause 1000
Loop

Using #b0, #w0 etc and it would also be possible to vary values in each message. There's a checksum ( after the * ) I'd forgotten about but the easy solution there is have the receiver code ignore it.

A lot depends upon what you are wanting to test; sometimes you'll want static data, sometimes changing data, and you'll perhaps want to test at different repeat rates to determine if things are being missed.

 

[MPep]

Hi MFB,

For testing a PC program, I programmed up a 08M with an RMC sentence, did not calculate the checksum, and left it off. Worked fine. Some software can be set to ignore the checksum, so no problems there.
Hippy's short program is just what's required.
For your own datalogger, you probably want to ignore the checksum anyway.
It should not be to difficult to have a changing COG, and SOG, so you know that there is a different sentence each 'second'.

Mark.

 

[MFB]

Many thanks for all the advice and Hippy’s example code. This approach should provide a very useful development tool. Might even try changing a few simulated GPS prameters via pots on the PICAXE analog inputs.