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[aprssig] RINO Position decoding (new subj)

scott at opentrac.org scott at opentrac.org
Wed Mar 8 18:19:59 UTC 2006


> rino data.... as it stands now, I have yet to find a small processor that 
> can deal with the 2^31 range of numbers that any garmin device uses for 
> coordinates.  I did find the "basic atom" that said it would do float math 
> up to 2^31, but it ended up with a small math error that put my positions 

No need for floating point math to do that.  It's the same format used for waypoints in all of the Garmin binary protocol packets, and it's also used by OpenTRAC.  The OpenTracker can encode it (and uses it as an intermediary for Base91 encoding), and the Tracker2 can decode it.  Both use 8-bit HC08 processors.  They just use some pre-computed values and an iterative process to convert between lat/lon and the binary format.  Rounding error, worst case, should be no more than a few lsb's - under a meter, anyway.

> not try any further to decode the audio data.  I do know that it is 600 bits 
> / sec zero crossing waveform... really this is the same info that you 

This is antipodal baseband FM, right?  The signal swings one way for 1 and the other for 0?  Odd that there's no scrambling.  Doesn't seem like it'd be suitable for decoding through the audio jack, anyway.

> I have modded one of the rino 110 units to hook to an external antenna.  I 

Isn't that a violoation of Part 95?  Or is it just that they can't be manufactured to easily accept an external antenna?

> 30 seconds).  Or maybe they are just crotchedy old men who don't like to see 
> change?? 8-)

What, in this hobby?  Surely you jest!  =]

Scott
N1VG





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