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ZL3AI > APRDIG 26.08.06 03:22l 61 Lines 2154 Bytes #999 (0) @ WW
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Message: 9
Date: Tue, 22 Aug 2006 09:50:22 -0700 (PDT)
From: "Curt, WE7U" <archer_at_eskimo.com>
Subject: RE: [aprssig] Tap into in-dash GPS Navigation for APRS?
On Tue, 22 Aug 2006, Curt, WE7U wrote:
>On Tue, 22 Aug 2006, Ron McCoy wrote:
>
>>My understanding is that you can access the GPS signal by breaking into the
>>box but that you have to play with the firmware to change from a proprietary
>>protocol to NEMA, and that breaks the normal OnStar functionality.
>
>A page I saw mentioned Motorola binary format. One should be able
>to convert that to something usable with a microprocessor.
>
>That's assuming it's not like one of the Trimble binary formats
>where the unit has to query the GPS for the data: In that case
>you'd need to OR the transmit signals from the box and from your
>microprocessor together so either could command the GPS to return a
>position. A bit of a pain.
>
>If it's a continuous stream of data from the GPS then you just need
>to tap into the GPS transmit line and convert it.
>
>Found this, code that switches to NMEA mode for the Motorola:
>
><http://www.kd7lmo.net/beacon_source.html>
>
>So you could program a PIC to switch the GPS to NMEA mode, get a
>position, then switch it back to Motorola... Probably better to
>leave it in Motorola mode and just convert to NMEA on the fly
>though. That way the OnStar wouldn't have a fit.
>
>This page talks about a PIC-based project to read the Motorola
>binary format:
>
><http://www.pacificsites.com/~brooke/electron.shtml>
"ntpd" sources (Network Time Protocol Daemon) appear to have motorola
binary format decoding as well. Probably a good set of sources to learn
from.
--
Curt, WE7U. APRS Client Comparisons: http://www.eskimo.com/~archer
"Lotto: A tax on people who are bad at math." -- unknown
"Windows: Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me: I picked the coordinate system!"
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