Subject: Re: Garmin hackers : enlist here !
Newsgroups: sci.geo.satellite-nav
References: <3vd159$8eh@cicg-communication.grenet.fr>
Distribution: 

Today I have more info about the GPS45.  It uses Amtel EPROM and the 
circut board has a trace to the /PGM line thats goes to a transistor.
If the VPP line goes to a supply then there is hope for adjusting the
program in the case.

I have more details on the Dallas Semiconductor device used to power
managment.  It is a real time clock and can be programmed to wake
up the process at a specific time.  It also generates interruptes
every second.  It also has three A/D converters and this is where the
battery voltage/external voltage and temp come from.  This device also
controls power and read/write access to the static ram.  Its hooked
to the 32.768Mhz crystal.  So Garmin, why can't I tell it to wake
up every 15 minutes to get a fix? 

After looking at the case design, I would not call it water proof.
It seems to be water reistant but on the GPS45 that was taken apart,
the seam was not welded all the way arround the device and I expect water
could easily enter a chamber where the connector is.  The buttons are made
of a single piece of rubber and its pressed into the case.  There is no
sealer other than the rubber.

Internaly the ground from the data port is not connected to the ground
of the batteries so the two might float relitve to each other.

As soon as I get the adapter for the rom, its going into the prom programer.

There has been some discussion about what to do with the device when
I'm finished with it.  There is a better than zero chance that it won't
be as rugged as a new unit.  It also looks like there will be a good
chance that the contrast will be  messed up.  To put the rom back in,
I will need to move the display more and every time that happens, the
contract gets worse.  I get the strong feeling that the display is a
4 shade monchrome.  Do they make these?

-tim