[aprssig] Garmin eTrex Legend Question

Mon Jul 9 12:43:54 EDT 2007

Yeah, and while embedded host controllers are becoming more common, they
don't solve the driver problem.  A manufacturer like Polstar might take an
off-the-shelf (FTDI, for example) USB interface chip and build it into their
GPS receiver.  FTDI hands them a set of supported drivers that they
customize with their own vendor and product names.  Polstar's engineers
likely have absolutely no idea what actually passes between the USB chip and
the FTDI-provided drivers.  If FTDI doesn't provide drivers for a particular
platform, and doesn't provide specs on their protocol, you're out of luck
unless you can reverse-engineer it.

It's one of the reasons I've been so reluctant to just drop a chip like that
in any of my trackers - I don't like not knowing what's going on, and not
being able to change it.  My prototype ARM7-based tracker from a while back
does have USB support, but I did it from scratch, and complied with the USB
CDC spec as well.  The advantage is that I can get as many virtual com ports
as I want with no added cost, and I can make it a mass storage device, input
device, or whatever else I want it to be as well.  On the other hand, it was
a major pain in the rear.

Still, there's a lot of satisfaction in plugging in your own device and
finally having Windows make that 'boo boop!' sound and show the device name
when it finally enumerates properly...

Scott
N1VG

> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of R. Simmons
> Sent: Monday, July 09, 2007 9:15 AM
> To: TAPR APRS Mailing List
> Subject: Re: [aprssig] Garmin eTrex Legend Question
> 
> Amen to that !
> 
>  This much-vaunted USB standard is a nightmare for little 
> guys who want to
> build their own interface... in spite of all the articles 
> describing how to
> make them, none seem to describe ( in detail ) the invisible 
> transactions
> that go on between the two devices, before a single byte of 
> data can be
> sent.
> 
> Basically, to do what this fellow is suggesting, the 
> destination device
> needs to behave like a full-tilt IBM PC "host" computer, not 
> some little
> device with an embedded micro.
> 
> Bob S.
> 
> 
> ----- Original Message -----
> From: "'Scott Miller'" <scott at opentrac.org>
> To: <gerheim at cox.net>; "'TAPR APRS Mailing List'" 
> <aprssig at lists.tapr.org>
> Sent: Monday, July 09, 2007 8:42 AM
> Subject: RE: [aprssig] Garmin eTrex Legend Question
> 
> 
> > You don't.  I really need to write up a FAQ on why you 
> can't really do the
> > other way with USB.
> >
> > The GPSmap 60CS has both USB and serial, so it's not an 
> issue with this
> > unit.  I hope to someday develop a host controller that'll 
> work with some
> of
> > the other units, but it's going to be a major development 
> project and I'm
> > not sure it's even possible with many of the models.
> >
> > Scott
> > N1VG
> >
> > > -----Original Message-----
> > > From: gerheim at cox.net [mailto:gerheim at cox.net]
> > > Sent: Monday, July 09, 2007 8:16 AM
> > > To: TAPR APRS Mailing List
> > > Cc: 'Scott Miller'
> > > Subject: RE: [aprssig] Garmin eTrex Legend Question
> > >
> > > How do you connect the USB GPSRX to a serial device like a
> > > D7?  I have some Serial/USB adapters, but they go "the wrong
> > > way" - from a PC to a serial device, not from a USB "device"
> > > to anything else.
> > >
> > >
> > > ---- 'Scott Miller' <scott at opentrac.org> wrote:
> > > > Same thing happened to mine.  Whacking it with the palm of
> > > my hand would fix
> > > > the display, usually.  As for it being watertight, the fact
> > > that I opened
> > > > mine up to try fixing the display issue may have
> > > contributed to the lack of
> > > > a good seal.  After several miles of riding underwater in
> > > my cargo pocket as
> > > > I hiked the Zion Narrows, my Legend finally died.  I
> > > actually resurrected
> > > > it, but the data input line never worked again, and in
> > > trying to fix that I
> > > > seem to have killed the rest of it.
> > > >
> > > > All of the ICs by Maxim on the board had corrosion around
> > > the pads.  I think
> > > > they were a different composition than the other parts -
> > > you could see
> > > > copper showing through.  In any case, I had a heck of a
> > > time trying to make
> > > > connections when the board had eroded right out from
> > > underneath the parts.
> > > > >From the looks of it, it had probably been corroding
> > > already before the Zion
> > > > trip.
> > > >
> > > > So yeah, it's probably time to upgrade.  My suggestion is
> > > the GPSmap 60CSx.
> > > > I've got the 60 CS and love it, and the CSx has the
> > > improved SiRF receiver
> > > > and external memory slot.
> > > >
> > > > Scott
> > > > N1VG
> > > >
> > > > > -----Original Message-----
> > > > > From: aprssig-bounces at lists.tapr.org
> > > > > [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of
> > > gerheim at cox.net
> > > > > Sent: Monday, July 09, 2007 5:28 AM
> > > > > To: APRSSIG Mailing List
> > > > > Subject: [aprssig] Garmin eTrex Legend Question
> > > > >
> > > > > Somewhat off topic, but I know some of you folks own the
> > > > > device in question.
> > > > >
> > > > > I've owned it for several years.  The glue holding the rubber
> > > > > bumper to the perimeter has weakened.  This may be a
> > > > > coincidence, but the display is also going freaky from
> > > time to time.
> > > > >
> > > > > 1) is it still watertight?
> > > > > 2) is it time to upgrade?
> > > > >
> > > > > If it still pumps out NMEA output, I can still keep it as a
> > > > > data source for GPS, but use another GPSRX for display and
> > > > > navigation.
> > > > >
> > > > >
> > > > > --
> > > > > -Al Gerheim
> > > > >
> > > > > HP-49G+ Software Page:
> > > > > http://members.cox.net/above
> > > > >
> > > > > _______________________________________________
> > > > > aprssig mailing list
> > > > > aprssig at lists.tapr.org
> > > > > https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > aprssig mailing list
> > > > aprssig at lists.tapr.org
> > > > https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig
> > >
> > > --
> > > -Al Gerheim
> > >
> > > HP-49G+ Software Page:
> > > http://members.cox.net/above
> > >
> > >
> > >
> >
> >
> >
> >
> > _______________________________________________
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> 
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