Date: Thu, 02 Jun 2005 01:16:28 +1000
From: Raymond <[EMAIL PROTECTED]>
Subject: Re: [LIB] PCMCIA Power & GPS
At 07:58 AM 1/06/2005 -0700, you wrote:
Date: Sun, 29 May 2005 13:47:25 EDT
From: [EMAIL PROTECTED]
Subject: PCMCIA Power & GPS
List folk,
I've been using my L100 as a GPS-routing software tool, using MS Streets &
Trips or Street Atlas or Autoroute, and a Garmin Etrex Venture GPS receiver.
The Etrex PC interface is serial, and I use a cable that splits to a 9-pin
connector and a DC cigaret lighter power supply, which powers the Etrex as
well as
enabling communication with the Libretto.
I recently bought a Holux "mouse" GPS receiver, which has no display and is
meant strictly to operate with a PC. It uses a USB connection, providing
both
signal and power.
Problem is this: the Belkin PCMCIA/USB2 card I use in the Libretto to provide
USB ports doesn't pass enough amps to the GPS through the PCMCIA connection.
The GPS works perfectly when connected to the USB port on the enhanced
replicator, and on other laptops with integrated USB ports. And it will
work with
the Belkin adapter if I use the Belkin external power supply.
The whole idea of the Holux GPS was to do away with some of the cabling mess
inside the vehicle. And I'd prefer not the have to use the L100 dock because
of size. Is there a way to increase the output to the PCMCIA slot?
Alternatively, are some PCMCIA/USB cards higher output/efficiency than
others? This
problem is odd, as I have an IBM external hard drive that runs strictly
off the
Libretto's PCMCIA interface, no external power required. Yet this
no-moving-parts GPS needs more juice than a hard drive?
Thanks for any suggestions.
Lee
The problem here is that a lot of USB PCMCIA cards (actually, all of them
in my experience) only run in low power (100mA) mode unless they have an
external power input (some cards have a jack where you can apply 5V or 12V
and kick the card into high power mode). In theory, this is actually done
in software/firmware (in theory, the device boots up in 100mA mode and
sends a request to the USB hub asking for more power, which the hub has the
option of denying ... if the request is granted, only then should the
device start to draw up to 500mA). Of course, I'm able to pull about an amp
out of my laptop USB ports (a big Dell Inspiron) without even touching the
data lines and it doesn't seem to flinch (or browning out the supply),
perhaps they're wising up to all these people running USB powered phone
chargers, lights, fans and coffee cup warmers :-)
Now the PCMCIA port *should* be able to provide a lot of power (500mA at
least, I *believe* it's rated to at least an amp on surge) but for some
weird and wonderful reason USB PCMCIA cards don't take advantage of this.
When I used my Libretto lots, I made a modification that allowed me to plug
an external PS/2 keyboard and mouse in (see my webpage), and as part of
that I tapped the internal 5V rail (which I've drawn in excess of 500mA
from without problems) ... so when I needed to run high powered USB
devices, I tapped 5V from there to supplement the USB power (in my case I
was running USB hard drives).
If you're handy with a soldering iron, I recon it's a modification that's
worth doing anyway - it gives you the option of using an external mouse
without using the EPR and it gives you the opportunity to tap 5V to run
things like the GPS.
If you don't want to do that, your options probably come down to things
like PCMCIA GPS units or the EPR. As a compromise though, if you also have
the docking bar, you can draw 5V from the PS/2 ports on that without any
dramas and is probably a little less bulky to keep around than the EPR ...
- Raymond
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