Garmin to Ipaq cable wiring ?

I purchased an Ipaq to USB cable, with the intention
of making a simple Garmin GPS to Ipaq cable by cutting
off the USB plug and wiring a 4 pin Garmin plug there
(it's a Garmin 12). Thats fine, I see 4 cables which
the Wikipedia USB pages ( http://en.wikipedia.org/wiki/Universal_s
erial_bus ) tells me a
Red (V+), Black (Gnd), White (D-), Green, D+). But
these pages explain USB uses duplex communication and
it's not clear to me which Data cable to connect to
the Garmin Tx/Rx pins. IE: D+ to Rx, or D+ to Tx?
Anybody already made one of these and can enlighten
me? I have a multimeter but the Ipaq end plug is TINY
and I don't believe I could tell if my multimeter probe
was on pin 7 (RXD, to Garmin T) or pin 8 (TXD, to GPS
R) (Ref. http://pinouts.ru/PDA/ipaq_22p_pinout.shtml
).

Bernie Baer wrote:
I purchased an Ipaq to USB cable, with the intention
of making a simple Garmin GPS to Ipaq cable by cutting
off the USB plug and wiring a 4 pin Garmin plug there
(it's a Garmin 12). Thats fine, I see 4 cables which
the Wikipedia USB pages ( http://en.wikipedia.org/wiki/Universal_s
erial_bus ) tells me a
Red (V+), Black (Gnd), White (D-), Green, D+). But
these pages explain USB uses duplex communication and
it's not clear to me which Data cable to connect to
the Garmin Tx/Rx pins. IE: D+ to Rx, or D+ to Tx?
Anybody already made one of these and can enlighten
me? I have a multimeter but the Ipaq end plug is TINY
and I don't believe I could tell if my multimeter probe
was on pin 7 (RXD, to Garmin T) or pin 8 (TXD, to GPS
R) (Ref. http://pinouts.ru/PDA/ipaq_22p_pinout.shtml
).

You are confusing USB with the older RS232 serial ports. They are
electrically different. The white wire is actually connected to pin 21,
the green wire to pin 19. You need to relocated these wires to pin 7
(RS232 RXD) and pin 8 (RS232 TXD) inside the connector at the iPAQ end.
I believe there may also be a resistor connected to pin 17 which
signals the iPAQ to use USB, which will have to be either disconnected,
or changed to a different value.

If you aren't comfortable soldering tiny wires to tiny pins, I suggest
you buy a pre-made iPAQ to Garmin cable:

https://www.bluehillsinnovations.com/store/
http://www.pc-mobile.net/grdc.htm

By the way, if you happen to have an iPAQ 1910, while it uses the same
22 pin connector as the other newer iPAQs, the RS232 serial port is not
wired to the connector, so you won't be able to connect it to a GPS 12...

Marc

Gotcha, thanks Marc!

Hi,

Are you trying to make a USB cable, or an RS-232 serial data cable. USB
would not work because both Garmin units and iPAQs are USB slaves. The PC
is the master when communicating with those units. Two slaves can't talk to
each other.

RS-232 communication is possible depending on the iPAQ model you have.
Which iPAQ and which Garmin are you using?

I sell and support cables for connecting most Pocket PCs to most GPS units.

Paul Remde
Cumulus Soaring, Inc.
http://www.cumulus-soaring.com

"Bernie Baer" wrote in message
...
I purchased an Ipaq to USB cable, with the intention
of making a simple Garmin GPS to Ipaq cable by cutting
off the USB plug and wiring a 4 pin Garmin plug there
(it's a Garmin 12). Thats fine, I see 4 cables which
the Wikipedia USB pages ( http://en.wikipedia.org/wiki/Universal_s
erial_bus ) tells me a
Red (V+), Black (Gnd), White (D-), Green, D+). But
these pages explain USB uses duplex communication and
it's not clear to me which Data cable to connect to
the Garmin Tx/Rx pins. IE: D+ to Rx, or D+ to Tx?
Anybody already made one of these and can enlighten
me? I have a multimeter but the Ipaq end plug is TINY
and I don't believe I could tell if my multimeter probe
was on pin 7 (RXD, to Garmin T) or pin 8 (TXD, to GPS
R) (Ref. http://pinouts.ru/PDA/ipaq_22p_pinout.shtml
).

Marc,

I also believe the power line in the USB is 5V and your Garmin requires 12
V. So you need some kind of a voltage regulator to drop the voltage from 12
to 5 (12 will fry your PDA.)

Wayne
HP-14 "6F"

"Bernie Baer" wrote in message
...
Gotcha, thanks Marc!

Wayne Paul wrote:
Marc,

I also believe the power line in the USB is 5V and your Garmin requires 12
V. So you need some kind of a voltage regulator to drop the voltage from 12
to 5 (12 will fry your PDA.)

Actually, the GPS 12 that the original poster mentioned is one of the
odd Garmins that needs a 5 to 8 VDC supply. I'm not sure how well it
will work, but if he is looking to supply power externally (which he may
not be), 5V may work for both...

Marc

Marc Ramsey wrote:
Actually, the GPS 12 that the original poster mentioned is one of the
odd Garmins that needs a 5 to 8 VDC supply. I'm not sure how well it
will work, but if he is looking to supply power externally (which he may
not be), 5V may work for both...

And, just to confuse things further, the "GPS 12" is different from the
"GPS 12XL" and "GPS 12MAP", which both take 10 to 32 VDC externally...

Marc

Wayne Paul wrote:
Marc,

I also believe the power line in the USB is 5V and your Garmin requires 12
V. So you need some kind of a voltage regulator to drop the voltage from 12
to 5 (12 will fry your PDA.)

If you're feeling handy with a soldering iron and want to save a little
cash, go out and buy the cable used to power an iPAQ from a car cigar
lighter socket. They are cheap and the plug on the cigar lighter end
contains a very small switch-mode 5v power supply. You can also find
iPAQ cable with 12v ans serial date lines in it, so you only need one
cable and plug on the iPAQ.

It may be a good idea to put the PSU in a metal box and add ferrite
suppressors to the cables connected to it because some switch mode PSUs
radiate RF like crazy.

I use exactly this setup, but the box is bigger: it also holds the
interconnect wiring to feed GPS data to my iPAQ, SDI C4 and EW logger as
well as distributing 12v to the GPS, logger and C4. All connections to
the box are D-9 connectors apart from 12v in, which is an XLR chassis
plug to match the glider's power cable. This way I can also plug a gel
cell directly into the interconnect box for bench testing at home.

The result is a neater setup behind the panel because there's just one
cable between the box and each instrument apart from the C4, which
requires a separate power cable.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

Guys, thanks for all the advice. I just wanted to transfer
data to/from the Garmin 12 to the Ipaq 3950, not power,
I'll live with the internal batteries of the units
for that.
Our club has a Jantar and DG-303 both fitted with Cambridge
302 varios, and I have a lead that connects the CAI
302 directly to the Ipaq, supplying power and data.
We also have an Astir and Junior that dont have CAI
302 but I will fly occasionally. I thought for the
occasions when I fly them I could live with a simple
battery powered Garmin to Ipaq setup. However as the
first reply has pointed out, the lead I procured and
butchered is wired differently at the Ipaq end than
what I require. I can buy the lead I need locally (Sydney)
for AUD$50 so will probably go that way, or maybe not
even bother and just fly with the GPS.
Thanks for all the advice though, much appreciated.

Just realised that since I already have an Ipaq to
Male 9 pin cable, all I need to do is to buy a Female
9 pin socket and wire it to the Garmin plug I have!
Now why didn't I think of that a week ago!