blackdiamond

I'm interested in constructing my own serial cable between my
Axim 5 and my Garmin Geko 201. I found two sites with directions
on how to do this:
(1) http://www.geocities.com/player5667/PPC/GPS2.htm
(2) http://www.wormley.com/axim

My problem is that the two sites don't seem compatible and don't
know which one to follow. According to reading the diagram on
(1), all you have to do is jumper the Tx and Rx pins(2 and 3) on
the Axim side and connect that to the data ouput line from the
Garmin. I don't see why you would need to jumper pins 2 and 3.
It would seem that you should only need to connect to pin 3(Tx)
and possibly pin 4(as described on the second site).

According to site (2), you need to activate the DTR line(pin 4) on
the Axim side in order to power up the electronics in the cable(the
cable has a circuit board 'converter'). It then offers a way to use
the data line from the GPS to activate the DTR. Thus, it would
seem right to link pins 3 and 4 on the Axim side.

If anyone could help me with this, it would be greatly appreciated.
Thank you.

Podge

Hi,
You can't just hook the garmin on to the AXIM, you'll probably destroy the the axim, the garmin or both.
I made a cable that works 100% for NMEA and Garmin protocol. I wrote a how-to document, with schematics and a list of websites where you can get the parts from. I don't have a website so if you're interested I'll attach a pdf here.

blackdiamond

Hi Podge,

Yes, I would very much like to see your schematics so please post
the pdf when you get a chance.
Thanks so much for your help. I wasn't aware that I could destroy
my Axim or Garmin and thought it was straigtforward. I'm shocked
how much conflicting information I'm seeing on this.

Howard2k

Just in case you don't feel like taking the risk.. You can also get a cable from http://www.pc-mobile.net

__________________
Always read stuff that will make you look good if you die in the middle of it.

blackdiamond

Yes, but the one in pc-mobile cleary states that it can't be used
bi-directionally. The only place I know of that sells bi-directional
cables is, http://www.hobbitleads.freeserve.co.uk/leads.htm.

Podge

Blackdiamond,
I'll get it out tomorrow, I was just organising some web space, I also wanted to take some better photos to add to the doc.
Another advantage of your own cable is you can make it any lenght you like. I made one 8m long for my mates 4x4.
rgds Podge

Podge

Blackdiamond,
Have look at this and tell me what you think

http://homepage.eircom.net/~podge001/index.html

kittymark

Any of these Mod work with Magellan too? Any related web site regarding Magellan and axim mod?

__________________
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Ya HOO as of Nov. 9th, 03 I am a member :) :) :)

Podge

Hi Kittmark,
I don't have any direct experience with magellan but from what I can see on the net they use a 2 wire rs232 interface plus gnd also.
So, I reckon a similar apprach will work, you would need a different connector at the GPS end. I don't know if you can supply power but I be surprized if you couldn't.

blackdiamond

Podge,

Wow, this is excellent work! If only I had found you before I
bought my Dell serial cable, and I would've built one per your
instructions.

I finally received my serial cable from Dell yesterday so I did some
experimenting. I connected the Garmin to the serial cable using
only ground, Tx and Rx pins. The info on, http://www.wormley.com/axim/, was totally correct I found.
Using a terminal program(ttl.exe) on my Axim, I found that I was
getting gargabe on the screen. After applying power to the DTR,
pin 4, via a resister from pin 3, I suddenly started seeing NMEA
sentences on the terminal screen. The Wormley site describes
how the inline RS232 driver in the Dell cable will only power up if
it seeings power on the DTR(pin 4).

I would really like a bi-directional cable, so I will try grounding the
SEL line inside the blob. If I get around to it, I'd like to build my
own much more compact cable like Podge's.

Thanks for all your help!

blackdiamond

Would grounding the SEL line affect communications with other
serial equipment besides GPS? I would also like to connect my
Axim with my cellphone via the same serial cable to use as a
modem for internet access. I assume that the SEL mod wouldn't
hurt, right?

Why didn't Dell have the SEL line grounded in their design? Is it
only to save power on keeping the RS232 driver running?

Podge

Blackdiamond,
The sel pin is joined to shutdown/powersave pin on the sipex line driver..... It's a power saving exercise... or dell could just b being awkward...

benbasat

Any one understand why not power the DTR line from the DSR line directly? in the http://www.wormley.com/axim/ solutions ??
In all solutions he connects DSR to DTR but also powers using the GPS data or external battery .

Podge

Benbasat,
Dsr isn't asserted all of the time so if you just wired it directly it wouldn't keep the Sipex line driver turned on.

I his first schematic he is using the power from 2 signals ie DSR and RX to keep the capacitor charged and hold up DTR. You would find if you looked at a NMEA bit steam that it is probably biased toward ones rather than zeros, which he uses to suppliment the DSR signal.

hope this helps.
rgds POdge

blackdiamond

Success!!!

Last night, I opened up the Dell dongle on my cable and soldered
between SEL and ground and bi-directional GPS works! No need
to assert DTR anymore so it makes things much cleaner. I
confirmed that bi-directional works through G7toCE.

Not only does my Garmin work, but now my Dell can talk to my
Motorola V66 cellphone. This connection was not working and I
confirmed that the cause was the V66 not asserting DTR. After the
above fix, I am using my V66 as a modem so that I have internet
connection on my Axim. Great!

Podge, I would like to build your cable but there seems to be a
problem with the pics on your site. It was working the first time I
clicked on it yesterday but the pic links are not working now.
Thanks for your help!