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View Full Version : NMEA data to multiple devices



michaelcarey
11th February 2006, 03:13 PM
Hi Everybody,
I am after a device to allow me to split my Garmin GPSMAP60CS NMEA data to five devices without loading down the data output.
I have seen some commercial units for use on fishing boat navigation equipment, but they are quite expensive. I've been trying to find a schematic for one, I'm not afraid to build it, but no luck going down that track (pardon the pun!).
I have one of Bob Keskull's GPS data loggers, a Tinytrak3 APRS encoder, a Compaq iPAQ running OziCE, an Icom IC-F7000 HF and sometimes a laptop with Oziexplorer! All of these are hungry for NMEA 0183 and I need to feed them.
Any ideas?
Regards,
Michael.

festy
11th February 2006, 04:00 PM
I've seen the commercial units you mentioned, they're hellishly expensive as they cater to the cruising community who can afford it.
What about something like 4 max232s - 1 amplifying the original signal, driving 3 more, which each drive one or two com ports?

michaelcarey
3rd March 2006, 02:07 PM
I was almost going to make my own, BUT.... I had a slack attack and bought one of these gadgets :-
http://www.pacmicro.com/DD20.html
It does exactly what I want in a nice compact package. Now I can run lots of devices of my GPS at the same time!!!
Regards,
Michael.

poundy
8th March 2006, 08:43 PM
so if you don't mind me asking, what did it set you back??

michaelcarey
9th March 2006, 04:39 AM
I got it from TMQ in Queensland. It's made by Pacific Micro in NZ. I paid "trade" rates through work. Cost me $200 +GST.

vincentvega
9th March 2006, 07:03 AM
holy crap!

maxim samples max232 etc series chips for free... you could have built yourself one for under 10 bucks! Or is this thing more than jsut a serial port breakout box?

Edit: Just read the specs, current loop / RS422 is nice but will you ever use them?

jrs
9th March 2006, 07:07 PM
This all seems a quite a bit more technical than is needed here.
RS232 drivers are tough, can drive lots of wire at 19k2 at least.
nmea is just 4800 baud. Just parallel all the loads. 5 or 6 loads should work fine.
Passive boxes with plugs and wires are usually reliable.

I am assuming its one-directional here, one at most box can talk to the gps.
Otherwise you need a splitter. Havn't seen one of them in a while.

michaelcarey
19th March 2006, 06:40 AM
I needed something in a hurry and didn't have time to get it together myself. I did modify the DD20 a bit to suit my requirements. Many of my devices can be powered through the GPS input socket, using pin 9 on the connector (eg the GPS logger and APRS tracker). So I changed the circuit board a little to allow the DD20 to be powered via pin 9 and output a fused 12V supply on pin 9 of each socket.
I can now happily run all my NEMA devices off the one GPS source, it works like a treat! I can add or remove devices any time (up to 8!).
I'll get some photos up on my web space soon.