Splitting Serial

**August** · 10-31-2004, 08:38 PM

I need to provide GPS data to a laptop and an APRS tracker simultanously. I don't really want to have to buy a second GPS. Can serial be split into two serial connectors in parallel? Is there an interface on the market that can do this?

**blurp** · 10-31-2004, 10:26 PM

Virtual COM Port Splitter

Come on, guys,

for 2 seconds before you post a question like this.

**danon** · 11-01-2004, 12:56 AM

wow, thx for the link!

.

**August** · 11-01-2004, 01:05 AM

Virtual com ports have nothing to do with my question. I don't need two software applications to access the GPS; I have two devices that need to access the GPS.

**kingtut** · 11-01-2004, 01:22 AM

you can't, you would risk blowing the 2 devices since each puts out current. Even if you would work around the current issue, one device would confuse the other since one might send a specific request to the GPS that the other did not expect. Serial is a protocol between 2 devices, that is the short answer.

**zPilott** · 11-01-2004, 01:24 AM

does the gps receive data from the PC, or is it only one way? If the gps is expecting config data from the PC, I think you might have trouble if both are trying to send something out.

If the gps is sending only you might be able to try something like this:
http://www.airborn.com.au/rs232.html#monitor

**zPilott** · 11-01-2004, 01:29 AM

another option might be to run a null modem cable from the first pc to the second, and somehow propagate the data across, so that the second device would think it is connected to the gps, not to a pc.

**August** · 11-01-2004, 03:14 AM

I found this in a PDF manual for a Ratheon GPS.

When using the NMEA 0183 format, the Raystar 112 can provide data
for at 2 or more navigation equipments when connected in parallel. Be
sure that all devices connected to the data output ( plotters, video
sounders, radars) are programmed to use the NMEA 0183 data format.

WARNING: Do NOT GROUND the Data, Data return lines, or the
Shield of the interface cable at any of the external navigation
equipments.

The ability to do this must be part of the NMEA standard. Any thoughts?

**Laidback** · 11-01-2004, 03:19 AM

If you're just reading there's no problem.

**Ricky327** · 11-01-2004, 11:12 AM

Originally Posted by August

Virtual com ports have nothing to do with my question. I don't need two software applications to access the GPS; I have two devices that need to access the GPS.

I though as much but relax man.

Heres your solution :

GPS <---> PC ( Normal 2 way using RX/TX, can read and write to GPS )
:
: -------> Another device (1 way using the TX line of the GPS, device can only read)

Dont forget the GND for both PC and other device.