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One GPS - Multiple devices...

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STiMULi

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Before working on setting up my new BCD996T I had done a little research on taking the NMEA output from one GPS and supporting a scanner and a Laptop. I also wanted to eventually use the same GPS to support my TMD700A for APRS.

I had first though about a Y cable like the one found here:

http://www.pccables.com/00819.htm

The only problem with that is if you are running 2 devices that want to send information to GPS they would be in competition with each other and corrupt the transmit signal. This means the transmit lead would have to cut and with a premade cable that would be tough to do without damaging the integrity of the cable.

Some applications or devices want to send waypoints to a GPS. The TMD700A uses this function to show stations local to the radio. APRS software does the same as well as some Navagational software uses it to display the gas stations and Subway sandwich spots.

I decided instead just to use phone cable (line cord) and RJ11 to DB9M or DB9F to acomplish this.

Pins 2,3 and 5 are the pins used for simple serial commuications on the DB9.

2 = XMIT
3 = RCV
5 = GND

So it became simple use the GREEN, RED and BLACK leads on one end and the RED GREEN and YELLOW leads on the other. This depends on the line cord used. For devices that you want to prohibit sending info just don't connect the "2" pin. This would eliminate the transmit from that device.

Then you plug it all into a telephone line splitter (267A). There are 2 different types one will split all 4 conductors from one input to two outputs (in a manner that would split one line to 2 phones) or the other type (267B) which splits the RED and GREEN from the BLACK and YELLOW leads (in a manner that would support 2 lines on one telephone jack and splitting 2 Phones)

There are 3 way splitters out there. SOme combine the properties of both the 267A and 267B but most 3ways are a lager version of the 267A. Remember 267A is what you want. If I had more time I would have taken the single GARMIN LEGEND and out put it to the BCD996T, TMD700A and the LAPTOP running Delorme SA using a 3 way splitter.

There has been a suggestion to use a product called GpsGATE.This seems to be a "software" only application and will not address multiple physical serial ports.

From the GpsGATE website:

GpsGate supports NMEA and Garmin USB as input and creates virtual serial ports for each GPS enabled application. The virtual serial port supports NMEA.
I will take photos and draw pictures when I get time :)
 

kb2vxa

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Hi Stim and all,

I have little knowledge of data systems but something comes to mind. In the days of DOS and the serial port before USB was invented there was the data bus controller and an address was manually assigned to each device on the bus. Then you quoted something about virtual ports, well, that's how USB works while the software automatically assigns the port and device addresses. It seems you're on the right track, now let's hope someone can fill in the blanks.

Never mind the 8X10 color glossy photos with the circles and arrows to be used as evidence against us, Officer Opie retired from the Stockbridge MA police 20 years ago. What's Alice up to these days, still working at the resturant?
 

Al42

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Connect the cathodes of two diodes to the data in pin of the GPS and the anode of each one to one of the devices. As long as both devices don't talk at the same time you can run more than one RS232 device together.
 

seamusg

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datainmotion said:
I'm probably missing what you're asking for, but wanted to post these anyway for 996 users.
Here's some software based COM port splitters I've used:

http://curioustech.home.insightbb.com/xport.html
http://www.franson.com/gpsgate/ (This is the GPS Gate you mentioned)

They allow one GPS (NMEA) to feed multiple devices (via virtual COM ports)

Good luck!
Remember software com port splitters are mostly virtual, ie not real and therefore connot be connected to a real device but to other programs. ie also not real. Unles you have a program that connects one serial port to another real serial port, and have more than one serial port on the system. It won't work.
 

datainmotion

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seamusg said:
Remember software com port splitters are mostly virtual, ie not real and therefore connot be connected to a real device but to other programs. ie also not real. Unles you have a program that connects one serial port to another real serial port, and have more than one serial port on the system. It won't work.
Not entirely correct. The Xport software I use connects directly to COM 3 (my integrated GPS). Then Xport feeds that data to up to 8 virtual ports.
 

STiMULi

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VIRTUAL PORTS

These are not real ports and you can not plug these VIRTUAL PORTS into your scanner because they are VIRTUAL PORTS and do not exist in REAL LIFE.

Yes you may run multiple applications off of this but you can not connect it to multiple REAL PHYSICAL devices.
 

datainmotion

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STiMULi said:
VIRTUAL PORTS

These are not real ports and you can not plug these VIRTUAL PORTS into your scanner because they are VIRTUAL PORTS and do not exist in REAL LIFE.

Yes you may run multiple applications off of this but you can not connect it to multiple REAL PHYSICAL devices.
Warn me before yelling next time.:eek: :)

My ignorance here is that the 996 must receive its GPS data through a legacy port and not the software. Too bad. Very limiting.
 

datainmotion

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I know I'm asking for trouble here, but would a split null modem cable work (if such a thing exists)?
 
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STiMULi

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datainmotion said:
Warn me before yelling next time.:eek: :)

My ignorance here is that the 996 must receive its GPS data through a legacy port and not the software. Too bad. Very limiting.
How would you install the software in the 996? :)
How would you put the 996 in your PDA or laptop? :D

I was not yelling, I was merely getting your attention. You were discussing this as if the 996 were an application in your PDA. It is a physical device that needs some physical connection that will eventually be serial and running standard NMEA sentences over a 4800 baud connection.

BTW in the 1st post I linked to this photo:



I stated that it would be difficult to modify w/o damaging it.

The photo you posted is the wrong gender for splitting the GPS. It would however allow the connection of 2 GPS's to one radio :)
 

datainmotion

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STiMULi said:
How would you install the software in the 996? :)
How would you put the 996 in your PDA or laptop? :D

I was not yelling, I was merely getting your attention. You were discussing this as if the 996 were an application in your PDA. It is a physical device that needs some physical connection that will eventually be serial and running standard NMEA sentences over a 4800 baud connection.

BTW in the 1st post I linked to this photo:

I stated that it would be difficult to modify w/o damaging it.

The photo you posted is the wrong gender for splitting the GPS. It would however allow the connection of 2 GPS's to one radio :)
The software would reside on the laptop, not the 996. We routinely send external GPS data to another legacy port (either a DE-9 or PCMCIA) to provide AVL data to dispatch via wireless. This is accompplished via software.

As far as the photo, I just used that pic to show a split cable (as you linked to in your original post) w/o regard for gender.

Pardon my ignorance, just trying to spit out some other possibilities here.

An idea like yours is how things get created. I'm just playing the "dumb guy who sweeps the place at night" part. :lol:
 

STiMULi

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Good find but that probably costs more than the radio. I couldn't find anyone that would price it online.

I think I spent $11.00 on my cable set up.

When you get a radio that needs GPS you'll understand what I mean :)

Thanks for trying though! :)
 

smokeybehr

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Apologies for the necropost, but here's a solution that I found on another board. It's rather expensive, but seems to be something that someone could fab up with a little time and ingenuity: An NMEA Multiplexer. There are several commercial units out on the market, and several of them can be found here: NavStore - Your Pro Marine Source - Product Catalog
 
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