BT GPS - how many simultaneous connections to PDA's/laptops?

ABeeBeeSee

Is a BT GPS (TomTom in my case) able to communicate with both a PDA (for voice nav for me) and a laptop (keeps the co-driver/wife awake on long journeys :D) at the same time?

lbendlin · Posted: Tue May 18, 2004 4:09 pm Post subject:

Nope. One connection at a time only
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icsys · Posted: Tue May 18, 2004 4:55 pm Post subject:

When you say one connection at a time only, if another device (other PDA, laptop etc..) has bluetooth and can 'see' the GPS I would expect that it could receive the gps data from it.
I assumed the GPS signal is being radiated out and any BT device in range could receive it.

Obviously if the 'active connection' is a two way communication then I can understand why there can be only one connection at a time.

DavidW · Posted: Wed May 19, 2004 11:14 am Post subject:

Bluetooth works in the second way you describe - I don't believe there's any such notion as broadcast, though I haven't read right through the Bluetooth specification.

It might well be at least theoretically possible for a Bluetooth GPS to keep offering a Serial Port Profile connection even when it was already connected, so you could connect multiple devices at once (obviously only the first connection would have to allow incoming data, for example, to reconfigure the GPS), but I'm not sure there'd be much demand for this feature. Whether there's enough demand for any manufacturer to develop such hardware and firmware, though, I doubt.

Another possibility may be a 're-radiating' driver on the Pocket PC - that is, that connects to the Bluetooth GPS, offers some connection for Pocket PC software (ideally presenting itself as a COM port) and allows a connection to the Pocket PC's incoming Bluetooth serial port for a read-only GPS feed. Again, this is just a possibility that occurs - I don't know how feasible it is and whether anyone would want to invest the time and effort in developing this.

David

icsys · Posted: Wed May 19, 2004 1:12 pm Post subject:

It would be good to allow several devices to share a single GPS transmission.
I have read some of the Bluetooth specs but alas it is a little too deep for casual reading. I did find the following info but I must admit, I dont fully understand some of the technical terms.

lbendlin · Posted: Wed May 19, 2004 1:52 pm Post subject:

Certainly BT can be anything to anybody. But remember we are talking Serial Port Profile here. That's point to point only. As DavidW said, the receiver would need to do some kind of reradiation (offering the service again to the next P2P connection. So best case this would be a bus, but not a piconet.

Enter Linux: Linux (also on the Pocket PC) features a gpsd daemon (deamon?) that does exactly that - get the data from one receiver and then broadcast it any imaginable way.
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icsys · Posted: Wed May 19, 2004 2:05 pm Post subject:

ABeeBeeSee · Posted: Fri May 21, 2004 10:27 am Post subject:

Thanks, everyone. Answers my question, and interesting discussion. Would be a nice feature, though ...

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