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Simultaneous access to multiple bluetooth devices

 
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mikej
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Joined: Nov 19, 2003
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PostPosted: Thu Dec 04, 2003 11:10 am    Post subject: Simultaneous access to multiple bluetooth devices Reply with quote

I have an iPaq 2210 and a BT tom tom GPS.
I also have an Ericsson T68i phone.

The iPaq will talk to either device separately but not both together. I was hoping to use something like Applian Phone King to control the phone so I didn't need more than one device cradled to the dashboard.

I got this response from Widcomm (Bluetooth developers for ipaq):

"Dear Sir,
On Pocket CP 2003 OS, the system is limited to 9 COM Ports, so at most there can only be 9 COM Ports active. The system takes up a couple of these for several things and we use some for our Bluetooth services, this does not leave room for additional COM Ports that generic applications can connect to, hence why we have one inbound/outbound COM port.

At this time there is not a way around this....

Thanks,
WIDCOMM Technical Support
support@widcomm.com "

I only want two com ports - it doesn't seem all that unreasonable to me!

Mike
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lbendlin
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PostPosted: Thu Dec 04, 2003 2:52 pm    Post subject: Reply with quote

The problem is that you only want ONE com port, and both devices are competing for that...

Not sure how the phone King works, but here is the general setup:

The BlueTooth GPS exposes a service (SPP) to the PDA. The PDA uses it's CLIENT com Port to listen to that service (the incoming GPS sequences)

And now you want the PDA (your CLIENT) talk to the Mobile Phone Service as well. But it can't since the port is already blocked by the GPS...

It would be a different story if the mobile phone as a CLIENT would request the services of the PDA (try it out). About the only useful thing from that would be the OBEX file transfer (contacts etc)...

BlueTootn wasn't designed as a network of equals - it is a strict client-server application with the idea that one client is served by one or more servers, but always serving different services, not the same.

You could also not connect to two headsets from one phone, or?
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mikej
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PostPosted: Thu Dec 04, 2003 3:24 pm    Post subject: Reply with quote

You're right (in a way).
My ericsson phone however, shows two com ports in the services it advertises. It is possible for example for the t68i to be connected to a bluetooth headset and the ipaq simultaneously. You hear the phone calls on the headset, and see the display/keypad on the ipaq.

So what I want, and again I don't think it's unreasonable, is for the ipaq to support two bluetooth com ports. (in the same way that it supports a wired com port at the same time as a BT one).

I can't find anything in the BT standard that says "you will only provide one emulated serial connection".
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lbendlin
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PostPosted: Thu Dec 04, 2003 4:14 pm    Post subject: Reply with quote

When your Ericsson phone connects to the headset and to the iPAQ, it connects to DIFFERENT services. (Is the phone connecting to the iPAQ or is the iPAQ connecting to the phone?)

In the GPS case you want to connect a client to two devices with the SAME service. That doesn't work as far as I am aware. Anyone here who knows BlueTooth technology?
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mikej
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PostPosted: Thu Dec 04, 2003 6:41 pm    Post subject: Reply with quote

You're absolutely right. What I'm asking for (and what I don't understand why it's not implemented) is two emulated com ports. ie the OS/BT drivers provide com1 and com2. So when you pair/install your devices/software, you connect one to com 1 and one to com 2.

Bluetooth can allow for more than one connection (as long as it's a different service), so it's not a physical layer problem. I imagine that the developers just never thought of it?
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lbendlin
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PostPosted: Fri Dec 05, 2003 2:33 am    Post subject: Reply with quote

That would be a logical explanation Laughing . I wonder what the folks at Widcomm would say to your request... I am pretty sure they could hack the existing BT server to "re-use" another service (for example the fax service) into a second COM port receive service...
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Dave
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PostPosted: Fri Dec 05, 2003 7:37 am    Post subject: Reply with quote

Diversifying slightly as I know it won't help with this problem, but the 2210's are very limited in terms of COM ports. Where as the older 38xx series iPAQ's and newer (I believe) 54xx/55xx, 41xx iPAQ's all support movable COM ports, if the regular COM port for say a CF card (COM 7) is taken, then it will assign another COM port, even down to COM0 if it had to. The iPAQ 2210 won't allow this, if something takes up COM 7 like RoyalTek's Bluetooth program, then you're . This may be more of a WM2003 issue, than a 2210, I'm not too sure, but COM ports are a real PITA.

Like I said, it wouldn't help this situation even if you went for a different iPAQ, but I have noticed a switch between 38xx and 22xx where COM ports are now static rather than virtually assigned.
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mikej
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PostPosted: Fri Dec 05, 2003 10:23 am    Post subject: Reply with quote

I think the com limitations are more of a windows mobile 2003 problem. See the post at the top of this thread where I asked Widcomm about it.

Microsoft are rumoured to be bringing out a new bluetooth stack next year that supports serial profiles, if I understand the XDA threads correctly. Anybody have any idea how we might persuade MS that there is an interest in more than one emulated com port?
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