Thread: bluetooth woes

Originally Posted by OLAS

gentoocar, your idea looks good, however if we can work out why the app/sco drops after a few seconds and fix that, I don't think much more coding will need to be done. That said, making the app stable and adding extra features would be good!

The SCO link should drop out after a few seconds of silence, and come back up as soon as there is more audio (from the phone) (To save power?) I think also if there is audio from the pc it should come back up too, but I don't think there is anything in the code that will do that right now.

If you keep making noise with the phone (the mic will be shut off, so keep pressing buttons or make a call and talk into the other phone), the sco link should stay active as long as you're making noise.

I wish there were some way to disable that behavior. Maybe there's an AT command to do that?

Anyways, stability is what I'm after here. Handsfree won't do me any good if I have to restart things while driving!

I wish I had seen this thread earlier.

I have written an app that connects to my cell as a hands-free device
and bridges it to my asterisk PBX. It's not finished, as it does have a
few bugs still with states, and when there is more than one phone
connected audio stops working, but it does work. I can pick up a phone
elsewhere in the house and the call goes out through my cell phone (I do
not have a POTS). As well as when a call comes in the phones in the
house ring.

When you scan the services on your phone you want the one that is "voice
gateway" or some such. On my phone that is channel 8. This rfcomm channel
only supports a subset of the at command set. This subset is laid out in
the Handsfree Profile doc. The doc is pretty straight forward. (As opposed to teh USB spec, wich I still haven't made sense of yet)

If you can find a program that simply listens for SCO connections
irregardless and sends/receives audio you could use that in conjunction
with another program that sends the at commands. SCO is channel-less. So
aside from BDADDR there is no way to know one connection from another.

I did not know that the bluez people had a handsfree program.

The documentation you are looking for to work on this is

http://bluetooth.com/NR/rdonlyres/94EAD32B-3E70-4AEC-9CD5-1E3F887A15F4/917/HFPSpecVersion1_0.pdf

I'll put together a tar-ball of my code. The program is designed to
connect to asterisk, and as I said above has a few quirks that I haven't
taken the time to fix. But hopefully it would be a good reference for
anyone trying to work on this. I'll post this soon.

I've actually been writing my own front-end for linux. But I haven't
gotten to the point of adding Handsfree support yet. (I intend to).

Edit: Link
biax-0.0.1.tar.bz2

--Nate

Originally Posted by gentoocar

The SCO link should drop out after a few seconds of silence, and come back up as soon as there is more audio (from the phone) (To save power?) I think also if there is audio from the pc it should come back up too, but I don't think there is anything in the code that will do that right now.

If you keep making noise with the phone (the mic will be shut off, so keep pressing buttons or make a call and talk into the other phone), the sco link should stay active as long as you're making noise.

I wish there were some way to disable that behavior. Maybe there's an AT command to do that?

Anyways, stability is what I'm after here. Handsfree won't do me any good if I have to restart things while driving!

The Phone should not drop the SCO conection, audio or not. If you only have one device on your bluetooth link the phone will take over as master. When a call comes in, it will establish a SCO link to your client. If you have more than one device, your bt adapter will act as master, and then (i think) you will have to establish the sco connection to the phone.

--Zims

Hey, thanks for that info Zimans! Looks like I have some reading ahead of me.

Originally Posted by Zimans

The Phone should not drop the SCO conection, audio or not. If you only have one device on your bluetooth link the phone will take over as master. When a call comes in, it will establish a SCO link to your client. If you have more than one device, your bt adapter will act as master, and then (i think) you will have to establish the sco connection to the phone.

Well, if you have a cell and a BT headset, give this a try. Connect to the headset, then make some noise with the keypad (on my phone i can hit up&down to scroll through the phonebook. It makes a beep every time you press those buttons). Now let it sit for a few seconds in silence. Now press those buttons again. The beginning of the first tone should be chopped off, as it has dropped the SCO connection and had to re-connect it. Having the SCO connection active drains the battery faster. Imagine you have your phone in your pocket connected to your earpiece, and you're not on the phone. If it sits that way for hours, you don't need that SCO channel active. Once you make some noise, it will reactivate itself. I'm not sure, but I'm guessing that during an actual call it wouldn't do that.

Now, all of that is just what I've gathered from playing around and watching the SCO link drop and reconnect in response to silence/noise. I have yet to find any documentation that confirms that. But in any case, I don't think it will really be a problem.

Good news, everybody. It looks like my company is going to let me release some code as open source for use in this project. Don't get too excited, it is not bluetooth-related code, but just some thread/socket/audio related utility classes. This is good news because it will make it easier for me to develop this handsfree stuff now.

When you are pressing buttons are you currently in a call?

With my phone (Samsung t629) when a call comes in it makes a SCO connection to my app. This SCO connection stays active for the duration of the call, silent or not.

Also, I believe the Headset and Handsfree profile are two different profiles, so the phone can probably tell the difference between the two. It may do a power save mode for a headset, but not for a handsfree (External power source assumed?). When i'm mucking with the menu with my phone and my app connected it does not create a SCO connection. When a call comes in it creates the SCO link before it even starts ringing (spec says it should for in-band ring tones, but my phone doesn't do in-band))

On a related but slightly different note:

I don't think you can get phone book entries from this rfcomm link, I think you need to make a secondary connection to the serial port channel. I could be wrong as I haven't messed with it (Don't need phone book stuff for an asterisk bridge) AT least it doesn't say anything aside from memory dialing in the HF profile spec.

--Zims

Originally Posted by Zimans

When you are pressing buttons are you currently in a call?

With my phone (Samsung t629) when a call comes in it makes a SCO connection to my app. This SCO connection stays active for the duration of the call, silent or not.

Ah. Mine works a little differently. When I'm pressing the buttons, I'm doing so without being in a call. It makes sense that it would keep the SCO link active while in a call but drop it during silence while not in a call. I think that's exactly what we want, right? I'll have to test whether it stays active during a call after work.

Originally Posted by Zimans

Also, I believe the Headset and Handsfree profile are two different profiles, so the phone can probably tell the difference between the two. It may do a power save mode for a headset, but not for a handsfree (External power source assumed?). When i'm mucking with the menu with my phone and my app connected it does not create a SCO connection. When a call comes in it creates the SCO link before it even starts ringing (spec says it should for in-band ring tones, but my phone doesn't do in-band))

I see the same behavior no matter which profile's channel I connect to. I'm not sure what you mean about in-band, I've never heard that term.

Originally Posted by Zimans

I don't think you can get phone book entries from this rfcomm link, I think you need to make a secondary connection to the serial port channel. I could be wrong as I haven't messed with it (Don't need phone book stuff for an asterisk bridge) AT least it doesn't say anything aside from memory dialing in the HF profile spec.

I've read that the headset profile does not support phonebook stuff but the handsfree profile does. In any case, if it doesn't I could always open a rfcomm channel to the serial port and get the phone book that way (I *know* that works since I've done it)

There is a patch for asterisk to get it to act as a handsfree for bluetooth phones so that it can be used to send/recieve calls. It is tested and working with the following:

LG TU500
RIM Blackberry 7250
Nokia 6230i

So far, it does not work with the Sony Ericsson T630

Read more about it here:
http://bugs.digium.com/view.php?id=8919

Originally Posted by gentoocar

I see the same behavior no matter which profile's channel I connect to. I'm not sure what you mean about in-band, I've never heard that term.

You know how when you call some people instead of a regular ring noise, you hear some audio clip (On your phone). That's in-band ring tones.

--Zims