Multiple headsets with one dongle

Bluez-devel Michael Puchol 2 participants 2 messages Jan 13, 2006 Bluetooth drivers

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Michael Puchol

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2006-01-13 00:50 UTC #0 lore raw

Hi everyone,

Firs, I'd like to introduce myself, having just joined the list. I'm the hardware engineer at Southwing, a Barcelona-based company that develops Bluetooth headsets and carkits. We do both software and hardware design in-house. We have a decent lab, and quite a nice range of phones, dongles and headsets for testing. Most of our designs are based on the BC3 AudioFlash, and now we're dwelling into the SiW3500 now, plus the BC4 External. As far as coding goes, I can understand C code, cannot really write it without following examples, and could modify code to do simple things.

I haven't studied the Bluetooth specs fully (not enough time!), but I have begun playing with Asterisk, a BT dongle and a couple of headsets.

Asterisk is configured OK, with a 2.6 kernel on a CentOS 4.2 distro, chan_bluetooth is working just fine, as is the BT stack. I have managed to have two headsets paired with the dongle, and thus visible to Asterisk, and either of them answer an incoming call, or dial a preset number, but what I haven't been able to get working is one headset calling the other. Well, actually, it *does* work, but the audio is totally unusable.

From what I have been able to gather so far, the headsets are using RFCOMM channel 2 (sdptool search --bdaddr 0x111E), and so when both are communicating with the dongle at the same time, they most likely are interfering each other. My questions are:

1. Am I correct in thinking the RFCOMM channel is derived from the BT address/MAC? If so, I could change the MAC of one of the headsets so that it would use a different hop sequence.

2. If 1) is incorrect, *where* is this RFCOMM channel configured in the CSR pskeys?

3. The dongle, configured as master, *should* support up to three slaves using the handsfree profile?

Best regards,

Mike

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Brad Midgley

2006-01-13 17:10 UTC #1 lore raw

Michael

Quoted 8 lines

number, but what I haven't been able to get working is one headset calling the other. Well, actually, it *does* work, but the audio is totally unusable.
From what I have been able to gather so far, the headsets are using RFCOMM channel 2 (sdptool search --bdaddr 0x111E), and so when both are communicating with the dongle at the same time, they most likely are interfering each other. My questions are:

The rfcomm channel communication is not where interference happens. It's when both headsets try to build the sco connection at the same time.

Quoted 2 lines

3. The dongle, configured as master, *should* support up to three slaves using the handsfree profile?

I'm not totally sure how to do this anyway. Marcel has hinted at it and apparently there's a boot-time parameter to set something to allow two sco connections. I tried to capture everything in the btsco bug for multiple headsets, but this is all I come up with there:

Marcel adds: "To get more than one SCO channel working the hci_usb driver must be fixed to dynamicaly change the alternate settting."

I think he was working on the generic case but if you know how many headsets you have paired with you could set the alternate setting once and leave it alone I think.

Brad