[maemo-developers] [maemo-developers] Bluetooth Headset Support - Status update?

From: Johan Hedberg johan.hedberg at nokia.com
Date: Sun Jan 14 00:18:47 EET 2007

On Sat, Jan 13, 2007, Gopi Flaherty wrote:
> Does anybody know if the N800 uses the same Bluetooth chipset as the  
> 770?

770 has a TI chip while the N800 uses a CSR chip (BlueCore4).

To use SCO audio using existing bluez software you need to get the chip 
into SCO over HCI mode (I think both devices are by default in SCO over 
PCM mode, i.e. try to transfer audio over a direct HW link between the 
bluetooth controller and the DSP). You'll probably find the procedure 
for manipulating the SCO routing on the CSR chip somewhere on bluez 
related web pages (maybe the available SW even does it automatically) 
since CSR dongles are quite popular. I don't know the exact procedure my 

AFAIK, the procedure of changing the SCO routing on the TI chip requires 
a proprietary TI HCI command. I'm not sure we can publish it since it's 
documented in TI docs which have quite strict publication restrictions.
I.e. this still needs some internal investigation. However, even with 
the command, neither the chip firmware nor the driver have been tested 
with SCO so there is guarantee that it'd work.

We are currently working on integrating SCO support (Headset Profile to 
be exact) nicely with the new and still experimental D-Bus based service 
infrastructure of bluez and the rest of the internet tablet software.  
The plan is to use the DSP routing instead of the HCI routing, which 
should improve latencies. So, you should see support for this in some SW 
update in the future. Unfortunately I can't give any exact schedule 
currently, but you can follow the progress quite well simply by looking 
at what's going on with bluez (i.e. CVS commits & mailing list 
discussions). You'll probably see some preliminary support in the next 
release of bluez-utils (version 3.9).

Oh, and it's possible that A2DP support will come along at some point 
too since from the bluez side the plan is to integrate it to the same 
audio daemon as HSP/HFP. However, from our (Nokia) perspective it hasn't 
been given the same priority as HSP so in the short term support for it 
will be very unofficial if it exists at all. Some ideas (a very early 
draft) for the planed architecture can be found at the bluetooth-alsa 
pages: http://bluetooth-alsa.sourceforge.net/future.html


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