Bluetooth headset routed over USB on Freerunner: why we need it and what problems i faced

Joerg Reisenweber joerg at
Tue Feb 24 05:15:57 CET 2009

Am Di  24. Februar 2009 schrieb Werner Almesberger:
> Paul Fertser wrote:
> > Following information is based on AN107 [1] (CSR, 2002, describes SCO
> > configuration for BC-01b and BC-02-External) and experience.
> Please let me reveal myself as the total BT ignoramus that I am:
> Is the bottom line that unidirectional audio (A2DP) over USB to the
> BT device works, but bidirectional audio (SCO) over USB doesn't ?
yup, exactly.

> And the reason for this is unknown, but you suspect an audio
> routing issue in the BT module ?
BT has USB interface and PCM interface. Seems there's no way to tell BT to 
accept audio data via USB in SCO (bidir) mode, though there is a way/command 
that *should* work to switch audio input source but doesn't apparently. Might 
be a bug in FW, or poorly or undocumented proprietary command needed.
For A2DP mode (stereo output only) audio data is happily accepted on USB.

Any document about details of actual FW used inside BT module would help a 
Also asking manufacturer of module rsp chip might be worth a try.

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