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NetBSD 6.1.5 - man page for ubt (netbsd section 4)

UBT(4)				   BSD Kernel Interfaces Manual 			   UBT(4)

     ubt -- USB Bluetooth driver

     ubt* at uhub? port ? configuration ? interface ?

     The ubt driver provides support for USB Bluetooth dongles to the Bluetooth protocol stack.

     USB Bluetooth dongles provide two interfaces, both of which the ubt driver claims.  The sec-
     ond interface is used for Isochronous data and will have several alternate configurations
     regarding bandwidth consumption, which can be set using the hw.ubtN.config sysctl(8) vari-
     able.  The number of alternate configurations is indicated by the value in the
     hw.ubtN.alt_config variable, and the isoc frame size for the current configuration is shown
     in the hw.ubtN.sco_rxsize and hw.ubtN.sco_txsize variables.

     By default, configuration 0 is selected, which means that no bandwidth is used on the
     Isochronous interface and no SCO data can be sent.  Consult the Bluetooth USB specification
     at https://www.bluetooth.org/ for complete instructions on setting bandwidth consumption.
     The following extract may be useful as a general guidance though details may differ between

     0	  No active voice channels
     1	  One voice channel with 8-bit encoding
     2	  Two voice channels with 8-bit encoding, or one voice channel with 16-bit encoding.
     3	  Three voice channels with 8-bit encoding
     4	  Two voice channels with 16-bit encoding
     5	  Three voice channels with 16-bit encoding

     bluetooth(4), uhub(4), sysctl(8)

     This ubt device driver was originally a character device written by David Sainty and Lennart
     Augustsson.  It was rewritten to support socket based Bluetooth access for NetBSD 4.0 by
     Iain Hibbert.

     Isochronous data is seemingly not well supported over USB in the current system and to get
     SCO working, you may have to calculate the SCO packet size that the stack will use.  This is
     the sco_mtu value reported by the btconfig(8) command, and when combined with the SCO header
     (3 bytes) should fit exactly into an integer number of Isochronous data frames where the
     frame size is indicated by the 'hw.ubtN.sco_txsize' sysctl variable.

     For example: I want one voice channel (which is all that is supported, for now) so am using
     configuration #2, with a frame length of 17 bytes.  This gives possible values of:

	   (17 * 1) - 3 = 14
	   (17 * 2) - 3 = 31
	   (17 * 3) - 3 = 48
	   (17 * 4) - 3 = 65
	   (17 * 5) - 3 = 82

     btconfig(8) shows the maximum SCO payload as 64 bytes, so I am using the next smaller size
     of 48, to minimize the overhead of the 3 header bytes.

     The SCO packet size can be changed using the 'scomtu' option to btconfig(8).

     The failure mode is that the USB Bluetooth dongle locks up though generally removal/reinser-
     tion will clear the problem.

     The Isochronous configuration can only be changed when the device is not marked up.

BSD					 August 27, 2006				      BSD

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