NAME

       soundmodem - amateur (AX.25) packet radio network driver for soundcards

SYNOPSIS

       #include <linux/soundmodem.h>
       #include <linux/hdlcdrv.h>

DESCRIPTION

       The  driver  currently supports both 1200 baud AFSK and 9600 baud FSK (G3RUH compatible) using a standard
       SoundBlaster compatible or WindowsSoundSystem  compatible  soundcard.  The  whole  decoding  is  done  in
       software, so you definitely do not want to use it on a 386SX class machine.

KEYING THE TRANSMITTER

       Soundcards  do  not have a DC coupled output that could serve as a PTT signal. So there are basically for
       possibilities  for  obtaining   a   PTT   signal.   Sample   schematic   diagrams   can   be   found   on
       http://www.ife.ee.ethz.ch/~sailer/pcf/ptt_circ/ptt.html.

   VOX circuitry
       A simple VOX circuitry that detects output signals at the output of the soundcard can be used, especially
       as  it  can  be  built with a single transistor plus a few passive components and typical soundcards have
       strong output signals.

   Parallel Port
       A parallel port line can also be used to signal PTT. If selected, the PTT signal is output on  the  DATA0
       line and DCD is output on the DATA1 line.

   Serial Port
       A standard serial port (8250, 16450, 16550) can also be used to output PTT. PTT is output on RTS and TxD,
       while DCD is output on DTR.

   MPU401 MIDI Port
       The  MIDI  port is basically an asynchronous serial interface and thus cannot output a straight DC level,
       however it may be used if connected through a retriggerable monoflop with about 15ms pulse duration. Note
       that only newer SoundBlaster models have a genuine MPU401 MIDI port. The older SB  MIDI  port  cannot  be
       used.

IOCTL CALLS

       The ioctl calls follow the implementation in the hdlcdrv.

       SMCTL_GETMODEMTYPE
              returns the modem type (i.e. SBC1200, SBC9600, WSS1200 or WSS9600)

       SMCTL_SETMODEMTYPE
              sets the modem type. Only superuser can do this.

       SMCTL_GETMIXER
              returns the mixer type and the contents of the specified mixer register.

       SMCTL_SETMIXER
              sets  the  specified  mixer  register,  if  the specified mixer type matches the mixer type of the
              soundcard. Only superuser can do this.

       SMCTL_DIAGNOSE
              returns the contents of the diagnose buffer, which is used  by  smdiag  to  display  the  eye  and
              oscilloscope diagrams.

       SMCTL_GETDEBUG
              return some debugging values. Not always available.

SEE ALSO

       baycom (9), soundmodem (9),smdiag (8),smmixer (9), linux/drivers/net/hdlcdrv.c,

AUTHOR

       soundmodem was written by Thomas Sailer, HB9JNX/AE4WA, (t.sailer@alumni.ethz.ch).

Linux 2.1.x                                       27 April 2008                                    SOUNDMODEM(9)