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).