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.\" Copyright 1996 Thomas Sailer (t.sailer@alumni.ethz.ch)
.\" May be distributed under the GNU General Public License
.\" "
.TH SOUNDMODEM 9 "27 April 2008" "Linux 2.1.x" "Kernel Reference Guide"
.SH NAME
soundmodem \- amateur (AX.25) packet radio network driver for soundcards
.SH SYNOPSIS
.nf
.B #include <linux/soundmodem.h>
.B #include <linux/hdlcdrv.h>
.fi
.SH 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.
.SH "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
\fIhttp://www.ife.ee.ethz.ch/~sailer/pcf/ptt_circ/ptt.html\fP.
.SS "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.
.SS "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.
.SS "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.
.SS "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.
.SH "IOCTL CALLS"
The \fBioctl\fP calls follow the implementation in the \fIhdlcdrv\fP.
.TP
.B SMCTL_GETMODEMTYPE
returns the modem type (i.e. \fISBC1200\fP, \fISBC9600\fP, \fIWSS1200\fP
or \fIWSS9600\fP)
.TP
.B SMCTL_SETMODEMTYPE
sets the modem type. Only superuser can do this.
.TP
.B SMCTL_GETMIXER
returns the mixer type and the contents of the specified
mixer register.
.TP
.B SMCTL_SETMIXER
sets the specified mixer register, if the specified
mixer type matches the mixer type of the soundcard. Only
superuser can do this.
.TP
.B SMCTL_DIAGNOSE
returns the contents of the diagnose buffer, which is used by
\fIsmdiag\fP to display the eye and oscilloscope diagrams.
.TP
.B SMCTL_GETDEBUG
return some debugging values. Not always available.
.SH "SEE ALSO"
.BR baycom " (9), " soundmodem " (9)," smdiag " (8)," smmixer " (9),"
linux/drivers/net/hdlcdrv.c,
.SH AUTHOR
soundmodem was written by Thomas Sailer, HB9JNX/AE4WA, (t.sailer@alumni.ethz.ch).
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