SOUNDMODEM(9)
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,
(sailer@ife.ee.ethz.ch).