soundmodem - amateur (AX.25) packet radio network driver for soundcards
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
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
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.
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
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.
The ioctl calls follow the implementation in the hdlcdrv.
returns the modem type (i.e. SBC1200, SBC9600, WSS1200 or
sets the modem type. Only superuser can do this.
returns the mixer type and the contents of the specified mixer
sets the specified mixer register, if the specified mixer type
matches the mixer type of the soundcard. Only superuser can do
returns the contents of the diagnose buffer, which is used by
smdiag to display the eye and oscilloscope diagrams.
return some debugging values. Not always available.
baycom (9), soundmodem (9),smdiag (8),smmixer (9),
soundmodem was written by Thomas Sailer, HB9JNX/AE4WA,