LINUX DRIVER FOR SOUNDCARDS AS AX.25 MODEMS
|
LINUX DRIVER FOR SOUNDCARDS AS AX.25 MODEMS
|
|
|
Thomas M. Sailer, HB9JNX/AE4WA,
|
Thomas M. Sailer, HB9JNX/AE4WA,
|
|
|
This driver allows either SoundBlaster (sbc) or WindowsSoundSystem (wss)
|
This driver allows either SoundBlaster (sbc) or WindowsSoundSystem (wss)
|
compatible soundcards to be used as either 1200 baud AFSK or 9600 baud FSK
|
compatible soundcards to be used as either 1200 baud AFSK or 9600 baud FSK
|
AX.25 packet radio modems. Only half duplex operation is supported by
|
AX.25 packet radio modems. Only half duplex operation is supported by
|
the SoundBlaster driver. Fullduplex is supported for WSS chipsets capable
|
the SoundBlaster driver. Fullduplex is supported for WSS chipsets capable
|
of addressing two DMA channels. The driver needs some processing power!
|
of addressing two DMA channels. The driver needs some processing power!
|
A 486DX/2 66MHz is a minimum requirement, otherwise interactive performance
|
A 486DX/2 66MHz is a minimum requirement, otherwise interactive performance
|
of the computer may become sluggish.
|
of the computer may become sluggish.
|
|
|
|
|
The Interface of the driver
|
The Interface of the driver
|
|
|
The driver provides a kernel network drivers named sm[0-3]. sethdlc
|
The driver provides a kernel network drivers named sm[0-3]. sethdlc
|
from the ax25 utilities may be used to set driver states etc. Users
|
from the ax25 utilities may be used to set driver states etc. Users
|
of userland AX.25 stacks may use the net2kiss utility (also available
|
of userland AX.25 stacks may use the net2kiss utility (also available
|
in the ax25 utilities package) to converts packets of a network interface
|
in the ax25 utilities package) to converts packets of a network interface
|
to a KISS stream on a pseudo tty. There's also a patch available from
|
to a KISS stream on a pseudo tty. There's also a patch available from
|
me for WAMPES which allows attaching a kernel network interface directly.
|
me for WAMPES which allows attaching a kernel network interface directly.
|
|
|
|
|
Configuring the driver
|
Configuring the driver
|
|
|
Some sound cards need to be initialized before they operate in either
|
Some sound cards need to be initialized before they operate in either
|
SoundBlaster or WSS compatibility mode. The driver does _NOT_ do this;
|
SoundBlaster or WSS compatibility mode. The driver does _NOT_ do this;
|
you may use the standard linux sound driver to initialize the soundcard;
|
you may use the standard linux sound driver to initialize the soundcard;
|
compile it as a module, and do
|
compile it as a module, and do
|
insmod sound
|
insmod sound
|
rmmod sound
|
rmmod sound
|
The soundcard should then be initialized correctly. isapnptools is another
|
The soundcard should then be initialized correctly. isapnptools is another
|
package that can configure PnP soundcards. If your soundcard contains
|
package that can configure PnP soundcards. If your soundcard contains
|
a Crystal CS423x chip, you may also try the setcrystal utility in the
|
a Crystal CS423x chip, you may also try the setcrystal utility in the
|
ax25-utilities package.
|
ax25-utilities package.
|
|
|
Every time the driver is inserted into the kernel, it has to know which
|
Every time the driver is inserted into the kernel, it has to know which
|
modems it should access at which ports. This can be done with the sethdlc
|
modems it should access at which ports. This can be done with the sethdlc
|
utility. If you are only using one modem, you can also configure the
|
utility. If you are only using one modem, you can also configure the
|
driver from the insmod command line (or by means of an option line in
|
driver from the insmod command line (or by means of an option line in
|
/etc/conf.modules).
|
/etc/conf.modules).
|
|
|
Examples: (use either method, not both)
|
Examples: (use either method, not both)
|
insmod soundmodem mode="sbc:afsk1200" iobase=0x220 irq=5 dma=1
|
insmod soundmodem mode="sbc:afsk1200" iobase=0x220 irq=5 dma=1
|
sethdlc -i sm0 -p hw sbc type afsk1200 io 0x220 irq 5 dma 1
|
sethdlc -i sm0 -p hw sbc type afsk1200 io 0x220 irq 5 dma 1
|
|
|
Both lines configure the first port to drive a soundblaster card
|
Both lines configure the first port to drive a soundblaster card
|
in 1200 baud AFSK mode.
|
in 1200 baud AFSK mode.
|
|
|
The channel access parameters can be set with sethdlc -a or kissparms.
|
The channel access parameters can be set with sethdlc -a or kissparms.
|
Note that both utilities interpret the values slightly different.
|
Note that both utilities interpret the values slightly different.
|
|
|
|
|
Input and output levels
|
Input and output levels
|
|
|
It is important that the input and output levels are adjusted properly.
|
It is important that the input and output levels are adjusted properly.
|
There are two utilities, available in the ax25 utilities distribution,
|
There are two utilities, available in the ax25 utilities distribution,
|
to facilitate this: smmixer and smdiag. smdiag allows you to display
|
to facilitate this: smmixer and smdiag. smdiag allows you to display
|
the input signal in an oscilloscope like display or an eye diagram.
|
the input signal in an oscilloscope like display or an eye diagram.
|
smmixer allows you to adjust input/output levels. See the respective
|
smmixer allows you to adjust input/output levels. See the respective
|
man pages. These two utilities have two counterparts: xfsmmixer and
|
man pages. These two utilities have two counterparts: xfsmmixer and
|
xfsmdiag. They both require the FORMS to compile, and provide a nicer
|
xfsmdiag. They both require the FORMS to compile, and provide a nicer
|
user interface. Functionality is the same, though.
|
user interface. Functionality is the same, though.
|
|
|
|
|
Transmitter keying
|
Transmitter keying
|
|
|
Since soundcards do not have a DC coupled output; PTT keying options include
|
Since soundcards do not have a DC coupled output; PTT keying options include
|
the following:
|
the following:
|
* VOX circuitry
|
* VOX circuitry
|
* Serial port pin
|
* Serial port pin
|
* Parallel port pin
|
* Parallel port pin
|
* MPU401 MIDI output via a retriggerable monoflop.
|
* MPU401 MIDI output via a retriggerable monoflop.
|
Circuit schematics may be found at
|
Circuit schematics may be found at
|
http://www.ife.ee.ethz.ch/~sailer/pcf/ptt_circ/ptt.html.
|
http://www.ife.ee.ethz.ch/~sailer/pcf/ptt_circ/ptt.html.
|
|
|
|
|
Compatibility with the rest of the Linux kernel
|
Compatibility with the rest of the Linux kernel
|
|
|
The sound driver and the soundcard modem driver compete for the same
|
The sound driver and the soundcard modem driver compete for the same
|
hardware resources. Of course only one driver can access a given
|
hardware resources. Of course only one driver can access a given
|
interface at a time. Worse yet, the sound driver grabs the soundcard
|
interface at a time. Worse yet, the sound driver grabs the soundcard
|
at startup time. Therefore the soundcard modem driver subsequently won't
|
at startup time. Therefore the soundcard modem driver subsequently won't
|
be able to access the soundcard. You might therefore find it necessary to
|
be able to access the soundcard. You might therefore find it necessary to
|
unload the sound driver before using the soundcard modem driver.
|
unload the sound driver before using the soundcard modem driver.
|
|
|
|
|
Further reading
|
Further reading
|
|
|
Please take a look at http://www.ife.ee.ethz.ch/~sailer/ham/linux/hdlc.html
|
Please take a look at http://www.ife.ee.ethz.ch/~sailer/ham/linux/hdlc.html
|
for further informations on the driver.
|
for further informations on the driver.
|
|
|
|
|
vy 73s de
|
vy 73s de
|
Tom Sailer, sailer@ife.ee.ethz.ch
|
Tom Sailer, sailer@ife.ee.ethz.ch
|
Packet Radio: hb9jnx@hb9w.che.eu
|
Packet Radio: hb9jnx@hb9w.che.eu
|
|
|
