Sound Card Packet with Linux

I write this with full acknowledgement of information taken 
from HB9JNX, Thomas Sailor's "Soundmodem on modern 
Operating Systems" August 1, 2000.

In 1995 Thomas Who produced a version of this for Linux 
following his earlier successful work with sound modules 
operating in DOS Flexnet.

Because the computational ability in those days was, by 
today's standards quite low this module had of necessity, 
to do most of the work that today is possible in the 
computer's CPU.

Thomas's original module was complicated to set up. It was 
desirable to re-compile the Kernel without including 
soundcard functionality, then a third party soundcard 
utility OSS had to be used to control the sound.

It was then a "brute" to set up and get operating correctly 
by the average Amateur or relative newcomer to Linux.

During the next 5 years computing power increased 
enormously, and because of this, Thomas produced a new 
generation soundmodem, that interfaced between the MKISS 
module and an OPERATING soundcard. It has proven to be very 
efficient and reliable, and (when you know how) very easy 
to set up and commission.

The big problem has been that the package has been released 
with no documentation as such, and in this paper I am 
attempting to, in a very small way, help out with that 
omission.

Soundmodem-0.4 does a similar job in Linux, as SV2AGW's 
AGWPE does in Windows. Each has its own strengths and 
weaknesses and because of this they are not directly 
comparable. Nevertheless it is fair to say that for 
ordinary 1200 packet they both perform superbly in their 
particular environments.

I will now explain how to set up Soundmodem-0.4 for a 
single channel 1200 baud packet. I am NOT attempting to 
write a Manual on Soundmodem-0.4 because I simply do not 
know enough about it and because that should have been done 
by the programmer. The fact that the package has been 
released under the terms of GNU (freebie) is not an excuse 
to inadequately document the package.

After many, many hours of frustrated attempts to find out 
how the package should work, I gave up a beaten and broken 
individual.

An extensive session of searching the Internet produced 
information that in 2000 Thomas had presented TAPR with a 
paper on Soundmodem packet. Then further searching found 
that paper on HB9JNX's site, and it contained JUST enough 
information to enable, with some experimentation, to get 
the thing to work.

Because I had had the experience of not being able to 
install RPM packages with version number greater that 3 in 
SUSE 6.4 (designed obsolescence??) I downloaded the TAR 
version and compiled that in. Later versions of SUSE and 
certainly Redhat 7 upwards will take the Soundmodem-0.4 and 
installation of an RPM, for most, will be the preferred 
option.

Currently I am using RedHat 7 (now 7.2) so comments are related to 
that release. For information, my Soundmodem finished up in 
/usr/sbin and the soundmodemconfig finished up in /usr/bin, 
but as both locations are normally in the "path" the run 
command can be typed anywhere.

Firstly you must have a Kernel compiled for ax25 and the 
appropriate ax25 apps and tools installed and have an 
operative soundcard, i.e. that will play CD's etc., and is 
controllable with an xwindow sound control facility or 
similar.

All configuration is done in xwindows (KDE, Gnome etc.).

Open a console window.
Type soundmodemconfig and "enter".
The configuration window should appear.
Select file, new, and alongside new, config

In the Configuration Name box type a name for this packet 
port such as "xxxx" (Guess what, I used packet).
Pick a name that already exist in the "axports" file or 
create a new entry in "axports" using the name that you 
have chosen. The name that you have entered will appear in 
the window under file.

To the right, IO and Channel Access tabs will appear.
Press the IO Tab.
Soundcard Mode should be default, soundcard - leave as is.
Audio Driver should be default /dev/dsb
For normal packet select "half duplex".
PTT Driver , whichever com port you use for PTT, S0=com1 
S1=com2.
Then press "Channel Access".
The only alteration here would be Txdelay, as 150 is a bit 
fast for a lot of transceivers, and a safer value 
to start off with, would be 350.

Now go back to window under "file".
Highlight the name that you have provided.
Click on file.
Now you should have Channel under the Configuration.
Click on Channel, now Channel0 should appear under the 
"name".
Click on the "Channel0" and a new config screen should 
appear to the right.
Packet IO  --    MKISS
Interface name  -- To prevent soundmodem complaining later, 
change this to ax0.
IP address   -- If you have an IP address then change 
accordingly otherwise leave as is.

This completes the configuration. Close the console. A 
configuration file will have been created in /etc/ax25

I will not go into the interfacing of the computer to the 
transceiver on the assumption that you have already used 
your computer for other soundcard digital programs such as 
PSK31 and the interfacing is the same.

I used the resident program "CALL" to test all this out, 
LINKT will certainly work, and will find the port that 
soundmodem has set up, but that was on SUSE 6.4 and I had 
other problems there.

To use Soundmodem and CALL you must have an entry in 
"axports" coinciding with the name that you gave the port 
when using soundmodemconfig.

You must have mkiss module installed (modprobe mkiss).

In KDE or GNOME open a console and type "soundmodem" enter.
If your soundcard has been operating with another digital 
program, and there is packet activity then you should see 
that traffic in the console that you ran soundmodem in.

If you don't, load (in my case) KDE's Sound Mixer Panel and 
the Receive audio was controlled by "REC MON " 7th from the 
left, and transmit audio by VOLUME 1st from left.

Now if all that is ok, then to use "call" to test the 
system open another console and type:
"call" "name" (of port)"station" (to be connected to), 
<enter> and you should connect. Eg call packet VK5OA 
<enter>

If there be any comments, please let them be constructive, 
for instance I have already been berated by a ZL for 
complaining about lack of documentation for which comment I 
do not apologise at all.

Through the use of soundmodem I hope that the use of all 
forms of ax25 in Linux, would eventually no longer be the 
sole domain of TNC owners.

I would appreciate that any comments be in the vain of 
improving this information, as a truly cooperative project.

Although I have had a lot of computer experience, right 
from the Commodore VIC20 days, I am quite a newcomer to 
LINUX, although the years of working at the DOS prompt did 
help the transition.

Kevin O'Rorke
VK5OA
kororke@winnet.com.au