Re: [amsat-bb] Programming for the soundcard

["laura halliday" <marsgal42@xxxxxxxxxxx>]

Soundcard programming can be fun - and a great way to chew
up massive quantities of disc space and computer time!

You didn't mention which operating system you run, but
you need to proceed in more-or-less the same way anyway.

To obtain samples from the sound card under Linux/FreeBSD/etc.
with the usual VOXWare driver, the soundcard is /dev/dsp.
Open it for reading with open(), configure it with ioctl(),
read samples with read(), and process.

Under Windows NT/95/98, use the waveform audio functions,
like waveInOpen(), waveInStart(), and so on. Look in the
manual under "waveform audio".

To extract frequencies from the data, use a Fast Fourier
Transform or related algorithm. All the usual references;
check the Net for sample code.

Depending on the frequencies you want to measure and how
fast a computer you have at your disposal, it may suffice
to use a Hamcomm-style zero-crossing detector plugged into
a serial port. Very simple, and possibly a better answer
for DOScynn. Again, all the usual references...

Laura Halliday VE7LDH     "Laisse le vent tout emporter..."  
Grid: CN88hk IOTA: NA036      - Foly/Viennet

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org