DSP PROJECTS OF STEFAN PETERSEN


Developing DSP programs under Linux

A good start are:

Generally

The programs below use: To see if your soundcard is up to the job I have made a little test program that opens you soundcard device (/dev/dsp) and asks what it can handle. When it comes to samplerate it simply sets the samplerate to different values to see if your soundcard driver accepts it. Here is both the sourcecode and statically linked binary. Oh, did I mention that this is for Linux only?

Receiver

The receiver I have used is an Icom PCR1000. I usually use the discriminator output from the receiver, but it is probably only necessary on GMSK reception.

Sound card

In my stationary computer I have an Ensoniq ES1371 and I insert the signal in the line connector. That works well, even for FSK/GMSK. In my laptop I have an ESS Technology ES1983S with only a microphone input. That doesn't seem to work equally well on FSK/GMSK reception.

AFSK

Amateur packet radio and MPT1327 uses a modulation I call AFSK, audio FSK. The ones and zeros are represented with different tones. The detection method for AFSK is based on the matched filter principle.

FSK (GMSK is a part of)

In FSK and GMSK the ones and zeroes are represented by frequency difference off the carrier. The detection method for FSK/GMSK I use a simple slicer. Signal in above 128 is a one and signal in below 128 is a zero. DC-correction...

Projects

Here is some source I have hacked together using the tools mentioned above. They are in different stages of ready, so if it doesn't do what you want to patches and ideas are welcome. And, as I am kind signal processing newbie, I would really really like comments and input on my signal processing solutions.

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