A really-really simple demodulator intended to teach Software Defined Radio to newcomers.
Latest commit 9bfa2fc Mar 26, 2014 @ha7ilm ha7ilm fixed comment



The purpose of minidemod-wfm.c is to have a few lines of code that can actually demodulate WFM from an I/Q input.

The whole DSP chain is built by OS pipes, just like this:

rtl_sdr -s 240000 -f 89500000 -g 20 - | tcc -lm -run minidemod-wfm.c \
    | sox -t raw -r 240000 -e unsigned -b 8 -c 1 - -t raw - rate 48000 \
    | mplayer -quiet -rawaudio samplesize=1:channels=1:rate=48000 -demuxer rawaudio -

Read like this:

rtl_sdr (acquires samples) | minidemod-wfm (demodulates) \
    | sox (low pass filter + decimation) | mplayer (audio output) `

To run it, you will need a Linux box with rtl_sdr tcc sox mplayer installed.

I've also added minidemod-wfm-atan.c with a detailed explanation of the demodulation process. It does sound better, but uses more CPU (still not more than 10% on my box).


András Retzler ha7ilm@sdr.hu

Also tnx dnet for the small fixes.