As SWL I try to use my Arduino board for SWL relationships.
I hacked some code stuff together from different internet sources and the result is a very basic CW decoder on a FFT basis and Nokia 3310 Display. I'm using a CW broadcast on WebSDR.org. Line out from the Notebook goes to analogue Port A5 directly. FFT displayed with reduced bandwidth (300hz to about 900hz, I guess).
Nokia 3310 LCD shield
3,5 mm Line out cable
Not more, not less.