This is an original version of previously posted AVR FFT analyser. It was developed by Chan some time ago and is stil good reference for those who are wiling to build or modify their own FFT analysers.
On SG12232C graphical LCD there are who parts displayed: waveform and spectrum. It really looks cool and real when playing music. The program runs on AVR Atmega8 microcontroller clocked at maximum 16MHz frequency. The signal is passed through 8th-order elliptic filter(anti-alias filter) implemented on MAX293. Hardest part in this project was to implement an FFT algorithm which require lots of processing. But Chan has reached 9.6kHz sampling with 75Hz resolution, what is enough for visualisation. Besides firmware author also provides fixed point FFT library optimized for Atmega microcontrollers so anyone could enjoy creating similar projects.