16-bit Real-Time FFT Demo on an 8bit AVR (ATMega88 @8Mhz)

This is a 64-point Fast Fourier Transform sampling at ~9.8 kS/s using 16-bit mathsss. The brain is an Atmel ATMega88 running at 8Mhz. Display is an OLED “ 128 x 64 SSD1308 (similar to SSD1306) using SPI (Bit-Banged). FTT takes to run, uses ~11% code space & ~25% data space. To make use of the FFT’s output takes considerably more time and space. Audio input is through a Condenser Mic with a Butterworth filter (-3db ~7khz). This is my “version 3“ FFT code. (All code in assembly language). The