Audio Spectrum Analyzer (STM32 Bare-Metal)

Real-time 8-band spectrum visualizer on bare-metal STM32F411. I2S MEMS-mic capture via double-buffered DMA, 512-point CMSIS-DSP FFT, Hanning windowing, automatic gain control, and dirty-rect rendering on an SSD1306 OLED at ~24 FPS. Watchdog + HardFault recovery; builds clean with the resource budget met.