Breadboard-only schematic for an ESP32-based LC electromagnetic response visualizer using a handmade coil oscillator, LM339 comparator, GPIO27 frequency input, SSD1306 I2C OLED, and calibrati... show moreBreadboard-only schematic for an ESP32-based LC electromagnetic response visualizer using a handmade coil oscillator, LM339 comparator, GPIO27 frequency input, SSD1306 I2C OLED, and...