Introduction If you’ve ever worked with a proximity card reader (125kHz or 13.56MHz), a fingerprint scanner, or an old-school magnetic stripe swipe, you’ve almost certainly encountered the Wiegand protocol. In the embedded world, the wiegand.h header file represents the standard interface for driving these devices via GPIO on microcontrollers like Arduino, ESP32, STM32, or Raspberry Pi Pico.

#ifndef WIEGAND_H #define WIEGAND_H #include <stdint.h> #include <stdbool.h>

// Example ISR (pseudo-code) void IRAM_ATTR on_d0_falling() record_bit(0);