GPIO.h

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#ifndef HARDWARE_AVR_GPIO_H
#define HARDWARE_AVR_GPIO_H

#include "Hardware/AVR/Board.h"

template<BOARD::pin_t PIN>
class GPIO {
public:
  GPIO<PIN>& input()
    __attribute__((always_inline))
  {
    GPIO_ATOMIC(SFR()->ddr &= ~MASK);
    return (*this);
  }

  void pullup()
    __attribute__((always_inline))
  {
    high();
  }

  void output()
    __attribute__((always_inline))
  {
    GPIO_ATOMIC(SFR()->ddr |= MASK);
  }

  void open_drain()
    __attribute__((always_inline))
  {
    input();
    low();
  }

  bool read()
    __attribute__((always_inline))
  {
    return ((SFR()->pin & MASK) != 0);
  }

  operator bool()
    __attribute__((always_inline))
  {
    return (read());
  }

  void low()
    __attribute__((always_inline))
  {
    GPIO_ATOMIC(SFR()->port &= ~MASK);
  }

  void high()
    __attribute__((always_inline))
  {
    GPIO_ATOMIC(SFR()->port |= MASK);
  }

  void toggle()
    __attribute__((always_inline))
  {
    GPIO_ATOMIC(SFR()->pin |= MASK);
  }

  void write(int value)
    __attribute__((always_inline))
  {
    if (value) high(); else low();
  }

  void operator=(int value)
    __attribute__((always_inline))
  {
    write(value);
  }

  void pulse(uint16_t width)
  {
    if (width == 0) return;
    uint16_t count = ((width * (F_CPU / 1000000L)) / 4);
    uint8_t sreg = SREG;
    __asm__ __volatile__("cli" ::: "memory");
    SFR()->pin |= MASK;
    _delay_loop_2(count);
    SFR()->pin |= MASK;
    SREG = sreg;
    __asm__ __volatile__("" ::: "memory");
  }

  int pulse()
  {
    bool s0 = read();
    while (read() == s0);
    uint16_t t0 = micros();
    while (read() != s0);
    return (micros() - t0);
  }

protected:
  struct gpio_reg_t {
    volatile uint8_t pin;       
    volatile uint8_t ddr;       
    volatile uint8_t port;      
  };

  gpio_reg_t* SFR()
    __attribute__((always_inline))
  {
    return ((gpio_reg_t*) GPIO_REG(PIN));
  }

  static const uint8_t MASK = GPIO_MASK(PIN);
};
#endif