GPIO.h

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#ifndef HARDWARE_SAM_GPIO_H
#define HARDWARE_SAM_GPIO_H

#include "Hardware/SAM/Board.h"

template<BOARD::pin_t PIN>
class GPIO {
public:
  GPIO()
  {
    pmc_enable_periph_clk(ID_PIO());
    SFR()->PIO_PER = MASK;
  }

  GPIO<PIN>& input()
    __attribute__((always_inline))
  {
    SFR()->PIO_ODR = MASK;
    return (*this);
  }

  void pullup()
    __attribute__((always_inline))
  {
    SFR()->PIO_PUER = MASK;
  }

  void output()
    __attribute__((always_inline))
  {
    SFR()->PIO_OER = MASK;
  }

  void open_drain()
    __attribute__((always_inline))
  {
    SFR()->PIO_CODR = MASK;
    SFR()->PIO_MDER = MASK;
  }

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

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

  void low()
    __attribute__((always_inline))
  {
    SFR()->PIO_CODR = MASK;
  }

  void high()
    __attribute__((always_inline))
  {
    SFR()->PIO_SODR = MASK;
  }

  void toggle()
    __attribute__((always_inline))
  {
    write(!read());
  }

  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;
    toggle();
    delayMicroseconds(width);
    toggle();
  }

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

protected:
  static const uint32_t MASK = GPIO_MASK(PIN);

  Pio* SFR()
    __attribute__((always_inline))
  {
    switch (GPIO_REG(PIN)) {
    case 0: return (PIOA);
    case 1: return (PIOB);
    case 2: return (PIOC);
    default:
      return (PIOD);
    }
  }

  uint32_t ID_PIO()
    __attribute__((always_inline))
  {
    switch (GPIO_REG(PIN)) {
    case 0: return (ID_PIOA);
    case 1: return (ID_PIOB);
    case 2: return (ID_PIOC);
    default:
      return (ID_PIOD);
    }
  }
};
#endif