mac-plus-ps2/mac_plus_ps2/PS2Keyboard.cpp

/*
  PS2Keyboard.cpp - PS2Keyboard library
  Copyright (c) 2007 Free Software Foundation.  All right reserved.
  Written by Christian Weichel <info@32leaves.net>

  ** Mostly rewritten Paul Stoffregen <paul@pjrc.com> 2010, 2011
  ** Modified for use beginning with Arduino 13 by L. Abraham Smith, <n3bah@microcompdesign.com> * 
  ** Modified for easy interrup pin assignement on method begin(datapin,irq_pin). Cuningan <cuninganreset@gmail.com> **

  for more information you can read the original wiki in arduino.cc
  at http://www.arduino.cc/playground/Main/PS2Keyboard
  or http://www.pjrc.com/teensy/td_libs_PS2Keyboard.html

  Version 2.4 (March 2013)
  - Support Teensy 3.0, Arduino Due, Arduino Leonardo & other boards
  - French keyboard layout, David Chochoi, tchoyyfr at yahoo dot fr

  Version 2.3 (October 2011)
  - Minor bugs fixed

  Version 2.2 (August 2011)
  - Support non-US keyboards - thanks to Rainer Bruch for a German keyboard :)

  Version 2.1 (May 2011)
  - timeout to recover from misaligned input
  - compatibility with Arduino "new-extension" branch
  - TODO: send function, proposed by Scott Penrose, scooterda at me dot com

  Version 2.0 (June 2010)
  - Buffering added, many scan codes can be captured without data loss
    if your sketch is busy doing other work
  - Shift keys supported, completely rewritten scan code to ascii
  - Slow linear search replaced with fast indexed table lookups
  - Support for Teensy, Arduino Mega, and Sanguino added

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "PS2Keyboard.h"

#define BUFFER_SIZE 45
static volatile uint8_t buffer[BUFFER_SIZE];
static volatile uint8_t head, tail;
static uint8_t DataPin;

// The ISR for the external interrupt
void ps2interrupt(void)
{
	static uint8_t bitcount=0;
	static uint8_t incoming=0;
	static uint32_t prev_ms=0;
	uint32_t now_ms;
	uint8_t n, val;

	val = digitalRead(DataPin);
	now_ms = millis();
	if (now_ms - prev_ms > 250) {
		bitcount = 0;
		incoming = 0;
	}
	prev_ms = now_ms;
	n = bitcount - 1;
	if (n <= 7) {
		incoming |= (val << n);
	}
	bitcount++;
	if (bitcount == 11) {
		uint8_t i = head + 1;
		if (i >= BUFFER_SIZE) i = 0;
		if (i != tail) {
			buffer[i] = incoming;
			head = i;
		}
		bitcount = 0;
		incoming = 0;
	}
}

static inline uint8_t get_scan_code(void)
{
	uint8_t c, i;

	i = tail;
	if (i == head) return 0;
	i++;
	if (i >= BUFFER_SIZE) i = 0;
	c = buffer[i];
	tail = i;
	return c;
}

int PS2Keyboard::getScanCode() {
    return get_scan_code();
}

PS2Keyboard::PS2Keyboard() {
  // nothing to do here, begin() does it all
}

void PS2Keyboard::begin(uint8_t data_pin, uint8_t irq_pin) {
  uint8_t irq_num=255;

  DataPin = data_pin;

  // initialize the pins
#ifdef INPUT_PULLUP
  pinMode(irq_pin, INPUT_PULLUP);
  pinMode(data_pin, INPUT_PULLUP);
#else
  pinMode(irq_pin, INPUT);
  digitalWrite(irq_pin, HIGH);
  pinMode(data_pin, INPUT);
  digitalWrite(data_pin, HIGH);
#endif

#ifdef CORE_INT_EVERY_PIN
  irq_num = irq_pin;

#else
  switch(irq_pin) {
    #ifdef CORE_INT0_PIN
    case CORE_INT0_PIN:
      irq_num = 0;
      break;
    #endif
    #ifdef CORE_INT1_PIN
    case CORE_INT1_PIN:
      irq_num = 1;
      break;
    #endif
    #ifdef CORE_INT2_PIN
    case CORE_INT2_PIN:
      irq_num = 2;
      break;
    #endif
    #ifdef CORE_INT3_PIN
    case CORE_INT3_PIN:
      irq_num = 3;
      break;
    #endif
    #ifdef CORE_INT4_PIN
    case CORE_INT4_PIN:
      irq_num = 4;
      break;
    #endif
    #ifdef CORE_INT5_PIN
    case CORE_INT5_PIN:
      irq_num = 5;
      break;
    #endif
    #ifdef CORE_INT6_PIN
    case CORE_INT6_PIN:
      irq_num = 6;
      break;
    #endif
    #ifdef CORE_INT7_PIN
    case CORE_INT7_PIN:
      irq_num = 7;
      break;
    #endif
  }
#endif

  head = 0;
  tail = 0;
  if (irq_num < 255) {
    attachInterrupt(irq_num, ps2interrupt, FALLING);
  }
}