/*
    PS/2 KEYBOARD INTERFACE FOR AVR v1.1
	Written by Jan Sixta, originaly from 13.01.2011
	jan.16@seznam.cz  http://jan16.czela.net/
	ICQ:225-664-188  Skype: sixta16
	Software interface for standard PS/2 (PC) keyboards
	Including basic functions:
	 - Software emulated PS/2 BUS using one external interrupt (INT0)
	   and one I/O pin as a DATA line
     - Processing functions for decoding received data packets
	 - A functions for translation from the SCAN-CODE to ASCII
    
	Change log:
	  Version 1.1, from 28.07.2011
	    - two decoding tables, for standard and extended keys
		- Flag PS2_EXT now only for internal use
		- Added a flag clearing function 
		- New ReadKey function for easier use 
		- New KeyPressed function for detecting if there was made a press
 
    This library is for non-comercial use only. Without any warranty.
*/

volatile unsigned char PS2_Bit;   //Bit counter
volatile unsigned char PS2_BitShift;
volatile unsigned char PS2_Data;  //keybd DATA register
volatile unsigned char PS2_ASCII;        //ASCII code of received key press

//PS2 Flag and Attribute register
volatile unsigned char PS2_Flag; 
//b0 - new key down event     - When key down event occur, this flag is set.
//b1 - new key up event       - When key up event occur, this flag is set.
//b2 - control code received  - Control code like 0xAA, 0xFF, 0xEE was received.
//b3 - 
//b4 - 
//b5 - key up event           - not a public flag, attribute, means key was released
//b6 - extended key code      - not a public flag, set when extended key indentifier was recvd
//b7 - data received          - not a public flag, set when new data received in PS2_Data
#define PS2_EVDOWN          0 
#define PS2_EVUP            1 
#define PS2_CTRL            2
#define PS2_KEYUP           5
#define PS2_EXT             6
#define PS2_RXD             7


//PS2 Bus line DATA signal 
#define PS2_D_PIN   PIND
#define PS2_D_PORT  PORTD
#define PS2_D_DDR	DDRD
#define PS2_D       PD4

/*
Standard keys have got classic ASCII codes. Other keys like F1..F12, Arrows, Shift, etc.
have selected ASCII numbers, as listed below. The Extended Keys has got special decoding table 
and they are given codes 128 and over, where there are none ASCII symbols writable by any 
standard key. It means, that the given ASCII codes of Extended Keys do not collide with standard
keys. Due to  some Extended Keys have got same codes as a standard ones, we  must use two
separate decoding tables.
*/

#define KEY_UP      128
#define KEY_DOWN    129
#define KEY_LEFT    130
#define KEY_RIGHT   131

unsigned char Scan2ASCII[] PROGMEM = {
 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0, 0, 0,
 0,81, 0, 0, 0, 0,90,83,65,87, 0, 0, 0,67,88,68,69, 0, 0, 0,
 0,32,86,70,84,82, 0, 0, 0,78,66,72,71,89, 0, 0, 0, 0,77,74,
85, 0, 0, 0, 0, 0,75,73,79, 0, 0, 0, 0,46,47,76,59,80,45, 0,
 0, 0,21, 0,91,61, 0, 0, 0, 0,13,93, 0,92, 0, 0, 0, 0, 0, 0,
 0, 0, 8, 0, 0,49, 0,52,55, 0, 0, 0,48,44,50,53,54,56,27, 0,
 0,43,51,45,42,57, 0, 0, 0, 0, 0, 0};

unsigned char Scan2ASCIIspc[] PROGMEM = {
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
  0,  0,  0,  0,  0,  0,  0, KEY_LEFT,  0,  0,  0,  0,  0,  0, KEY_DOWN,  0, KEY_RIGHT, KEY_UP,  0,  0
};

//External INT0, reacting on the positive slope of CLOCK signal
//on the PS/2 BUS.
ISR(INT0_vect)
{
  if ((PS2_Bit==0) && (PS2_D_PIN & (1<<PS2_D))) //If this is the first received bit,  
  {                                            //and the DATA is LOW (startbit)
    PS2_Bit++;  //increment the bit counter
  } 
  else if(PS2_Bit==9) //if this is 9th bit, it is parity, so ignore this
  {
    PS2_Bit++;  //bit counter increment
  }
  else if(PS2_Bit==10) //if this is the 10th bit (the last, STOPBIT)
  {                    //DATA line should be HIGH
    PS2_Bit=0;         //reset the bit counter
	PS2_Data = PS2_BitShift; //Copy the temporary register to PS2_Data register
	PS2_Flag |= (1<<PS2_RXD); //set flag "data reception completed" 
  } 
  else  //bit 1..8 are data bits. 1st is LSB, 8th is MSB
  {
    PS2_Bit++; //increment bit counter
	      //shift the bits into data register    
	PS2_BitShift = (PS2_BitShift >> 1) | ((PS2_D_PIN & (1<<PS2_D))<<(7-PS2_D)); 
  }
}


/* Initialization function. Sets all variables to defaults.
   Note: You must enable INT0 yourself! because it depends on the AVR type
   so the interrupt setting registers are different for each type of AVR.
*/
void PS2_Init(void)
{
  PS2_D_DDR &=~(1<<PS2_D);  //DATA I/O pin as input with pull-up
  PS2_D_PORT |= (1<<PS2_D);
  PS2_Bit = 0;      //Defaults
  PS2_BitShift = 0;
  PS2_Data = 0;
  PS2_Flag = 0;
  PS2_ASCII = 0;
}


/* This function processes the data from the keyboard
Call this function repeatively in the MAIN cycle.
*/
void PS2_Poll(void)
{
  unsigned int adr;
  if (PS2_Flag & (1<<PS2_RXD))   //if new data received, then:
  {
    PS2_Flag &=~(1<<PS2_RXD); //clear the data rx flag
	switch (PS2_Data)
	{
      case (0xF0):  //key release code 0xF0
	    PS2_Flag |= (1<<PS2_KEYUP); //key release flag set
		break;
      case (0xE0):  //extended key code 0xE0
	    PS2_Flag |= (1<<PS2_EXT); //extended key flag set
		break;	     
      default:      //Other codes are key codes
	    if (PS2_Flag & (1<<PS2_KEYUP))  //if there was received a key release code (0xF0):
		{  
		  PS2_Flag |= (1<<PS2_EVUP);  //Set Event KeyUp
          PS2_Flag &=~(1<<PS2_EVDOWN); //Clear the second flag, for sure, that the data was read
		}       
        else
		{
		  PS2_Flag |= (1<<PS2_EVDOWN); //Set Event KeyDown
          PS2_Flag &=~(1<<PS2_EVUP);  //Clear the second flag, for sure, that the data was read
        }
        if (PS2_Flag & (1<<PS2_EXT))  //If it is an extended key,
		{ 
		  adr = (unsigned int)Scan2ASCIIspc+PS2_Data;    //use the specials decoding table
          PS2_ASCII = pgm_read_byte_near(adr);   //naplneni vysledku 
		  PS2_Flag &=~(1<<PS2_EXT);
        }
        else
		{
		  adr = (unsigned int)Scan2ASCII+PS2_Data;   //otherwise decode as a normal key.
		  PS2_ASCII = pgm_read_byte_near(adr);   //naplneni vysledku 
        }
		//PS2_Flag &=~((1<<PS2_EXT)|(1<<PS2_KEYUP)); //after decoding, clear all unnecessary flags
		
		PS2_Flag &=~(1<<PS2_KEYUP);
		break;
	}
  }
}


char PS2_ReadKey(void)
{
  while (!(PS2_Flag & (1<<PS2_EVDOWN)))
  {
    PS2_Poll();
  }
  PS2_Flag &=~(1<<PS2_EVDOWN);
  return PS2_ASCII;
}

char PS2_KeyPressed(void)
{
  char psf;
  psf = PS2_Flag;
  if (psf & (1<<PS2_EVDOWN)) 
    return 0xFF;
  else 
    return 0x00;
}