//
// Cornell 2005
// Edward Lo and Sihan Goi
// ECE476 final project
// Temperature sensor and fan wireless transmitter
//
#include <Mega32.h>
#include <stdio.h>
#include <stdlib.h>

//I like these definitions
#define begin {
#define end   }

//task scheduling timers
#define t1 30  //30 ms debounce state machine

//wireless packet definitions (maintain DC balance)
#define start_packet 0b10100110
#define stop_packet  0b11010010

enum { NoPush, MaybePush, Pushed, MaybeNoPush };

unsigned int  time1;                        //task scheduling timeout counter
unsigned char buttons, buttons2, inbutton;  //saves the button press
unsigned char butstate;	                    //debounce state machine
unsigned char cdata;                        //data byte to transmit

void initialize(void);  //set everything up
void getInput(void);    //debounce buttons


//**********************************************************
//Timer0 compare ISR
//  Simply ticks down the task timers.
interrupt [TIM0_COMP] void timer0_compare(void)
{
  if (time1>0)  --time1;
}


//**********************************************************
//Transmit the data byte
//  Encapsulates the data packet with a start and end packet.
//  Send 0xaa's to setup receiver gain.
void senddata(void)
{
  //setup the receiver for proper gain and sync
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xaa);
  putchar(0xff);
  putchar(0x00);
  //send data
  putchar(start_packet);
  putchar(cdata);
  putchar(stop_packet);
  
  cdata = 0;
}
                   

//**********************************************************
//Button debouncing state machine
//  Gets the button presses into "inbutton" and then encodes it
//  into the "cdata" variable.  This becomes the data packet.
void getInput(void)
{
  time1=t1;

  //button debounce
  switch( butstate )
  begin
    case NoPush:
      buttons = PINA;
      if( ~buttons != 0 ) butstate = MaybePush; break;
                 
    case MaybePush:
      buttons2 = PINA;
      if( buttons2 == buttons )
      begin
        butstate = Pushed;
        inbutton = ~buttons;
      end  
      else butstate = NoPush;
      break;
             
    case Pushed:
      buttons2 = PINA;
      if( buttons2 == buttons ) butstate = Pushed;
      else                      butstate = MaybeNoPush; break;
             
    case MaybeNoPush:
      buttons2 = PINA;
      if( buttons2 == buttons ) butstate = Pushed;
      else
      begin
         butstate = NoPush;
         inbutton = 0;
      end
      break;
  end

  //parse input
  switch( inbutton ) {
    case 0b10000000:
    case 0b01000000:
    case 0b00100000:
    case 0b00010000: cdata = 0b10000000 | (inbutton >> 1) | 0b10;
                     inbutton = 0;
                     break;
    case 0b00000001: cdata = 0b10000110;
                     inbutton = 0;
                     break;
  }
}


//**********************************************************
//Main program
//  Debounce buttons and send presses to serial port.
void main(void)
{
  initialize();

  while(1)
  {
    if( time1 == 0 ) getInput();  //get debounced input
    if( cdata != 0 ) senddata();  //transmits button press
  }
}


//**********************************************************
//Get everyting started
void initialize(void)
{
  //setup ports
  DDRA  = 0x00;		// buttons
  PORTA = 0xff;		// pull-up resistors
  DDRD  = 0xff;		// output for status light and transmitter
  PORTD = 0xff;		// power status on

  //serial setop for debugging using printf, etc.
  UCSRB = 0x18;
  UBRRL = 207;  //4800

  //setup timer0 for 1ms
  TIMSK = 2;
  OCR0  = 249;
  TCCR0 = 0b00001011;
	
  //initialize timers
  time1 = t1;
  time2 = t2;
	
  //setup debounce states
  butstate = NoPush;
  inbutton = 0;

  cdata = 0;

  #asm ("sei");
  
  //turns on LED
  PORTD.7 = 0;
}