// ECE476 Project Remote unit with RF receiver and ultrasonic transmitter
// 4/5/2006
//
// connect RF receiver to port D.0 (RX)
// connect Ultrasonic transducer to OC2 (PD7)

// Includes
#include <Mega32.h>
#include <stdio.h>

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

#define sync_char  0b10101010   //170
#define start_char 0b11001010   //202
#define end_char   0b11010100   //212
#define SOUNDSPEED 0.033        // cm per us

//the encoding
flash char code[16] = {0b10001011,0b10001101,0b10010011,0b10010101,0b10010110,
0b10011001,0b10011010,0b10011100,0b10100011,0b10100101,0b10100110,0b10101001,
0b10101100,0b10110001,0b10110010,0b10110100};

// constants
#define TXBUFSIZE	30	// transmit string buffer size
#define RXBUFSIZE	15	// receive string buffer size

// declare functions
void puts_int(void);				// initialize transmit to PC
void gets_int(void);				// initialize receiver from PC

// misc variables
unsigned int soundTimer;	// count down time in ms
unsigned char soundOn;

//RXC ISR variables
unsigned char r_index;		//current string index
unsigned char r_buffer[RXBUFSIZE];	//input string
unsigned char r_ready;		//flag for receive done
unsigned char r_char;		//current character
unsigned char r_started;   // packet started

//TX empth ISR variables
unsigned short int t_index;			//current string index
unsigned char t_buffer[TXBUFSIZE];	//output string
unsigned char t_ready;			//flag for transmit done
unsigned char t_char;			//current character

//****************************************************************
// Interrupt Service Routines
//****************************************************************

//========================================================
// TIMER 0: Compare match ISR
//========================================================

interrupt [TIM0_COMP] void timer0_comp(void)
begin
  if (soundTimer > 0) --soundTimer;
end

//========================================================
// UART character-ready ISR
//========================================================
interrupt [USART_RXC] void uart_rec(void)
begin
//  if(UCSRA.4 == 0) // check for frame error
//  begin
    //-------------------------------------------------------
    // check for sync byte
	if(r_index==0)
    begin
      r_buffer[r_index]=UDR;

	  if(r_buffer[0]==sync_char) r_started=1;
      else r_started=0;
	        	                        
  	  if(r_buffer[0]==sync_char && r_started == 1)
      begin
        r_index++;
//        PORTD.7 = 0;
      end				
    end
	//-------------------------------------------------------
	// check for start byte
    else if (r_index==1)
	begin
      r_buffer[r_index]=UDR;
      if(r_buffer[1]==start_char)
      begin
	    r_index++;
      end
//      else if(!(r_buffer[1]==sync_char))
//      begin
	    // wrong stuff
//        r_index = 0;
//        r_started = 0;
//        PORTD.7 = 1;
//      end
    end
    //-------------------------------------------------------
    // rest of the packet
    else
    begin
	  r_buffer[r_index++]=UDR;
//		if (r_index==4)
//      begin
//	      rx_length = decode(rx_data[3],rx_data[4]);			
//		  end		
//      else if(r_index>=max_rx_length || rx_data[r_index]==212)
//	    begin
      if(UDR == end_char || r_index > 4)
      begin
//        PORTD.7=1;
        r_ready=1;			//signal cmd processor
        UCSRB.7=0;			//stop rec ISR
      end
    end
//  end // check for frame
//  else
//  begin
//    PORTD.7 = 0;
//                    end
end

//========================================================
// UART xmit-empty ISR
//========================================================
interrupt [USART_DRE] void uart_send(void)
begin
  t_char = t_buffer[++t_index];
  if (t_char == 0) 	
  begin
    UCSRB.5=0; //kill isr 
    t_ready=1; //transmit done 
  end
  else UDR = t_char;	//send the char 
end

//****************************************************************
// -- non-blocking keyboard check initializes ISR-driven
// receive. This routine merely sets up the ISR, which then
// does all the work of getting a command.
//****************************************************************
void gets_int(void)
begin
  r_ready=0;
  r_started=0;
  r_index=0;
  UCSRB.7=1;
end

//****************************************************************
//  -- nonblocking print: initializes ISR-driven
// transmit. This routine merely sets up the ISR, then
//send one character, The ISR does all the work.
//****************************************************************   
void puts_int(void) 
begin
  t_ready=0;
  t_index=0;
  if (t_buffer[0]>0)
  begin
    putchar(t_buffer[0]);
    UCSRB.5=1;
  end
end


//****************************************************************
// MAIN
//****************************************************************
void main(void)
begin

  //========================================================
  // Initialization
  //========================================================

  // setup USART
  UCSRB = 0x18 ;
//  UCSRC = 0xA6;          // set even parity
//  UBRRL = 103 ;		// sets baud rate to 9600
  UBRRL = 249 ;		// sets baud rate to 4000
//  UBRRL = 416 ;		    // sets baud rate to 2400
//  UBRRL = 207 ;		    // sets baud rate to 4800

  // set I/O ports
  DDRD = 0x82;      // port D is used as RX, and OC2 output
  PORTD.7 = 1;

  soundTimer = 0;
  soundOn = 0;

  r_ready = 0;
  t_ready = 1;

  // set timer0
  OCR0 = 249;		// makes a 1 ms interrupt
  TIMSK = 0b00000010;
//  TIMSK.1 = 1;          // turn on timer 0 compare match ISR
  TCCR0 = 0b00001011;	  // prescalar of 64 and clear on match
//  TCCR2  = 0b00011000;    // CTC mode with prescalar of 0 (stopped), should be 8 when on
  OCR2 = 40;              // make 24.4 kHz output on OC2

  #asm
  sei
  #endasm

  // start receiving commands
  gets_int();
  
  // MAIN loop
  while(1) 
  begin

//    #asm("sleep");

    if(r_ready && soundOn == 0)
    begin
      if(r_buffer[2] == code[0] && r_buffer[3] == code[15])
      begin
        // make ultrasound noise
        r_buffer[2] = 0;
        r_buffer[3] = 0;
        soundTimer = 20;  // how many ms to make sound
        soundOn = 1;
        TCCR2  = 0b00011010;      // CTC mode with prescalar of 8
      end
      else
      begin
        r_buffer[2] = 0;
        r_buffer[3] = 0;
        gets_int();
      end
    end // r_ready\
    
    if(soundOn == 1 && soundTimer == 0)
    begin
      // stop sound
      soundOn = 0;
      TCCR2  = 0b00000000;      // stop timer 2
      PORTD.7 = 1;
      gets_int();
    end

//    else
//    begin
//      while(!t_ready);
//      sprintf(t_buffer,"%d ",soundTimer);
//      puts_int();
//    end

//    while(!t_ready);
//    sprintf(t_buffer,"end ");
//    puts_int();
    
  end // end while 
end  //end main