//video gen and sound
//D.5 is sync:1000 ohm + diode to 75 ohm resistor
//D.6 is video:330 ohm + diode to 75 ohm resistor  
//B.3 is sound  and should have a 10k resistor to gnd
#pragma regalloc-    //I allocate the registers myself
#pragma optsize-     //optimize for speed
                    
#include <Mega32.h>   
#include <stdio.h>
#include <stdlib.h> 
#include <math.h> 
#include <delay.h>   

//=======================
// video stuff
char* screen_pointer;
char lastInputFlag;
unsigned int screen_counter;

//NOTE that v1 to v8 and i must be in registers!  
register char v1 @4; 
register char v2 @5;
register char v3 @6;
register char v4 @7;
register char v5 @8;
register char v6 @9;
register char v7 @10;
register char v8 @11; 
register int i @12;

char screen[1600];

//cycles = 63.625 * 16 Note NTSC is 63.55 
//but this line duration makes each frame exactly 1/60 sec
//which is nice for keeping a realtime clock 
#define lineTime 1018
 
#define begin {
#define end }
#define ScreenTop 30
#define ScreenBot 230

#define t1 60

#pragma regalloc+ 

char syncON, syncOFF; 
int LineCount;

unsigned char increment;
unsigned char accumulator;
char sineTable[256];  //need loc to avoid glitch
unsigned char soundMode, playSound;


//==================================
//This is the sync generator and raster generator. It MUST be entered from 
//sleep mode to get accurate timing of the sync pulses
#pragma warn-
interrupt [TIM1_COMPA] void t1_cmpA(void) {
	//generate sound
	accumulator = accumulator + increment;
	OCR0 = 128 + sineTable[accumulator];

  //start the Horizontal sync pulse    
  PORTD = syncON;     
  //update the curent scanline number
  LineCount ++ ;   
  //{ inverted (Vertical) synch after line 247
  if (LineCount==248)
  { 
    syncON = 0b00100000;
    syncOFF = 0;
  }
  //back to regular sync after line 250
  if (LineCount==251)	
  {
    syncON = 0;
    syncOFF = 0b00100000;
  }  
  //start new frame after line 262
  if (LineCount==263) 
  {
     LineCount = 1;
  } 
  
  //delay_us(2); //adjust to make 5 us pulses

		
  //} sync pulse
  PORTD = syncOFF;   
  
  if (LineCount<ScreenBot && LineCount>=ScreenTop)  { 
  
  //read from master
    if(PINB.0!=lastInputFlag) {
			if(PINB.2==1) {
				screen_pointer = screen;          
				//pad instructions
            #asm   
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop  
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            #endasm
			} else {
   			*screen_pointer++ = PINA;
				*screen_pointer++ = PINC;
			}                          
			lastInputFlag = PINB.0;
			PORTB = PORTB ^ 0x02; //flag ready
    } else {
		//pad instructions
		#asm   
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop  
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
			nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop  
            nop
			nop
            nop
            nop
            nop
            nop
            nop
			
		#endasm

	}	
   
	//delay_us(1);
       
       //compute byte index for beginning of the next line
       //left-shift 4 would be individual lines
       // <<3 means line-double the pixels 
       //The 0xfff8 truncates the odd line bit
       //i=(LineCount-ScreenTop)<<3 & 0xfff8; //
       
       #asm
       push r16
       lds   r12, _LineCount
       lds   r13, _Linecount+1
       ldi   r16, 30
       sub  r12, r16 
       ldi  r16,0
       sbc  r13, r16 
       lsl  r12
       rol  r13
       lsl  r12
       rol  r13
       lsl  r12    
       rol  r13
       mov  r16,r12
       andi r16,0xf0
       mov  r12,r16
       pop r16 
       #endasm
        
       //load 16 registers with screen info
       #asm
       push r14
       push r15
       push r16
       push r17
       push r18 
       push r19 
       push r26
       push r27
       
       ldi  r26,low(_screen)   ;base address of screen
       ldi  r27,high(_screen)   
       add  r26,r12            ;offset into screen (add i)
       adc  r27,r13
       ld   r4,x+   	       ;load 16 registers and inc pointer
       ld   r5,x+
       ld   r6,x+  
       ld   r7,x+
       ld   r8,x+ 
       ld   r9,x+
       ld   r10,x+  
       ld   r11,x+
       ld   r12,x+ 
       ld   r13,x+
       ld   r14,x+  
       ld   r15,x+
       ld   r16,x+   
       ld   r17,x+  
       ld   r18,x+
       ld   r19,x 
       
       pop  r27
       pop  r26
       #endasm  

       
       //blast 16 bytes to the screen   
       #asm
       ;but first a macro to make the code shorter  
       ;the macro takes a register number as a parameter
       ;and dumps its bits serially to portD.6   
       ;the nop can be eliminated to make the display narrower
       .macro videobits ;regnum
        BST  @0,7
	IN   R30,0x12
	BLD  R30,6
	nop
	OUT  0x12,R30  
	
	BST  @0,6
	IN   R30,0x12
	BLD  R30,6
	nop
	OUT  0x12,R30 
	
	BST  @0,5
	IN   R30,0x12
	BLD  R30,6 
	nop
	OUT  0x12,R30 
	
	BST  @0,4
	IN   R30,0x12
	BLD  R30,6
	nop
	OUT  0x12,R30 
	
	BST  @0,3
	IN   R30,0x12
	BLD  R30,6
	nop
	OUT  0x12,R30 
	
	BST  @0,2
	IN   R30,0x12
	BLD  R30,6
	nop
	OUT  0x12,R30 
	
	BST  @0,1
	IN   R30,0x12
	BLD  R30,6 
	nop
	OUT  0x12,R30 
	
	BST  @0,0
	IN   R30,0x12
	BLD  R30,6
	nop
	OUT  0x12,R30 
       .endm     
        
	videobits r4 ;video line -- byte 1
        videobits r5 ;byte 2  
        videobits r6 ;byte 3
        videobits r7 ;byte 4
        videobits r8 ;byte 5
        videobits r9 ;byte 6
        videobits r10 ;byte 7
        videobits r11 ;byte 8 
        videobits r12 ;byte 9
        videobits r13 ;byte 10  
        videobits r14 ;byte 11
        videobits r15 ;byte 12
        videobits r16 ;byte 13
        videobits r17 ;byte 14
        videobits r18 ;byte 15
        videobits r19 ;byte 16
	clt   ;clear video after the last pixel on the line
	IN   R30,0x12
	BLD  R30,6
	OUT  0x12,R30
								
       pop r19
       pop r18
       pop r17 
       pop r16  
       pop r15
       pop r14
       #endasm
    
		//read from master
		if(PINB.0!=lastInputFlag) {
			if(PINB.2==1) {
				screen_pointer = screen;          
            #asm   
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop  
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            nop
            #endasm
			} else {
   			*screen_pointer++ = PINA;
				*screen_pointer++ = PINC;
			}                          
			lastInputFlag = PINB.0;
			PORTB = PORTB ^ 0x02; //flag ready
		}
    }            
    
}  
#pragma warn+


//==================================
// set up the ports and timers
void main(void)
{ 
	//init timer 1 to generate sync
	OCR1A = lineTime; 	//One NTSC line
	TCCR1B = 0b00001001; 		//full speed; clear-on-match
	TCCR1A = 0x00;		//turn off pwm and oc lines
	TIMSK = 0x10;		//enable interrupt T1 cmp 	
  
  	TCCR0 = 1;
	OCR0 = 0;
  
  	//init ports
	DDRD = 0xf0;		//video out and switches
	//D.5 is sync:1000 ohm + diode to 75 ohm resistor
	//D.6 is video:330 ohm + diode to 75 ohm resistor
  
	//initialize synch constants 
	LineCount = 1;
	syncON = 0b00000000;
	syncOFF = 0b00100000;

	//set up communication ports
	DDRB=0b00001010;	//PORTA[0,2] = input, rest output
	PINB.1 = 1;
	DDRA=0x00;	//PORTA = input
	DDRC=0x00;	//PORTC = input
	
	screen_pointer = screen;
	lastInputFlag = 0;
	screen_counter = 0;
	
	screen[100] = 0xff;
	screen[101] = 0xff;
	screen[102] = 0xff;
	screen[103] = 0xff;
	screen[104] = 0xff;
  
  	for (i=0; i<256; i++) {
		sineTable[i] = (char)(63.5 * sin(6.283*((float)i)/256.0)) ;
	}
	soundMode = 0;
	playSound = 0;
  
	//enable sleep mode
	MCUCR = 0b10000000;
	#asm ("sei");

	//The following loop executes once/video line during lines
	//1-230, then does all of the frame-} processing
	while(1)
	{
  
    //stall here until next line starts
    //sleep enable; mode=idle  
    //use sleep to make entry into sync ISR uniform time  
     
    #asm ("sleep");
		
		if(LineCount>230 && LineCount<260) {
			if(PINB.0!=lastInputFlag) {
				if(PINB.2==1) {
					screen_pointer = screen;          
				} else {
					*screen_pointer++ = PINA;
					*screen_pointer++ = PINC;
				}                          
				lastInputFlag = PINB.0;
				PORTB = PORTB ^ 0x02; //flag ready
			}
			if(LineCount==259) {
				//check for audio flags
				soundMode = 0;
				if(PINB.4) soundMode++;
				if(PINB.5) soundMode+=2;
				
				if(soundMode>0) {
					TCCR0 = 0b01101001;
					if(soundMode==1) {	//walking
						increment = 6;
					} else if(soundMode==2) {	//error
						increment = 4;
					} else if(soundMode==3) {	//win
						increment = 8;
					}
				} else {
					TCCR0 = 1;
				}
			}
		}
		
	}  //while
}  //main