//Voice decompressor example
#include <Mega32.h>
#include <delay.h> 

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

#define TableSize 6040 //refers to the following incl file
//Contains the packed 2-bit codes for syntehsis
//Generated by the program Make2code476.m
#include "DPCMcode.h"
//reconstruction differentials 
flash char PCMvalue[4] = {-78, -16, 16, 78};

int outI, tableI;      	//indexes
char cycle ;  			//decode phase counter
char out, lastout;		//output values
char p1, p2, p3, p4	 ;	//hold 4 differentials
char packed	;			//byte containing 4 2-bit values	

//generate waveform at 7812 scamples/sec
interrupt [TIM0_OVF] void voicegen(void)
begin 
	//compute next sample
	cycle = outI%4;
	if (cycle==0)      //do we need to unpack more data?
	begin
        	if (tableI<TableSize)  //end of stored wave?
        	begin
        		//unpack a table entry
        		packed = dpcmtable[tableI];
        	    p1 = (packed & 192)>>6;
           		p2 = (packed & 48)>>4;
        	    p3 = (packed & 12)>>2;
        	    p4 = (packed & 3); 
        	    tableI++ ; 
        	end //end unpack table entry 
 		//compute the output and send to PWM
     	out = lastout + PCMvalue[p1] - lastout>>4 ;
     	OCR0 = out;
     	lastout = out;
     	outI++;
 	end
 	else if (cycle==1)    //don't need to unpack yet--just ouput
 	begin
 		out = lastout + PCMvalue[p2] - lastout>>4 ;
     	OCR0 = out;
     	lastout = out;
     	outI++;
   end
  	else if (cycle==2)
  	begin
  		out = lastout + PCMvalue[p3] - lastout>>4 ;
     	OCR0 = out;
     	lastout = out;
     	outI++;  
    end
  	else if (cycle==3) 
  	begin
  		out = lastout + PCMvalue[p4] - lastout>>4 ;
     	OCR0 = out;
     	lastout = out;
     	outI++;
	end //next sample
	
	//at end, turn off TCCRO
	if (tableI==TableSize) TCCR0 = 0;	  
end 
 
void main(void)
begin 
   
   DDRB=0xff; 
   
   #asm
   sei
   #endasm
   
   while(1) 
   begin  
         //turn on pwm with period= 256*8 cycles  = 2048 cycles 
         // or 7812 samples/sec //fast PWM mode,
         TCNT0 = 0; 
         OCR0 = 128;
         TCCR0 = 0b01101010 ; 
         TIMSK = 0b00000001 ;
         
         //init the output indexes
         outI = 0; 
         tableI = 0; 
         //init the ouptut value
         lastout = 128; 
         //wait until the speech is done then
         //time delay the next utterance.
         while (TCCR0>0){} 
         delay_ms(1000);
               
   end // end while  
end  //end main