/*8515play
Copyright 2007 Richard Cappels
www.projects.cappels.org

Complied with 	avr-gcc (GCC) 3.4.6
The compiler can be downloaded from http://sourceforge.net/

This assumes an R/2R DAC (or other DAC) connected to PORTA, and a 4 MHz clock.

The frequency measured at the output of the DAC is 1.00045 kHz.
The power supply voltage on the breadboard is 5.00 V.
The maximum output voltage was measured at 4.96 V.
The minimum output voltage was measured at 0 V.
The spurious components are -30 with repsect to the 1 kHz signal.
Light filtering, by placing a .015 uf capacitor on the R-2R DAC output resulted in
reducing the 1 kHz signal by 3 db and makes the spurious components 50 db below the 1 kHz signal


8515sine080210B 1.00045 kHz as measured on the tek scope.
8515sine080210A	NOT SAVED 	Corrected LUT. Works at 488 Hz with 4 MHz Chrystal
8515sine08020A	NOT SAVED Kind of working from interrupts. Wrong frequency, glitch.

*/

#include <avr/interrupt.h>
#include <stdlib.h>
	
	char sinetable [32];
	int  i ;	
	void ioinit (void)								// Initialize  I/O.
	
	/*
	I/O Pin assignments for AT90S8515:
	Port A is the R/2R DAC
	PORT B is Test output
	PORT C is unused
	PORT D is unused
	*/
{		
												//Initialize output ports
	PORTA = 0b00000000;	
	PORTB = 0b11111111;
	PORTC = 0b11111111;
	PORTD = 0b11111111;
	DDRA  = 0b11111111;
	DDRB  = 0b11111111;
	DDRC  = 0b00000000;
	DDRD  = 0b00000000;
}




void timer0_setup (void)									
{
	TCCR0 = 0b00000001;  
	TCNT0 = 175;   
	TIMSK = 0b00000010;
}


 


ISR (SIG_OVERFLOW0)							// Counter0 Interrupt Service
{
PORTA = (sinetable[i++]);
	TCNT0 = 175;	
	if (i==32)		
	{
		i=0;
	}							
}




void arraysettup (void)

{										
	sinetable[0]=127;					// Put 32 step 8 bit sine table into array.
	sinetable[1]=152;	
	sinetable[2]=176;	
	sinetable[3]=198;
	sinetable[4]=217;
	sinetable[5]=233;
	sinetable[6]=245;
	sinetable[7]=252;
	sinetable[8]=254;
	sinetable[9]=252;
	sinetable[10]=245;
	sinetable[11]=233;
	sinetable[12]=217;
	sinetable[13]=198;
	sinetable[14]=176;
	sinetable[15]=152;
	sinetable[16]=128;
	sinetable[17]=103;
	sinetable[18]=79;
	sinetable[19]=57;
	sinetable[20]=38;
	sinetable[21]=22;
	sinetable[22]=10;
	sinetable[23]=3;
	sinetable[24]=0;
	sinetable[25]=3;
	sinetable[26]=10;
	sinetable[27]=22;
	sinetable[28]=38;
	sinetable[29]=57;
	sinetable[30]=79;
	sinetable[31]=103;	
}










int	main (void)		
{
	ioinit();
	arraysettup();
	timer0_setup();
	i = 0;
	sei();
	
	while (1)
	{	
//	if (i == 32)
//	{i=0;}
	}	
    return (0);
}