#include <avr/io.h>
#include <math.h>


#define NUM_SAMPLES 1000   /* change the number of data samples */
#define MAX_REG_LENGTH 2   /* this says that the max length of a register is 2 bytes */


Writetoreg (int);


Read (int,char);


char *datapointer = store;


char store[NUM_SAMPLES*MAX_REG_LENGTH + 30];


void main()

{
	
	char a;


	DDRB |= 0x08;  /* PB3 is an output  */

	PORTB |= 0x08; /* /CS set to high */


	Writetoreg(0x10); /* set the gain to 1, standby off and set the next operation as write to the setup register */

	Writetoreg(0x68); /* set bipolar mode, buffer off, no filter sync, confirm clock as 2.4576MHz, 
	                     set output rate to 60Hz and do a self calibration */


	while(PORTB & 0x04); /* wait for /DRDY to go low ---- /DRDY is PB3   */


	for(a=0;a<NUM_SAMPLES;a++);
		{
			Writetoreg(0x38); /*set the next operation for 16 bit read from the data register */
			Read(NUM_SAMPLES,2);
		}


}


Writetoreg(int byteword);


{ 
	int q;


	SPCR = 0x3F;
	SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0);

	SPCR = 0X7F; /* this sets the WiredOR mode(DWOM=1), Master mode(MSTR=1), SCK idles high(CPOL=1), /SS
             	can be low always (CPHA=1), lowest clock speed(slowest speed which is master clock /32 */


	DDRB |= 0xA0; /* SCK, MOSI outputs */


	q = SPSR;
	q = SPDR; /* the read of the staus register and of the data register is needed to clear the interrupt
				which tells the user that the data transfer is complete */


	PORTB &= 0xF7;   /* /CS set to low */


	SPDR = byteword; /* put the byte into data register */


	while(!(SPSR & (1<<SPIF))); /* wait until port ready before reading */


	PORTB |= 0x08; /* /CS set to high */


}


Read(int amount, int reglength)


{


	int q;


	SPCR = 0x3F;

	SPCR = 0x7F; /* clear the interrupt */

	DDRB = 0x80; /* MOSI output, MISO input, SCK output */


	while(PORTB & 0x04); /* wait for /DRDY to go low */
	

	PORTB &= 0xF7;   /* /CS set to low */


	for(b=0; b < reglength; b++)
	{
		SPDR = 0;
		
		while(!(SPSR & (1<<SPIF))); /* wait until port ready before reading */
		
		*datapointer++=SPDR; /* read SPDR into store array via datapointer */
	}


	PORTB |= 0x08; /* /CS set to high */

}