/*
 * DACProject.c
 *
 * Created: 10/20/2016 9:59:41 AM
 * Author : Hector Farias & Jose Flores
 */

#define F_CPU 16000000 			//define internal CLK speed
// assumes vdd = 3.3v, your voltages may vary for 5v
#define MOSI 3  				// PB pin 3
#define SCK  5  				// PB pin 5
#define SS   2  				// PB pin 2

#include <avr/io.h>
#include <util/delay.h>

void Initialize_SPI_Master(void);
void Transmit_SPI_Master(int Data);

int main(void)
{
	int count = 0;
	DDRB = 1<<MOSI | 1<<SCK | 1<<SS;	// make MOSI, SCK and SS outputs
	Initialize_SPI_Master();
	while(1)
	{
		/**
		Transmit_SPI_Master(0x666); 	//0xAAA / 0xFFF = 2730 / 4096 * 5V (ref) = ~ 3.33V
		_delay_ms(100);

		Transmit_SPI_Master(0x333); 	//0x333 / 0xFFF = 819 / 4096 * 5V (ref)  ~ 0.99
		_delay_ms(100);
		**/
		int start = 819;
		int top = 1638;
		int step_value = 8;
		while(start <= top)
		{
			Transmit_SPI_Master(start);
			start = start + step_value;

		}

		start = 819;

		while(top >= start)
		{
			Transmit_SPI_Master(top);
			top -= step_value;
		}

	}  // end while
	return 0;
}  // end main

void Initialize_SPI_Master(void)
{
	SPCR = (0<<SPIE) | 		//No interrupts
	(1<<SPE) | 			//SPI enabled
	(1<<MSTR) ; 			//master
	SPSR = 0x00;	 		//clear flags
	PORTB = 1 << SS;  		// make sure SS is high

}

void Transmit_SPI_Master(int Data) {
	PORTB &= ~(1 << SS); 			  //Assert slave select (active low)
	SPDR = ((Data >> 8) & 0xF) | 0x70; 	  //Attach configuration Bits onto MSB
	while (!(SPSR & (1<<SPIF)));
	SPDR = 0xFF & Data;
	while (!(SPSR & (1<<SPIF)));
	PORTB |= 1 << SS; 			  //Turn off slave select
}