#include <avr/io.h>

// Mega16 Pinout
#define MOSI	4
#define MISO	6
#define SCLK	7
#define SS		4



unsigned int get_adc(unsigned char adata)
{
	static unsigned int temp=0;
	
	PORTB &= ~(1<<SS);									// set cs on low to activied the adc
																			// maybe here a little delay
	SPDR = adata;												// put the data into send register
	while(!(SPSR & (1<<SPIF)));					// send 1 Byte over HW SPI and wait for tx complete int	
	temp = SPDR;												// put the received data to a static temp variable
	temp = temp << 8;										// shift the temp variable 8 steps left
	SPDR = adata;												// put the data into send register
	while(!(SPSR & (1<<SPIF)));					// send 1 Byte over HW SPI and wait for tx complete int		
	temp |= SPDR;												// put the received data to a static temp variable
	PORTB |= (1<<SS);										// set cs on high to disable the adc
	return temp;												// return the adc value
}



void spim_init(void)
{
	// SET the Ports to output/input 
	DDRB |= (1<<MOSI) | (1<<MISO) | (1<<SCLK) | (1<<SS);
	// SPI Enable, SPI Master, SPI CLK XTAL/16, LSB First
	SPCR |= (1<<SPE)|(1<<MSTR)|(1<<SPR0);		
	PORTB |= (1<<SS);		// CS High because the SPI ADC is low active
}

int main (void)
{
	static unsigned int adc_value=0;	// uint variable
	
	spim_init();						 					// Init HW SPI Master
	adc_value = get_adc(0xFF);				// Get data from SPI ADC send anything to generate the clock

	for(;;){}
}