//SPI example using ADC0832 from National Semi
//connect MOSI B.5 to DI on ADC0832
//connect MISO B.6 to DO on ADC0832
//connect SCLK B.7 to CLK on ADC0832
//connect B.4 to chip select on the ADC0832

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

#define begin {
#define end }

// bit handling macros for i/o registers
#define READ(U, N) ((U) >> (N) & 1u)
#define SET(U, N) ((void)((U) |= 1u << (N)))
#define CLR(U, N) ((void)((U) &= ~(1u << (N))))
#define FLIP(U, N) ((void)((U) ^= 1u << (N)))

uint8_t Ain, junk, ADC_cntl ;

int main(void)
begin

	DDRC = 0xff; // LEDs

    //set up i/o data direction
    //DDRB.4 = 1; //output chip select for DAC (notSYNC)
    //DDRB.5 = 1; //output MOSI to ADC
    //DDRB.6 = 0; //input MISO from ADC
    //DDRB.7 = 1; //output SCLK   
	DDRB = (1<<DDB4) | (1<<DDB5) | (1<<DDB7) ; 
	// initialize notSYNC
	SET(PORTB,4) ;

	//set up SPI
    //bit 7 SPIE=0 no ISR
    //bit 6 SPE=1 enable spi
    //bit 5 DORD=0 msb first 
    //bit 4 MSTR=1 Mega32 is spi master
    //bit 3 CPLO=1 clock polarity
    //bit 2 CPHA=1 clock phase
    //bit 1,0 rate sel=10 along with SPRC=1 sets clk to f/32 = 500 kHz
    SPCR = (1<<SPE) | (1<<MSTR) | (1<<CPOL) | (1<<CPHA) | (1<<SPR1) ; //SPCR SPCR = 0b01011110 ;                                                                               
    SPSR = (1<<SPI2X) ; //SPSR = 1; 
    
	// Set single-ended, channel 0 for AD0832:
	// The data sheet suggests that the 
	// last three bits of the input byte set:
	//  (start bit, mode bit, channel bit) 
	// but due to a 1 bit delay for mux settling, 
	// the input byte has to be sent 
	// (msb first) as [0 0 0 0 1 mode chan 0] 
	// with the extra zero padding the end. 
	// The mode is 1 if single-ended or 0 if differential 
	// and chan is either 0 or 1. 
	// The start bit is part of the ADC protocol, 
	// but not part of the SPI transfer protocol.
	ADC_cntl = 0b00001100 ;

    while (1)
    begin 
        CLR(PORTB,4) ;   //chip select low begins conversion 
		//set ADC parameters               
        SPDR = ADC_cntl ;        
		//wait until SPIF is set (SPI done)
        while (!(SPSR & (1<<SPIF))) ;
		junk = SPDR ; // get back junk
		//Now send junk to get back ADC value
        SPDR = junk ;  
		//wait until SPIF is set (SPI done)
        while (!(SPSR & (1<<SPIF))) ;
		Ain = SPDR ;
		//SYNC high ends load for the AD0832
        SET(PORTB,4) ;  //chip select high ends conversion

		// put the conversion on the LEDs
        PORTC = ~Ain ;
    end

end