//---------------------------------------------------------------------------------------
// Programm Nr.: 09
// Content     : ADC (free running) output high byte on PORT D
// Author      : digital AG Halle
// Date        : 16.07.2008
// System      : ATmega8-16PU - Dai Hoc Hue Development Board
//---------------------------------------------------------------------------------------

//--included Files-----------------------------------------------------------------------

#include <avr/io.h>

//--declarations-------------------------------------------------------------------------

#ifndef F_CPU
#define F_CPU 8000000	//CPU frequency = 8 MHz
#endif


uint8_t result_H;
uint8_t result_L;


//--MAIN PROGRAMM------------------------------------------------------------------------

int main(void)
{

	//--INITIALISATION---------------------------------------------------------------

	//ADC_INIT:
		ADMUX |= (1<<REFS0) | (1<<ADLAR);
		//ext. Vref = AVcc, left adjusted result, channel 0
		ADCSRA |= (1<<ADEN) | (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0); 
		//ADC = on, prescaler = 128 (rate = 62,5 kHz)
	
	//PORT_INIT:
		DDRC=0x00;	//Port C Eingang
		PORTC=0xff;	//Pullup
		
		DDRD=255; 	//Port D: all Bits defined as output (for the status LEDs)
		PORTD=255; 	//all LEDs off

	//--PROGRAMM CODE BEFORE MAIN LOOP (USED JUST ONE TIME)--------------------------

		ADCSRA |= (1<<ADFR) | (1<<ADSC); //free run mode, start enable

	//--MAIN LOOP--------------------------------------------------------------------
	
	while(1)
	{
        	while(!(ADCSRA & 0x10));	// wait for ADIF flag '1'
						// (end of messuring)
			

		// 	    *** ALLWAYS READ ADCL REGISTER FIRST !!! ***
		// *** READ ALLWAYS BOTH REGISTERS OR THE ADC WILL HANG UP !!! ***


				result_L = ADCL;// read ADCL register
				result_H = ADCH;// read ADCH register
				
		//output:   
			PORTD=result_H;		//send the lower byte to PORTD	

	}
	return 0;
}

//--MAIN PROGRAMM END--------------------------------------------------------------------
//--EXTERNAL ROUTINES (FOR THE LCD)------------------------------------------------------
//--PROGRAMM END-------------------------------------------------------------------------