//---------------------------------------------------------------------------------------
// Programm Nr.: 10
// Content     : ADC (single conversion) on pressing a key + 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 KEYS;
uint8_t KEYS_OLD;

	//internal 10-bit analog digital converter

uint8_t result_H;	//high byte result ADC (bit 9-8)
uint8_t result_L;	//low byte result ADC  (bit 7-0)


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

int main(void)
{

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

	//ADC_INIT:
		ADMUX |= (1<<REFS0) | (1<<ADLAR);
		//ext. Vref = AVcc, left adjusted result, channel 0
		ADCSRA |=  (1<<ADPS2) | (1<<ADPS1) | (1<<ADPS0) | (1<<ADEN); 
		//prescaler = 128 (rate = 62,5 kHz), single conversion
	
	//PORT_INIT:
		DDRC=224;	//Port C key inputs and bit0 analog channel 0 input
		PORTC=30;	//Pullup (keys and analog input)
		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)--------------------------

		KEYS_OLD=PINC;

	//--MAIN LOOP--------------------------------------------------------------------
	
	while(1)
	{
	 	KEYS=PINC;

		if (KEYS_OLD!=KEYS) 
		{
			//mask  = 1110 0010 = 226 dec.
			if ((KEYS&226)==!(0x02))	//if key 1 was pressed
			{
				ADCSRA |= (1<<ADSC);
				//ADC enable
			while(ADCSRA & (1<<ADSC)); //wait for first complete messure cycle
						   //(first cycle is a dummy cycle)
        
			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
				
		//stop the internal ADC after the messure
			ADCSRA ^= (1<<ADSC);	
	
		//output
			PORTD=result_H;		//send the lower byte to PORTD	
			}
		}
		KEYS_OLD=KEYS;
	}
	return 0;
}

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