//***********************************************************************
//
// rpm1.c
//
// Author:	Jeremy Greenwood
//
// Microcontroller:	ATtiny2313	
//
// Description:
//
//			Calculate and display revolutions per minute of an optical
//		encoder with eight state changes per revolution.  A millisecond
//		counter is used to determine the elapsed time.
//
// Changes:	
//
//***********************************************************************

#define F_CPU 1000000UL											// 1 MHz

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avriomacros.h>
#include <stdlib.h>
#include <math.h>

#define WAIT	2

// Define display outputs
#define DB0		PB0
#define DB1		PB1
#define DB2		PB2
#define DB3		PB3
#define DB4		PB4
#define DB5		PB5
#define DB6		PB6
#define DB7		PB7

#define ENABLE	PA0
#define RS		PA1

// Define inputs
#define IR		PD2  	// INT0

// Macro to initilize timer1
#define init_timer()		{TCCR1B |= (1 << WGM12) | (0 << CS10) | (1 << CS11); OCR1A = 125; TIMSK |= (1 << OCIE1A);}

// Macro to initialize interrupts
#define init_interrupts()	{MCUCR |= (0 << ISC01) | (1 << ISC00); GIMSK |= (1 << INT0); sei();}

// Display macros
#define	enable()			{on(ENABLE, A); _delay_ms( WAIT ); off(ENABLE, A);}
#define init_display()		{off(RS, A); PORTB = 0b1100; enable()}
#define clear_display()		{off(RS, A); PORTB = 0b1; enable();}
#define return_home()		{off(RS, A); PORTB = 0b10; enable();}
#define write_display(val)	{on(RS, A); PORTB = val; enable();}
#define set_digit(dig)		{off(RS, A); PORTB = 0b10000000 | dig; enable();}

#define clear_str(str)		{for( int z = 0; z < sizeof(str)/sizeof(char) - 1; z++ ) str[z] = 0;}
#define write_number(num)	write_display( 0b00110000 | num );
#define write_string(str) 	for( int z = 0; z < sizeof(str)/sizeof(char) - 1; z++ ) { if( str[z] == 0 ) break; write_display( str[z] );}
#define write_string_right_adj(str,dig) 	int dig_val = dig; for( int z = sizeof(str)/sizeof(char) - 1; z >= 0; z-- ) { if( str[z] != 0 ){set_digit( dig_val-- );write_display( str[z] );}}

char	NAME[] = "Lets make robots",
		STATEMENT[] = "Wheel RPM:",
		BUFF[4];


volatile int	tic = 0, count = 0, second_has_elapsed = 1;


// 1ms timer interrupt
ISR( TIMER1_COMPA_vect ) {

	tic++;					// incremet 1ms counter
	
//	if( tic >= 1000 ) {

	if( tic >= 500 ) {

		tic = 0;
		second_has_elapsed = 1;
	}
}

ISR( INT0_vect ) {

	count++;
}


int main (void) {

	int digit, rpm;

	// define outputs
	DDRB = 0xff;			// DB outputs
	out(ENABLE, A);
	out(RS, A);
	off(ENABLE, A);

	init_timer();
	init_interrupts();
	_delay_ms( 200 );

	init_display();
	clear_display();

	set_digit(2);
	write_string( NAME );

	_delay_ms( 2000 );
	clear_display();

	set_digit(3);
	write_string( STATEMENT );
	digit = sizeof(STATEMENT)/sizeof(char) - 1;
	digit += 6;

	while(1) {

		if( second_has_elapsed ) {		// calculate and display rpm every second

			set_digit(13);
			write_string("       ");

//			rpm = (count * 15) / 2;		// calculation of rpm derived from 60 seconds / 8 state changes per revolution

			rpm = (count * 15);

			clear_str( BUFF );
			itoa( rpm, BUFF, 10);

			write_string_right_adj( BUFF, digit );
			
			second_has_elapsed = 0;
			count = 0;
		}
	}
}