/*
rpm measurements using the Orangutan
Atmega8 version, last update 6/4/2007
FOSC=8MHz
sjames_remington at yahoo dot com

*/
#include <avr/interrupt.h>
#include <avr/io.h>
#include <stdio.h>
#include <stdlib.h>

#define F_CPU 8000000UL

/*
 *  Function prototypes
 *	Use home-rolled delays in main
 */
 
void	Delay_us ( unsigned int microseconds );
void	Delay_ms ( unsigned int milliseconds );
void LCDInit(void);
void LCDSendData(unsigned char data);
void LCDSendCommand(unsigned char command);
void LCDPrintString(const unsigned char *string);
void LCDGotoXY(unsigned char x,unsigned char y);
extern int lcd_putchar(char c, FILE *stream);

// globals

volatile unsigned long ticks;
volatile int secs;

FILE lcd_str = FDEV_SETUP_STREAM(lcd_putchar, NULL, _FDEV_SETUP_WRITE);

#include "lcd.c"

int lcd_putchar(char c, FILE *stream) {
/*
 * Send character c to the LCD for use with printf
 */
	LCDSendData(c);
	return 0;
}
	
/*
 * Timer0 overflow interrupt handler. Counts system clock/8/250 -- provides global ticks at 4 kHz
 */

ISR(TIMER0_OVF_vect)
{
	static unsigned int pcount = 4000;	//4000 ticks per second

	TCNT0 = 6; 	ticks++; 	//reload counter; 250 to overflow
	if (pcount-- == 0) {  	//decrement tick counter and update runtime seconds
		secs++; pcount=4000;
		}
}

void timer_init(void) {

// set up Timer0 to provide 0.25 ms ticks

	TCCR0  = (1<<CS01);  //clock/8
	TIMSK |= (1<<TOIE0); // enable int on overflow
	TCNT0=6;	//250 counts to overflow
}

int main( void )
{
	long int now,then;
	int t,period,rpm;

	timer_init();
	LCDInit();
	stdout = &lcd_str;			// associate stream with stdout

	ticks=0;

	printf("RPM 0.1");
	Delay_ms(2000);				//allow user to admire the splash screen
	sei();						//enable timer interrupts

	//first pass synchronizes edges

	while( (PINC&(1<<PC5)) ==0);	//seeing white, wait till black
	while( (PINC&(1<<PC5)) !=0);	//seeing black, wait till white

	while(1){
	then=ticks;						//now time one full revolution
	while( (PINC&(1<<PC5)) ==0);	//seeing white, wait till black
	while( (PINC&(1<<PC5)) !=0);	//seeing black, wait till white
	now=ticks;
	period=now-then;

	rpm=2400000L/(long) period;		//convert to rpm*10 (1 rev/second = 4000 ticks)
	t=rpm%10; 						//one decimal point (avoid loading floating point routines)
	rpm=rpm/10;						//integer value

	LCDSendCommand(LCD_Clear);
	printf("rpm %d.%d",rpm,t);		//print rpm string
	LCDSendCommand(LCD_Line2);	
	printf("ms %d",period>>2);		//print period in milliseconds

	} //end while(1)

//end of main
}

/*
 *  Delay_us
 *
 *  wait in a loop for the specified number of microseconds.
 *
 */

void Delay_us( unsigned int microseconds )
{
    register unsigned int loop_count;
    /* 8mhz clock, 4 instructions per loop_count  */
    loop_count = microseconds<<1;

    __asm__ volatile (
        "1: sbiw %0,1" "\n\t"
        "brne 1b"
        : "=w" ( loop_count )
        : "0"  ( loop_count )
    );
}

/* Delay_ms
 *
 *  wait in a loop for the specified number of milliseconds.
 *
 */

void Delay_ms( unsigned int milliseconds )
{
    uint16_t i;

    for ( i = 0; i < milliseconds; ++i )
    {
        Delay_us( 1000 );
    }
}