relay.c

MICROCHIP pic-demo板 液晶官方驱动

#include	<pic.h>

/*
 *	Interrupt demo for PIC; wait for button press on RB0/INT,
 *	turn on a relay on another port bit for a period of time.
 *
 *	Copyright (C)1997 HI-TECH Software.
 *	Freely distributable.
 */


/*	Defines; change as appropriate */

#define	XTAL		4MHz		// crystal frequency
#define	CLKINTR		250		// microseconds per clock interrupt

static bit		RELAY @ (unsigned)&PORTB*8+7;	// use this bit to drive
							// the relay - active low.

#define	OFF		1		// bit is 1 to turn off
#define	ON		0		// and 0 to turn on
#define	RELAY_TIME	1000ms		// how long to turn the relay on for

/* this stuff is not likely to change */

#define	MHz		*1000000	// this many cycles to megahertz
#define	CLKDIV		4l		// xtal is divided by this many
#define	ms		*1000l		// this many microseconds in a millisecond

static unsigned int	relay_timer;	// timer value for relay driver

#define	TIMER_RELOAD	((((XTAL)/CLKDIV)*CLKINTR)/1000000)
#define	RELAY_VALUE	((RELAY_TIME)/(CLKINTR))

void
main(void)
{
	/* setup stuff */

	RELAY = OFF;		// ensure relay is off before enabling output
	TRISB = 0x3F;		// Port B bits 7 and 6 are output 
	T0CS = 0;		// Timer increments on instruction clock
	T0IE = 1;		// Enable interrupt on TMR0 overflow
	INTEDG = 0;		// falling edge trigger the interrupt
	INTE = 1;		// enable the external interrupt
	GIE = 1;		// Global interrupt enable
	for(;;)
		CLRWDT();	// Idly kick the dog
}

static void interrupt
isr(void)			// Here be interrupt function - the name is
				// unimportant.
{
	if(T0IF) {				// timer interrupt
		TMR0 -= TIMER_RELOAD;		// reload the timer
		T0IF = 0;			// clear the interrupt flag
		if(relay_timer != 0)		// is the relay timer running?
			relay_timer--;		// decrement it
		if(relay_timer == 0)		// if it has time out
			RELAY = OFF;		// turn the relay off
		PORTB ^= 0x40;			// toggle a bit to say we're alive
	}
	if(INTF) {				// did we see a button press?
		RELAY = ON;			// turn the relay on
		relay_timer = RELAY_VALUE;	// start the timer
		INTF = 0;			// clear the interrupt
	}
}