a2demo.c

pic单片机例程

#include <htc.h>

/* Basic A2D sample code for an PIC16F87x device.
 * This code willl set up the A2D module to return an
 * 8-Bit result. If greater precision is needed, a 10-Bit
 * result can be returned if read_a2d() is modified to
 * return the short ((ADRESH<<8)+(ADRESL)). Note also that
 * ADCON1 should be set to 0x80 in the init_a2d() routine
 * instead of zero.
 *
 * This code will sample an A2D value on analog port RA0, and it's value
 * will be used to move a LED's position across PORTB.
 *
 * This project can be demonstrated on the Microchip PICDEM2 board.
 */

__CONFIG(DEBUGEN & WDTDIS & LVPDIS);	// Setup the configuration word for ise with ICD2

/* Sample code to set up the A2D module */
void init_a2d(void){
	ADCON0=0;	// select Fosc/2
	ADCON1=0;	// select left justify result. A/D port configuration 0
	ADON=1;		// turn on the A2D conversion module
}

/* Return an 8 bit result */
unsigned char read_a2d(unsigned char channel){
	channel&=0x07;	// truncate channel to 3 bits
	ADCON0&=0xC5;	// clear current channel select
	ADCON0|=(channel<<3);	// apply the new channel select
	ADGO=1;	// initiate conversion on the selected channel
	while(ADGO)continue;
	return(ADRESH);	// return 8 MSB of the result
}

void main(void){
	unsigned char x;

	init_a2d();	// initialise the A2D module
	GIE=0;		// we don't want interrupts
	TRISB=0xF0;	// the lower four bits of POTRB will be used in output mode
	
	for(;;){
		x=read_a2d(1);		// sample the analog value on RA0
		PORTB = (8>>(x>>6));	// Use the 2 MS Bits of the result to select the bit position of the LED on PORTB
	}
}