a2demo.c

picc_18v 8.35pl35 PIC18系列单片机开发C编译器

#include <pic18.h>
#include "a2demo.h"
#include <stdio.h>

void init(void);
void putch(unsigned char);

volatile unsigned char CHANNEL = 0;	/* current analog input channel selected */
volatile unsigned char LEDCHAN = 1;	/* show which LED to light, corresponds to channel */

void main(void)
{
	unsigned char volts;
	unsigned char decivolts;
	unsigned char last_value;
	unsigned char last_channel=2;	// to force an update at startup
	
	init();
	
	while(1)
	{
		/* update the channel select LEDS */
		PORTD=LEDCHAN;
		/* update A2D configuration control */
		/* result is left justified */
		ADCON1=(PORTC&0x0F);
		/* update the channel to the A2D converter */
		CHS0=(CHANNEL&0b00000001);
		CHS1=((CHANNEL&0b00000010)>>1);
		CHS2=((CHANNEL&0b00000100)>>2);
			
		/* request the A2D conversion */
		GODONE=1;
		while(GODONE)continue;
		ADIF=0;
		if((ADRESH!=last_value)||(CHANNEL!=last_channel))
		{
		/* if update required, output the results */
		/* calculate the output voltage */
			volts=0;
			for(decivolts=(ADRESH*50/255);decivolts>=10;decivolts-=10)
				volts++;
			printf("%cChannel %d has %d.%d volts.  ",0x0D,(CHANNEL&0x07),volts,decivolts);
		}
		last_value=ADRESH;
		last_channel=CHANNEL;
	}
}

void init(void)
{
	RBIE=1;	/* enable PORTB interrupts so that */
	GIEH=1;	/* pushbuttons can be used to change */
	GIEL=1;	/* A2D channel select */
	
	TXEN=1;	/* enable serial port transmissions */
	SPEN=1;	
	TXIE=0;	/* not interrupt driven */		
	
	TRISA=0x2F;	/* Some PORTA pins are analog input channels */
	TRISB=0x30;	/* Pushbutton switches to change channel are on PORTB */
	PORTB=0;
	TRISD=0;	/* LED panel to indicate current channel is on PORTD */
	TRISC=0x0F;/* switch panel to control A2D config is on PORTC */
	TRISE=0x07;	/* Some PORTE inputs are analog input channels */
	
	ADON=1;	/* enable A2D converter */
	ADIE=0;	/* not interrupt driven */
	ADCON1=0b00000000;

}

void putch(unsigned char c)
{
	TXREG=c;	/* transmit a character to Serial IO */
	while(!TXIF)continue;
	TXIF=0;
}