zero_pwr.c

这是《并行口编程指南》的附盘的源代码 很有参考价值哦

/*zero_pwr.c*/
#include <stdio.h>
#include <dos.h>
#include <conio.h>
#include <process.h>
						/* C3* C2 C1* C0* */
#define RESET_VALUE		0X04		/* 0   1  0   0   */
#define START_ADC_CONV		0X0c		/* 1   1  0   0	  */
#define READ_UPPER_NIBBLE	0X01		/* 0   0  0   1   */
#define	READ_LOWER_NIBBLE	0X02		/* 0   0  1   0   */


void main(void)
{
int modem_control_reg, dport_lpt1, cport_lpt1, sport_lpt1;
unsigned char adc_status, adc_val, upper_nib, lower_nib, intr_status;

/* Sign ON */
clrscr();
printf("Zero Power (Well, almost!) ADC for the printer adapter, Version 1.0");
printf("\nD.V.GADRE");

/* Get COM1 register address */

modem_control_reg = peek(0x40,0)+4;
if(modem_control_reg == 4)
	{printf("\n\n\nCOM1 not available... aborting\n\n\n");
	exit(1);
	}
printf("\n\n\nCOM1 address = %X",peek(0x40,0) );

/*Get LPT1 port addresses */

dport_lpt1 = peek(0x40,0x08);
if(dport_lpt1 ==0)
	{
	printf("\n\n\nLPT1 not available... aborting\n\n\n");
	exit(1);
	}
printf("\nLPT1 address = %X", dport_lpt1);
cport_lpt1 = dport_lpt1 +2; 	/* control port address */
sport_lpt1 = dport_lpt1 + 1;	/* status port address */

/* put power On on COM1 */
outportb(modem_control_reg, 03);
printf("\nPutting Power ON...");

/* check if ADC is connected & working*/

/*start ADC conversion & wait for 1 ms, this puts INTR to logic '0' */

/* reset the control port */
outportb(cport_lpt1, RESET_VALUE);
sleep(1);
/* start conversion */
outportb(cport_lpt1, START_ADC_CONV);
outportb(cport_lpt1, RESET_VALUE );
sleep(1);

/* hopefully the conversion is over, so read the INTR status */
/* if everything is OK, INTR should be '0' */

adc_status = inportb(sport_lpt1) & 0x08;
outportb(cport_lpt1, READ_LOWER_NIBBLE);
outportb(cport_lpt1, RESET_VALUE);


/* read the INTR status again */
/* if everything is OK, INTR should be '1' */
intr_status = inportb(sport_lpt1) & 0x08;

if( !( (adc_status == 0) && (intr_status == 0x08) )  )
		{ printf("\n\n\nADC not connected... aborting\n\n\n");
		exit(1);
		}



/* acquire ADC sample */

while(!kbhit())

		{
			outportb(cport_lpt1, RESET_VALUE);

start_conv:		outportb(cport_lpt1, START_ADC_CONV);
			outportb(cport_lpt1, RESET_VALUE);

wait_for_conv:		adc_status = inportb(sport_lpt1) & 0x08;
			while(adc_status)
			{
			adc_status = inportb(sport_lpt1) & 0x08;
			}

read_upper_nibble:      outportb(cport_lpt1, READ_UPPER_NIBBLE);
			upper_nib = inportb(sport_lpt1) & 0x0f0;
			outportb(cport_lpt1, RESET_VALUE);

read_lower_nibble:	outportb(cport_lpt1, READ_LOWER_NIBBLE);
			lower_nib = inportb(sport_lpt1) >> 4;
			outportb(cport_lpt1, RESET_VALUE);
	adc_val = (lower_nib | upper_nib) ^ 0x88;
	delay(10);
	printf("sample = %X ", adc_val);


		}

}