/*
	A program to read out an ADC 08031 from the parallel port.
	Currently hooked up: 6 LEDs on the data pins D0...D5
	ADC's chipselect on D6 (pc->adc), clock on D7 (pc->adc), data out on BUSY (adc->pc)
	Software by Michiel Overtoom, motoom@xs4all.nl, november 2007 
	Uses FreeBSD's ppi 'geek' interface
 */

#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <time.h>
#include <dev/ppbus/ppi.h>
#include <dev/ppbus/ppbconf.h>

/* Handle of parallel port /dev/ppiN */
int fd=-1;

/* mirrors current value of data port */
u_int8_t val=0;

/* current value of status port */
u_int8_t inval=0;


// Chip select to ADC 08031
void cs(int hi)
{
	if (hi)
		val|=0x40;
	else
		val&=0xbf;
	ioctl(fd,PPISDATA,&val);
}


// Clock to ADC 08031
void clk(int hi)
{
	if (hi)
		val|=0x80;
	else
		val&=0x7f;
	ioctl(fd,PPISDATA,&val);
}


// LEDs are on D0...D5
void leds(unsigned char ledpart)
{
	ledpart&=0x3F;
	val&=0xC0;
	val|=ledpart;
	ioctl(fd,PPISDATA,&val);
}


// Data out from ADC 08031
int d0(void)
{
	ioctl(fd,PPIGSTATUS,&inval);
	return (inval&0x80)==0; // high bit of status port is the BUSY line, which is active low
}


main()
{
  char *device="/dev/ppi0";

  fd=open("/dev/ppi0",O_RDWR);
  if (fd==-1) {
	printf("Can't open %s: %s\n",device,strerror(errno));
	exit(1);
  	}

	// Initialize; data port 0, CS and CLK high
	val=0;
	cs(1);
	clk(1);
	usleep(100000);
	
	for (;;) {
		printf("Start conversion: ");
		// start conversion
		clk(0);
		cs(0);
		clk(1);
		clk(0);
		int i;
		unsigned char adc=0;
		for (i=0;i<8;i++) {
			adc<<=1;
			clk(1);
			clk(0);
			if (d0()) {
				adc|=1;
				printf("1");
				}
			else
				printf("0");
			}
		printf("  0x%02X  %3d\n",adc,adc);
		// end of conversion, return to normal
		cs(1);	
		clk(1);
		// display result on LEDs
		int lit=adc*6/255;
		unsigned char ledval=0;
		for (i=0;i<lit;i++) {
			ledval<<=1;
			ledval|=1;
			}
		leds(ledval);
		// wait a bit and do it again
		usleep(100000);
		}			
	close(fd);
	exit(0);
}

// TODO: Push it to the max. The ADC 08031 still works at a clock of of 1.750 Mhz.