/* Nick Chernyy <nico@routed.net> 		*/
/* simple, three control line card reader 	*/
/* not optimized, so read card slowly 		*/


#include <at89x51.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* stolen from http://www.cse.cuhk.edu.hk/~khwong/ceg3430/mrobot5.pdf */

char getch() {	
	char cin;
	_asm
		push ACC
	_endasm;
	_asm
		lcall 0x0032;
	_endasm;
	cin=ACC;
	_asm
		pop ACC
	_endasm;
	return(cin);
}

void putchar(char cout) {
	/* send '\n' for a new line and '\r' for a return */
	ACC=cout;
	_asm
		lcall 0x0030;
	_endasm;
}

void phex(char i) {
	/* prints a 8 bit number as 2 digit hex */
	ACC=i;
	_asm
		lcall 0x0034;
	_endasm;
}

void putstr(char *c) {
        int i = 0;
        while (c[i] != 0) {
                putchar(c[i]);
                i++;
        }
}

/* CLD2 -> P1.0  (goes low when card is present)*/
/* RCL2 -> P1.1  (goes low when clock is "high")*/
/* RDT2 -> P1.2  (low for data 1 and high for data 0)*/

void main (void) {
	/* to wait for hardware to initialize */
	int i,j,l;
	int k[16];
	char c, e[2];
	char d[] = "magnetic card reader v10^-6 (nico@routed.net)\n\r\0";
	putstr(d);
	P1 = 0xFF;
	
	while (1) {
		for (i = 0; i < 255; i++) {
			for (j = 0; j < 128; j++) {
				c = P1;
			}
		}
		j = 0;
		while (P1_0 == 1);
		/* we have a card! */
		while (P1_0 == 0) {
			for (i = 0; i < 16; i++) {
				while ((P1_1 == 1) && (P1_0 == 0));
					if (P1_2 == 0) {
						k[j]++;
					}
					k[j] = k[j] << 1;
				while ((P1_1 == 0) && (P1_0 == 0));
				if (P1_0 == 1) {
					break;
				}
			}
			j++;
		}
		/* we read all of the bits, but they dont get shifted out right */
		/* this is because we had to wait for serial io for each bit */
		memcpy(e,&j,2); /* to print the number of bytes read */
		phex(e[1]);
		phex(e[0]);
		putchar(':');
		putchar('0');
		putchar('x');
		/* this next code will skip the leading zeros and the trailing zeros */
		i = 0;
		while ((k[i] == 0) && (i < 16)) {
			i++;
		}
		j = i;
		l = 0;
		while (j < 16) {
			if (k[j] != 0) {
				l = j;
			}
			j++; 
		}
		for (; i < l; i++ ) {
			memcpy(e, &k[i], 2);
			phex(e[1]); /* high byte */
			phex(e[0]); /* low byte */
		}
		putchar('\n');
		putchar('\r');

		for (i = 0; i < 16; i++) {
			k[i] = 0; /* dont want to include bzero */
		}
	}
}