Magnetic card reader revisited

[Ed Arnold]

<font face="Courier New" size=-1>First, I would like to thank PCM Programmer for posting code to help me a few weeks ago. But, even though it was well documented, it was way over my head. I took a look at the MicroChip's App Note 727 on reading Mag Stripes and this was much clearer to me. Currently, I am using a LCD to display results, but the final use of this reader will simply buffer the data for the Master uController to poll for it. This is the first time I have mixed 'C' and assembly. So, I am not sure what I have done wrong. By the looks of my 'list' file, everything looks like it should work. Have a look at my code. Currently, I am getting no data in the buffer and a 'hex 3F' for my flags. Which translates into start sentinal found, end sentinal found, parity error is true, LRC error is true, and there is a buffer overrun. The cards I am using have a start sentinal(;), 10 data bytes, and an end sentinal(?). I am reading track 2, which has 5 bit data width. My code mostly follows the App Note. Does anyone know what I have done wrong here.

Thanks in advance

Ed Arnold

#include <16f84.h>
#reserve 0x20,0x2F
#fuses HS, NOWDT, NOPROTECT
#use delay(clock=8000000)
#use fast_io(a)
#use fast_io(b)
#zero_ram

#include <lcd.c>

#define _CD PIN_A2 //Card Detect line (active low)
#define _CLK PIN_A3 //Card Clock Line (active low)
#define _CDATA PIN_A4 //Card Data Line (active low)
#define START_CODE 0x58
#define END_CODE 0xF8
#define STATUS 0x03
#define FSR 0x04
#define INDF 0x00
#bit C = STATUS.0
#bit Zero_Flag = STATUS.2
#define P 7

typedef enum {NULL, BUSY, BAD_SWIPE, INVALID, VALID} POLL;
POLL fCARD_POLL;

#define BUF_SIZE 16
char CR_buf[BUF_SIZE];
#locate CR_buf=0x20
int test=0;
int flags;
int PLRC;

#bit next_byte = test.0

#bit found_start = flags.0 // found start sentinel
#bit found_end = flags.1 // found end sentinel
#bit parity_err = flags.2 // bad parity
#bit LRC_err = flags.3 // bad LRC
#bit buf_end = flags.4 // end of buffer
#bit read_write = flags.5 // read / write flag

///............................................................................

main()
{
int i;
set_tris_a(0xFF);
lcd_init();
fCARD_POLL=NULL;
printf(lcd_putc,"Access Card Reader v1.0\n");
while(1)
{
while(input(_CD))
{
if(!flags)fCARD_POLL=NULL;
else if(flags==0x23)fCARD_POLL=VALID;
else fCARD_POLL=BAD_SWIPE;
switch(fCARD_POLL)
{
case NULL :
PLRC=START_CODE;
flags=0; // clear all flags
#asm
MOVLW 0x20 // load buffer pointer into W
MOVWF FSR // move pointer to FSR
#endasm
break;
case VALID :
for(i=0;i<16;i++)
{
lcd_goto_xy(i+1,2);
printf(lcd_putc,"\%c",CR_buf[i]);
}
break;
case BAD_SWIPE :
lcd_goto_xy(18,2);
printf(lcd_putc,"\%x \%d",flags, test);
for(i=0;i<16;i++)
{
lcd_goto_xy(i+1,2);
printf(lcd_putc,"\%c",CR_buf[i]);
}
break;
default:
lcd_goto_xy(20,2);
printf(lcd_putc,"\%d",fCARD_POLL);
break;
}

}
fCARD_POLL=BUSY;
LRC_err=1;
while(input(_CLK))
{
if(next_byte)
{
#asm
RLF CR_buf // discard parity pit by shfting out
SWAPF CR_buf,W // swap nibbles, put data in lower nibble
ANDLW 0x3F // convert to ASCII
MOVWF CR_buf // move back into buffer
INCF FSR,F // inrement buffer pointer FSR++
MOVLW 0x0F // find end of buffer and loop
ANDWF FSR,F // if end is reached
BTFSS Zero_Flag // set buffer end
BSF buf_end // buffer overrun error
BCF PLRC,P // clear parity bit
CLRF CR_buf // clear next buffer byte
BSF CR_buf,4 // set 'check bit'
BCF next_byte
#endasm
}
}
if(input(_CDATA)) //get next incoming bit
{
#asm // data is inverted
BCF STATUS,0 // data bit is '0' clear carry flag
#endasm
}
else
{
#asm
BSF STATUS,0 // data bit is '1' set carry flag
MOVLW 0x80 // toggle parity bit in
XORWF PLRC,F // PLRC register
#endasm
}
#asm
RRF CR_buf // shift bit in current btye
BTFSS STATUS,0 // test carry flag for 'check bit'
GOTO test_start // test for start sentinal
BTFSS PLRC,P // test parity bit, if '1' passed
BSF parity_err // set parity error flag
MOVF CR_buf,W // update LRC nibble
XORWF PLRC,F // test LRC bit if '0' passed
//.............................................................
BTFSS found_end // was end sentinal found before
GOTO test_end // test for end sentinal
MOVF PLRC,W // load LRC into W
ANDLW 0x78 // mask off unwanted bits
BTFSC Zero_Flag // test LRC if '0' passed
BCF LRC_err // clear LRC error flag
BSF read_write // set read_write bit
GOTO end // done ready for read
//.............................................................
test_end:
MOVLW END_CODE // load end code into W
XORWF CR_buf,W // compare with end code
BTFSC Zero_Flag // is this the end sentinal?
BSF found_end // set found_end flag
GOTO next // prepare for next byte
//.............................................................
test_start:
BTFSC found_start // was start sentinal found before
GOTO end // yes, go to end
MOVLW 0xF8 // load mask into W
ANDWF CR_buf // mask current byte in buffer
MOVLW START_CODE // load start code into W
XORWF CR_buf,W // compare with start code
BTFSS Zero_Flag // is this the start sential?
GOTO end
BSF found_start // set found_start flag
//...........................................................
next:
BSF next_byte
end:
#endasm
while(!input(_CLK));
}
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 8861

[Ed Arnold]

Adding 'Please Help' seems to work for others so I'll try it. I have made very little progress with this code. I am not sure if my use of #reserve and #locate are correct. I am tring to use the same ram loctions for a buffer. So the 'C' code and assembly use the same buffer. I am not sure if my use of FSR and INDF is correct either. I have placed test points all over. At the end of a swipe, the FSR is 0x2E, which doesn't make sense. I also use test2 to see how many times next_byte routine is run. That equals 12 times which is correct for the cards I am using. Does anyone know what could be happening?

Thanks in advance

Ed Arnold

:=#include <16f84.h>
:=#reserve 0x20,0x2F
:=#fuses HS, NOWDT, NOPROTECT
:=#use delay(clock=8000000)
:=#use fast_io(a)
:=#use fast_io(b)
:=#zero_ram
:=
:=#include <lcd.c>
:=
:=#define _CD PIN_A2 //Card Detect line (active low)
:=#define _CLK PIN_A3 //Card Clock Line (active low)
:=#define _CDATA PIN_A4 //Card Data Line (active low)
:=#define START_CODE 0x58
:=#define END_CODE 0xF8
:=#define STATUS 0x03
:=#define FSR 0x04
:=#define INDF 0x00
:=#bit C = STATUS.0
:=#bit Zero_Flag = STATUS.2
:=#define P 7
:=
:=typedef enum {NULL, BUSY, BAD_SWIPE, INVALID, VALID} POLL;
:=POLL fCARD_POLL;
:=
:=#define BUF_SIZE 16
:=char CR_buf[BUF_SIZE];
:=#locate CR_buf=0x20
:=int test=0;
:=int flags;
:=int PLRC;
:=
:=#bit next_byte = test.0
:=
:=#bit found_start = flags.0 // found start sentinel
:=#bit found_end = flags.1 // found end sentinel
:=#bit parity_err = flags.2 // bad parity
:=#bit LRC_err = flags.3 // bad LRC
:=#bit buf_end = flags.4 // end of buffer
:=#bit read_write = flags.5 // read / write flag
:=
:=///............................................................................
:=
:=main()
:={
:= int i;
:= set_tris_a(0xFF);
:= lcd_init();
:= fCARD_POLL=NULL;
:= printf(lcd_putc,"Access Card Reader v1.0\n");
:= while(1)
:= {
:= while(input(_CD))
:= {
:= if(!flags)fCARD_POLL=NULL;
:= else if(flags==0x23)fCARD_POLL=VALID;
:= else fCARD_POLL=BAD_SWIPE;
:= switch(fCARD_POLL)
:= {
:= case NULL :
:= PLRC=START_CODE;
:= flags=0; // clear all flags
:= #asm
:= MOVLW 0x20 // load buffer pointer into W
:= MOVWF FSR // move pointer to FSR
:= #endasm
:= break;
:= case VALID :
:= for(i=0;i<16;i++)
:= {
:= lcd_goto_xy(i+1,2);
:= printf(lcd_putc,"\%c",CR_buf[i]);
:= }
:= break;
:= case BAD_SWIPE :
:= lcd_goto_xy(18,2);
:= printf(lcd_putc,"\%x \%d",flags, test2);
:= for(i=0;i<16;i++)
:= {
:= lcd_goto_xy(i+1,2);
:= printf(lcd_putc,"\%c",CR_buf[i]);
:= }
:= break;
:= default:
:= lcd_goto_xy(20,2);
:= printf(lcd_putc,"\%d",fCARD_POLL);
:= break;
:= }
:=
:= }
:= fCARD_POLL=BUSY;
:= LRC_err=1;
:= while(input(_CLK))
:= {
:= if(next_byte)
:= {
:= test2++; // test how many times entered here
:= #asm
:= RLF CR_buf // discard parity pit by shfting out
:= SWAPF CR_buf,W // swap nibbles, put data in lower nibble
:= ANDLW 0x3F // convert to ASCII
:= MOVWF CR_buf // move back into buffer
:= INCF FSR,F // inrement buffer pointer FSR++
:= MOVLW 0x0F // find end of buffer and loop
:= ANDWF FSR,F // if end is reached
:= BTFSC Zero_Flag // set buffer end
:= BSF buf_end // buffer overrun error
:= BCF PLRC,P // clear parity bit
:= CLRF CR_buf // clear next buffer byte
:= BSF CR_buf,4 // set 'check bit'
:= BCF next_byte
:= #endasm
:= }
:= }
:= if(input(_CDATA)) //get next incoming bit
:= {
:= #asm // data is inverted
:= BCF STATUS,0 // data bit is '0' clear carry flag
:= #endasm
:= }
:= else
:= {
:= #asm
:= BSF STATUS,0 // data bit is '1' set carry flag
:= MOVLW 0x80 // toggle parity bit in
:= XORWF PLRC,F // PLRC register
:= #endasm
:= }
:= #asm
:= RRF CR_buf // shift bit in current btye
:= BTFSS STATUS,0 // test carry flag for 'check bit'
:= GOTO test_start // test for start sentinal
:= BTFSS PLRC,P // test parity bit, if '1' passed
:= BSF parity_err // set parity error flag
:= MOVF CR_buf,W // update LRC nibble
:= XORWF PLRC,F // test LRC bit if '0' passed
:= //.............................................................
:= BTFSS found_end // was end sentinal found before
:= GOTO test_end // test for end sentinal
:= MOVF PLRC,W // load LRC into W
:= ANDLW 0x78 // mask off unwanted bits
:= BTFSC Zero_Flag // test LRC if '0' passed
:= BCF LRC_err // clear LRC error flag
:= BSF read_write // set read_write bit
:= GOTO end // done ready for read
:= //.............................................................
:= test_end:
:= MOVLW END_CODE // load end code into W
:= XORWF CR_buf,W // compare with end code
:= BTFSC Zero_Flag // is this the end sentinal?
:= BSF found_end // set found_end flag
:= GOTO next // prepare for next byte
:= //.............................................................
:= test_start:
:= BTFSC found_start // was start sentinal found before
:= GOTO end // yes, go to end
:= MOVLW 0xF8 // load mask into W
:= ANDWF CR_buf // mask current byte in buffer
:= MOVLW START_CODE // load start code into W
:= XORWF CR_buf,W // compare with start code
:= BTFSS Zero_Flag // is this the start sential?
:= GOTO end
:= BSF found_start // set found_start flag
:= //...........................................................
:= next:
:= BSF next_byte
:= end:
:= #endasm
:= while(!input(_CLK));
:= }
:=}
:= ___________________________
This message was ported from CCS's old forum
Original Post ID: 8936

[Laurent chouinard]

I don't know about others, but I'm certainly not an expert in assembly, which is why I bought CCS's compiler. From what I see in your code, there's a heck of a lot of ASM code!! I can't really grasp what your program is doing because frankly, I don't really like assembly...

About adding "Please help" to gain more attention, i bet that the reason you had no reply yet is because it's mostly ASM code and we're all a bunch of C programmers :)

Laurent

:=Adding 'Please Help' seems to work for others so I'll try it. I have made very little progress with this code. I am not sure if my use of #reserve and #locate are correct. I am tring to use the same ram loctions for a buffer. So the 'C' code and assembly use the same buffer. I am not sure if my use of FSR and INDF is correct either. I have placed test points all over. At the end of a swipe, the FSR is 0x2E, which doesn't make sense. I also use test2 to see how many times next_byte routine is run. That equals 12 times which is correct for the cards I am using. Does anyone know what could be happening?
:=
:=Thanks in advance
:=
:=Ed Arnold
:=
:=:=#include <16f84.h>
:=:=#reserve 0x20,0x2F
:=:=#fuses HS, NOWDT, NOPROTECT
:=:=#use delay(clock=8000000)
:=:=#use fast_io(a)
:=:=#use fast_io(b)
:=:=#zero_ram
:=:=
:=:=#include <lcd.c>
:=:=
:=:=#define _CD PIN_A2 //Card Detect line (active low)
:=:=#define _CLK PIN_A3 //Card Clock Line (active low)
:=:=#define _CDATA PIN_A4 //Card Data Line (active low)
:=:=#define START_CODE 0x58
:=:=#define END_CODE 0xF8
:=:=#define STATUS 0x03
:=:=#define FSR 0x04
:=:=#define INDF 0x00
:=:=#bit C = STATUS.0
:=:=#bit Zero_Flag = STATUS.2
:=:=#define P 7
:=:=
:=:=typedef enum {NULL, BUSY, BAD_SWIPE, INVALID, VALID} POLL;
:=:=POLL fCARD_POLL;
:=:=
:=:=#define BUF_SIZE 16
:=:=char CR_buf[BUF_SIZE];
:=:=#locate CR_buf=0x20
:=:=int test=0;
:=:=int flags;
:=:=int PLRC;
:=:=
:=:=#bit next_byte = test.0
:=:=
:=:=#bit found_start = flags.0 // found start sentinel
:=:=#bit found_end = flags.1 // found end sentinel
:=:=#bit parity_err = flags.2 // bad parity
:=:=#bit LRC_err = flags.3 // bad LRC
:=:=#bit buf_end = flags.4 // end of buffer
:=:=#bit read_write = flags.5 // read / write flag
:=:=
:=:=///............................................................................
:=:=
:=:=main()
:=:={
:=:= int i;
:=:= set_tris_a(0xFF);
:=:= lcd_init();
:=:= fCARD_POLL=NULL;
:=:= printf(lcd_putc,"Access Card Reader v1.0\n");
:=:= while(1)
:=:= {
:=:= while(input(_CD))
:=:= {
:=:= if(!flags)fCARD_POLL=NULL;
:=:= else if(flags==0x23)fCARD_POLL=VALID;
:=:= else fCARD_POLL=BAD_SWIPE;
:=:= switch(fCARD_POLL)
:=:= {
:=:= case NULL :
:=:= PLRC=START_CODE;
:=:= flags=0; // clear all flags
:=:= #asm
:=:= MOVLW 0x20 // load buffer pointer into W
:=:= MOVWF FSR // move pointer to FSR
:=:= #endasm
:=:= break;
:=:= case VALID :
:=:= for(i=0;i<16;i++)
:=:= {
:=:= lcd_goto_xy(i+1,2);
:=:= printf(lcd_putc,"\%c",CR_buf[i]);
:=:= }
:=:= break;
:=:= case BAD_SWIPE :
:=:= lcd_goto_xy(18,2);
:=:= printf(lcd_putc,"\%x \%d",flags, test2);
:=:= for(i=0;i<16;i++)
:=:= {
:=:= lcd_goto_xy(i+1,2);
:=:= printf(lcd_putc,"\%c",CR_buf[i]);
:=:= }
:=:= break;
:=:= default:
:=:= lcd_goto_xy(20,2);
:=:= printf(lcd_putc,"\%d",fCARD_POLL);
:=:= break;
:=:= }
:=:=
:=:= }
:=:= fCARD_POLL=BUSY;
:=:= LRC_err=1;
:=:= while(input(_CLK))
:=:= {
:=:= if(next_byte)
:=:= {
:=:= test2++; // test how many times entered here
:=:= #asm
:=:= RLF CR_buf // discard parity pit by shfting out
:=:= SWAPF CR_buf,W // swap nibbles, put data in lower nibble
:=:= ANDLW 0x3F // convert to ASCII
:=:= MOVWF CR_buf // move back into buffer
:=:= INCF FSR,F // inrement buffer pointer FSR++
:=:= MOVLW 0x0F // find end of buffer and loop
:=:= ANDWF FSR,F // if end is reached
:=:= BTFSC Zero_Flag // set buffer end
:=:= BSF buf_end // buffer overrun error
:=:= BCF PLRC,P // clear parity bit
:=:= CLRF CR_buf // clear next buffer byte
:=:= BSF CR_buf,4 // set 'check bit'
:=:= BCF next_byte
:=:= #endasm
:=:= }
:=:= }
:=:= if(input(_CDATA)) //get next incoming bit
:=:= {
:=:= #asm // data is inverted
:=:= BCF STATUS,0 // data bit is '0' clear carry flag
:=:= #endasm
:=:= }
:=:= else
:=:= {
:=:= #asm
:=:= BSF STATUS,0 // data bit is '1' set carry flag
:=:= MOVLW 0x80 // toggle parity bit in
:=:= XORWF PLRC,F // PLRC register
:=:= #endasm
:=:= }
:=:= #asm
:=:= RRF CR_buf // shift bit in current btye
:=:= BTFSS STATUS,0 // test carry flag for 'check bit'
:=:= GOTO test_start // test for start sentinal
:=:= BTFSS PLRC,P // test parity bit, if '1' passed
:=:= BSF parity_err // set parity error flag
:=:= MOVF CR_buf,W // update LRC nibble
:=:= XORWF PLRC,F // test LRC bit if '0' passed
:=:= //.............................................................
:=:= BTFSS found_end // was end sentinal found before
:=:= GOTO test_end // test for end sentinal
:=:= MOVF PLRC,W // load LRC into W
:=:= ANDLW 0x78 // mask off unwanted bits
:=:= BTFSC Zero_Flag // test LRC if '0' passed
:=:= BCF LRC_err // clear LRC error flag
:=:= BSF read_write // set read_write bit
:=:= GOTO end // done ready for read
:=:= //.............................................................
:=:= test_end:
:=:= MOVLW END_CODE // load end code into W
:=:= XORWF CR_buf,W // compare with end code
:=:= BTFSC Zero_Flag // is this the end sentinal?
:=:= BSF found_end // set found_end flag
:=:= GOTO next // prepare for next byte
:=:= //.............................................................
:=:= test_start:
:=:= BTFSC found_start // was start sentinal found before
:=:= GOTO end // yes, go to end
:=:= MOVLW 0xF8 // load mask into W
:=:= ANDWF CR_buf // mask current byte in buffer
:=:= MOVLW START_CODE // load start code into W
:=:= XORWF CR_buf,W // compare with start code
:=:= BTFSS Zero_Flag // is this the start sential?
:=:= GOTO end
:=:= BSF found_start // set found_start flag
:=:= //...........................................................
:=:= next:
:=:= BSF next_byte
:=:= end:
:=:= #endasm
:=:= while(!input(_CLK));
:=:= }
:=:=}
:=:= ___________________________
This message was ported from CCS's old forum
Original Post ID: 9020