Subject: Mag Stripe Card Info SUMMARY (long)
From: tmkk@uiuc.edu (K. Khan)
Date: 14 Jan 92 16:33:04 GMT
Summary of information on the SR&D MCR-175-1R-0803 mag stripe card reader. Due to the large volume of summary requests I received, I am posting this summary instead of mailing it. It's somewhat long, so hit 'n' now if you're not interested in this stuff.

[Editor's Note: The following is a concatenation of the replies I received to a net.request about my mag stripe card reader. After the replies I have included some software that I threw together to play with the card reader. This file contains all the information I have on this subject. Additions are most welcome. Note also that there was another summary post in recent days with information on how the data on the cards is encoded. See article for this info.

You'll notice I didn't get any farther than simply reading the raw signal from the card; of the two card readers I ordered, one was completely DOA, and the other had a faulty clock output (at least I assume that it was a clock output; I was never able to read any sort of signal from that line). Someone with a fully functional reader can easily extend what I wrote to get it to decode the actual data content of the card. If you do decide to make modifications and/or extensions, I'd appreciate a copy of whatever changes you make (email to tmkk@uiuc.edu). Enjoy!]

Subject: Re: Mag Card Swipe Reader: Need Help

I am truly amazed that someone else is trying to use this device! I got mine about 2 years ago and spent some time trying to find the manufacturer. I found a listing for SR&D in the Noth America technical directory at the public library. I found the listing for the American sales office in Los Angeles. I tried calling but the company had gone out of business. There was no listing in the local phone directory either. I then tried calling the head office in Japan, but they also had gone out of business. I haven't seen the company listed in any recent electronics directories, so I think they really are gone.

I have spent about an hour looking at the signals on the outputs of the device. One signal line is a /STATUS line which indicates when a card is been moved through the unit. The other 2 lines pulse in response to a magnetic card. I believe the IC performs Manchester decoding and clock recovery for the read channel, so one output line is DATA and the other is CLOCK.

That is as far as I got 2 years ago and I had forgot about it until now. If you receive any other info, please send a copy to me!

Finally, there are 5 wires coming from the assembly and terminating in a small connector similar to power supply connectors for 3.5" floppy drives. The wires are red, yellow, green, blue, and black.

If its anything like the units I worked with, I think you will find that the five wires are:

 
        +5v
	Gnd
	Clock
	Data
	Card detected
 
But I don't know active levels, or which wire is what.
I picked few week ago a magnetic credit card reader from a another surplus outfit. It cost about the sam es yours. My card reader was made by MAGTEK and was diffrent from your reder in many ways. The reader I have has 4 ICs and some of them are standard TTL chip, so I could easily quess the power requiments (5V) and power connectors. My card reader had 6 pin connector. I put the power to the reader and started to examine the signals with multimeter and a little crystal earphine (my favourite electronics hacking tool). I found that output signals were something like that: data out, data clock out, data readable and and card ath the end of the reader. Then I connected the reader to the joystick port of my 386SX and made a little Turbo Pascal program for reading the card.

Spare printer port is the interface I use very often to connect diffrent hardware circuit to my computer. This time I decided to use game port beacuse it can also provide the power to the reader.

My program simply prints out the bits from the card. I have not found the way to decode the bits to corresponding numbers. The program so prints all 237 bits form the card to screen. If you have any information about data coding, I an interrested in hearing that.

Here is the meanings of the bytes in port $201:
D7: 0 -> card pushed to the end of the reader
D6: the read data from card
D5: 0 -> data stream readable
D4: the data clock

Program CardReader;
 
Uses Crt,Binary;
 
Const
   gameport=$201;
 
 
Procedure Wait_start;
Begin
   Repeat Until (Port[gameport] and 32)=0;
End;
 
Function data_readable:boolean;
Begin
   data_readable:=((Port[gameport] and 32)=0);
End;
 
Procedure Wait_clock;
Begin
   Repeat Until (Port[gameport] and 16)=0;
End;
 
Procedure Wait_clock_end;
Begin
   Repeat Until (Port[gameport] and 16)=16;
End;
 
Function data_input:byte;
Begin
   If (Port[gameport] and 64)=0 Then data_input:=0
      Else data_input:=1;
End;
 
Function card_at_end:boolean;
Begin
   card_at_end:=((Port[gameport] and 128)=0);
End;
 
Procedure test;
Begin
   Wait_start;
   Repeat
      Writeln(ByteBin(Port[$201]));
   Until keypressed;
End;
 
Begin
   ClrScr;
   Wait_start;
   While data_readable Do Begin
      Wait_clock;
      Write(data_input);
      Wait_clock_end;
   End;
   Repeat Until KeyPressed;
End.


Wiring color code for the SR&D MCR-175-1R-0803 mag stripe card reader: Red: +5V Black: Gnd Yellow: /Card Detect Green: Clock (?? - non-functional on the unit I have) Blue: /Data The leading '/' indicates an active low TTL signal.

Quick 'n Dirty guide to the enclosed reader software

Hooking the SR&D MCR-175-1R-0803 card reader to your PC:

The included software is written specifically for the following configuration; if your wiring is different, you'll need to make corresponding changes to the software. Note also that the port address is hard-coded to look for LPT2's status port (at address 0x279). If you're using a different port address, be sure to change the port address value.

SR&D Wire       Printer Port Pin        Port Bit        Signal
---------       ----------------        --------        ------
Yellow          11                      7               /CARD DETECT
Blue            10                      6               /DATA
Black           18                      N/A             (Ground)
Power to the reader was provided by a separate power supply, basically one of those black plastic DC power packs fed through a 7805 regulator chip.

Compiling the software:

Compile SWIPE.C (using SMALL memory model), assemble SWIPEISR.ASM, and link the two together.

Using the software:

To use SWIPE.EXE, simply hook the reader up to your LPT2: port, power it up, then run SWIPE. When you're ready, press the ENTER key, and swipe a card through the reader. The program will read the data from the card and store it in a buffer (but will not decode the data; that is left as an excercise ;-). After the card has been read, press ENTER again and the contents of the buffer will be dumped to stdout. To save the card data to a file, simply redirect SWIPE's output on the command line, e.g.

SWIPE > citibank.out

Please let me know of any changes, bug fixes, or improvements you make to this code. Send email to tmkk@uiuc.edu.

Thanks, and have fun!

--- CUT HERE ---
 
/*
 * S W I P E . C
 *
 * Written:
 *     1/11/92
 *
 * Description: Quick 'n Dirty reader program for SR&D mag stripe card reader.
 *     Reads data from the input port as long as a card is detected in the
 *     card slot. After sampling, the data is dumped to stdout, and may
 *     be redirected to a file if desired.
 *
 * Note: Written for Borland C++ 3.0 - may require changes to compile under
 *     MSC or others. Compile in SMALL model.
 *
 */
 
#include < stdio.h >
#include < conio.h >
#include < process.h >
#include < dos.h >
#include < math.h >
#include < stdlib.h >
#include < assert.h >
#include < string.h >
 
/* timer chip programming register port addresses */
#define COMMAND_REG 0x43
#define CHANNEL0 0x40
 
/* size of sample buffer */
#define MAXSAMPLE 4096
 
typedef unsigned char byte;
 
 
/* global variables */
byte *databuf;  /* buffer for the sampled data */
 
/* interprocess communication data */
byte *bufp;         /* data buffer pointer */
unsigned nsamp;     /* number of samples to be made */
unsigned port;      /* input port address */
int enab=0;         /* flag to enable/disable sampling */
int start=0;        /* flag indicating that sampling has begun */
 
/* ISR prototype */
extern void interrupt shand(void);
 
 
 
void program_timer(int channel, unsigned count)
/*
 * P R O G R A M _ T I M E R
 *
 * Description: Programs the given count value into the specified channel of
 *     the IBM 825x timer chip. Channel 0 is the time-of-day-clock interrupt;
 *     channel 2 is the speaker pulser.
 *
 * Parameter:
 *     channel (in) - Channel to be programmed.
 *     count (in) - Count value with which to program timer chip.
 *
 */
{
 
    outportb(COMMAND_REG, 0x36);  /* set up for reprogramming */
    outportb(CHANNEL0 + channel, count & 0xff);  /* lo byte first */
    outportb(CHANNEL0 + channel, count >> 8);  /* then hi byte */
}
 
void sample_data(int count)
/*
 * S A M P L E _ D A T A
 *
 * Description: Sets up for data collection from the printer port using
 *     the SHAND interrupt service routine (see SWIPEISR.ASM). This routine
 *     reprograms the timer chip for the desired sampling rate, sets up
 *     the interprocess communication area, and starts the sampling process.
 *     The actual sampling is done in the SHAND procedure. This routine
 *     waits until sampling has been completed before returning.
 *
 */
{
void interrupt (*oldhand)(void);  /* pointer to old interrupt vector */
 
    /* save old interrupt vector */
    oldhand = getvect(0x1c);
 
    /* clear enable flag */
    enab = 0;
    start = 0;
 
    /* install new vector */
    setvect(0x1c, shand);
 
    /* set up interprocess communications area */
    nsamp = 0;
    bufp = databuf;
    port = 0x279;  /* address of printer status register */
 
    cprintf("Sampling at %fHz (= %fms)....",
       1193180.0 / (float)count, (float)count / 1193.18);
 
    /* reprogram timer chip */
    program_timer(0, count);
 
    /* enable sampling */
    enab = 1;
 
    /* wait until sampling is completed */
    while (enab) ;
 
    /* restore standard timing value */
    program_timer(0, 0);
 
    /* reinstall old handler vector */
    setvect(0x1c, oldhand);
 
    cprintf(" completed.\r\n");
 
}
 
 
void main()
{
unsigned i;
 
    /* allocate memory */
    databuf = calloc(MAXSAMPLE, sizeof(byte));
    assert (databuf != NULL);
 
    cprintf("Press < ENTER > when ready to swipe card:");
    getchar();
    sample_data(12);  /* This works out to about a 100kHz sampling rate  */
 
    cprintf("Sampling completed, %u samples total.\r\n", nsamp);
    cprintf("Press < ENTER > to dump data.\r\n\r\n");
    getchar();
 
    /* dump data to stdout */
    for (i=0; i < nsamp; ++i)
	if (kbhit())
	    break;
	else
	    printf("%u\n", databuf[i]);
 
    free (databuf);
 
}
 
--- CUT HERE ---
 
;
; S W I P E I S R . A S M
;
; Interrupt Service Routine to sample swipe reader.
;
 
_TEXT   segment byte public 'CODE'
DGROUP	group	_DATA,_BSS
	assume	cs:_TEXT,ds:DGROUP,ss:DGROUP
_TEXT	ends
 
_DATA	segment word public 'DATA'
; Nuthin' in here!
_DATA   ends
 
_BSS	segment word public 'BSS'
; Nuthin' in here either!
_BSS	ends
 
_TEXT	segment	byte public 'CODE'
;
; S H A N D
;
; Description: Sample interrupt handler for timer extension interrupt 0x1c.
;
; Note: Assumes that the /CARD DETECT line appears on bit 7 of the input
;     port. This bit corresponds to pin 11 on the standard PC printer port.
;     Also, the PC printer port card inverts the signal on this pin; thus,
;     bit 7 is *set* when a card is in the reader, even though /CARD DETECT
;     is an active low signal.
;
_shand	proc	far
	push	ax
	push	bx
	push	dx
	push	ds
	push	si
	push	di
	push	bp
	mov	bp,DGROUP
	mov	ds,bp
 
        cmp     word ptr DGROUP:_enab, 0                ; Are we turned on?
        je      ciao                                    ; Nope - goodbye!
 
        mov     dx, word ptr DGROUP:_port               ; Get port address
        cmp     word ptr DGROUP:_start, 0               ; Has sampling begun?
        jne     doit                                    ; Yup - hop to it!
 
;
; Sampling is enabled but has not actually begun because no card has yet been
;     detected in the slot of the reader. Check to see if a card has arrived
;     yet and, if it has, set the flag to indicate that sampling should begin.
;
        in      al, dx                                  ; sample port
        test    al, 80h                                 ; card detected?
        jz      ciao                                    ; nope - later!
 
        mov     word ptr DGROUP:_start, 1               ; card's there,
                                                        ; start reading it
        jmp     saveit
;
doit:
        in      al, dx                                  ; Read the port
        test    al, 80h                                 ; card detect bit set?
        jz      disable                                 ; if not, quit
;
; Data is still valid; get buffer pointer and save the data
;
saveit:
        mov     bx,word ptr DGROUP:_bufp                ; get addr. to write
        mov     byte ptr [bx],al                        ; save sampled value
        inc     word ptr DGROUP:_bufp                   ; and bump the ptr
 
        inc     word ptr DGROUP:_nsamp                  ; update sample count
        jmp     ciao                                    ; and skeedaddle
 
disable:
        mov     word ptr DGROUP:_enab,0                 ; card no longer
                                                        ; detected - disable
                                                        ; sampling
ciao:
        pop     bp                                      ; restore context
	pop	di
	pop	si
	pop	ds
	pop	dx
	pop	bx
	pop	ax
	iret	
_shand	endp
_TEXT	ends
 
_DATA	segment word public 'DATA'
;s@      label   byte
_DATA	ends
        extrn   _nsamp:word
	extrn	_port:word
	extrn	_bufp:word
	extrn	_enab:word
        extrn   _start:word
_TEXT	segment	byte public 'CODE'
	extrn	_inportb:near
_TEXT	ends
	public	_shand
	end