TTL magnetic card reader reads but unprintable char

[dima shawahneh]

hello every one

I have TTL card reader connected with pic18f4620 on port B
Im using the driver found with picc compiler (ex_mcr)
which is supposed to read magnetic card correctly

the problem that it reads , but the data are not correct --> not printable characters
like this..(w
??n?]??)

I have been searching but finding nothing to help
the number of characters is also not correct.

I tried many different magnetic cards but nothing worked well.
here is the code..

this is the driver



// Redefine the following pins in
// the main file as needed.
#ifndef MCR_CARD_PRESENT
#define MCR_CARD_PRESENT PIN_B0
#define MCR_DATA1 PIN_B1
#define MCR_STROBE1 PIN_B2
#define MCR_DATA2 PIN_B4
#define MCR_STROBE2 PIN_B5
#endif

// The following define the error codes.
// To check for a specific error, check
// the cooresponding bit in the value
// returned by mcr_read().
#define MCR_ERR_PARITY1 1
#define MCR_ERR_PARITY2 2
#define MCR_ERR_LRC1 4
#define MCR_ERR_LRC2 8


// Date: 7/28/2003
int mcr_read(char* track1, char* track2)
{
int error = 0;
int1 dataBit = 0;

int1 ST1 = 1;
int1 ST1_old = 1;
int1 firstOne1= 0;
int1 parity1 = 0;
int count1 = 0;
int index1 = 0;
int LRC1 = 0;

int1 ST2 = 1;
int1 ST2_old = 1;
int1 firstOne2= 0;
int1 parity2 = 0;
int count2 = 0;
int index2 = 0;
int LRC2 = 0;

// Wait for card to be present
while(input(MCR_CARD_PRESENT))
{
// printf("outside\n");
restart_wdt();
}

// Loop until a card is not present
while(!input(MCR_CARD_PRESENT))
{
// printf("inside\n");
restart_wdt();
// Check for NULL pointer and an index less than 79
if(track1 != 0 && index1 < 79)
{
// Get strobe number one
ST1 = input(MCR_STROBE1);
restart_wdt();
// If the strobe was high and is now low (falling edge),
// then data is present
if(ST1 == 0 && ST1_old == 1)
{
ST1_old = 0;

// Check if the first 1 was received
if(firstOne1 == 1)
{
// Check if 6 bits of data were received
if(count1 == 6)
{
// Set the data bit count back to 0
count1 = 0;

// Shift the bits right by 2
*(track1+index1) >>= 2;

// Verify the LRC
if(*(track1+index1-1) == '?' && LRC1 != *(track1+index1))
{
error |= MCR_ERR_LRC1;
}
else
{
LRC1 ^= *(track1+index1);
}

// Add 0x20 to convert to ASCII
*(track1+index1) += 0x20;

// Check the parity bit. The parity on a space is not checked
// because of the trailing zeros after the LRC character
if(!input(MCR_DATA1) != parity1 && *(track1+index1) != ' ')
{
error |= MCR_ERR_PARITY1;
}

// Reset the parity check
parity1 = 1;

// Increment the index into the array
++index1;
}
else
{
// Get a bit of data from the card
dataBit = !input(MCR_DATA1);

// XOR the data with the parity bit
parity1 ^= dataBit;

// Store the new bit of data
shift_right(track1+index1, 1, dataBit);

// Increment the bit counter
++count1;
}
}
else
{
// Check if the first 1 has appeard on the data line
if(!input(MCR_DATA1))
{
// Set the first 1 received flag
firstOne1 = 1;

// Store the first 1
shift_right(track1, 1, 1);

// Increment the bit counter
++count1;
}
}
}
else if(ST1 == 1)
{
ST1_old = 1;
}
}
// our code
// printf("%c\n",track1[index1]);
// if(track1[index1]=='?')
// {
// return error;
// }
//

// Check for NULL pointer and an index less than 40
if(track2 != 0 && index2 < 40)
{
// Get strobe number 2
ST2 = input(MCR_STROBE2);

// If the strobe was high and is now low (falling edge),
// then data is present
if(ST2 == 0 && ST2_old == 1)
{
ST2_old = 0;

// Check if the first 1 was received
if(firstOne2 == 1)
{
// Check if 4 bits of data were received
if(count2 == 4)
{
// Reset the bit counter back to 0
count2 = 0;

// Shift the bits right by 4
*(track2+index2) >>= 4;

// Verify the LRC
if(*(track2+index2-1) == '?' && LRC2 != *(track2+index2))
{
error |= MCR_ERR_LRC2;
}
else
{
LRC2 ^= *(track2+index2);
}

// Add 0x30 to convert to ASCII
*(track2+index2) += 0x30;

// Check the parity bit. The parity on a 0 is not checked
// because of the trailing zeros after the LRC character
if(!input(MCR_DATA2) != parity2 && *(track2+index2) != '0')
{
error |= MCR_ERR_PARITY2;
}

// Reset the parity check
parity2 = 1;

// Increment the index into the array
++index2;
}
else
{
// Get a bit of data from the card
dataBit = !input(MCR_DATA2);

// XOR the data with the parity bit
parity2 ^= dataBit;

// Store the new bit of data
shift_right(track2+index2, 1, dataBit);

// Increment the bit counter
++count2;
}
}
else
{
// Check if the first 1 has appeard on the data line
if(!input(MCR_DATA2))
{
// Set the first 1 received flag
firstOne2 = 1;

// Store the first 1
shift_right(track2, 1, 1);

// Increment the bit counter
++count2;
}
}
}
else if(ST2 == 1)
{
ST2_old = 1;
}
}
}

// Return any errors
return error;
}


Any suggestions ...
thanks alot

[Charles Linquis]

One suggestion:

Write the code in PBP and ask again if that doesn't work.

[Melanie]

There's even a Mag Card Reader example on the MeLabs website.

[Acetronics2]

Hi,

Wrong forum, may be ...

BUT



// Add 0x20 to convert to ASCII


Wasn't the Magic number 48d or 0x30 ???

just my 2 cents ...

Alain