Hello folks, Im planning on building an magstripe reader, I found the code by stephen king, and it works great, but i want to modify it so it can read swipes from the other direction.
I've changed the writebit function so it writes the binaries to the buffer in reversed order, it should work, and it does... in about 1 swipe out of 5, the program gets very buggy, in most swipes it just prints half the track or nothing at all. Anyone here who knows what might be wrong?
Original code can be found here:
http://arduino.cc/forum/index.php/topic,7909.0.html
Here is the modified code:
/*
* Magnetic Stripe Reader
* by Stephan King http://www.kingsdesign.com
*
* Reads a magnetic stripe.
*
*/
int cld1Pin = 5; // Card status pin
int rdtPin = 2; // Data pin
int reading = 0; // Reading status
volatile int buffer[400]; // Buffer for data
volatile int i = 0; // Buffer counter
volatile int bit = 0; // global bit
char cardData[40]; // holds card info
int charCount = 0; // counter for info
int DEBUG = 0;
int ib = 400;
void setup() {
Serial.begin(9600);
// The interrupts are key to reliable
// reading of the clock and data feed
attachInterrupt(0, changeBit, CHANGE);
attachInterrupt(1, writeBit, FALLING);
}
void loop(){
// Active when card present
while(digitalRead(cld1Pin) == LOW){
reading = 1;
}
// Active when read is complete
// Reset the buffer
if(reading == 1) {
if (DEBUG == 1) {
printBuffer();
}
decode();
reading = 0;
i = 0;
int l;
for (l = 0; l < 40; l = l + 1) {
cardData[l] = '\n';
}
charCount = 0;
}
}
// Flips the global bit
void changeBit(){
if (bit == 0) {
bit = 1;
} else {
bit = 0;
}
}
// Writes the bit to the buffer
void writeBit(){
buffer[ib] = bit;
ib--;
}
// prints the buffer
void printBuffer(){
int j;
for (j = 0; j < 200; j = j + 1) {
Serial.println(buffer[j]);
}
}
int getStartSentinal(){
int j;
int queue[5];
int sentinal = 0;
for (j = 0; j < 400; j = j + 1) {
queue[4] = queue[3];
queue[3] = queue[2];
queue[2] = queue[1];
queue[1] = queue[0];
queue[0] = buffer[j];
if (DEBUG == 1) {
Serial.print(queue[0]);
Serial.print(queue[1]);
Serial.print(queue[2]);
Serial.print(queue[3]);
Serial.println(queue[4]);
}
if (queue[0] == 0 & queue[1] == 1 & queue[2] == 0 & queue[3] == 1 & queue[4] == 1) {
sentinal = j - 4;
break;
}
}
if (DEBUG == 1) {
Serial.print("sentinal:");
Serial.println(sentinal);
Serial.println("");
}
return sentinal;
}
void decode() {
int sentinal = getStartSentinal();
int j;
int i = 0;
int k = 0;
int thisByte[5];
for (j = sentinal; j < 400 - sentinal; j = j + 1) {
thisByte[i] = buffer[j];
i++;
if (i % 5 == 0) {
i = 0;
if (thisByte[0] == 0 & thisByte[1] == 0 & thisByte[2] == 0 & thisByte[3] == 0 & thisByte[4] == 0) {
break;
}
printMyByte(thisByte);
}
}
Serial.print("Stripe_Data:");
for (k = 0; k < charCount; k = k + 1) {
Serial.print(cardData[k]);
}
Serial.println("");
}
void printMyByte(int thisByte[]) {
int i;
for (i = 0; i < 5; i = i + 1) {
if (DEBUG == 1) {
Serial.print(thisByte[i]);
}
}
if (DEBUG == 1) {
Serial.print("\t");
Serial.print(decodeByte(thisByte));
Serial.println("");
}
cardData[charCount] = decodeByte(thisByte);
charCount ++;
}
char decodeByte(int thisByte[]) {
if (thisByte[0] == 0 & thisByte[1] == 0 & thisByte[2] == 0 & thisByte[3] == 0 & thisByte[4] == 1){
return '0';
}
if (thisByte[0] == 1 & thisByte[1] == 0 & thisByte[2] == 0 & thisByte[3] == 0 & thisByte[4] == 0){
return '1';
}
if (thisByte[0] == 0 & thisByte[1] == 1 & thisByte[2] == 0 & thisByte[3] == 0 & thisByte[4] == 0){
return '2';
}
if (thisByte[0] == 1 & thisByte[1] == 1 & thisByte[2] == 0 & thisByte[3] == 0 & thisByte[4] == 1){
return '3';
}
if (thisByte[0] == 0 & thisByte[1] == 0 & thisByte[2] == 1 & thisByte[3] == 0 & thisByte[4] == 0){
return '4';
}
if (thisByte[0] == 1 & thisByte[1] == 0 & thisByte[2] == 1 & thisByte[3] == 0 & thisByte[4] == 1){
return '5';
}
if (thisByte[0] == 0 & thisByte[1] == 1 & thisByte[2] == 1 & thisByte[3] == 0 & thisByte[4] == 1){
return '6';
}
if (thisByte[0] == 1 & thisByte[1] == 1 & thisByte[2] == 1 & thisByte[3] == 0 & thisByte[4] == 0){
return '7';
}
if (thisByte[0] == 0 & thisByte[1] == 0 & thisByte[2] == 0 & thisByte[3] == 1 & thisByte[4] == 0){
return '8';
}
if (thisByte[0] == 1 & thisByte[1] == 0 & thisByte[2] == 0 & thisByte[3] == 1 & thisByte[4] == 1){
return '9';
}
if (thisByte[0] == 0 & thisByte[1] == 1 & thisByte[2] == 0 & thisByte[3] == 1 & thisByte[4] == 1){
return ':';
}
if (thisByte[0] == 1 & thisByte[1] == 1 & thisByte[2] == 0 & thisByte[3] == 1 & thisByte[4] == 0){
return ';';
}
if (thisByte[0] == 0 & thisByte[1] == 0 & thisByte[2] == 1 & thisByte[3] == 1 & thisByte[4] == 1){
return '<';
}
if (thisByte[0] == 1 & thisByte[1] == 0 & thisByte[2] == 1 & thisByte[3] == 1 & thisByte[4] == 0){
return '=';
}
if (thisByte[0] == 0 & thisByte[1] == 1 & thisByte[2] == 1 & thisByte[3] == 1 & thisByte[4] == 0){
return '>';
}
if (thisByte[0] == 1 & thisByte[1] == 1 & thisByte[2] == 1 & thisByte[3] == 1 & thisByte[4] == 1){
return '?';
}
}
Original function:
void writeBit(){
buffer[i] = bit;
i++;
}
My function:
int ib = 400;
...
void writeBit(){
buffer[ib] = bit;
ib--;
}
Also its worth to mention that i found the modified code by user 'wan' in this old thread: http://arduino.cc/forum/index.php/topic,7909.0.html
But that code only works if you are certain of the ending char on the track, wich is not always the case unfortunately.
Would be awesome if someone could give me a hint on what might be wrong.
Thanks!
