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Code Review
The first part is the data reading loop, which grabs the first ~80 non-zero bytes. We have to toss out the zeros as they are just buffers on the edge of the magstripe. There should be at least 4 but we don't use them so they get ignored in the loop.
// for lots more info, see
// http://stripesnoop.sourceforge.net/devel/magtek-app.pdf
void loop()
{
// wait till the card ready pin is low
while (digitalRead(CARD2));
uint8_t zeros = 0;
uint8_t parityok = 0;
// card was swiped!
// check clocked in data
for (uint8_t t1 = 0; t1 < TRACK1_LEN; t1++) {
track1[t1] = 0;
for (uint8_t b=0; b < BYTELENGTH; b++) {
// wait while clock is high
while (digitalRead(CLOCK2) && !digitalRead(CARD2));
// we sample on the falling edge!
uint8_t x = digitalRead(DATA2);
if (!x) {
// data is LSB and inverted!
track1[t1] |= _BV(b);
}
// heep hanging out while its low
while (!digitalRead(CLOCK2) && !digitalRead(CARD2));
}
if ((t1 == 0) && (track1[t1] == 0)) {
// get rid of leading 0's
zeros++;
t1--;
continue;
}
// we must have some leading zeros!
if (zeros < 4) {
t1--;
continue;
}
// if the second byte is a zero, theres noise, backtrack
if ((t1 == 1) && (track1[t1] == 0)) {
t1 = -1;
zeros = 1;
continue;
}
}
// all the data is read into the track1 buffer
// shift left until we have no more starting zero bits!
while ((track1[0] & 0x1) == 0 ) {
shifttrack(track1, scratch, LEFT);
}
And here is the part after the parsing where we use the Teensy's built in Keyboard emulation to plug the data right into the virtual terminal. Note how it takes the raw data from the track and uses Keyboard.print() to output it as well as tab through the browser entries.
// FIND PAN
uint8_t i=2;
while ((track1[i] & 0x3F) != 0x3E) {
#ifdef SERIAL
Serial.print((track1[i] & 0x3F)+0x20, BYTE);
#endif
#ifdef KEYBOARD
Keyboard.print((track1[i] & 0x3F)+0x20, BYTE);
#endif
i++;
}
...
#ifdef KEYBOARD
Keyboard.print('\t');
Keyboard.print(m1, BYTE);
Keyboard.print(m2, BYTE);
Keyboard.print(y1, BYTE);
Keyboard.print(y2, BYTE);
Keyboard.print('\t'); // tab to amount
Keyboard.print('\t'); // tab to invoice
Keyboard.print('\t'); // tab to description
Keyboard.print("HOPE conference kits from Adafruit.com");
Keyboard.print('\t'); // tab to customer ID
Keyboard.print('\t'); // tab to first name
Keyboard.print(fname);
Keyboard.print('\t'); // tab to last name
Keyboard.print(lname);
for (uint8_t i=0; i<5; i++) {
Keyboard.set_modifier(MODIFIERKEY_SHIFT);
Keyboard.set_key1(KEY_TAB);
Keyboard.send_now();
Keyboard.set_modifier(0);
Keyboard.set_key1(0);
Keyboard.send_now();
}
#endif
beep(PIEZO, 4000, 200);
Once it's been swiped, the form is filled automatically, tabbing between the entries and then back-tabbing to the amount box so that can be filled out.
Page last edited March 08, 2024
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