The Gallagher reader uses a bespoke encrypted protocol so cant be interfaced with directly.
We need to connect it to a Gallagher weigand protocol converter (see attached data sheet). This has a data0 and data1 line and presents a 40 bit Weigand code - first 16 bits facility code, next 24 bits card number.
You can use the Arduino to decode the weigand output (no need for an rs232 converter here - in fact most are unlikely to work since they are hardwired for 26 bit Weigand format).
The protocol converter needs a 13v power supply and has no pull up resistors - the manual suggests 1.5k pull ups. I am powering the Arduino off the USB so have to link the grounds to get any consistent data.
A neater solution would be to use the same power supply with a voltage converter thus linking the grounds, or using Vin which should take the 13V - never been brave enough to test this though!!
/* Gallagher T11 reader with Weigand Protocol Converter
* Jonathan Richardson April 2012
* Base don Crazy People By Mike Cook April 2009
* Three RFID readers outputing 26 bit Wiegand code to pins:-
* Reader A (Head) Pins 2 & 3
* Interrupt service routine gathers Wiegand pulses (zero or one) until 40 have been recieved
* Gallager format is 16 bits facility code, next 24 bits card number.
*/
volatile int64_t reader1 = 0; //can't use an int as there are not enough bytes
volatile int reader1Count = 0;
void reader1One(void) {
reader1Count++;
reader1 = reader1 << 1;
reader1 |= 1;
}
void reader1Zero(void) {
reader1Count++;
reader1 = reader1 << 1;
}
void setup()
{
Serial.begin(57600);
// Attach pin change interrupt service routines from the Wiegand RFID readers
attachInterrupt(0, reader1Zero, RISING);//DATA0 to pin 2
attachInterrupt(1, reader1One, RISING); //DATA1 to pin 3
delay(10);
// the interrupt in the Atmel processor mises out the first negitave pulse as the inputs are already high,
// so this gives a pulse to each reader input line to get the interrupts working properly.
// Then clear out the reader variables.
// The readers are open collector sitting normally at a one so this is OK
for(int i = 2; i<4; i++){
pinMode(i, OUTPUT);
digitalWrite(i, HIGH); // enable internal pull up causing a one
digitalWrite(i, LOW); // disable internal pull up causing zero and thus an interrupt
pinMode(i, INPUT);
digitalWrite(i, HIGH); // enable internal pull up
}
delay(10);
// put the reader input variables to zero
reader1 = 0;
reader1Count = 0;
digitalWrite(9, HIGH); // show Arduino has finished initilisation - normally pin 13 but I using an Ethernet board
}
void loop() {
if(reader1Count >=40){
//can't serial.println an int64_t so need to use a char buffer
char buffer[100];
sprintf(buffer, "%0ld", (reader1 >> 24) & 0xffff);
Serial.print(buffer);
Serial.print(" ");
sprintf(buffer, "%0ld", reader1 & 0xffffff);
Serial.print(buffer);
reader1 = 0;
reader1Count = 0;
}
}
Jorich
