Are interrupts handled differently on the Uno 3 vs Uno 4?

Official Hardware Classic UNO R4 WiFi
1

I have this code here in my setup

pinMode(2, INPUT); // DATA0 (INT0)
pinMode(3, INPUT); // DATA1 (INT1)
pinMode(RELAY, OUTPUT);

// binds the ISR functions to the falling edge of INTO and INT1
attachInterrupt(digitalPinToInterrupt(2), ISR_INT0, FALLING);
attachInterrupt(digitalPinToInterrupt(3), ISR_INT1, FALLING);

and the sketch works perfectly fine on my Uno 3 but not my Uno 4. I haven't been able to find any information about if interrupts work different on the Rev 4 vs the Rev 3. The code compiles and uploads but the interrupts don't work.

2

Please show the code in full.

Of course, the interrupts are worked differently because the very different controllers.

3

Im away from my computer at this time but this is the sketch my sketch was based off of.

  • HID RFID Reader Wiegand Interface for Arduino Uno
  • Written by Daniel Smith, 2012.01.30
  • www.pagemac.com
  • This program will decode the wiegand data from a HID RFID Reader (or, theoretically,
  • any other device that outputs weigand data).
  • The Wiegand interface has two data lines, DATA0 and DATA1. These lines are normall held
  • high at 5V. When a 0 is sent, DATA0 drops to 0V for a few us. When a 1 is sent, DATA1 drops
  • to 0V for a few us. There is usually a few ms between the pulses.
  • Your reader should have at least 4 connections (some readers have more). Connect the Red wire
  • to 5V. Connect the black to ground. Connect the green wire (DATA0) to Digital Pin 2 (INT0).
  • Connect the white wire (DATA1) to Digital Pin 3 (INT1). That's it!
  • Operation is simple - each of the data lines are connected to hardware interrupt lines. When
  • one drops low, an interrupt routine is called and some bits are flipped. After some time of
  • of not receiving any bits, the Arduino will decode the data. I've only added the 26 bit and
  • 35 bit formats, but you can easily add more.

*/

#define MAX_BITS 100 // max number of bits
#define WEIGAND_WAIT_TIME 3000 // time to wait for another weigand pulse.

unsigned char databits[MAX_BITS]; // stores all of the data bits
unsigned char bitCount; // number of bits currently captured
unsigned char flagDone; // goes low when data is currently being captured
unsigned int weigand_counter; // countdown until we assume there are no more bits

unsigned long facilityCode=0; // decoded facility code
unsigned long cardCode=0; // decoded card code

// interrupt that happens when INTO goes low (0 bit)
void ISR_INT0()
{
//Serial.print("0"); // uncomment this line to display raw binary
bitCount++;
flagDone = 0;
weigand_counter = WEIGAND_WAIT_TIME;

}

// interrupt that happens when INT1 goes low (1 bit)
void ISR_INT1()
{
//Serial.print("1"); // uncomment this line to display raw binary
databits[bitCount] = 1;
bitCount++;
flagDone = 0;
weigand_counter = WEIGAND_WAIT_TIME;
}

void setup()
{
pinMode(13, OUTPUT); // LED
pinMode(2, INPUT); // DATA0 (INT0)
pinMode(3, INPUT); // DATA1 (INT1)

Serial.begin(9600);
Serial.println("RFID Readers");

// binds the ISR functions to the falling edge of INTO and INT1
attachInterrupt(0, ISR_INT0, FALLING);
attachInterrupt(1, ISR_INT1, FALLING);

weigand_counter = WEIGAND_WAIT_TIME;
}

void loop()
{
// This waits to make sure that there have been no more data pulses before processing data
if (!flagDone) {
if (--weigand_counter == 0)
flagDone = 1;
}

// if we have bits and we the weigand counter went out
if (bitCount > 0 && flagDone) {
unsigned char i;

Serial.print("Read ");
Serial.print(bitCount);
Serial.print(" bits. ");

// we will decode the bits differently depending on how many bits we have
// see www.pagemac.com/azure/data_formats.php for mor info
if (bitCount == 35)
{
  // 35 bit HID Corporate 1000 format
  // facility code = bits 2 to 14
  for (i=2; i<14; i++)
  {
     facilityCode <<=1;
     facilityCode |= databits[i];
  }

  // card code = bits 15 to 34
  for (i=14; i<34; i++)
  {
     cardCode <<=1;
     cardCode |= databits[i];
  }

  printBits();
}
else if (bitCount == 26)
{
  // standard 26 bit format
  // facility code = bits 2 to 9
  for (i=1; i<9; i++)
  {
     facilityCode <<=1;
     facilityCode |= databits[i];
  }

  // card code = bits 10 to 23
  for (i=9; i<25; i++)
  {
     cardCode <<=1;
     cardCode |= databits[i];
  }

  printBits();  
}
else {
  // you can add other formats if you want!
 Serial.println("Unable to decode."); 
}

 // cleanup and get ready for the next card
 bitCount = 0;
 facilityCode = 0;
 cardCode = 0;
 for (i=0; i<MAX_BITS; i++) 
 {
   databits[i] = 0;
 }

}
}

void printBits()
{
// I really hope you can figure out what this function does
Serial.print("FC = ");
Serial.print(facilityCode);
Serial.print(", CC = ");
Serial.println(cardCode);
}

4

I'd suggest creating an absolutely minimal sketch to test interrupts.

Be careful of this:

attachInterrupt(0, ISR_INT0, FALLING);  // pin 2 represented as interrupt 0
attachInterrupt(1, ISR_INT1, FALLING);

use digitalPinToInterrupt() instead of directly giving interrupt numbers such as 0 and 1 which may be platform dependent.

EDIT
In your code snippet in the OP you appear to have already made this correction to the original code.