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I am using an arduino mega 2560. I have 2 RFID readers connect to 2 different serial ports. during my prototyping phase, everything was fine, my 2 readers worked together perfectly. I am now moving into my expansion process. However, when testing new readers, I found that no data was coming up. If each reader is connected individually, everything works fine, but once I connect 2 at once, my problem begins.

But my 2 original readers still work perfectly together?

here are my circuit diagrams

Schematic view

Breadboard view

any help is appreciated, here is my code below:


int RFIDResetPin = 13;


void setup()
{
  Serial.begin(9600);
  Serial1.begin(9600);
  Serial2.begin(9600);
  pinMode(RFIDResetPin, OUTPUT);
  digitalWrite(RFIDResetPin, HIGH);
}

void loop() {

  char tagString1[13];
  int index = 0;
  boolean reading1 = false;
  boolean reading2 = false;
  ///////////////////////////////////////
  //this reads from the reader installed
  //on serial1, which is pin 19
  //////////////////////////////////////
  while (Serial1.available() > 0) {

    int readByte1 = Serial1.read(); //read next available byte

    if (readByte1 == 2) reading1 = true;
    if (readByte1 == 3) reading1 = false;

    if (reading1 && readByte1 != 2 && readByte1 != 10 && readByte1 != 13) {
      tagString1[index] = readByte1;
      index++;
    }
  }
  Serial.println(String("Reader 1: ") + tagString1); //the tag itself

delay(1);
  clearTag(tagString1); //Clear the char of all value
  resetReader(); //reset the RFID reader
  //////////////////////////////////////////////////
  // This bit reads from serial2, located on pin 17
  /////////////////////////////////////////////////
  while (Serial2.available() > 0) {

    int readByte2 = Serial2.read();

    if (readByte2 == 2) reading2 = true;
    if (readByte2 == 3) reading2 = false;

    if (reading2 && readByte2 != 2 && readByte2 != 10 && readByte2 != 13) {
      tagString1[index] = readByte2;
      index++;
    }
  }
  Serial.println(String("Reader 2: ") + tagString1);

  clearTag(tagString1);
  resetReader();
}




void resetReader() {
  ///////////////////////////////////
  //Reset the RFID reader to read again.
  ///////////////////////////////////
  digitalWrite(RFIDResetPin, LOW);
  digitalWrite(RFIDResetPin, HIGH);
  delay(150);
}

void clearTag(char one[]) {
  ///////////////////////////////////
  //clear the char array by filling with null – ASCII 0
  //Will think same tag has been read otherwise
  ///////////////////////////////////
  for (int i = 0; i < strlen(one); i++) {
    one[i] = 0;
  }
}

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