Problem with RS485 and Serial print and ModbusMaster

Projects Programming
4

Since you are using a Mega2560, just connect your modbus to Serial1 (Rx1=pin19, Tx2=18) instead of Serial. Serial is the only port connected to the Serial Monitor.

void setup() {
 
  //Encoder
  pinMode(21, INPUT_PULLUP); // internal pullup input pin  21
  pinMode(20, INPUT_PULLUP); // internal pullup input pin  20
  //Setting up interrupt A rising pulse from encodenren activated ai0(). AttachInterrupt 2 is DigitalPin nr 20.
  attachInterrupt(2, ai0, RISING); //0 & 1 taken by RS485
  //B rising pulse from encodenren activated ai1(). AttachInterrupt 3 is DigitalPin nr 21.
  attachInterrupt(3, ai1, RISING); //0 & 1 taken by RS485
  //Encoder
 
  //RS 485
  pinMode(MAX485_RE_NEG, OUTPUT);
  pinMode(MAX485_DE, OUTPUT);
  // Init in receive mode
  digitalWrite(MAX485_RE_NEG, 0);
  digitalWrite(MAX485_DE, 0);
  //RS 485
  Serial.begin(9600);  // for debugging
  Serial1.begin(9600);  // for modbus
  
  pinMode(RELAY1, OUTPUT);
  digitalWrite(RELAY1, HIGH);  //RELAY 1 is OFF

  // Modbus slave ID 1
  node.begin(1, Serial1);
  ...