Connecting ESP8266 via IN1 and IN0 fails

[Arcires]

Hi there,

I'm trying to connect an ESP8266-01 module to my Controllino MEGA. However, when I connect the TX and RX pins of the ESP to the appropriate IN1 and IN0 respectively, I get no reaction when I try to enter AT-commands via the serial connection. The IN1 and IN0 pins works the same way as the pin 19(RX1) and pin 18(TX1) on a standard Arduino Mega. I have verified that the ESP-module works as intended via a regular Arduino Mega, yet it doesn't work on the Controllino.

I use a very simple script like so to create two serial connections, so that I can use the serial input in the Arduino IDE as a command line:

void setup() {
  Serial.begin(9600);
  Serial1.begin(115200);

  Serial.println("Ready for input");
}

void loop() {
while (Serial.available()){
  char ch = Serial.read();
  Serial1.print(ch);
  }

while (Serial1.available()){
  char ch = Serial1.read();
  Serial.print(ch);
  }
}

Any help would be greatly appreciated, as I have not been able to identify the issue. Is it because I need to define the interrupt pins to a specific state?