I am trying to control an Arduino Leonardo R3 to run some code when "triggered" from a Raspberry Pi. This would be in a loop so that it can be run multiple times. I have set up the Raspberry Pi and tested it with an LED and the output is working fine.

I then connected this to the Arduino and checked for a HIGH input from the RPi using an if statement.

void setup() {
  pinMode(7,INPUT);
  if(digitalRead(7)==HIGH) {
    // CODE IN HERE
  }
}

I found that this did not work as the if statement was always true because of pullup resistors not being used. I would greatly appreciate some guidance on this.