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 ran multiple times. I have setup the Raspberry Pi and tested it with an LED and the output is working fine.

I then connected this up 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 pull up resistors not being used. I would greatly appreciate some guidance on this.