Robot Follow Project

Projects General Guidance
5

Hello all,
I am trying to make a robot that will follow a person around using the hc-sr04 ultrasonic sensor. I have 3 hc-sr04's and 2 Arduino Uno's. At the moment I am not going to worry about motors so I am not listing them. 2 receiver sensors are connected to one Arduino and the other transmitter sensor is connected to the other Arduino. I saw this code that I modified (credit to element14 presents - YouTube) and am having some trouble with it. This is the code for the robot:

boolean oneFire = false;
boolean twoFire = false;
boolean finished = false;
long setPoint1 = 0;
long setPoint2 = 0;
long difference = 0;

const int echoPin1 = 7;
const int echoPin2 = 6;

void setup(){
  pinMode(echoPin1, INPUT);
  pinMode(echoPin2, INPUT);
  Serial.begin(9600);
}

void loop(){
  long timeout = 0;
  long distance = 0;
  oneFire = false;
  twoFire = false;
  finished = false;
  setPoint1 = 0;
  setPoint2 = 0;
  difference = 0;
  
  while ((oneFire == 0) || (twoFire == 0)){
    if (((PIND & 0x10) == 0) && !oneFire){
      oneFire = true;
      setPoint1 = timeout;
    }
    if (((PIND & 0x20) == 0) && !twoFire){
      twoFire = true;
      setPoint2 = timeout;
    }
    delayMicroseconds(1);
    timeout++;
    if (timeout > 19000)
      break;
  }
  difference = setPoint1 - setPoint2;
  distance = (setPoint1 + setPoint2)/10;
Serial.println(difference);
}

The code for what the human wears is simply:

const int trigPin = 12;

void setup()
{
  pinMode(trigPin, OUTPUT);
}

void loop() {
      digitalWrite(trigPin, LOW);
      delayMicroseconds(2);
      digitalWrite(trigPin, HIGH);
      delayMicroseconds(5);
      digitalWrite(trigPin, LOW);
}

Again, I am not worrying about motors because once I get valid readings, The motor part will be easy. When I upload both, point them at each other, and start the serial monitor, all I get is 0. Any help is welcome.
Thanks