Using millis() to get elapsed time

Projects Programming
15

Hi PaulS,

I think it is only a 4 digit integer number that i am sending, Well here is the code,

Arduino:

int ledTX = 12; //Receives InfraRed signal
int photodiodePin = 2;              // Photodiode connected to digital pin 2
int lastState;
unsigned long startTime;
unsigned long elapsedTime;
void setup() {                
  Serial.begin(9600);          
  pinMode(ledTX, OUTPUT); 
  pinMode(photodiodePin, INPUT);    // sets the digital pin as input to read photodiode
}
void loop() {
  byte currentState = digitalRead(photodiodePin);
  digitalWrite(ledTX, HIGH);   // turn the TX Infrared LED on
  if(currentState == LOW && lastState == HIGH){
    startTime = millis();
  }
  if(currentState == HIGH && lastState == LOW){
    elapsedTime = millis() - startTime;
    Serial.println(elapsedTime);
    Serial.write(elapsedTime);
  }
  lastState = currentState;
}

Processing: the elapsedTime variable has been declared as an integer but I am only getting a print out of 0. There is no change when I put anything in the photogate.

import processing.serial.*;

Serial port;
int elapsedTime;

void setup() {
  size(200, 200);
  background(204);
  noStroke();
  port = new Serial(this, 9600);
}

void draw() {
  if (0 < port.available()) {
    elapsedTime = port.read();
  }
  println(elapsedTime);
}

Thanks,

Shane