rough...

src/main.cpp

@@ -14,13 +14,18 @@ LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
 elapsedMillis timeElapsed;
 unsigned int startTime;
 
-#define PIN_INPUT 2 // D2;
+#define PIN_RESET 2
+#define PIN_CAR1 3
 
 void setup()
 {
+
   Serial.begin(9600);
-  pinMode(PIN_INPUT, INPUT_PULLUP);
+
+  pinMode(PIN_RESET, INPUT_PULLUP);
+  pinMode(PIN_CAR1, INPUT_PULLUP);
   pinMode(LED_BUILTIN, OUTPUT);
+
   startTime = timeElapsed;
   Serial.println("Starting");
   Serial.println(startTime);
@@ -38,18 +43,42 @@ bool tripped = false;
 char buffer[40];
 unsigned int elapsedTime;
 
+bool started = false;
+bool runnning = false;
+unsigned int car1elapsed = 0;
+
 void loop()
 {
-  if (digitalRead(PIN_INPUT) == LOW) {
-    tripped = true;
-    Serial.println(timeElapsed - startTime);
 
+  if (digitalRead(PIN_RESET) == LOW) {
     lcd.clear();
     lcd.setCursor(0,0);
-    elapsedTime = timeElapsed - startTime;
-    sprintf(buffer, "Elapsed: %dms", elapsedTime);
-    lcd.print(buffer);
+    lcd.print("Ready?");
+    started = false;
+    car1elapsed = 0;
+    digitalWrite(LED_BUILTIN, LOW);
+  } else {
+    // if we just started, record current millis counter
+    if (!started) {
+      startTime = elapsedMillis;
+      started = true;
+    }
+
+    elapsedTime = elapsedMillis - startTime;
+
+    if (digitalRead(PIN_INPUT) == LOW && car1elapsed == 0) {
+      car1elapsed = elapsedTime;
+    }
+
+    if (car1elapsed <> 0) {
+      // stop if all cars are complete or threshold reached
+      lcd.clear();
+      lcd.setCursor(0,0);
+      sprintf(buffer, "Car1: %dms", car1elapsed);
+      lcd.print(buffer);
+      digitalWrite(LED_BUILTIN, HIGH);
+    }
 
   }
-  digitalWrite(LED_BUILTIN, tripped? HIGH : LOW);
+
 }