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--- arduino:arduino_crash_course:basic_interaction [2012/11/05 22:13] – mithat
+++ arduino:arduino_crash_course:basic_interaction [2012/11/12 04:36] – mithat
@@ Line 17: / Line 17: @@
 The following examples use polling to determine the state of a switch. If the switch is pressed, Arduino will turn an LED on. If it is not pressed, it will turn the LED off.
-==== Using external pulldown resistors ====
+==== With external pulldown resistors ====
 The following example requires **pulldown resistors** on the input switch.
@@ Line 100: / Line 100: @@
 </file>
-==== Using internal pullups ====
+==== With internal pullup resistors ====
 Using extenal resistors as part of switch state detection is so common that the microchip that is at the heart of the Arduino has built-in pullup resistors that can be turned on manually. Internal pullup resistors can be enabled with:
@@ Line 132: / Line 132: @@
   // set LED state accordingly
-  // note the inverted logic
+  // becasue we are using pullup resistors, the logic is inverted;
+  // in other words, pressed produces LOW, un-pressed produces HIGH.
   if (buttonState == LOW)        // if the button is pushed
     digitalWrite(ledPin, HIGH);  // turn the LED on
@@ Line 158: / Line 159: @@
 void loop() {
-  buttonState = !digitalRead(pushButtonPin);  // read the input pin
+  buttonState = digitalRead(pushButtonPin);  // read the input pin
-  digitalWrite(ledPin, buttonState);              // turn the LED on or off
+  // set LED state accordingly
+  // becasue we are using pullup resistors, the logic is inverted;
+  // in other words, pressed produces LOW, un-pressed produces HIGH.
+  digitalWrite(ledPin, !buttonState);        // turn the LED on or off
 }
 </file>