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--- arduino:arduino_crash_course:digital_input [2012/11/05 23:33] – mithat
+++ arduino:arduino_crash_course:digital_input [2012/11/12 18:29] – [Software debouncing] mithat
@@ Line 101: / Line 101: @@
 boolean lastButtonState = HIGH; // value of buttonState from previous loop iteration
 boolean buttonState = HIGH;
-/* boolean debounce(int pinNum, boolean lastState) {
-  boolean nowState = digitalRead(pinNum);
-  if (lastState != nowState) {
-    delay(debounceTime);
-    nowState = digitalRead(pinNum);
-  }
-  return nowState;
-} */
 boolean debounce(int pinNum) {
@@ Line 124: / Line 115: @@
 void loop() {
-//  buttonState = debounce(pushButtonPin, lastButtonState);  // read the input pin
   buttonState = debounce(pushButtonPin);  // read the input pin
@@ Line 288: / Line 278: @@
   lastButtonState = buttonState;
+}
+</file>
+===== Switch-case selection structure =====
+Both examples above use the //nested if-else// selection structure. Arduino's programming language also includes another selection structure that is useful in these situations: the //switch-case// structure. Below we have rewritten MultipleLEDsPushButton to use a //swich-case// structure.
+<file c MultipleLEDsTimer2.ino>
+/*
+ MultipleLEDsTimer2
+ Cycle through three LEDs with a timer.
+ This version uses a switch-case selection structure.
+ */
+const int delayTime = 500;  // time to wait between LED changes
+const int led0 = 13;        // connect an LED to pin 13
+const int led1 = 12;        // connect an LED to pin 12
+const int led2 = 11;        // connect an LED to pin 11
+int ledState;               // used to decide which LED is on (0 to 2)
+void setup() {
+  // make LED pins outputs
+  pinMode(led0, OUTPUT);
+  pinMode(led1, OUTPUT);
+  pinMode(led2, OUTPUT);
+  // initialize state
+  ledState = 0;
+  // turn the correct LED on and the others off
+  digitalWrite(led0, HIGH);
+  digitalWrite(led1, LOW);
+  digitalWrite(led2, LOW);
+}
+void loop() {
+  delay(delayTime);
+  ledState = (ledState + 1) % 3;    // cycle through 0,1,2
+  // turn the correct LED on and the others off
+  switch (ledState) {
+    case 0:
+      digitalWrite(led0, HIGH);
+      digitalWrite(led1, LOW);
+      digitalWrite(led2, LOW);
+      break;
+    case 1:
+      digitalWrite(led0, LOW);
+      digitalWrite(led1, HIGH);
+      digitalWrite(led2, LOW);
+      break;
+    case 2:
+      digitalWrite(led0, LOW);
+      digitalWrite(led1, LOW);
+      digitalWrite(led2, HIGH);
+      break;
+    default:
+      digitalWrite(led0, HIGH);
+      digitalWrite(led1, HIGH);
+      digitalWrite(led2, HIGH);
+      break;
+  }
 }
 </file>