Implement debounce

DDRuino.ino

@@ -1,21 +1,29 @@
 /*@ file DDRunino.ino
- * 
+ *
  * Simple Arduino sketch to run a DDR pad as a keyboard
- * 
+ *
  * https://git.beesbuzz.biz/fluffy/DDRuino/
  */
 
 #include <Keyboard.h>
 
-// Uncomment this to enable the serial debugger to determine the pin mappings
+//! Uncomment this to enable the serial debugger to determine the pin mappings
 //#define DEBUG
 
+//! Debounce time in milliseconds
+constexpr int debounceTime = 20;
+
+//! Input button
 struct Input {
-    int pin;
-    int keyCode;
-    bool state;
+    int pin;        //!< Input pin
+    int keyCode;    //!< Mapped key
+    bool pressed;   //!< Last read state
+    unsigned long lastChange;   //!< Last update time
 };
 
+/*! Map the input pins to a button on the pad; use debug mode to determine
+ *  your button layout if you're not sure
+ */
 Input mapping[] = {
     { 4, KEY_RETURN },
     { 5, KEY_ESC },
@@ -27,17 +35,20 @@ Input mapping[] = {
 
 void setup()
 {
+#ifdef DEBUG
     Serial.begin(9600);
 
-#ifdef DEBUG
     for (int i = 0; i < 12; i++) {
       pinMode(i, INPUT_PULLUP);
     }
 #endif
 
+    unsigned long now = millis();
+
     for (auto i : mapping) {
         pinMode(i.pin, INPUT_PULLUP);
-        i.state = HIGH;
+        i.pressed = false;
+        i.lastChange = now;
     }
 
     Keyboard.begin();
@@ -51,18 +62,19 @@ void loop()
     }
     Serial.print('\n');
 #endif
-  
+
     for (auto& i : mapping) {
+        unsigned long now = millis();
         bool val = !digitalRead(i.pin);
-        if (val != i.state) {
+        if (val != i.pressed && (i.lastChange + debounceTime) < now) {
             if (val) {
-                // TODO debounce
                 Keyboard.press(i.keyCode);
             } else {
                 Keyboard.release(i.keyCode);
             }
 
-            i.state = val;
+            i.pressed = val;
+            i.lastChange = now;
         }
     }
 }