Fix bug where isPressed returns True a second time

As currently implemented, if the button is pressed and immediately released
before the next `loop` call, e.g., due to a blocking action like a `delay`
call, the subsequent `loop` call will still consider the button as pressed. The
same behavior occurs with unpressed when holding the button, and only
momentarily releasing it.

To fix this issue, we need to do away with the `previousSteadyState` variable
so that it does not require two calls to `loop` in order to change the state.

Author: bboe

src/ezButton.cpp

@@ -38,6 +38,7 @@ ezButton::ezButton(int pin, int mode) {
 	debounceTime = 0;
 	count = 0;
 	countMode = COUNT_FALLING;
+	transition = NEITHER;
 
 	if (mode == INTERNAL_PULLUP || mode == INTERNAL_PULLDOWN) {
 		pinMode(btnPin, mode);
@@ -54,9 +55,8 @@ ezButton::ezButton(int pin, int mode) {
 		unpressedState = HIGH;
 	}
 
-	previousSteadyState = digitalRead(btnPin);
-	lastSteadyState = previousSteadyState;
-	lastFlickerableState = previousSteadyState;
+	lastSteadyState = digitalRead(btnPin);
+	lastFlickerableState = lastSteadyState;
 
 	lastDebounceTime = 0;
 }
@@ -74,17 +74,11 @@ int ezButton::getStateRaw(void) {
 }
 
 bool ezButton::isPressed(void) {
-	if(previousSteadyState == unpressedState && lastSteadyState == pressedState)
-		return true;
-	else
-		return false;
+	return transition == PRESSED;
 }
 
 bool ezButton::isReleased(void) {
-	if(previousSteadyState == pressedState && lastSteadyState == unpressedState)
-		return true;
-	else
-		return false;
+	return transition == UNPRESSED;
 }
 
 void ezButton::setCountMode(int mode) {
@@ -116,25 +110,21 @@ void ezButton::loop(void) {
 		lastFlickerableState = currentState;
 	}
 
-	if ((currentTime - lastDebounceTime) >= debounceTime) {
+	if ((currentTime - lastDebounceTime) >= debounceTime && currentState != lastSteadyState) {
 		// whatever the reading is at, it's been there for longer than the debounce
 		// delay, so take it as the actual current state:
 
-		// save the the steady state
-		previousSteadyState = lastSteadyState;
+		// save the the steady state and set the transition
 		lastSteadyState = currentState;
-	}
+		transition = currentState == pressedState ? PRESSED : UNPRESSED;
 
-	if(previousSteadyState != lastSteadyState){
 		if(countMode == COUNT_BOTH)
 			count++;
-		else if(countMode == COUNT_FALLING){
-			if(previousSteadyState == HIGH && lastSteadyState == LOW)
-				count++;
-		}
-		else if(countMode == COUNT_RISING){
-			if(previousSteadyState == LOW && lastSteadyState == HIGH)
-				count++;
-		}
+		else if(countMode == COUNT_FALLING && currentState == LOW)
+		 	count++;
+		else if(countMode == COUNT_RISING && currentState == HIGH)
+		 	count++;
+	} else {
+		transition = NEITHER;
 	}
 }

src/ezButton.h

@@ -49,6 +49,12 @@
 #define EXTERNAL_PULLUP   0xFE
 #define EXTERNAL_PULLDOWN 0xFF
 
+enum Transition : byte {
+	NEITHER,
+	PRESSED,
+	UNPRESSED
+};
+
 class ezButton
 {
 	private:
@@ -59,9 +65,9 @@ class ezButton
 		int pressedState;     // the state when the button is considered pressed
 		int unpressedState;   // the state when the button is considered unpressed
 
-		int previousSteadyState;  // the previous steady state from the input pin, used to detect pressed and released event
-		int lastSteadyState;      // the last steady state from the input pin
+		int lastSteadyState;      // the last steady state from the input pin, used to detect pressed and released event
 		int lastFlickerableState; // the last flickerable state from the input pin
+		Transition transition;
 
 		unsigned long lastDebounceTime; // the last time the output pin was toggled