Cache reverse button state for shifter

With the implementation of connection in the base class, caching this value allows us to clear it on disconnect. It also reinforces the idiom that peripheral state is only changed on 'update()'.

Author: dmadison

src/SimRacing.cpp

@@ -741,7 +741,8 @@ AnalogShifter::AnalogShifter(
 	/* Two axes, X and Y */
 	analogAxis{ AnalogInput(pinX), AnalogInput(pinY) },
 
-	pinReverse(sanitizePin(pinRev))
+	pinReverse(sanitizePin(pinRev)),
+	reverseState(false)
 {}
 
 void AnalogShifter::begin() {
@@ -759,6 +760,9 @@ bool AnalogShifter::updateState(bool connected) {
 		analogAxis[Axis::X].setPosition(calibration.neutralX);
 		analogAxis[Axis::Y].setPosition(calibration.neutralY);
 
+		// set reverse state to unpressed
+		this->reverseState = false;
+
 		// set gear to neutral
 		this->setGear(0);
 
@@ -772,6 +776,9 @@ bool AnalogShifter::updateState(bool connected) {
 	const int x = analogAxis[Axis::X].getPosition();
 	const int y = analogAxis[Axis::Y].getPosition();
 
+	// poll the reverse button and cache in the class
+	this->reverseState = this->readReverseButton();
+
 	// check previous gears for comparison
 	const Gear previousGear = this->getGear();
 	const bool prevOdd = ((previousGear != -1) && (previousGear & 1));  // were we previously in an odd gear
@@ -834,15 +841,21 @@ int AnalogShifter::getPositionRaw(Axis ax) const {
 	return analogAxis[ax].getPositionRaw();
 }
 
-bool AnalogShifter::getReverseButton() const {
-	// if the reverse pin is not set *or* if the device is not currently
-	// connected, avoid reading the floating input and just return 'false'
+bool AnalogShifter::readReverseButton() {
+	// if the reverse pin is not set, avoid reading the
+	// floating input and just return 'false'
 	if (pinReverse == UnusedPin) {
 		return false;
 	}
 	return digitalRead(pinReverse);
 }
 
+bool AnalogShifter::getReverseButton() const {
+	// return the cached reverse state from updateState(bool)
+	// do NOT poll the button!
+	return this->reverseState;
+}
+
 void AnalogShifter::setCalibration(
 	GearPosition neutral,
 	GearPosition g1, GearPosition g2, GearPosition g3, GearPosition g4, GearPosition g5, GearPosition g6,

src/SimRacing.h

@@ -721,6 +721,17 @@ namespace SimRacing {
 		virtual bool updateState(bool connected);
 
 	private:
+		/**
+		* Read the state of the reverse button
+		* 
+		* This function should *only* be called as part of updateState(bool),
+		* to update the state of the device.
+		* 
+		* @returns the state of the reverse button, 'true' if pressed,
+		*          'false' otherwise
+		*/
+		virtual bool readReverseButton();
+
 		/**
 		* Distance from neutral on Y to register a gear as
 		* being engaged (as a percentage of distance from
@@ -756,6 +767,7 @@ namespace SimRacing {
 
 		AnalogInput analogAxis[2];  ///< Axis data for X and Y
 		PinNum pinReverse;          ///< The pin for the reverse gear button
+		bool reverseState;          ///< Buffered value for the state of the reverse gear button
 	};
 
 	/// @} Shifters