Debounce hx616 pulse counting to prevent extraneous accumulated value

Don't count pulses caused by reconnecting coin signal pin

Or powering on the hx616

Or changing the physical switches on the hx616

Still possible but less likely as pulse high/low must be 20-200ms

src/coin-acceptor/hx616.cpp

@@ -13,8 +13,20 @@ namespace {
 	uint16_t numPulses = 0;
 	unsigned short coinSignalPin;
 
+	uint8_t minPulseTime = 20;// milliseconds
+	uint8_t maxPulseTime = 200;// milliseconds
+	unsigned long pinFallTime;
+
 	void IRAM_ATTR onPinStateChange() {
-		numPulses++;
+		const auto pinState = digitalRead(coinSignalPin);
+		if (pinState == LOW) {
+			pinFallTime = millis();
+		} else if (pinFallTime > 0) {
+			const unsigned long diffTime = millis() - pinFallTime;
+			if (diffTime >= minPulseTime && diffTime <= maxPulseTime) {
+				numPulses++;
+			}
+		}
 	}
 }
 
@@ -33,7 +45,7 @@ namespace coinAcceptor_hx616 {
 			} else {
 				logger::write("Initializing HX616 coin acceptor...");
 				pinMode(coinSignalPin, INPUT_PULLUP);
-				attachInterrupt(coinSignalPin, onPinStateChange, RISING);
+				attachInterrupt(coinSignalPin, onPinStateChange, CHANGE);
 				state = State::initialized;
 			}
 		}