WIRING of KY-040 Rotary Encoder plus Demo Code

Other Hardware General Electronics
20

Thanks guys! I just received my KY-040 encoders for a project I'm going to start (a B737 MSC panel) so this example was very useful for me to understand encoders principles!

Btw, I suggest enabling internal pull-up for SW pin, as KY-040 SW output is not pulled-up (there is a spot for a 10k resistor below, but the resistor isn't there...), then a few other little changes like adding a LED to show current value, so this is my version.

const int PinCLK = 2;                   // Used for generating interrupts using CLK signal
const int PinDT = 3;                    // Used for reading DT signal
const int PinSW = 4;                    // Used for the push button switch
const int PinLED = 9;

int SW;
int oldSW;

volatile boolean encChanged;
volatile long encPosition = 0;
volatile boolean up;

void isr()  {                    // Interrupt service routine is executed when a HIGH to LOW transition is detected on CLK
	volatile boolean CLK = digitalRead(PinCLK);
	volatile boolean DT = digitalRead(PinDT);
	up = ((!CLK && DT) || (CLK && !DT));
	if (!up)
		encPosition++;
	else
		encPosition--;
	if (encPosition < 0) encPosition = 0;
	encChanged = true;
	delay(10);
}


void setup()  {
	pinMode(PinCLK, INPUT);
	pinMode(PinDT, INPUT);
	pinMode(PinSW, INPUT_PULLUP);
	pinMode(PinLED, OUTPUT);
	SW = HIGH;
	oldSW = HIGH;
	attachInterrupt(0, isr, FALLING);   // interrupt 0 is always connected to pin 2 on Arduino UNO
	Serial.begin(115200);
	Serial.println("Start");
}

void loop()  {
	SW = digitalRead(PinSW);
	if ( SW == LOW && oldSW == HIGH) {      // check if pushbutton is pressed
		encPosition = 0;              // if YES, then reset counter to ZERO
		Serial.print("Reset");
		encChanged = true;
	}
	oldSW = SW;

	if (encChanged)  {		    // do this only if rotation was detected
		encChanged = false;          // do NOT repeat IF loop until new rotation detected
		Serial.print("Count = ");
		Serial.println(encPosition);
		analogWrite(PinLED, encPosition);
	}
}