Sunfounder Rotery Encoder

//Rotary Encoder
/*You will see the angular displacement of the rotary encoder printed on Serial Monitor.
When you turn the rotary encoder clockwise, the angular displacement is increased;
when turn it counterclockwise, the displacement is decreased.
If you press the switch on the rotary encoder, the readings will return to zero.*/
//Email: support@sunfounder.com
//Website: www.sunfounder.com
//2015.5.7
const int clkPin= 2; //the clk attach to pin 2
const int dtPin= 3; //the dt pin attach to pin 3
const int swPin= 4 ;//the sw pin attach to pin 4
int encoderVal = 0;
void setup()
{
//set clkPin,dePin,swPin as INPUT
pinMode(clkPin, INPUT);
pinMode(dtPin, INPUT);
pinMode(swPin, INPUT);
digitalWrite(swPin, HIGH);
Serial.begin(9600); // initialize serial communications at 9600 bps
}
void loop()
{
int change = getEncoderTurn();//
encoderVal = encoderVal + change;
if(digitalRead(swPin) == LOW)//if button pull down
{
encoderVal = 0;
}
Serial.println(encoderVal);
}
int getEncoderTurn(void)
{
static int oldA = HIGH; //set the oldA as HIGH
static int oldB = HIGH; //set the oldB as HIGH
int result = 0;
int newA = digitalRead(clkPin);//read the value of clkPin to newA
int newB = digitalRead(dtPin);//read the value of dtPin to newB
if (newA != oldA || newB != oldB) //if the value of clkPin or the dtPin has changed
{
// something has changed
if (oldA == HIGH && newA == LOW)
{
result = (oldB * 2 - 1);
}
}
oldA = newA;
oldB = newB;
return result;
}