Project19.Rotary Encoder
===========================


Description
------------
The rotary encoder can count the pulse outputting times during the process of 
rotation in positive and reverse direction.

This rotating counting is unlimited, not like potential counting. It can be 
restored to initial state to count from 0.

Specification
--------------
- Power Supply: 5V
- Interface: Digital
- Size: 30*20mm
- Weight: 7g

Connect
--------
.. image:: /img/connect/19_bb.png

Code
-----
.. code-block:: c

    #define SERIAL_BAUDRATE 115200
    #define CLK_PIN 2 // define connection pin
    #define DT_PIN 3
    #define SW_PIN 4

    #define interruptA 0 // UNO pin2 is interrupt 0，refer to the official website of other board

    volatile long count = 0;
    unsigned long t = 0;

    void setup() {
    Serial.begin(SERIAL_BAUDRATE);
    // when the state is down, the rotary encoder is rotated.
    attachInterrupt(interruptA, rotaryEncoderChanged, FALLING);
    pinMode(CLK_PIN, INPUT_PULLUP); // Input mode and enable internal pull up resistor
    pinMode(DT_PIN, INPUT_PULLUP); 
    pinMode(SW_PIN, INPUT_PULLUP); 
    }
    void loop() {
    if(digitalRead(SW_PIN) == LOW){ // Press the switch, return to zero
        count = 0;  
        Serial.println("count reset to 0");
        delay(300);
    }
    }
    void rotaryEncoderChanged(){ // when CLK_PIN is FALLING
    unsigned long temp = millis();
    if(temp - t < 200) // remove bounce
        return;
    t = temp;
    
    // DT_PIN state represents a forward or reverse.
    count += digitalRead(DT_PIN) == HIGH ? 1 : -1;
    Serial.println(count);
    }




Phenomenon
-----------
.. image:: /img/phenomenon/19.jpg