t09 - olikraus/m2tklib GitHub Wiki

Tutorial 9: Incremental Rotary Encoder

This tutorial will describe setup and use of an incremental rotary encoder.

Support for incremental rotary encoder is added for v1.09 of M2tklib.

Theory

Hardware

The incremental rotary encoder has two outputs. These outputs must be connected to the microcontroller (Arduino board).

Setup

Event source: The event source must support the incremental rotary encoder. The event source m2_es_arduino_rotary_encoder for the Arduino environment supports normal keys (one per pin) and one attached rotary encoder (see M2tk).
Pin numbers: An incremental rotary encoder has two output pins. These pins must be attached to the microcontroller. The pin numbers must be provided to the event source. Use setPin() to set the pin numbers for the event source (M2_KEY_ROT_ENC_A, M2_KEY_ROT_ENC_B).

Action

The event source converts the signal values from the incremental rotary encoder into M2_KEY_NEXT and M2_KEY_PREV messages. This is done by calling checkKey(). Ensure to call this procedure very often.

Example

The following code is taken from the RecEnc example of the Arduino environment (U8glib variant).

This is a suitable constructor for M2tk with incremental rotary encoder:

M2tk m2(&top_menu, m2_es_arduino_rotary_encoder, m2_eh_4bd, m2_gh_u8g_bf);

The event handler m2_eh_4bd will use M2_KEY_NEXT and M2_KEY_DOWN to change the data and to move between elements.

For minimum user input M2tk requires two lines for the rotary encoder and one select button:

void setup(void) {
  // Connect u8glib with m2tklib
  m2_SetU8g(u8g.getU8g(), m2_u8g_box_icon);

  // Assign u8g font to index 0
  m2.setFont(0, u8g_font_7x13r);

  // define button for the select message
  m2.setPin(M2_KEY_SELECT, 7);          // dogm128 shield, 2nd from top
  
  // The incremental rotary encoder is conected to these two pins
  m2.setPin(M2_KEY_ROT_ENC_A, 3);
  m2.setPin(M2_KEY_ROT_ENC_B, 2);
}

The checkKey() procedure must be called outside and inside of the picture loop (U8glib):

void loop() {
  // check rotary encoder also inside the picture loop
  m2.checkKey();  
  // process events and redraw menu if required
  if ( m2.handleKey() != 0 ) {
    // picture loop starts here
    u8g.firstPage();  
    do {
      // check rotary encoder also inside the picture loop
      m2.checkKey();
      // draw menu
      m2.draw();
    } while( u8g.nextPage() );
  }
}

Conclusion