Rotary Encoder with micro:bit

Learn to use the rotary encoder with micro:bit

Written By: Cherie Tan

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The rotary encoder is an electro-mechanical switch. Its output signal can be used to determine the direction that its knob is being rotated. Not only that, but it is also capable of continuous rotation, unlike a regular potentiometer.

In this guide, learn to connect it to a micro:bit and program it using the MakeCode editor.

After completing this guide, you will understand the basics in using a rotary encoder. It has wide applications from robotics to computer input.

Step 1   The Module

  • Let's take a closer look at the rotary encoder module. It has five pins:

    Encoder Pin 1 (CLK)

    Encoder Pin 2(DT)

    Switch (SW)

    3.3V  : This pin on the module is labelled '+'. We'll connect the VCC pin to 3.3V on the micro:bit

    GND: In electronics, we define a point in a circuit to be a kind of zero volts or 0V reference point, on which to base all other voltage measurements. This point is called  ground or GND.

  • Voltage is the difference in potential between two points. As it is difficult to talk about voltage without a reference point, we need another point to compare it to. 
  • Please use the M-F jumper wires included in the kit to connect this module to the breadboard.

Step 2   Connect GND to GND

Step 3   Connect 3.3V to +

Step 4   Connect P1 to DT

Step 5   Connect P2 to CLK

Step 6   Upload the code

  • Connect the micro:bit to your computer using a microUSB cable
  • Click on the 'Download' button in MakeCode editor
  • Open up Finder on the Mac OSX or if you are using Windows, open up Windows explorer. Find the downloaded hex file in your Downloads folder
  • Drag and drop this hex file to the MICRO:BIT drive
  • The micro:bit will flash as the code is being uploaded.Now, if you turn the rotary encoder knob, the number will change and display on the micro:bit's LED matrix!

Step 7   Download the KY-040 package

  • First, open up MakeCode editor and start a new project. We will need to download the KY-040 package for the rotary encoder module to work.  So click on the 'Advanced' tab
  • Click on 'Extensions' tab
  • Type 'KY-040' in the search bar
  • Click on 'rotary-encoder-KY-040' library and it will be added to the MakeCode editor

Step 8   Turn it left or right

RotaryEncoder.onRotateEvent(RotationDirection.Left, function () {
RotaryEncoder.onRotateEvent(RotationDirection.Right, function () {
RotaryEncoder.init(Pins.P2, Pins.P1, Pins.P0)
  • Copy and paste this code into the Javascript interface.

Step 9   Connect P0 to SW

Step 10   Show numbers

let Num = 0
RotaryEncoder.onRotateEvent(RotationDirection.Right, function () {
    Num += 0 + 5
RotaryEncoder.onRotateEvent(RotationDirection.Left, function () {
    Num += 0 - 5
RotaryEncoder.init(Pins.P2, Pins.P1, Pins.P0)
basic.forever(function () {
  • Replace the code with this in the Javascript interface
  • What happens:
    • Minus 5 from the variable, 'Num,' each time the rotary encoder is rotated left
    • Add 5 to the variable, 'Num' each time the rotary encoder is rotated right

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