Introduction

Within this tutorial we are going to create a countdown timer using a micro:bit and the MakeCode editor.

Getting Started

You Will Need

  • 1 x micro:bit
  • 1 x micro USB cable
  • 1 x computer with internet connection

Open Google Chrome on your computer by clicking this icon

Chrome browser icon

Once Chrome has opened type: makecode.microbit.org into the search bar and press enter and click on new preoject once the pages has loaded.

Let's Get Coding!

Code

Click and drag the forever block to the left until you see a bin icon. Now drop it, this has deleted that block as we don't need it.

Create a variable

  1. Click on Variables.

  2. Click on Make a Variable.

  3. Type "seconds" into the text box and click Ok.

Setting seconds to 0 on start

Click and drag a set seconds to 0 block to within the on start block. Your code should now look like this:

Setting seconds to 0

Increasing the timer by 1 when button A is pressed

  1. Click on Input.

  2. Click and drag an on button A pressed block to the coding area.

  3. Click on Logic.

  4. Click and drag an if true then block into the coding area and attach within on button A pressed.

  5. Click on Logic.

  6. Click and drag a 0 < 0 block and drop it where it says true within the if then code block. Your code should now look like this:

if 0 is less than 0 then do
  1. Click on Variables.

  2. Click and drag a seconds block and attach it within the first 0 of the if then code block.

  3. Where the second 0 is type 20. Your code should now look like this:

If seconds is less than 20 do
  1. Click on Variables.

  2. Click and drag a change seconds by 1 block to the coding area and attach it within the if then block.

  3. Click on Basic.

  4. Click and drag a show number and attach it under the change seconds by block.

  5. Click on Variables.

  6. Click and drag a seconds block and attach it into the 0 of the show number block.

  7. Click on Basic.

  8. Click on more.

  9. Click and drag a clear screen block and attach it under the show number block. Your code should now look like this:

if seconds is less than 20 then change seconds by 1. Display seconds on screen. clear screen

Start the timer when B is pressed

  1. Click on Input.

  2. Click and drag an on button A pressed and drag it to the coding area.

  3. Click on the small arrow next to "A" and click on B.

  4. Click on Loops.

  5. Click and drag a while true do block on to the coding area and attach it to on button B pressed.

  6. Click on Logic.

  7. Click and drag a 0 = 0 block to the code area and attach it to where it says true within the while do block. Your code should look like this:

when button B is pressed while 0 minus 0 do
  1. Click on Variables.

  2. Click and drag a seconds block and attach it to the first 0 in the while do block.

  3. Click on the small arrow next to the = sign and click on the > sign. Your code should now look like this:

When buttionB is pressed while seconds is greater than 0 do
  1. Click on Basic.

  2. Click and drag a Show number block to the code area and attach it within the while do block.

  3. Click on Variables.

  4. Click and drag the seconds block and attach it within the 0 of the show number block. Your code should look like this:

When button B is pressed do while seconds is greater than 0 do show number seconds on screen
  1. Click on Basic.

  2. Click and drag a pause (ms) 100 block and attach it under show number.

  3. Click on the small arrow next to 100 and click on 1 second.

  4. Click on Variables.

  5. Click and drag a change seconds by 1 block and attach it under the pause block.

  6. Click on Math.

  7. Click and drag a 0 - 0 block to the coding area and attach it within the 1 of the change seconds by block. Change the second 0 to 1. Your code should look like this:

When button B is pressed do. While seconds is greater than 0 show number seconds on screen pause for 1 second change seconds by 0 minus 1
  1. Click on Basic.

  2. Click and drag a show icon block to the code area and attach it under the while do block.

  3. Click on the little arrow next to the heart and click on the X image.

Well done you have completed the code!

Completed Code

Completed code 

Testing

Let's grab a micro:bit and test our code. If you don't have a micro:bit use the virtual micro:bit within the MakeCode editor.

Downloading Your Code

  1. Click on the Download button.

  2. Save your code to the Downloads folder on your computer.

  3. Connect the micro:bit to your computer using the micro USB cable.

  4. Drag the .hex file from the Downloads folder to your micro:bit drive.

Running The Code

Press button A on your micro:bit to count up to 20 seconds. or anywhere in-between.

When you are ready to start your timer press button B and watch your micro:bit count down to 0 and display the X.

Challenges

  1. Try to increase your timer to 60 seconds.

  2. Look up how long it takes to boil an egg.

  3. Try and adapt your code to time a boiling egg.