ForeverCode.md

Code the forever block

In the previous step you started writing some code for the first part of the algorithm when the micro:bit starts. In this step you will write the code that will run in the forever block.

The algorithm

The main part of our algorithm is:

• Run forever:
  • Send a message
  • Check our counter:
    • If the counter is more than 0:
      • Show a smiley face
      • Take 1 away from the counter
    • If the counter is 0
      • Show an X
  • Wait for 1 second

This code will all be put in the forever block.

Send a message

• Select Radio from the toolbox

  

• Drag the radio send string "" block and drop it inside the forever block

• Select the empty string value " ". Type inside this to set the value to be something unique to you and your friends. This is your secret code that means your micro:bits will only smile when your friends are around, not just anyone with the same program. In the image below, I used the value BitsCrew.

  

Check the counter

To check the counter, you will need a conditional - a block that does different things depending on if a condition is met, such as if a value is the same as another. Conditionals can also have what is known as an else block - a block that is run if the condition is not met.

Conditionals are in the Logic section of the toolbox.

• Select Logic from the toolbox

  

• Drag the if ... else block inside the forever block, below the radio send string block

  

Conditions can be boolean, so if a value is true or false. They can also be comparisons, comparing two values to see if they are the same, one is larger than the other, or whatever comparison is needed.

The algorithm checks the counter variable and has one block if the counter is greater than 0, and another block if the counter is not greater than 0.

The if ... else block has a section where you can drag comparisons, and comparisons have sections where you can drag variables.

• Select Logic from the toolbox

• Drag the 0 = 0 comparison block from the toolbox and drop it over the true value in the if ... else block

  

• Select Variables from the toolbox

• Drag the counter block and drop it over the first 0 in the comparison.

  

• Change the comparison from = to >. The statement should read if counter > 0 then.

  

Light the LEDs with a smiley face

If the counter is greater than one, then the LEDs will need to show a smiley face, and the counter will need to count down by 1.

• Select Basic from the toolbox

• Drag the show leds block into the top part of the conditional so that it is run if the condition is matched

• Select squares in the 5x5 grid to draw a smiley face

  

Reduce the counter by 1

• Select Variables from the toolbox

• Drag the change counter by 1 block to below the show leds block

• Select the value to change by and set this to -1

  

Light the LEDs with an X

This completes the algorithm for if the counter is greater than 0. The logic for if the counter is 0 will go into the else part of the if ... else block.

• Select Basic from the toolbox

• Drag the show leds block into the else part of the conditional so that it is run if the condition is not matched

• Select squares in the 5x5 grid to draw an X

  

Pause between loops of the forever block

The counter needs to count down the number of seconds, so at the end of the forever block it needs to wait one second before this block runs again. Waits use the pause block, and these pause for a number of milliseconds - a millisecond being one thousandth of a second.

• Select Basic from the toolbox

• Drag the pause (ms) 100 block into the forever block below the if ... else block.

• Select the pause time of 100ms. A menu will pop up with other times, so select 1 second.

  

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In this step you wrote the code that will run in the forever block. In the next step you will write the code to detect messages over the radio.