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60 mins
245 points
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Microbit Finder

In this lesson we will use one Microbit to detect how close you are to another Microbit using radio signals.

Learning Goals Learning Outcomes Teacher Notes Lesson Files

1 - Introduction

For this project you will need 2 Microbits. Both of them will need to be powered on and one of the power sources will need to let you walk around with the Microbit, so either a Microbit battery pack or a USB power bank.

The code that we create will be downloaded onto both Microbits and we will use the A and B buttons to set which Microbit is "lost" and which one is the "finder".

2 - Create a new Microbit project

Go to the website and create a new project.

3 - Create 2 variables

For this project we will need to create the following 2 variables:

  1. mode - this will store if the Microbit is acting as the "lost" Microbit or the "finder" Microbit.
  2. signal - this will store the signal strength that we will use to determine how close the Microbits are to each other.

Create a variable called mode and a variable called signal and then add the following code to setup the 'mode' variable to a blank string "".

let mode = ""

4 - Set the radio group

We need to set the radio group that our Micorbits will be broadcasting on so that they can communicate with each other. A radio group is the channel that the Microbit both sends it's messages and listens for other messages. A Microbit can only send or receive in one group at a time.

Add the following code to set the radio group to 1.

let mode = ""
mode = ""

5 - Set the mode

Next we are going to program the A and the B buttons to set the mode of each Microbit.

If you press the button A then you will set that Microbit to be the finder Microbit.

If you press the button B then you will set that Microbit to be the lost Microbit.

Add the following code:

input.onButtonPressed(Button.A, function () {
    mode = "finder"

input.onButtonPressed(Button.B, function () {
    mode = "lost"
We set an icon to show for the lost Microbit so we can tell them apart. You can choose any icon to display.

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