Goal
Connect two micro:Bits together
Send signals from the first micro:Bit to the second micro:Bit by pressing the A and B buttons
Receive signals from the first micro:Bit
Learn how to code in MakeCode
Materials
2 x micro:Bits
4 x Crocodile Clips
1 x micro USB cable
Step 0 – Preview
We will be writing two sets of code: one for the sending micro:Bit and another for the receiving micro:Bit
In order for the receiver to know which signal is being sent, we will adjust the length of time between when the signal turns “on” and “off”
That way, we can differentiate the two signals by the pause length
Step 1 – Crocodile Clips
We want to send signals from pin 1 of the first micro:Bit to pin 2 of the second micro:Bit (and vice versa)
Connect:
GND to GND
3V to 3V
Pin 1 to Pin 2
Pin 2 to Pin 1
Step 2 – Sender: button A
We want a signal to be sent when the A button is pressed. Let’s make this one the “dot” signal.
Open up MakeCode and name this file “Sender”
Drag and drop an if-then-else block from the Logic drawer to the Forever block
From the Input drawer, attach a button A is pressed block to the if section
From the Basic drawer, attach a show led block in the then section to display the “dot” on the sender screen
Add a digital write pin block from the Pins drawer (under Advanced) and set it to 1
This means the signal will turn “on”
Make sure to change it to p1 since that’s where we attached the clip
Add a pause block from the Basic drawer and set it to 230 ms
This pause will be associated with the “dot” signal
Add another digital write pin block and set it to 0
This means the signal will turn “off”
Add another pause for 50 ms just to give it some time
Step 3 – Sender: Button B
We want a “dash” signal to be sent when the B button is pressed.
Add an else if block to the if-then-else block from earlier
Repeat the steps as with Step 2, except
Use button B is pressed
Display a “dash” in the LED
Pause for 470 ms
Add a clear screen block from Basic or an icon to the else statement
Step 4 – Receiver: detecting the signal
We want to record the duration of time between whenever the signal is received and when it stops. We will be using the running time (ms) block for this.
Create another project on MakeCode called “Receiver”
Drag a while loop from the Loops drawer
From the Logic drawer, attach an equals sign block to the while loop
Attach a digital read pin block to the equals sign block and set it equal to 1
This means that a signal is being detected
Make sure to change it to p2 since that’s where the crocodile clip is
In the Variables drawer, make a variable called “keyDownTime”
Attach an if-then block to the body of the while loop
Attach a not block from the Logic drawer to the if statement and then attach the keyDownTime variable to it
Drag and drop a set variable to block to the body of the if-then block and change the variable to keyDownTime and attach the running time (ms) block to it
You can find the running time (ms) block by searching for it in the search bar
Step 5 – Receiver: displaying the signal
We want to display the correct signal on the screen.
Drag and drop an if-then block underneath the while loop and attach the keyDownTime variable to it
This is so that this block of code will only run if a signal has been detected
Create another variable called “duration” and set it to be the difference between running time and keyDownTime
The minus operation is under the Math drawer
This variable tells us how long it’s been since the program started running and when the signal was detected
Drag an if-then block and attach a less than block from the Logic drawer and make it so that it’s duration < 250
We chose 250 ms since the “dot” takes 230 ms
Display the “dot” led in the body of the if statement
Add an else if block to the if-then-else block from earlier and do the same thing as above except the “dash” threshold is 500 since the “dash” takes 470 ms and then show the “dash” led
Add a clear screen so that the screen clear after a signal comes in
After the first if-then block make sure to set keyDownTime to 0 so that it works every time you send a new signal
Done!
Make sure to flash the code to the respective micro:bits and test it out! It should display the same signal on both screen when you press a button.
For an added challenge, try to translate the morse code on the second micro:bit.
We're Done!
Looking for more projects to tinker and explore? We’re a launch partner for IMDA’s Digital Maker Programme, where we’ve been developing micro:bit kits, apps, and conducting workshops for schools and the public in Singapore. Read more here, and get in touch if you’d like to join our workshops!
