Draft activity for CoderDojo starter pack (Micro:Bit Python)

MB_CD_python.md

Making a Crowd Display with Micro:Bits and Python

Program a set of Micro:Bits so that they talk to each other via radio to create a synchonised light show.

Design your image

1. Connect the Micro:Bit to your computer using the USB cable.

2. Open the Mu editor.

3. Add the following code to import the Micro:Bit libraries you'll need.

   import radio
   import random
   from microbit import display, Image, button_a, sleep

4. Create an image to be shown on LEDs:

   pic = Image("90009:"
           "07070:"
           "00500:"
           "07070:"
           "90009")
   display.show(pic, delay=100, wait=False)

5. Click the Flash button at the top of the Mu window. Your image should appear on the LEDs. Can you edit your code to display a different image?

Setup the radio

1. Add some code to turn on the radio.

   radio.on()

2. Now add some code that will trigger when Button A is pressed and send a radio message. Enter some text to send as the message ("now" is used as an example here).

   	while True:
          if button_a.was_pressed():
              radio.send('now')

3. Move your ```display_show`` line so that it is only triggered when the same radio message is received.

           message = radio.receive()
           if message == 'now':
               display.show(pic, delay=100, wait=False)

4. Find someone else who is at the same point and test your code? Does pressing the A button cause their image to appear on their Micro:Bit?

5. Can you add sleep and display.clear() code so that the image disappears after a short delay?

   

Triggering an avalanche of messages

1. The Micro:Bit should sometimes re-broadcast the message after it has received it. Use random.randint to choose a number and only transmit the message again if it matches a certain value.

2. Use random.randint again to include a slight pause of up to 5 seconds before re-transmission.

   while True:
       if button_a.was_pressed():
           radio.send('now') 
   
       message = radio.receive()
       if message == 'now':
           display.show(pic, delay=100, wait=False)
           sleep(300)
           display.clear()
           if random.randint(0, 9) == 0:
               sleep(random.randint(0,5000))
               radio.send('now') 

3. Test your code as group. depending on how many Micro:Bits are taking part, you should adjust the random values so that avalanches occur with a frequency you're happy with.

4. Work as a group to extend the project.

• Modify the code that so pressing button B has a different effect.
• Can you coordinate your Micro:Bits so that pressing a button on one causes a text message to be displayed on the Micro:Bits one letter at a time?