3. Radio secrets

3.1. Unique groups

Set up the group with a value 0-255 by changing the group value from 8 in: radio.config(group=8).

Turn on the radio using: radio.on()

Use button_a.was_pressed() to send a message, “A”.

Scroll any received messages.

if incoming_message is not None: relies on radio.receive() returning None when there is no message received.

from microbit import *
import radio

# Choose own group in pairs 0-255
radio.config(group=8)
# Turn on the radio
radio.on()

while True:
    # send
    if button_a.was_pressed():
        radio.send("A")
    # receive
    incoming_message = radio.receive()
    if incoming_message is not None:
        display.scroll(incoming_message)

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Exercise

1. Modify the code to send “Y” when A is pressed, and “N” when B is pressed in order to answer Yes/No questions in secret.

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3.2. Caesar cipher

Set up the group with a value 1 to 25 by changing the group value from 8 in: radio.config(group=8).

Turn on the radio using: radio.on()

Enter a secret message to send.

Scroll any received messages.

if incoming_message is not None: relies on radio.receive() returning None when there is no message received.

from microbit import *
import radio

# Set up radio with group from 1 to 25 to reuse it for the shift
radio.on()
group = 25
radio.config(channel=7, group=group)

# Caesar cipher parameters
SHIFT = group
ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
SECRET = 'WE_ARE_GROUP' + str(group)

def caesar_cipher(message, shift):
    """
    Apply a Caesar cipher to a message.
    """
    cipher_text = ''
    for char in message:
        if char in ALPHABET:
            # Shift character
            index = (ALPHABET.index(char) + shift) % len(ALPHABET)
            cipher_text += ALPHABET[index]
        else:
            cipher_text += char
    return cipher_text

while True:
    # Check for incoming messages
    incoming = radio.receive()
    if incoming:
        # Decode and display the message
        message = caesar_cipher(incoming, -SHIFT)
        display.scroll(message)

    # Check button presses to send a secret message
    if button_a.was_pressed():
        cipher_text = caesar_cipher(SECRET, SHIFT)
        radio.send(cipher_text)

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Exercises

1. Modify the group and secret.

2. Try setting up random groups by setting the group to a random integer from 1 to 9. Also use a secret message based on that group number.

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3.3. Caesar cipher 2

What does this code do?

What happens when the black reset button is pressed?

from microbit import *
import radio
import random

# Set up radio with group from 1 to 6 to reuse it for the shift
radio.on()

# Caesar cipher parameters

ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
groupx = random.randint(1, 3)
radio.config(channel=7, group=groupx)
SHIFT = groupx
SECRET = 'UR' + str(groupx)

def caesar_cipher(message, shift):
    """
    Apply a Caesar cipher to a message.
    """
    cipher_text = ''
    for char in message:
        if char in ALPHABET:
            # Shift character
            index = (ALPHABET.index(char) + shift) % len(ALPHABET)
            cipher_text += ALPHABET[index]
        else:
            cipher_text += char
    return cipher_text

while True:
    # Check for incoming messages
    incoming = radio.receive()
    if incoming:
        # Decode and display the message
        message = caesar_cipher(incoming, -groupx)
        display.scroll(message)
    # Check button presses to send a secret message
    if button_a.was_pressed():
        cipher_text = caesar_cipher(SECRET, SHIFT)
        radio.send(cipher_text)
    elif button_b.was_pressed():
        display.scroll(SHIFT)