14. Radio Treasure Hunt

For a treasure hunt, have some microbits to act as hidden treasure beacons; some as treasure hunters.

14.1. Treasure

Set multiple devices to act as treasure beacons each with their own id as a string. treasure_id = '1'
Set up the group value in radio.config(group=8).
Set the radio power to 0 so it can only be detected from close range radio.config(power=0). Power level 0 usually has a range less than 1 metre.
Hide the treasure beacons.

from microbit import *
import radio


# Set radio group and transmit power
radio.config(group=8, power=0)
radio.on()

treasure_id = '1' # change the number string for each treasure beacon
display.scroll(treasure_id)
sleep(2000)
display.clear()

while True:
    radio.send(treasure_id)
    sleep(200)

Tasks

Modify the code so that on pressing the A button the treasure_id is scrolled.

14.2. Treasure hunters

The treasure hunters look for treasure beacons and display the treasure id value.

from microbit import *
import radio


# Set radio group
radio.config(group=8)
radio.on()

while True:
    incoming_message = radio.receive()
    if incoming_message:
        display.scroll(incoming_message)
        sleep(200)

Challenges

See who can find the treasure first.

14.3. Buried Treasure

Use the random module to set the treasure beacons id to a random single digit integer as a string. treasure_id = str(random.randint(1, 9))
Use the power module deep_sleep method to conserve power: power.deep_sleep(wake_on=button_a, ms=min_ms, run_every=True)
Use run_every as a decorator to send the radio message every 5 seconds using send_id.

from microbit import *
import power
import radio
import random

# Set radio group and transmit power
radio.config(group=8, power=0)
# Set the received message handler
radio.on()

treasure_id = str(random.randint(1, 9))
display.show(treasure_id)
sleep(2000)
display.clear()

@run_every(s=5)
def send_id():
    radio.send(treasure_id)
    display.scroll(treasure_id)

min_ms = 60 * 1000
while True:
    # renew deep sleep every minute
    power.deep_sleep(wake_on=button_a, ms=min_ms, run_every=True)
    # display treasure_id
    if button_a.was_pressed():
        display.scroll(treasure_id)

Tasks

Modify the code so that pressing the B button changes the treasure_id to a new random integer between 1 and 9.

14.4. Treasure collectors

The treasure collectors remember the treasure ids that they have collected.

Use a list to store the treasure ids, but check if the treasure_id is in the list to avoid adding duplicate values.

from microbit import *
import radio

# Set radio group
radio.config(group=8)
# Set the received message handler
radio.on()

# Create a set to store unique ids
unique_ids = list()

while True:
    incoming_message = radio.receive()
    if incoming_message:
        # If the message is not already in the list, append it
        if incoming_message not in unique_ids:
            unique_ids.append(incoming_message)
        display.scroll(incoming_message)
        sleep(200)
    if button_a.was_pressed():
        display.scroll("-")
        for treasure_id in unique_ids:
            display.scroll(treasure_id)
        display.scroll("-")

14.5. Sorting a list using a function as a sort key

list.sort(reverse=True | False, key=myFunc)

Sorts the list, ascending by default.

Parameters:

Optional (key) – reverse=True will sort the list descending. Default is reverse=False
Optional – A function to specify the sorting criteria.

See: https://www.w3schools.com/python/ref_list_sort.asp

The list below has strings of integers.
A sort key is required to sort them numerically.
The sort_int_strings function is used as the key. It returns the integer from each string.
For each item in int_strings, the sort_int_strings function uses the item as an argument (which becomes the list_value in the function).
The sort_int_strings function converts the string to an integer and returns it.
The sort method then sorts the items in the list based on these integer values returned by the sort_int_strings function.
So, in essence, list_value is a placeholder for each item in the list as the sort method goes through the list.

from microbit import *

# A function that returns the integer from a string:
def sort_int_strings(list_value):
    return int(list_value)

int_strings = ['5', '4', '6', '3']
int_strings.sort(key=sort_int_strings)
for int_str in int_strings:
    display.scroll(int_str, delay=70)

Alternatively, a function, sort_int_strings, can return the sorted list.

from microbit import *

# A function that sorts a list of integer strings based on their integer values:
def sort_int_strings(lst):
    lst.sort(key=int)
    return lst

int_strings = ['5', '4', '6', '3']
int_strings = sort_int_strings(int_strings)
for int_str in int_strings:
    display.scroll(int_str, delay=70)

Tasks

Modify the treasure collector code to scroll the treasure ids in ascending order.

14.6. Find all the treasure

Rather than using random treasure ids from 1 to 9, the ids can be automatically incremented and looped.

The hunters can show when they have collected all the treasure ids.

Tasks

Modify the treasure beacon code so that the treasure_id is changed every 12 seconds. Increment the id and loop it.
Modify the treasure collector code so that the B button is used to display the number of treasure ids collected.