Solutions to Exercises

Micro:bit - Getting Started

  1. A micro:bit is a pocket sized computer that you can make all sorts of projects like musical instruments or games.
  2. A magnetometer can detect the direction the micro:bit is facing, like a compass.
  3. A micro:bit can be powered on by 2x AAA Batteries or through USB.
  4. What are the 4 steps in coding the micro:bit. Design, Edit/Coding, Compile and Copy/Flash to micro:bit and Test.

Hello World!

  1. Here is the solution code
from microbit import *

while True:
        display.scroll('John')
        sleep(2000)
        display.scroll(15)
        sleep(1000)
  1. Answer: The display on the micro:bit will be updated to 4.
  2. Answer: You will see the value of 5 printed on the REPL window

LED Display

  1. Here is one of the solution
from microbit import *

display.show(STICKFIGURE)
sleep(1000)
  1. Here is the solution
from microbit import *

while True:
display.show(Image.ALL_ARROWS,delay=200)

To change the speed of animation, change delay to another value

  1. Here is one of the solution
from microbit import *

while True:
    image1 = Image("00000:"
                  "00000:"
                  "00000:"
                  "00000:"
                  "00000")
    image2 = Image("50000:"
                   "55000:"
                   "50500:"
                   "50050:"
                   "55555")
    image3 = Image("90000:"
                   "9900:"
                   "90900:"
                   "90090:"
                   "99999")
    image4 = Image("50000:"
                   "55000:"
                   "50500:"
                   "50050:"
                   "55555")
    image5 = Image("00000:"
                  "00000:"
                  "00000:"
                  "00000:"
                  "00000")
    all_image = [image1, image2, image3, image4, image5]
    display.show(all_image,delay=300)
  1. Here is the solution
from microbit import *

while True:
    # display pixel at bottom of screen
    display.set_pixel(2,4,9)
    if button_a.is_pressed():
        # range = 9 is the total number of frames for the jumping animation
        for i in range(9):
            # abs operator means absolute value
            y = abs(4-i)
            display.set_pixel(2,y,9)
            sleep(100)
            # clears display every frame
            display.clear()

Buttons

  1. Here is the solution
from microbit import *

i=0
j=0
display.show(Image.PACMAN)
sleep(100)
while True:
    if pin0.is_touched():
        sum=i+j
        display.show("=")
        sleep(200)
        display.show(sum)
        sleep(300)
        i,j=0,0
    elif button_a.is_pressed():
        i = i+1
        display.show(str(i))
        sleep(500)
    elif button_b.is_pressed():
        j=j+1
        display.show('+' +str(j))
        sleep(50)
  1. Here is the solution
from microbit import *

vote_A = 0
vote_B = 0
display.scroll("Vote? A-ham B-eggs")
while True:
    if button_a.is_pressed() and button_b.is_pressed():
        display.scroll("ham= " +str(vote_A) + " eggs= " + str(vote_B))
    elif button_a.is_pressed():
        vote_A = vote_A + 1
        display.show(Image.YES)
        sleep(100)
        display.scroll('ham')
    elif button_b.is_pressed():
        vote_B = vote_B + 1
        display.show(Image.YES)
        sleep(100)
        display.scroll('eggs')
    sleep(500)

Accelerometer

  1. Solution
from microbit import *

while True:
    if accelerometer.get_x() < -200:
        display.show(Image.ARROW_W)
    elif accelerometer.get_x() > 200:
        display.show(Image.ARROW_E)
    else:
        display.show(Image.SQUARE_SMALL)
    sleep(300)
  1. Solution
from microbit import *
import math

while True:
    x = accelerometer.get_x()
    y = accelerometer.get_y()
    z = accelerometer.get_z()
    acceleration = math.sqrt(x**2 + y**2 + z**2)
    if acceleration > 2000:
        display.show(Image.SQUARE)
        sleep(500)
    else:
        display.set_pixel(2,2,9)
    sleep(100)
    display.clear()
  1. Solution
from microbit import *

while True:
    # checks if there was a 'shake' gesture since the last was_gesture()
    if accelerometer.was_gesture('shake'):
       display.show(Image.HEART_SMALL)
       sleep(1000)
    else:
        display.clear()
  1. Solution
from microbit import *
import random

while True:
    if button_a.was_pressed():
       display.show(random.randrange(1,7))
       sleep(500)

Compass

  1. Solution
from microbit import *

while True:
        direction = compass.heading()
        if direction < 23 or direction >= 338:
                display.show(Image.ARROW_N)
        elif direction < 68 and direction >= 23:
                display.show(Image.ARROW_NW)
        elif direction < 113 and direction >= 68:
                display.show(Image.ARROW_W)
        elif direction < 158 and direction >= 113:
                display.show(Image.ARROW_SW)
        elif direction < 203 and direction >= 158:
                display.show(Image.ARROW_S)
        elif direction < 248 and direction >= 203:
                display.show(Image.ARROW_SE)
        elif direction <= 293 and direction >= 248:
                display.show(Image.ARROW_E)
        elif direction < 338 and direction >= 293:
                display.show(Image.ARROW_NE)

2. Use the command compass.calibrate to do this. Magnetic forces from metals or electronic gadgets will affect the calibration.

Thermometer

1. Temperature reading should change, but it will largely depend on the temperature of the chip in the micro:bit. Turned on for extended period of time will make the reading become higher than the surroundings.

  1. Solution
from microbit import *

while True:
    temp = temperature()
    display.show(str(temp) + 'C')
    sleep(500)
  1. Here is the solution
from microbit import *

while True:
    temp_C = temperature()
    temp_F = temp_C * 1.8 + 32
    temp_K = temp_C + 273
    display.scroll(str(temp_C)+'C')
    if button_a.was_pressed():
        display.scroll(str(temp_F)+'F')
    elif button_b.was_pressed():
        display.scroll(str(temp_K)+'K')
    sleep(100)

Music

  1. Solution
from microbit import *
import music

while True:
    # checks only the acceleration on x axis
    acc = accelerometer.get_x()
    # length of tone, negative number means continuous
    length = -1
    music.pitch(abs(acc), length)

Radio

  1. Solution
from microbit import *
import radio


radio.on()
radio.config(channel=19)        # Choose your own channel number
radio.config(power=7)           # Turn the signal up to full strength

my_message = "YOLO!"
another_message = "What's up?"

# Event loop.
while True:
        if button_a.was_pressed():
            radio.send(my_message)
            display.show(Image.YES)
            sleep(500)
        if button_b.was_pressed():
            radio.send(another_message)
            display.show(Image.YES)
            sleep(500)
        incoming = radio.receive()
        if incoming is not None:
            display.show(incoming)
            print(incoming)
        sleep(500)
  1. Solution
from microbit import *
import radio


radio.on()
radio.config(channel=19)        # Choose your own channel number
radio.config(power=7)           # Turn the signal up to full strength

my_message = "YOLO!"
another_message = "What's up?"

# Event loop.
while True:
        temp = radio.receive()
        if temp is not None:
            display.show("Temp=" + str(temp))
            print("Temp=" + str(temp))
        sleep(300)
  1. Solution

micro:bit in PC receiving the message

from microbit import *
import radio


radio.on()
radio.config(channel=19)        # Choose your own channel number
radio.config(power=7)           # Turn the signal up to full strength

# Event loop.
while True:
        temp = radio.receive()
        if temp is not None:
            display.show("Temp=" + str(temp))
            print("Temp=" + str(temp))
        sleep(300)

micro:bit sending the temperature

from microbit import *
import radio


radio.on()
radio.config(channel=19)        # Choose your own channel number
radio.config(power=7)           # Turn the signal up to full strength

# Event loop.
while True:
        temp = temperature()
        radio.send(str(temp))
        display.show(temp)
        sleep(300)

Control Structures

  1. Solution
from microbit import *
import math

def fib(max_num):
    a,b=0,1
    for i in range(max_num):
        display.scroll(a)
        if b > max_num:
            return
        sleep(500)
        a,b = b,b+a
fib(200)
display.show(Image.YES)
  1. Solution
from microbit import *
import random

# welcome message
display.show(Image.HEART)
sleep(500)

while True:
    if button_a.was_pressed():
        flip = random.randint(0,1)
        if flip:
            # display head, represented by a skull
            display.show(Image.SKULL)
        else:
            # display tails, represented by a small square
            display.show(Image.SQUARE_SMALL)
        sleep(300)

Data Types

  1. Solution
from microbit import *
import random

# welcome message
display.show(Image.HEART)
sleep(500)

number = []
for i in range(20):
    number.append(random.randint(2,100))

for num in number:
    for i in range(2,num):
        if num%i == 0:
            display.scroll(str(num)+" is not prime")
            sleep(1000)
            break
    else:
        display.scroll(str(num)+" is a prime")
        sleep(1000)
  1. Solution
from microbit import *

# welcome message
display.show(Image.HEART)
sleep(500)

count = 0
message = "Python is the best programming language in the world!"
vowel = ["a","e","i","o","u","A","I","O","U"]

# convert message into list, each elemet is a letter
mess = list(message)

# iterate on each element on list
for letter in mess:
    # iterate on each vowel
    for v in vowel:
        if v == letter:
            count = count+1

display.scroll("vowels="+str(count))
  1. Solution
from microbit import *
import random

value = [0,]
while True:
    value[0] = random.randint(0,1000)
    tuple1 = tuple(value)
    print(tuple(tuple1))
    sleep(300)
    del tuple1