3. Pixel Class

3.1. Pixel animation using classes

The Class LED is used to create several LED objects used in the animation.

e.g led02 = LED(0, 2) creates a pixel at x = 0 and y = 2.

The on method controls the microbit LED brightness.

e.g. led02.on() set the pixel at x = 0 and y = 2 to the default brightnes of 9.

The off method sets the pixel to 0 brightness.

A list of LED objects can be used in an animation: led_list = [led02, led12, led22, led32, led42]

from microbit import *


class LED():
    def __init__(self, x=2, y=2):
        self.x = x
        self.y = y

    def on(self, brightness=9):
        display.set_pixel(self.x, self.y, brightness)

    def off(self):
        display.set_pixel(self.x, self.y, 0)


led02 = LED(0, 2)
led12 = LED(1, 2)
led22 = LED(2, 2)
led32 = LED(3, 2)
led42 = LED(4, 2)

led_list = [led02, led12, led22, led32, led42]

while True:
    for ledxy in led_list:
        ledxy.on()
        sleep(100)
    for ledxy in led_list:
        ledxy.off()
        sleep(100)

Tasks

1. Modify the code to use a default brightness of 6.

2. Modify the code to use a brightness of 3 when the led is turned on in the for-loop.

3. Modify the code to use a brightness of 1, 3, 5, 7, 9 for each led from left to right. DO this by incrementing a counter called brightness_val.

4. Modify the code to use brightness_val_list = [9, 7, 5, 3, 1] to store the led brightnesses for the 5 leds from left to right. Use the zip function to zip the led lsit and the brightness lsit. Then loop though the zipped list to display the leds with decreasing brightness.

Q1

Modify the code to use a default brightness of 6.

from microbit import *


class LED():
    def __init__(self, x=2, y=2):
        self.x = x
        self.y = y

    def on(self, brightness=6):
        display.set_pixel(self.x, self.y, brightness)

    def off(self):
        display.set_pixel(self.x, self.y, 0)


led02 = LED(0, 2)
led12 = LED(1, 2)
led22 = LED(2, 2)
led32 = LED(3, 2)
led42 = LED(4, 2)

led_list = [led02, led12, led22, led32, led42]

while True:
    for ledxy in led_list:
        ledxy.on()
        sleep(100)
    for ledxy in led_list:
        ledxy.off()
        sleep(100)

Q2

Modify the code to use a brightness of 3 when the led is turned on in the for-loop.

from microbit import *


class LED():
    def __init__(self, x=2, y=2):
        self.x = x
        self.y = y

    def on(self, brightness=6):
        display.set_pixel(self.x, self.y, brightness)

    def off(self):
        display.set_pixel(self.x, self.y, 0)


led02 = LED(0, 2)
led12 = LED(1, 2)
led22 = LED(2, 2)
led32 = LED(3, 2)
led42 = LED(4, 2)

led_list = [led02, led12, led22, led32, led42]

while True:
    for ledxy in led_list:
        ledxy.on(brightness=3)
        sleep(100)
    for ledxy in led_list:
        ledxy.off()
        sleep(100)

Q3

Modify the code to use a brightness of 1, 3, 5, 7, 9 for each led from left to right. Do this by incrementing a counter called brightness_val.

from microbit import *


class LED():
    def __init__(self, x=2, y=2):
        self.x = x
        self.y = y

    def on(self, brightness=6):
        display.set_pixel(self.x, self.y, brightness)

    def off(self):
        display.set_pixel(self.x, self.y, 0)


led02 = LED(0, 2)
led12 = LED(1, 2)
led22 = LED(2, 2)
led32 = LED(3, 2)
led42 = LED(4, 2)

led_list = [led02, led12, led22, led32, led42]

while True:
    brightness_val = 1
    for ledxy in led_list:
        ledxy.on(brightness=brightness_val)
        brightness_val += 2
        sleep(100)
    for ledxy in led_list:
        ledxy.off()
        sleep(100)

Q4

Modify the code to use brightness_val_list = [9, 7, 5, 3, 1] to store the led brightnesses for the 5 leds from left to right. Use the zip function to zip the led lsit and the brightness lsit. Then loop though the zipped list to display the leds with decreasing brightness.

from microbit import *


class LED:
    def __init__(self, x=2, y=2):
        self.x = x
        self.y = y

    def on(self, brightness=9):
        display.set_pixel(self.x, self.y, brightness)

    def off(self):
        display.set_pixel(self.x, self.y, 0)


led02 = LED(0, 2)
led12 = LED(1, 2)
led22 = LED(2, 2)
led32 = LED(3, 2)
led42 = LED(4, 2)

led_list = [led02, led12, led22, led32, led42]
brightness_val_list = [9, 7, 5, 3, 1]
leds_brightness_list = zip(led_list, brightness_val_list)

while True:
    for ledxy, brightness_val in leds_brightness_list:
        ledxy.on(brightness=brightness_val)
        sleep(100)
    for ledxy in led_list:
        ledxy.off()
        sleep(100)

---

3.2. Pixel Classes using accelerometer

The code below draws a pixel on the display. The Pixel class keeps track of the pixel position.

The acc_x_change() and acc_y_change() functions return the change in x and y as the microbit is tilted.

These are passed to the move method of the Pixel object as in mypix.move(acc_x_change(),acc_y_change())

The move method uses min amd max to prevent the x or y values going outside the range 0 to 4, as seen in self.x_position = min(4, max(0, self.x_position + x_delta))

The show method sets the pixel with brightness 9, then 2, so that it appears to blink.

# pixel class with accelerometer
from microbit import *


class Pixel:
    def __init__(self, x_position=2, y_position=2):
        self.x_position = x_position
        self.y_position = y_position

    def move(self, x_delta, y_delta):
        self.x_position = min(4, max(0, self.x_position + x_delta))
        self.y_position = min(4, max(0, self.y_position + y_delta))

    def show(self):
        display.set_pixel(self.x_position, self.y_position, 9)
        sleep(50)
        display.set_pixel(self.x_position, self.y_position, 2)


def acc_x_change():
    sensitivity = 100
    accx = accelerometer.get_x()
    if accx < -sensitivity:
        xd = -1
    elif accx > sensitivity:
        xd = 1
    else:
        xd = 0
    return xd


def acc_y_change():
    sensitivity = 300
    accy = accelerometer.get_y()
    if accy < sensitivity:
        yd = -1
    elif accy > sensitivity:
        yd = 1
    else:
        yd = 0
    return yd


# Create an instance of a pixel object
mypix = Pixel()
mypix.show()
while True:
    mypix.move(acc_x_change(),acc_y_change())
    mypix.show()
    sleep(500)

---

Tasks

1. Modify the code to use a brightness parameter in the init function and replace the 2 in the show method with the parameter variable. Create mypix with a brightness of 6.

2. Add a clear method to the class, and use it to clear the display if the A-button was pressed.

Q1

Modify the code to use a brightness parameter in the init function and replace the 2 in the show method with the parameter variable. Create mypix with a brightness of 6.

from microbit import *


class Pixel:
    def __init__(self, x_position=2, y_position=2, brightness=2):
        self.x_position = x_position
        self.y_position = y_position
        self.brightness = brightness

    def move(self, x_delta, y_delta):
        self.x_position = min(4, max(0, self.x_position + x_delta))
        self.y_position = min(4, max(0, self.y_position + y_delta))

    def show(self):
        display.set_pixel(self.x_position, self.y_position, 9)
        sleep(50)
        display.set_pixel(self.x_position, self.y_position, self.brightness)


def acc_x_change():
    sensitivity = 100
    accx = accelerometer.get_x()
    if accx < -sensitivity:
        xd = -1
    elif accx > sensitivity:
        xd = 1
    else:
        xd = 0
    return xd


def acc_y_change():
    sensitivity = 300
    accy = accelerometer.get_y()
    if accy < sensitivity:
        yd = -1
    elif accy > sensitivity:
        yd = 1
    else:
        yd = 0
    return yd


# Create an instance of a pixel object
mypix = Pixel(brightness=6)
mypix.show()
while True:
    mypix.move(acc_x_change(),acc_y_change())
    mypix.show()
    sleep(500)

Q2

Add a clear method to the class, and use it to clear the display if the A-button was pressed.

from microbit import *


class Pixel:
    def __init__(self, x_position=2, y_position=2, brightness=2):
        self.x_position = x_position
        self.y_position = y_position
        self.brightness = brightness

    def move(self, x_delta, y_delta):
        self.x_position = min(4, max(0, self.x_position + x_delta))
        self.y_position = min(4, max(0, self.y_position + y_delta))

    def show(self):
        display.set_pixel(self.x_position, self.y_position, 9)
        sleep(50)
        display.set_pixel(self.x_position, self.y_position, self.brightness)

    def clear(self):
        for x in range(5):
            for y in range(5):
                display.set_pixel(x, y, 0)


def acc_x_change():
    sensitivity = 100
    accx = accelerometer.get_x()
    if accx < -sensitivity:
        xd = -1
    elif accx > sensitivity:
        xd = 1
    else:
        xd = 0
    return xd


def acc_y_change():
    sensitivity = 300
    accy = accelerometer.get_y()
    if accy < sensitivity:
        yd = -1
    elif accy > sensitivity:
        yd = 1
    else:
        yd = 0
    return yd


# Create an instance of a pixel object
mypix = Pixel(brightness=6)
mypix.show()
while True:
    if button_a.was_pressed():
        mypix.clear()
    mypix.move(acc_x_change(), acc_y_change())
    mypix.show()
    sleep(500)