15. Pixel Class

15.1. 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 brightness 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 led_xy in led_list:
        led_xy.on()
        sleep(100)
    for led_xy in led_list:
        led_xy.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 list and the brightness list. 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 led_xy in led_list:
        led_xy.on()
        sleep(100)
    for led_xy in led_list:
        led_xy.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 led_xy in led_list:
        led_xy.on(brightness=3)
        sleep(100)
    for led_xy in led_list:
        led_xy.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 led_xy in led_list:
        led_xy.on(brightness=brightness_val)
        brightness_val += 2
        sleep(100)
    for led_xy in led_list:
        led_xy.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 list and the brightness list. 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]
# Convert zip object to list since the zip object would be used up in a for-loop
leds_brightness_list = list(zip(led_list, brightness_val_list))


while True:

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

---

15.2. Pixel Classes using accelerometer

The code below draws a pixel on the display.

The Pixel class keeps track of the pixel position, but leaves a trail of where it has been.

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 my_pix.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
    acc_x = accelerometer.get_x()
    if acc_x < -sensitivity:
        xd = -1
    elif acc_x > sensitivity:
        xd = 1
    else:
        xd = 0
    return xd


def acc_y_change():
    sensitivity = 100
    acc_y = accelerometer.get_y()
    if acc_y < -sensitivity:
        yd = -1
    elif acc_y > sensitivity:
        yd = 1
    else:
        yd = 0
    return yd


# Create an instance of a pixel object
my_pix = Pixel()
my_pix.show()
while True:
    my_pix.move(acc_x_change(),acc_y_change())
    my_pix.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 my_pix 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 my_pix with a brightness of 3.

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
    acc_x = accelerometer.get_x()
    if acc_x < -sensitivity:
        xd = -1
    elif acc_x > sensitivity:
        xd = 1
    else:
        xd = 0
    return xd


def acc_y_change():
    sensitivity = 100
    acc_y = accelerometer.get_y()
    if acc_y < -sensitivity:
        yd = -1
    elif acc_y > sensitivity:
        yd = 1
    else:
        yd = 0
    return yd


# Create an instance of a pixel object
my_pix = Pixel(brightness=3)
my_pix.show()
while True:
    my_pix.move(acc_x_change(),acc_y_change())
    my_pix.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
    acc_x = accelerometer.get_x()
    if acc_x < -sensitivity:
        xd = -1
    elif acc_x > sensitivity:
        xd = 1
    else:
        xd = 0
    return xd


def acc_y_change():
    sensitivity = 100
    acc_y = accelerometer.get_y()
    if acc_y < -sensitivity:
        yd = -1
    elif acc_y > sensitivity:
        yd = 1
    else:
        yd = 0
    return yd


# Create an instance of a pixel object
my_pix = Pixel(brightness=3)
my_pix.show()
while True:
    if button_a.was_pressed():
        my_pix.clear()
    my_pix.move(acc_x_change(), acc_y_change())
    my_pix.show()
    sleep(500)