2. Potentiometer Class

A potentiometer can be connected to a microbit using a breadboard.

Create a class for the Potentiometer that makes it easy to:

• get the potentiometer analog reading,

• keep track of the last reading,

• be able to tell if the potentiometer analog reading has changed

• and to convert the reading to a particular range, such as, from 0 to 10.

The code below, first checks to see if the value of the potentiometer has changed, and then if it has, displays the value as a scaled value in the range 0 to 10 via display.show(pot.get_range(10)).

pot = Potentiometer() uses the default pin: pin0.

The pin is kept track of via the self.io_pin variable.

To use pin1 instead, use pot = Potentiometer(pin1) instead of pot = Potentiometer()

The line self.last_val = -1 sets last_val to be a value it cannot be, -1, so that the first reading will be recognised as a change.

# potentiometer using class
from microbit import *


class Potentiometer:
    def __init__(self, io_pin=pin0):
        self.io_pin = io_pin
        self.last_val = -1

    def get_val(self):
        return self.io_pin.read_analog()

    def was_changed(self):
        curr_val = self.get_val()
        if self.last_val != curr_val:
            self.last_val = curr_val
            return True
        else:
            return False

    def get_range(self, rng):
        analog_read = self.get_val()
        scaled = rng * (analog_read / 1023)
        return int(scaled)

# this defaults to pin0
# to use pinl1 instead use pot = Potentiometer(pin1)
pot = Potentiometer()
while True:
    if pot.was_changed():
        display.show(pot.get_range(10))

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Tasks

1. Modify the code so there is a short sleep between potentiometer readings.

2. Modify the code so that the potentiometer only displays values from 0 to 5.

---

Tasks

1. Modify the code to use a potentiometer to set the image to display.

   from microbit import *
   
   images = [
       Image.ARROW_N,
       Image.ARROW_NE,
       Image.ARROW_E,
       Image.ARROW_SE,
       Image.ARROW_S,
       Image.ARROW_SW,
       Image.ARROW_W,
       Image.ARROW_NW,
   ]
   
   img_num = 0
   while True:
       display.show(images[img_num])
   

2. Modify the code to use a potentiometer to set the image to display.

   from microbit import *
   
   images = [
       Image.HAPPY,
       Image.SMILE,
       Image.SAD,
       Image.CONFUSED,
       Image.ANGRY,
       Image.ASLEEP,
       Image.SURPRISED,
       Image.SILLY,
       Image.FABULOUS,
       Image.MEH,
   ]
   
   img_num = 0
   while True:
       display.show(images[img_num])
   

Q1

Modify the code to use a potentiometer to set the image to display.

from microbit import *

images = [
    Image.ARROW_N,
    Image.ARROW_NE,
    Image.ARROW_E,
    Image.ARROW_SE,
    Image.ARROW_S,
    Image.ARROW_SW,
    Image.ARROW_W,
    Image.ARROW_NW,
]
images_rng = len(images) - 1

class Potentiometer:
    def __init__(self, io_pin=pin0):
        self.io_pin = io_pin
        self.last_val = -1

    def get_val(self):
        return self.io_pin.read_analog()

    def was_changed(self):
        curr_val = self.get_val()
        if self.last_val != curr_val:
            self.last_val = curr_val
            return True
        else:
            return False

    def get_range(self, rng):
        analog_read = self.get_val()
        scaled_read = rng * (analog_read / 1023)
        return int(scaled_read)


pot = Potentiometer(pin1)
while True:
    if pot.was_changed():
        img_num = pot.get_range(images_rng)
        display.show(face_images[img_num])

Q2

Modify the code to use a potentiometer to set the image to display.

from microbit import *

images = [
    Image.HAPPY,
    Image.SMILE,
    Image.SAD,
    Image.CONFUSED,
    Image.ANGRY,
    Image.ASLEEP,
    Image.SURPRISED,
    Image.SILLY,
    Image.FABULOUS,
    Image.MEH,
]
images_rng = len(images) - 1


class Potentiometer:
    def __init__(self, io_pin=pin0):
        self.io_pin = io_pin
        self.last_val = -1

    def get_val(self):
        return self.io_pin.read_analog()

    def was_changed(self):
        curr_val = self.get_val()
        if self.last_val != curr_val:
            self.last_val = curr_val
            return True
        else:
            return False

    def get_range(self, rng):
        analog_read = self.get_val()
        scaled_read = rng * (analog_read / 1023)
        return int(scaled_read)


pot = Potentiometer(pin1)
while True:
    if pot.was_changed():
        img_num = pot.get_range(images_rng)
        display.show(images[img_num])