Why PWM is needed for analog-like control in Raspberry Pi - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start PWM on pin 18 with a frequency of 1000 Hz.

Raspberry Pi

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)
pwm = GPIO.PWM(18, [1])
pwm.start(0)

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A50

B500

C1000

D2000

Attempts:

3 left

💡 Hint

Common Mistakes

Using too low or too high frequency causing flickering or no effect.

The frequency for PWM is set to 1000 Hz to control the output signal speed.

2fill in blank

medium

Complete the code to set the duty cycle to 75%, which controls the analog-like output level.

Raspberry Pi

pwm.ChangeDutyCycle([1])

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A25

B75

C50

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing duty cycle with frequency or using values outside 0-100.

The duty cycle of 75% means the signal is ON 75% of the time, simulating an analog output.

3fill in blank

hard

Fix the error in the code to properly stop PWM and clean up GPIO.

Raspberry Pi

pwm.[1]()
GPIO.cleanup()

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Astop

Bclose

Cend

Dterminate

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like close() or end() causing runtime errors.

The correct method to stop PWM is stop(). This stops the PWM signal before cleaning up GPIO.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps each brightness level to its duty cycle if the level is greater than 50.

Raspberry Pi

brightness_levels = [30, 60, 90]
duty_cycles = {level: [1] for level in brightness_levels if level [2] 50}

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Alevel

B>

C<

Dlevel * 2

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong comparison operators or incorrect value expressions.

The dictionary comprehension uses the level as the duty cycle and filters levels greater than 50.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps the uppercase level name to its duty cycle if the duty cycle is less than 80.

Raspberry Pi

levels = {'low': 30, 'medium': 60, 'high': 90}
filtered = { [1]: [2] for [3] in levels.items() if [2] < 80 }

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Alevel.upper()

Bduty

Clevel, duty

Dlevels

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names or forgetting to unpack items.

The comprehension maps uppercase level names to duty cycles, filtering duty cycles less than 80.