Software PWM with RPi.GPIO in Raspberry Pi - Mini Project: Build & Apply

Software PWM with RPi.GPIO

📖 Scenario: You have a Raspberry Pi and want to control the brightness of an LED using software PWM (Pulse Width Modulation). This means turning the LED on and off very quickly to simulate different brightness levels.We will use the RPi.GPIO library to control the GPIO pin connected to the LED.

🎯 Goal: Create a Python program that uses software PWM with RPi.GPIO to control the brightness of an LED connected to GPIO pin 18.

📋 What You'll Learn

Use the RPi.GPIO library to control GPIO pins

Set up GPIO pin 18 as an output

Create a software PWM instance on GPIO pin 18 with a frequency of 100 Hz

Start PWM with 0% duty cycle

Change the duty cycle to 50%

Stop PWM and clean up GPIO at the end

💡 Why This Matters

🌍 Real World

Software PWM is used to control devices like LEDs, motors, and buzzers by simulating analog output using digital pins.

💼 Career

Understanding PWM and GPIO control is essential for embedded systems, robotics, and IoT device programming.

1

Set up GPIO and pin

Import the RPi.GPIO library as GPIO. Set the GPIO mode to GPIO.BCM. Set up GPIO pin 18 as an output pin.

Raspberry Pi

import RPi.GPIO as GPIO

# Set GPIO mode to BCM
# Set up GPIO pin 18 as output
# Your code here

Need a hint?

Use GPIO.setmode(GPIO.BCM) to select pin numbering by BCM. Use GPIO.setup(18, GPIO.OUT) to set pin 18 as output.

2

Create PWM instance

Create a PWM instance called pwm on GPIO pin 18 with a frequency of 100 Hz.

Raspberry Pi

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)

# Create PWM instance pwm on pin 18 with 100 Hz frequency
# Your code here

Need a hint?

Use GPIO.PWM(pin, frequency) to create a PWM object.

3

Start PWM with 0% duty cycle and change to 50%

Start the PWM on pwm with a duty cycle of 0 percent. Then change the duty cycle to 50 percent.

Raspberry Pi

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)

pwm = GPIO.PWM(18, 100)

# Start PWM with 0% duty cycle
# Change duty cycle to 50%
# Your code here

Need a hint?

Use pwm.start(0) to start PWM with 0% brightness. Use pwm.ChangeDutyCycle(50) to set brightness to 50%.

4

Stop PWM and clean up GPIO

Stop the PWM on pwm and clean up the GPIO pins using GPIO.cleanup(). Then print "PWM stopped and GPIO cleaned up".

Raspberry Pi

import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.OUT)

pwm = GPIO.PWM(18, 100)

pwm.start(0)
pwm.ChangeDutyCycle(50)

# Stop PWM
# Clean up GPIO
# Print confirmation message
# Your code here

Need a hint?

Use pwm.stop() to stop PWM and GPIO.cleanup() to reset GPIO pins.