Controlling Raspberry Pi GPIO with RPi.GPIO

The GPIO interface of the Raspberry Pi is like the nerve endings of a small computer, capable of sensing external signals and controlling various peripherals. Using the RPi.GPIO module, we can easily manipulate these pins with Python code. Whether it’s lighting up a small bulb, controlling a motor, or reading sensor data, it’s all possible. In short, this is the bridge that allows the Raspberry Pi to interact with the real world.

Basic GPIO Setup

To get started with GPIO, you need to import the module:

import RPi.GPIO as GPIO

# Set numbering mode, I usually use BCM
GPIO.setmode(GPIO.BCM)

# Turn off warning messages, to avoid annoyance
GPIO.setwarnings(False)

⚠️ Tip: BCM and BOARD are two different numbering methods, don’t get them mixed up! BCM uses GPIO numbering, while BOARD uses physical pin numbering. Newcomers are advised to use BCM first, it’s easier to remember.

Light Up an LED

Let’s start with the simplest LED light:

# Set pin 18 as output mode
GPIO.setup(18, GPIO.OUT)

# Light up the LED
GPIO.output(18, GPIO.HIGH)

# Wait for 2 seconds
import time
time.sleep(2)

# Turn off the light
GPIO.output(18, GPIO.LOW)

Remember to clean up after the experiment:

# Clean up before going home
GPIO.cleanup()

Read Button Status

Buttons are also essential for hardware projects:

# Set pin 23 as input, enable internal pull-up resistor
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_UP)

while True:
    # Read button status
    if GPIO.input(23) == GPIO.LOW:
        print("Button has been pressed!")
    time.sleep(0.1)

⚡ Tip: Adding a <span>try-except</span> can help the program exit gracefully:

try:
    while True:
        if GPIO.input(23) == GPIO.LOW:
            print("Button has been pressed!")
        time.sleep(0.1)
except KeyboardInterrupt:
    GPIO.cleanup()

PWM Dimming and Speed Control

To adjust the brightness of an LED or the speed of a motor, you need to use PWM (Pulse Width Modulation):

# Create a PWM object with frequency 100Hz
led_pwm = GPIO.PWM(18, 100)

# Start PWM with a duty cycle of 0%
led_pwm.start(0)

# Gradually brighten
for dc in range(0, 101, 5):
    led_pwm.ChangeDutyCycle(dc)
    time.sleep(0.1)

# Stop PWM
led_pwm.stop()

🎯 Note: Don’t set the PWM frequency too high, generally 100Hz is sufficient. The duty cycle ranges from 0-100, indicating the proportion of time the power is on.

Using Event Detection for Buttons

Constantly checking the button status in a loop wastes resources; using event detection is more advanced:

def button_callback(channel):
    print(f"Button triggered on pin {channel}!")

# Set up edge detection
GPIO.add_event_detect(23, GPIO.FALLING, callback=button_callback, bouncetime=200)

# Main program continues to do other tasks
while True:
    time.sleep(1)
    print("Program is running...")

💡 Knowledge point: <span>bouncetime</span> is used to eliminate button bouncing, measured in milliseconds. When the button is pressed, it can generate multiple signals; setting a delay can prevent repeated triggers.

These are the most commonly used operations in RPi.GPIO! Mastering these will allow you to develop fun hardware projects. The most interesting part of hardware development is seeing tangible results, unlike pure software development, which only involves staring at a screen. Just think, with this knowledge, you could create an automatic watering device or a remotely controlled car; isn’t that cool?