Button with interrupt (GPIO.add_event_detect) in Raspberry Pi - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does GPIO.add_event_detect do in Raspberry Pi programming?

It sets up an interrupt to watch a GPIO pin for a specific event, like a button press, so the program can react immediately without constantly checking the pin.

beginner

Why use interrupts with buttons instead of checking the button state in a loop?

Interrupts let the program respond instantly when the button is pressed, saving CPU time and making the program more efficient and responsive.

intermediate

What are the common event types you can detect with GPIO.add_event_detect?

You can detect GPIO.RISING (button press going from low to high), GPIO.FALLING (high to low), or GPIO.BOTH (any change).

intermediate

How do you attach a function to run when a button press is detected using GPIO.add_event_detect?

Use the callback parameter to give the function name. This function runs automatically when the event happens.

intermediate

What is 'debounce' and why is it important when using button interrupts?

Debounce is a short delay to ignore extra signals caused by the button's mechanical bounce, preventing multiple unwanted triggers.

What parameter do you use with GPIO.add_event_detect to specify the event type?

A GPIO.RISING

B GPIO.PIN

C GPIO.MODE

D GPIO.CALLBACK

GPIO.RISING, GPIO.FALLING, or GPIO.BOTH specify the event type to detect.

Which argument lets you run a function automatically when a button event is detected?

A callback

B event

C pin

D mode

The callback argument is used to assign a function to run on the event.

Why is debouncing needed when using button interrupts?

A To detect long presses

B To speed up the program

C To change the button's voltage

D To prevent multiple triggers from one press

Debouncing prevents multiple triggers caused by the button's mechanical bounce.

What happens if you don't use interrupts and check button state in a loop?

A The program runs faster

B The button won't work

C The program wastes CPU time constantly checking

D The button triggers automatically

Polling wastes CPU time and can make the program less responsive.

Which event type detects when a button is released (goes from high to low)?

A GPIO.RISING

B GPIO.FALLING

C GPIO.BOTH

D GPIO.NONE

GPIO.FALLING detects when the signal goes from high to low, like a button release.

Explain how to set up a button interrupt using GPIO.add_event_detect on a Raspberry Pi.

Think about the steps to watch a pin and run code when the button changes state.

Describe why using interrupts with buttons is better than checking the button state in a loop.

Consider how the program behaves when waiting for a button press.