attachInterrupt() function in Arduino - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the attachInterrupt() function in Arduino?

The attachInterrupt() function is used to set up an interrupt on a specific pin. It tells the Arduino to watch for a change on that pin and run a special function (called an interrupt service routine) when that change happens.

beginner

What are the three main parameters of attachInterrupt()?

The three main parameters are:<br>1. interrupt number: which interrupt to use (often linked to a pin)<br>2. ISR function: the function to run when the interrupt happens<br>3. mode: the condition that triggers the interrupt (like RISING, FALLING, CHANGE, or LOW)

beginner

What does the mode parameter in attachInterrupt() control?

The mode parameter controls when the interrupt triggers. It can be:<br>- RISING: when the pin goes from LOW to HIGH<br>- FALLING: when the pin goes from HIGH to LOW<br>- CHANGE: when the pin changes in any way<br>- LOW: when the pin is LOW (only on some boards)

intermediate

Why should the function called by attachInterrupt() be short and fast?

Because interrupt functions stop the main program to run immediately, they should be quick to avoid delaying the rest of the program. Long or slow code in interrupts can cause missed events or unstable behavior.

beginner

How do you detach an interrupt that was set with attachInterrupt()?

You use the detachInterrupt() function with the interrupt number to stop the Arduino from watching that interrupt pin.

Which parameter of attachInterrupt() specifies the function to run when the interrupt triggers?

A Interrupt number

B Pin number

C Mode

D ISR function

The ISR (Interrupt Service Routine) function is the code that runs when the interrupt happens.

What does the RISING mode mean in attachInterrupt()?

A Pin stays LOW

B Pin changes from HIGH to LOW

C Pin changes from LOW to HIGH

D Pin changes in any way

RISING triggers the interrupt when the pin goes from LOW to HIGH.

Why should interrupt service routines be kept short?

A To avoid blocking the main program for too long

B To make the code easier to read

C To save memory

D To use more CPU power

Long interrupt routines can delay the main program and cause missed events.

Which function stops an interrupt set by attachInterrupt()?

A stopInterrupt()

B detachInterrupt()

C removeInterrupt()

D disableInterrupt()

detachInterrupt() disables the interrupt watching the pin.

What happens if you use CHANGE mode in attachInterrupt()?

A Interrupt triggers on any change from HIGH to LOW or LOW to HIGH

B Interrupt triggers only on LOW state

C Interrupt triggers only on RISING edge

D Interrupt triggers only on FALLING edge

CHANGE mode triggers the interrupt on any change in the pin's state.

Explain how to use attachInterrupt() to run a function when a button is pressed.

Think about what happens electrically when the button is pressed.

Describe why interrupt service routines should be short and what problems can happen if they are not.

Imagine stopping your friend while they are talking for a quick question versus a long story.