Arduino Interrupt

Arduino Interrupt
Arduino Interrupt

Have you ever wished your Arduino to multitask? Your new best friend is interrupts. Arduino interrupts let it pause and run a different set of code. Ideal for time-sensitive operations including sensor reading, button detection, and communication line monitoring. They can be hard to grasp at first. Start at the beginning and master interrupts quickly with our beginner’s tutorial. You’ll study how interrupts can improve project responsiveness and efficiency. Interrupts will be demonstrated using real code. By the conclusion, you’ll know how to use interrupts like a coding ninja on Arduino.

What are Arduino Interrupts?

Arduino interrupts: let your Arduino stop what it’s doing and execute another function. An interrupt occurs when a timer overflows, a pin changes state, or serial data is received.

Hardware Interrupts

External events like button presses or sensor triggers cause hardware interrupts. Arduino runs interrupt-related function when this happens. You can attach an interrupt to pin 2 to execute when it gets HIGH.

Software Interrupts

Software interrupts are caused by internal events like timer overflows. A timer can trigger an interrupt at a given frequency. An interrupt every 100ms is possible with a timer.

Interrupts make your Arduino appear multitasking. The Arduino runs one process, but interruptions let it pause, execute another function, and restart. This is useful for reactive projects or timing-sensitive tasks.

Interrupts have drawbacks. Interrupts can cause uncertain main program timing since they pause it. The Arduino needs time to store its location, perform the interrupt function, and continue the main program, so interrupts should be short.

In Arduino programming, you must create an interrupt service routine (ISR) to run when an interrupt is triggered. Attach that ISR to a pin change or timer overflow interrupt. ISR runs when interrupt triggers. In conclusion, interruptions let your Arduino respond to events while running its main program. Interrupts allow Arduino projects to react at time by halting, running an interrupt service procedure, and restarting the main program.

External, Pin Change, Timer, Software Interrupts
External Interrupts

Button presses and sensor inputs cause external interrupts. These are useful when you require your Arduino to react promptly to real-world events. Connect an interrupt service routine (ISR) to one of the Arduino’s external interrupt pins (2 or 3 on the Uno) to use an external interrupt.

Pin-change interrupts

Changing pin values generate pin change interrupts. You can use them to detect changes on any pin, not only interrupt pins. Attaching an ISR to PCINT0 allows pin change interrupts. Check the PCMSK0 and PCIF0 registers in your ISR to see which pin changed.

Timers Interrupt

Arduino internal timers trigger interrupts. These help run code at precise intervals. Attach an ISR to the TIMER0_OVF vector for Timer 0 or TIMER1_OVF vector for Timer 1 to use timer interrupts. Reset the timer in your ISR to keep it running.

Software Interrupts

You invoke interrupt() in code to trigger software interrupts. They help you precisely control program interrupts. Attaching an ISR to PCINT0 allows software interrupts. Call noInterrupts() and interrupts() in your ISR to clear the interrupt flag.

With interrupts, the Arduino may respond to events instantaneously while running a main application. Complex projects that blend real-world and software events can use many interrupt types. Learn Arduino interrupts quickly with practice!

Utilizing ISRs

A function that executes on interrupt is an ISR. Instead of checking for events, ISRs let you run code when they happen. This helps with:

Button press detection

A button pin can be connected to an interrupt to call the ISR when pressed. This detects button presses without polling the button pin.

Timing Events

ISRs with timers execute code at precise intervals. To blink an LED at 1Hz, configure a timer to trigger an interrupt every second and toggle the LED in the ISR.

Communication Serial

Serial data detection is prevalent with ISRs. ISRs read and process received data.

Use attachInterrupt() to attach an interrupt to a pin or timer to set up an ISR. You specify the pin, interrupt type (rising, falling, or changing), and ISR function name. As an example:

void blink() Toggle LED digitally.Write(LED_PIN,!digitalRead(LED_PIN));

void setup() { pinMode(BUTTON_PIN, INPUT_PULLUP); attachInterrupt(BUTTON_PIN, blink, FALLING); // Call blink() on falling edge

When the button pin moves HIGH to LOW, this calls blink(). Quick execution is key in ISRs. Avoid delays and complicated tasks. Just flip a flag or increase a counter and handle the reasoning in your main loop. Since interrupts can happen at any time, you don’t want an ISR to interrupt itself!

ISRs enable responsive Arduino projects without inefficient polling. Enjoy coding!

Interrupt Best Practices

After enabling Arduino interrupts, implement recommended practices. Follow these recommendations to make interrupts efficient and bug-free.

Keep ISRs Keep interrupt service routines (ISRs) brief. ISRs momentarily interrupt the main program to run code, therefore you want to reduce their time. Use the ISR only when essential, such as setting a flag the main program may verify.

Avoid Delays

ISR delay() functions should never be used. This will pause the ISR and stop the main program for the delay. Set an ISR flag that the main program can check to delay if needed.

Beware Serial Communication

ISRs should avoid serial communication (Serial.print). Serial communication might lag and disrupt the main program.

Limit Global Variables

Use global variables in ISRs only when necessary. If altered from the ISR and main program, global variables might cause complex issues. Setting ISR flags that the main program acts on is preferable.

Restores State as Needed

Make sure to reset I/O pins and interrupts before the ISR terminates. This keeps the main application running.

Disable Interrupts When Needed

You may need to disable interrupts in your main program to avoid the ISR from running during essential code. Never disable interruptions without caution and re-enable them immediately to prevent missing them.

These best practices can help you master Arduino interrupts and construct bug-free interactive applications. Have more questions? Let me know!


Our Arduino interrupt beginner’s tutorial is complete! We explained interrupts, their types, and some easy projects to give you practice. Start simple and add complexity as you get used to it. Feel free to experiment with the example code. Arduino is best learned by doing. Now you can improve your talents. Mastering interrupts opens unlimited opportunities. Try what you learned today and make something cool. Only your creativity limits you! Share your newest interrupt-driven Arduino project in the comments. Happy creating!

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