![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/Raspberry-Pi-Pico-Interrupts.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nNew to the Raspberry Pi Pico? <\/strong>Check out our eBook: Learn Raspberry Pi Pico\/Pico W with MicroPython<\/a>. <\/p>\n\n\n\n In this guide, we’ll cover the following subjects:<\/p>\n\n\n\n To follow this tutorial, you need MicroPython firmware installed on your Raspberry Pi Pico board. You also need an IDE to write and upload the code to your board.<\/p>\n\n\n\n The recommended MicroPython IDE for the Raspberry Pi Pico is Thonny IDE. Follow the next tutorial to learn how to install Thonny IDE, flash MicroPython firmware, and upload code to the board.<\/p>\n\n\n\n Interrupts are useful for making things happen automatically in microcontroller programs and can help solve timing problems. Interrupts and event handling provide mechanisms to respond to external events, enabling your Raspberry Pi Pico to react quickly to changes without continuously polling (continuously checking the current value of a pin or variable).<\/p>\n\n\n\n Interrupts are signals that pause the normal execution flow of a program to handle a specific event. When an interrupt happens, the processor stops the execution of the main program to execute a task and then gets back to the main program. That task is also referred to as an interrupt handling routine<\/em>, as shown in the figure below.<\/p>\n\n\n Using interrupts is especially useful to trigger an action whenever motion is detected or whenever a pushbutton is pressed without the need for constantly checking its state; or to make something happen periodically without constantly checking the time.<\/p>\n\n\n\n There are different types of interrupts: external interrupts and timed interrupts.<\/p>\n\n\n\n To set an interrupt in MicroPython, you need to follow the next steps:<\/p>\n\n\n\n 1<\/strong>. Define an interrupt handling function<\/strong><\/p>\n\n\n\n The interrupt handling function should be as simple as possible, so the processor gets back to the execution of the main program quickly. The best approach is to signal the main code that the interrupt has happened by using a global variable. <\/p>\n\n\n\n The interrupt handling function should accept a parameter of type Pin<\/span>. This parameter is returned to the callback function and it refers to the GPIO that caused the interrupt. You\u2019ll better understand these concepts when we start testing some examples.<\/p>\n\n\n\n 2. <\/strong>Set up the interrupt pin as an input. For example:<\/p>\n\n\n\n 3.<\/strong> Attach an interrupt to that pin by calling the irq()<\/span> method:<\/p>\n\n\n\n The irq()<\/span> method accepts the following arguments:<\/p>\n\n\n\n The following picture will help you better understand the different trigger modes.<\/p>\n\n\n To demonstrate how to handle interrupts, we\u2019ll build some simple projects with a pushbutton and an LED. Wire a pushbutton to GPIO 21 and an LED to GPIO 20.<\/p>\n\n\n\n Here\u2019s a list of the parts you need for these examples:<\/p>\n\n\n\n You can use the preceding links or go directly to MakerAdvisor.com\/tools<\/a> to find all the parts for your projects at the best price!<\/p> For the examples in this section, connect an LED to GPIO20 and a pushbutton to GPIO21. You can use the following diagram as a reference.<\/p>\n\n\n Recommended reading<\/strong>: Raspberry Pi Pico and Pico W Pinout Guide: GPIOs Explained<\/a>.<\/p>\n\n\n\n This is one of the simplest examples to demonstrate how interrupts work. Copy the following code to Thonny IDE.<\/p>\n\n\n View raw code<\/a><\/p>\n\n\n\n In this example, you create an input object called button<\/span>. [Learn more about RPi Pico Inputs here<\/a>]<\/p>\n\n\n\n Then, you add an interrupt to that pin as follows:<\/p>\n\n\n\n This line means that when the button signal goes into RISING<\/span> mode (from LOW<\/span> to HIGH<\/span>), the button_pressed<\/span> function will be called.<\/p>\n\n\n\n The button_pressed<\/span> function, simply prints on the Shell that the button was pressed.<\/p>\n\n\n\n Notice that the definition of the function comes before creating the interrupt. In MicroPython, any user-defined function must be defined before being called.<\/p>\n\n\n\n Run the previous code on your Raspberry Pi Pico board. You\u2019ll get a message on the Shell every time you press the pushbutton.<\/p>\n\n\n In this example, we\u2019ll count the number of button presses with the help of a global variable. This will help you better understand how global variables work.<\/p>\n\n\n View raw code<\/a><\/p>\n\n\n\n In this example, we create a global variable called counter<\/span> \u2014 it is declared and initialized outside the button_pressed<\/span> function.<\/p>\n\n\n\n To use that variable inside the function, we need to use the keyword global<\/span> within the function\u2014 this way, the variable counter<\/span> is defined globally, making it accessible and modifiable both inside and outside the function.<\/p>\n\n\n\n When the button is pressed and the button_pressed<\/span> function is called, the global counter<\/span> variable is incremented, and its updated value is printed.<\/p>\n\n\n\n Note:<\/strong> counter +=1 is short for counter = counter +1<\/p>\n\n\n\n Run the previous code on your Raspberry Pi Pico. Notice that it will print on the Shell the number of times you pressed the button.<\/p>\n\n\n This is similar to the previous example, but we also toggle an LED when you press the pushbutton.<\/p>\n\n\n View raw code<\/a><\/p>\n\n\n\n In this example, we just need to declare a new Pin<\/span> object for the LED, in this case on GPIO 20.<\/p>\n\n\n\n Then, we add the instruction to toggle the LED inside the button_pressed<\/span> function.<\/p>\n\n\n\n You must have noticed that sometimes, the pushbutton will count more than one press when in fact, you just pressed once. This is called mechanical bouncing, and it\u2019s very common in mechanical buttons like pushbuttons.<\/p>\n\n\n This happens because the electrical contacts inside the button connect and disconnect very quickly before reaching a steady state, which will cause the system to register multiple press events, causing an inaccurate count.<\/p>\n\n\n\n To prevent this issue, we can add some debouncing techniques using delays or timer interrupts. We\u2019ll take a look at timer interrupts and events in the following section, where you\u2019ll learn how to debounce a button.<\/p>\n\n\n\n Besides buttons, external interrupts can be used for a wide variety of applications on the Raspberry Pi Pico, including sensor inputs, rotary encoders, and other real-time event-driven scenarios.<\/p>\n\n\n\n One of the most common applications is for PIR motion sensors. These sensors go to a triggered state (HIGH<\/span>) for a few seconds after motion is detected. So, using an interrupt in rising mode is a great way to detect when the sensor detects motion.<\/p>\n\n\n\n Recommended reading<\/strong>: Raspberry Pi Pico: Detect Motion using a PIR Sensor (MicroPython)<\/a>.<\/p>\n\n\n There are also other sensors like smoke sensors, rain sensors, water level sensors, and sound sensors, among others, that send a digital signal when the readings cross a certain threshold. Detecting when the sensor sends such a signal can also be achieved with interrupts because we can detect that state without having to constantly poll the value on a certain GPIO.<\/p>\n\n\n\n Using timer interrupts is especially useful to make something happen periodically or after a predefined period without constantly checking the elapsed time.<\/p>\n\n\n The Micropython machine<\/span> module comes with a class called Timer<\/span> that provides methods to execute a callback function periodically within a given period or once after some predefined delay. This is useful to schedule events or to run periodic tasks without the need to constantly check the elapsed time.<\/p>\n\n\n\n Let\u2019s take a quick look at the Timer<\/span> constructors.<\/p>\n\n\n\n To create a timer, call the Timer()<\/span> constructor as follows:<\/p>\n\n\n\n Then, you initialize a timer using the init()<\/span> method on the Timer()<\/span> object and you pass as argument the timer mode, period, and the callback function. Here\u2019s an example:<\/p>\n\n\n\n This initializes a periodic timer that will run the timer_callback<\/span> function every 1000 milliseconds (1 second). You can change the period parameter to any desired period.<\/p>\n\n\n\n Instead of calling the callback function periodically, you may also want to run it once after a predefined time. For that, you can use the Timer.ONE_SHOT<\/span> mode as follows:<\/p>\n\n\n\n This line of code configures a timer (my_timer<\/span>) to run in a one-shot mode, triggering the specified callback function (timer_callback<\/span>) after 1000 milliseconds.<\/p>\n\n\n\n In this example, you\u2019ll learn how to blink an LED using a Timer. This will help you understand how periodic timers work.<\/p>\n\n\n\n We\u2019ll blink an LED connected to GPIO 20. So, wire an LED to your Raspberry Pi Pico on that GPIO. You can use the following diagram as a reference.<\/p>\n\n\n The following example makes use of the Timer<\/span> class to blink an LED every half a second.<\/p>\n\n\nTable of Contents<\/h2>\n\n\n\n
\n
\n
\n
Prerequisites \u2013 MicroPython Firmware<\/h2>\n\n\n\n
\n
Introducing Interrupts<\/h2>\n\n\n\n
What are Interrupts?<\/h3>\n\n\n\n
![\"How](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2019\/03\/interrupt.png?resize=992%2C291&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nTypes of Interrupts<\/h3>\n\n\n\n
\n
External Interrupts in MicroPython<\/h2>\n\n\n\n
def handle_interrupt(pin):<\/code><\/pre>\n\n\n\ninterrupt_pin = Pin(21, Pin.IN)<\/code><\/pre>\n\n\n\ninterrupt_pin.irq(trigger=Pin.IRQ_RISING, handler=handle_interrupt)<\/code><\/pre>\n\n\n\n\n
\n
![\"Interrupt](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/interrupt-modes.png?resize=750%2C438&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n
\n\n\n\nExternal Interrupts with a Pushbutton (Examples)<\/h2>\n\n\n\n
\n
![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\nCircuit Diagram<\/h3>\n\n\n\n
![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-Pushbutton-LED.png?resize=842%2C606&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nExample 1: Detecting a Pushbutton Press<\/h3>\n\n\n\n
# Rui Santos & Sara Santos - Random Nerd Tutorials\r\n# Complete project details at https:\/\/RandomNerdTutorials.com\/raspberry-pi-pico-interrupts-micropython\/\r\n\r\nfrom machine import Pin\r\n\r\nbutton = Pin(21, Pin.IN, Pin.PULL_DOWN)\r\n\r\ndef button_pressed(pin):\r\n print("Button Pressed!")\r\n\r\n# Attach the interrupt to the button's rising edge\r\nbutton.irq(trigger=Pin.IRQ_RISING, handler=button_pressed)<\/code><\/pre>\n\tbutton = Pin(21, Pin.IN, Pin.PULL_DOWN)<\/code><\/pre>\n\n\n\nbutton.irq(trigger=Pin.IRQ_RISING, handler=button_pressed)<\/code><\/pre>\n\n\n\ndef button_pressed(pin):\n print(\"Button Pressed!\")<\/code><\/pre>\n\n\n\nTesting the Code<\/h4>\n\n\n\n
![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-Button-Press-Interrupt.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-Detect-Button-Press-Python-Shell-Demonstration.png?resize=643%2C205&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nExample 2: Counting the Number of Button Presses<\/h3>\n\n\n\n
# Rui Santos & Sara Santos - Random Nerd Tutorials\r\n# Complete project details at https:\/\/RandomNerdTutorials.com\/raspberry-pi-pico-interrupts-micropython\/\r\n\r\nfrom machine import Pin\r\n\r\nbutton = Pin(21, Pin.IN, Pin.PULL_DOWN)\r\ncounter = 0 # Initialize the button press count\r\n\r\ndef button_pressed(pin):\r\n global counter # Declare variable as global\r\n counter +=1\r\n print("Button Pressed! Count: ", counter)\r\n\r\n# Attach the interrupt to the button's rising edge\r\nbutton.irq(trigger=Pin.IRQ_RISING, handler=button_pressed)\r\n<\/code><\/pre>\n\tcounter = 0 # Initialize the button press count<\/code><\/pre>\n\n\n\nglobal counter # Declare variable as global\ncounter +=1\nprint(\"Button Pressed! Count: \", counter)<\/code><\/pre>\n\n\n\nTesting the Code<\/h4>\n\n\n\n
![\"pushbutton](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/pushubtton-counter-testing-Micropython-RPi-Pico-Shell.png?resize=689%2C329&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nExample 3: Toggling an LED on each Button Press<\/h3>\n\n\n\n
# Rui Santos & Sara Santos - Random Nerd Tutorials\r\n# Complete project details at https:\/\/RandomNerdTutorials.com\/raspberry-pi-pico-interrupts-micropython\/\r\n\r\nfrom machine import Pin\r\n\r\nled = Pin(20, Pin.OUT)\r\nbutton = Pin(21, Pin.IN, Pin.PULL_DOWN)\r\ncounter = 0 # Initialize the button press count\r\n\r\ndef button_pressed(pin):\r\n global counter # Declare variable as global\r\n counter +=1\r\n print("Button Pressed! Count: ", counter)\r\n \r\n # Toggle the LED on each button press\r\n led.value(not led.value())\r\n\r\n# Attach the interrupt to the button's rising edge\r\nbutton.irq(trigger=Pin.IRQ_RISING, handler=button_pressed)<\/code><\/pre>\n\tled = Pin(20, Pin.OUT)<\/code><\/pre>\n\n\n\nled.value(not led.value())<\/code><\/pre>\n\n\n![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/06\/Raspberry-Pi-Pico-Pushbutton-LED-demonstration.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nButton Bouncing<\/h4>\n\n\n\n
![\"debounce](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/button-bounce.png?resize=750%2C476&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nOther Applications<\/h4>\n\n\n\n
![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2023\/09\/Raspberry-Pi-Pico-PIR-Motion-Sensor-Detect-Motion-Demonstration.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n
\n\n\n\nTimer Interrupts<\/h2>\n\n\n\n
![\"Timer](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/timer-interrupts.png?resize=250%2C250&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nThe MicroPython class Timer<\/em><\/h3>\n\n\n\n
Creating a Timer<\/h4>\n\n\n\n
my_timer = Timer()<\/code><\/pre>\n\n\n\nmy_timer.init(mode=Timer.PERIODIC, period=1000, callback=timer_callback)<\/code><\/pre>\n\n\n\nmy_timer.init(mode=Timer.ONE_SHOT, period=1000, callback=timer_callback)<\/code><\/pre>\n\n\n\nExample 1: Blinking an LED with a Timer<\/h2>\n\n\n\n
Circuit Diagram<\/h3>\n\n\n\n
![\"RPi](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-with-LED-circuit-diagram.jpg?resize=681%2C500&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\nCode<\/h3>\n\n\n\n
# Rui Santos & Sara Santos - Random Nerd Tutorials\r\n# Complete project details at https:\/\/RandomNerdTutorials.com\/raspberry-pi-pico-interrupts-micropython\/\r\n\r\nfrom machine import Pin, Timer\r\nfrom time import sleep\r\n\r\n# LED pin\r\nled_pin = 20\r\nled = Pin(led_pin, Pin.OUT)\r\n\r\n# Callback function for the timer\r\ndef toggle_led(timer):\r\n led.value(not led.value()) # Toggle the LED state (ON\/OFF)\r\n\r\n# Create a periodic timer\r\nblink_timer = Timer()\r\nblink_timer.init(mode=Timer.PERIODIC, period=500, callback=toggle_led) # Timer repeats every half second\r\n\r\n# Main loop (optional)\r\nwhile True:\r\n print('Main Loop is running')\r\n sleep(2)<\/code><\/pre>\n\t
![\"RPi](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-main-loop-running-timer-thonny-ide.png?resize=689%2C239&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"RPi](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-Blinking-LED-2.jpg?resize=714%2C402&quality=100&strip=all&ssl=1\")
<\/figure>\n<\/div>\n\n\n\n![\"RPi](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/RPi-Pico-Blinking-LED-1.jpg?resize=714%2C402&quality=100&strip=all&ssl=1\")
<\/figure>\n<\/div>\n<\/div>\n\n\n\n![\"Raspberry](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2025\/05\/Rpi-Pico-Wiring-two-LEDs.png?resize=969%2C683&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n