Raspberry Pi Pico GPIO Programming with MicroPython – LED Blinking Examples

In this tutorial, we will learn about how to use GPIO pins of Raspberry Pi Pico using MicroPython programming. For demonstration purposes, Firstly, we will see GPIO pins introduction of Raspberry Pi Pico. After that, we will take an LED blinking example. In the end, we will see an LED chaser example in MicroPython using Thonny IDE.

Prerequisites Raspberry Pi Pico GPIO Programming

In order to start, make sure you have performed the following procedures already:

1. Downloaded and installed the latest version of Python 3 on your PC.
2. Downloaded and installed the latest version of Thonny IDE.
3. Set up MicroPython in Raspberry Pi Pico.

If you want to know how to perform above steps, you can follow this step by step guide:

• Getting Started with Raspberry Pi Pico using Thonny IDE

If you are using uPyCraft IDE, you can check this getting started guide:

• Getting Started with Raspberry Pi Pico using uPyCraft IDE

After the above-mentioned procedures have been followed now, we will learn how to blink a single LED with our Raspberry Pi Pico board using MicroPython and Thonny IDE. Let us learn about the GPIOs for Raspberry Pi Pico to help us better understand the connections.

What are GPIOs?

GPIO is the abbreviated form of General Purpose Input/Output. These are digital signal pins found on the module which can be used as the input, output, and even both of them can be used together. These are controlled by us during run time.

Raspberry Pi Pico GPIO Pins

Raspberry Pi Pico exposes 26 multi-function GPIO pins from a total of 36 GPIO pins available in RP2040 microcontroller. Out of these 26 pins, 23 pins are digital pins, and only 3 pins have Analog read capability. These digital pins are marked as GP0, GP1, and up to GP22. GP23, GP24, and GP25 are not exposed on the pinout. Therefore cannot be used. GP26, GP27, and GP28 are the next digital pins available. These 26 GPIO pins can be used both in digital input and digital output mode. 

Recommended Reading: Raspberry Pi Pico – Getting Started Guide

Blinking LED Example Raspberry Pi Pico

Now we will start our project to blink an LED using Raspberry Pi Pico in MicroPython with the help of Thonny IDE.

In order to perform this project, we need the following equipment:

1. Breadboard
2. One LED
3. One 220  ohm resistor
4. Connecting Wires
5. Raspberry Pi Pico board

LED Blinking Connection Raspberry Pi Pico

Now make connections of Raspberry Pi Pico with an LED. Connect GPIO13 of Raspberry Pi Pico with an LED anode terminal through a 220 ohm current limiting resistor. Also, make sure to connect cathode terminal of an LED with the ground pin of the board.

Connect the components as shown in the schematic diagram below:

LED	Raspberry Pi Pico
Cathode (-)	GND
Anode (+)	GPIO13

LED Blinking MicroPython Script

Now let’s create an LED blinking script for Raspberry Pi Pico MicroPython.

First, create a new file by clicking on File > New in Thonny IDE.

Copy this code to the new opened untitled window:

import time
from machine import Pin
led=Pin(13,Pin.OUT)        #create LED object from pin13,Set Pin13 to output

while True:
  led.value(1)            #Set led turn on
  time.sleep(0.5)
  led.value(0)            #Set led turn off
  time.sleep(0.5)

After that click on the “Save” icon. This gives two options to save this file either to your computer or directly to your devices such as Raspberry Pi Pico. That means we can also directly upload files to a device. But for now, save it on your computer. You can select any location in your computer where you want to save this file. Save it as blink.py

You can use any other name as well just make sure it ends in .py

Now click on the “Run” button to upload code to Raspberry Pi Pico. Before uploading code make sure the correct board is selected.

How Code Works?

In this section, we will see how codes work.

Importing MicroPython GPIO and Time Libraries

In MicroPython, a machine module contains classes of different peripherals of a microcontroller such as GPIO, ADC, PWM, I2C, SPI, etc. In this tutorial, we are using GPIO pins of Raspberry Pi Pico. Therefore, we will import GPIO class from a machine module. Hence, here we import the Pin class from the machine module. We can create multiple instances of the Pin class to configure different GPIO pins of Raspberry Pi Pico.

from machine import Pin

Adding Delays

The time module in MicroPython contains different methods such as delay, sleep, etc. For example, we can use a sleep() method to insert delays into our MicroPython script.

import time

Creating Instance of Pin Class

As mentioned earlier, we can create multiple objects of an “led” class which we defined above. In this line, we create an instance of the Pin object “led”. But user can give any name to an object such as led13, led_13, etc.

led=Pin(13, Pin.OUT)

The Pin() class takes three parameters as shown below:

Pin(Pin_number, pin_mode, pull, value)

• First argument is a pin number to which we want to configure in different modes such as input, output, etc.
• Second argument defines the pin mode such as digital input (Pin.IN), digital output (Pin.OUT), open-drain (OPEN_DRAIN).
• Third argument specifies if we want to enable pull-up and pull-down internal resistor of a GPIO pin. These pull-up and pull-down resistors become handy when we want to use GPIO pins as a digital input pin (PULL_UP, or PULL_DOWN).
• Last argument defines the initial state of GPIO pin as either active high (1) or active low (0). But, by default, the GPIO initial state on reset is 0 (active low).

This is an infinite loop which keeps on running endlessly.

while True:      //infinite loop

Setting GPIO Pin State

Pin class contains a function known as value() which is used to set the state of GPIO pins. Passing 1 to this function will set the GPIO pin to an active high state. Similarly, passing 0 to this routine sets the GPIO pin to an active low state. Here, we have set the GPIO13 to an active high state by accessing a value() routine through an object “led”.

led.value(1)     // LED is turned on

This gives a delay of 0.5 seconds before the Led turns off again.

time.sleep(0.5)      //Delay of 0.5 seconds

Here, we have set the GPIO13 to an active low state by accessing a value() routine through an object “led”.

led.value(0)            //LED is turned off

This gives a delay of 0.5 seconds before the Led turns on again, therefore, producing the blinking effect.

time.sleep(0.5)       //Delay of 0.5 seconds

Demonstration

After we have saved the code press the Run button to upload the file to your Raspberry Pi Pico module.

You will see an LED blinking at a rate of one second as shown below:

Alternate Method

MicroPython Pin class also provides a method to set GPIO pins to active high or active low state without using any input such parameter know as led.on() and led.off(), where led is an object of a class Pin. This example shows the use of these methods.

import time
from machine import Pin
led=Pin(13,Pin.OUT)        #create LED object from pin13,Set Pin13 to output

while True:
  led.on()            #Set led turn on
  time.sleep(0.5)
  led.off()            #Set led turn off
  time.sleep(0.5)

Chasing Three LEDs using Raspberry Pi Pico

Now we will learn how to perform a chasing effect using three LEDs using the given modules in MicroPython. In other words, we will learn to use multiple GPIO pins of the pico board as output pins.

In order to perform this project we need the following equipment:

1. Breadboard
2. Three LEDs
3. Three 300 ohm resistors
4. Connecting Wires
5. Raspberry Pi Pico

Connect the components as shown in the schematic diagram below:

LED Chaser Script MicroPython

from machine import Pin
from time import sleep

led_13 = Pin(13, Pin.OUT)
led_14 = Pin(14, Pin.OUT)
led_12 = Pin(12, Pin.OUT)


while True:
  led_12.value(0)
  led_13.value(1)
  led_14.value(0)
  sleep(0.5)
  led_12.value(1)
  led_13.value(0)
  led_14.value(0)
  sleep(0.5)
  led_12.value(0)
  led_13.value(0)
  led_14.value(1)
  sleep(0.5)

To see the demo of the above code, save this code to a new file in Thonny IDE and upload it to your board.

In summary, in this tutorial, we have learned to use GPIO pins of Raspberry Pi Pico in digital output mode using MicroPython.