RaspberryPi Pico with C: Blinking LED

Introduction

In this article, we'll explore embedded programming and show you how to make a blinking LED on the Raspberry Pico
using C language. Whether you're a beginner or have some experience, we'll go through each step to help you get the most
out of your Raspberry Pico.

We will use CMake. CMake is a open-source cross-platform tool that simplifies the process of building and managing
software projects. It helps developers create consistent and platform-independent build configurations, making it easier
to work on different systems.

Setup

Preparations

To ensure a comprehensive working environment, install the necessary libraries. On Ubuntu you can run the following
command:

sudo apt install cmake gcc-arm-none-eabi libnewlib-arm-none-eabi libstdc++-arm-none-eabi-newlib

In addition to this we will need pico_sdk_import.cmake file. In order to get this we copy it
from $PICO_SDK_PATH/external

git clone https://github.com/raspberrypi/pico-sdk.git

Development environment

We'll be using CLion by JetBrains as our IDE for this project. CLion streamlines coding with features like intelligent
code completion and robust debugging tools, making our development process more efficient.

Remember to set essential evironment variables like PICO_BOARD or PICO_SK_PATH

Let's code it

To begin, create or update the CMakeLists.txt file with the following content:

cmake_minimum_required(VERSION 3.26)

include(pico_sdk_import.cmake)
project(raspberry_pico_c_blinking_led C CXX ASM)
pico_sdk_init()
add_executable(raspberry_pico_c_blinking_led main.c)
target_link_libraries(raspberry_pico_c_blinking_led pico_stdlib)
pico_add_extra_outputs(raspberry_pico_c_blinking_led)

Here's a breakdown of the key elements:

• include(pico_sdk_import.cmake): This line imports the pico_sdk, an essential component for Raspberry Pico development.
• project(raspberry_pico_c_blinking_led C CXX ASM): Declares the project, specifying support for C, C++, and Assembly languages.
• pico_sdk_init(): Initializes the pico_sdk for the project.
• add_executable(raspberry_pico_c_blinking_led main.c): Defines the executable and points to the main source file ( main.c).
• target_link_libraries(raspberry_pico_c_blinking_led pico_stdlib): Links the pico_stdlib library to the executable.
• pico_add_extra_outputs(raspberry_pico_c_blinking_led): Adds extra outputs for the project.

Now, let's move on to the main.c file:

#include "pico/stdlib.h"

void gpio_toggle(uint pin) {
    gpio_put(pin, !gpio_get(pin));
}

int main() {
#ifndef PICO_DEFAULT_LED_PIN
#warning blink example requires a board with a regular LED
#else
    const uint LED_PIN = PICO_DEFAULT_LED_PIN;
    gpio_init(LED_PIN);
    gpio_set_dir(LED_PIN, GPIO_OUT);
    while (true) {
        gpio_toggle(LED_PIN);
        sleep_ms(250);
    }
#endif
}

Here's a breakdown of the code:

• Include Statement: The code includes the necessary header file pico/stdlib.h which is part of the Pico SDK.
• gpio_toggle Function:
  • This function takes a GPIO pin as a parameter.
  • It toggles the state of the specified GPIO pin (switches it from high to low and vice versa).
• main Function:
  • The #ifndef PICO_DEFAULT_LED_PIN block, checks if the default LED pin is defined for the board. If not, it emits a compilation warning.
  • Inside the #else block (indicating that a regular LED pin is available):
    • The LED pin is set as PICO_DEFAULT_LED_PIN.
    • GPIO initialization and configuration are performed to set the LED pin as an output.
    • The main loop toggles the LED state and sleeps for 250 milliseconds, creating a blinking effect.

The code is available on
my GitHub repository

Flashing Raspberry Pico

To begin the update process, reload your CMake project in CLion. Once reloaded, proceed by clicking the 'Build' button.
This action initiates the compilation process, resulting in the creation of a .uf2 file. You can find this file within
the build folder of your project directory.

To flash your raspberry follow steps from the previous article.

Summary

I've guided through the process of implementing a blinking LED on the Raspberry Pico using the C programming language.
We set up the development environment within CLion, installed necessary libraries, and coded the LED blinking
functionality. To conclude, we've learned the flashing procedure, creating a .uf2 file for the Raspberry Pico by
reloading the CMake project and initiating the Build operation.

References

• Raspberry Pico C/C++ SDK Documentation