Your First Program in C

Write and upload your very first C program for the Raspberry Pi Pico – a custom "Hello, world!" using the onboard serial console.

You’ve set up your toolchain — now let’s write and upload your very first C program to the Raspberry Pi Pico!

Instead of just blinking an LED, we’ll start with a classic: “Hello, world!”
But this time, it will run on real hardware.

Step 1: Create a New Project

Let’s make a folder for your own code:

mkdir -p ~/pico/my-project
cd ~/pico/my-project

Create these files:

CMakeLists.txt

The CMake file tells the build system how to compile your code. Create a file named CMakeLists.txt with the following content:

cmake_minimum_required(VERSION 3.13)
include(pico_sdk_import.cmake)

project(my_project)

pico_sdk_init()

add_executable(hello
    hello.c
)

target_link_libraries(hello pico_stdlib)

pico_add_extra_outputs(hello)

hello.c

Create a file named hello.c - this is the main program. Add the following content to it:

#include <stdio.h>
#include "pico/stdlib.h"

int main() {
    stdio_init_all();

    while (true) {
        printf("Hello, world from the Pico!\n");
        sleep_ms(1000);
    }
}

pico_sdk_import.cmake

Copy this file from ~/pico/pico-examples:

cp ~/pico/pico-examples/pico_sdk_import.cmake .

Step 2: Build the Program

mkdir build
cd build
cmake ..
make

You should now have hello.uf2 in the build folder.

Step 3: Upload to Your Pico

1. Hold down BOOTSEL
2. Plug in your Pico
3. Drag and drop hello.uf2 onto the RPI-RP2 USB drive

The Pico will reboot and start running your program.

Step 4: View Output Over USB Serial

Use minicom, screen, or a serial monitor to view the output:

On Linux/macOS:

screen /dev/ttyACM0 115200

You may need to install screen:

sudo apt install screen

You should see:

Hello, world from the Pico!
Hello, world from the Pico!
...

Summary

You just:

• Created your own C project from scratch
• Compiled it using CMake and the Pico SDK
• Uploaded the binary to your Pico
• Saw real-time output using USB serial

🎉 Congratulations — you’re now officially writing C code on the Raspberry Pi Pico!

Next up: GPIO Basics, where we’ll learn how to interact with the outside world by controlling physical pins.

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