PX4 Hello World guide

These instructions guide you through the process of building and flashing a custom “Hello World” example on the Pixhawk 4. I was using Ubuntu (version 2404.1.66.0) on a Windows 10 computer.

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Prerequisites

1. Download QGroundControl: Follow the instructions here to install QGroundControl on your system.
2. Clone the PX4 Repository: Open a terminal and enter the following command:

   git clone https://github.com/PX4/PX4-Autopilot.git --recursive
   

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Build the PX4 Firmware

a) Run Initial Build Command (for Pixhawk 4):

   make px4_fmu-v5_default

b) Install Required Dependencies: If the build process gives errors about missing dependencies, use the following commands:

   pip3 install kconfiglib
   sudo apt update
   sudo apt install gcc-arm-none-eabi
   pip3 install empy==3.3.4 pyros-genmsg future lxml

After installing the dependencies, retry the build command:

   make px4_fmu-v5_default

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Create the “Hello World” Example

1. Navigate to the Examples Directory:

   cd PX4-Autopilot/src/examples/
   

2. Create a New Folder for Your Example:

   mkdir hello_world
   

3. Inside hello_world, create three files: CMakeLists.txt, hello_world_main.c, and Kconfig. Add the following content to each file:

   • CMakeLists.txt:

     px4_add_module(
         MODULE examples__hello_world
         MAIN hello_world
         STACK_MAIN 2000
         SRCS
             hello_world_main.c
         DEPENDS
     )
     

   • hello_world_main.c:

     #include <px4_platform_common/log.h>
     
     __EXPORT int hello_world_main(int argc, char *argv[]);
     
     int hello_world_main(int argc, char *argv[])
     {
         PX4_INFO("Hello World!");
         for (size_t i = 0; i < 6; ++i) {
             PX4_INFO("hello");
         }
         return OK;
     }
     

   • Kconfig:

     menuconfig EXAMPLES_HELLO_WORLD
         bool "hello_world"
         default n
         ---help---
             Enable support for hello_world
     

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Configure Board Settings

1. Run the Configuration Command:

   make px4_fmu-v5_default boardconfig
   

2. Navigate in the GUI Window:
   • Use the arrow keys and the Enter key to navigate.
   • Go to the examples directory, find your newly created hello_world example, and select it by pressing Enter or Space. A [ * ] or [ X ] should appear next to it.
   • Save and exit the GUI.

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Build the Firmware

Now, build the firmware with your custom example included:

make px4_fmu-v5_default

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Flash the Firmware onto Pixhawk

1. Open QGroundControl:
   • Go to Vehicle Setup > Firmware.
2. Connect the Pixhawk:
   • Connect your Pixhawk device to the computer. A “Firmware Setup” window should pop up.
3. Select the Firmware:
   • Choose PX4 Pro v1.15.1 (or similar) and click on Advanced Settings.
   • Select Custom firmware file… and browse to your built file. It is typically located at:

     PX4-Autopilot/build/px4_fmu-v5_default/px4_fmu-v5_default.px4
     

4. Flash the Firmware:
   • Click OK and wait for the flash to complete. You should see “Upgrade complete” in yellow text followed by a separator line.
5. Complete Setup:
   • When prompted, click OK in the “Vehicle components setup” pop-up.
   • Return to the map view by clicking the Back button (it looks like a Telegram icon in the top-left corner).

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Run the “Hello World” Example

1. Access MAVLink Console:
   • In QGroundControl, click the Q logo in the top-left corner, select Analyze Tools, and then MAVLink Console.
2. Run the Example:
   • Type hello_world (the name of your executable) and press Enter. You should see the “Hello World” and some “hello” outputs printed in the console.