If you’re looking to write programs that are more than simple test apps or demos and are willing to try something a bit more involved, we recommend following the Using Docker to Cross-Compile tutorial instead of this one.
This tutorial walks you through writing a simple C program, compiling it on your ev3dev device, and running it. We will assume that you have already configured a means of connecting to your device from a PC.
Note that C is not a particularly friendly language, especially for beginners. It would be recommended to use Python or another easier language.
For this tutorial, we will be using a text editor called
nano. You can refer
to our nano cheat sheet for information on
Before you start, make sure that you have configured a network connection to your ev3dev device and have opened an SSH connection to it.
To understand what you will be doing in this tutorial, you’ll first need to
understand the way that C programs are run. C is a “compiled” language; that
means that the code that you write must be converted into a different kind of
code that a computer understands before it can run. This is the job of the
compiler. The compiler is a program that takes your C code and converts it
into something that can be run. If you are familiar with Windows, the final
product is the equivalent of a
On ev3dev, you will need to run the compiler over SSH to create the executable file. Once you have the binary file, you can run it whenever you want from the terminal or Brickman.
We need to install the compiler and some other tools. Execute the following command to install them:
We need a place to store the code that you’ll write. In the terminal, run the following commands:
The code that you write will live in its own file. Let’s reate a file called
main.c and open it in nano:
Now paste the following code into the file (in many cases, you can paste by right-clicking on the terminal window):
Save the file by pressing Ctrl+O and exit the editor with Ctrl+X.
A makefile is a file that gives instructions on how your program should be compiled. Makefiles can be very simple (as ours will be here) but it can get more complicated if you have additional C source files or need to include other libraries.
Create a file called
Makefile and open it:
Copy the following contents into the file:
When you paste the contents into nano, the indentation will likely disappear. Move your cursor using the arrow keys to the beginning of the lines that are indented above and press Tab to indent them.
Now we’re ready to use the makefile to compile your code. Run the command
make. If it is successful, the output should look like this:
gcc -I . -c main.c gcc main.o -o bin
ls and hit Enter. If the compilation did what it was
supposed to do, you should see an item called
You can run your new file by typing
./bin in the SSH terminal. You should
see the text
Hello world! printed back. Congratulations! You have written
your first C program on ev3dev.
To make changes to your code, you can open the
main.c file in nano and edit
it. You must then go through the “Running the compiler” step again.
To test your skills, try changing the text in the code to print something other than “Hello world!”
If you want to use the motors, sensors, etc. of the EV3, you will need to either use an existing C library (not C++) or manually read from and write to the files that let you control devices. You can find a list of the known libraries on our programming languages page.