Application Development Directory Structure

Each application resides in a uniquely-named application directory created by the developer, typically, in the developer’s workspace directory. The application developer also creates a src directory for the application’s source code.

Note

The Zephyr Kernel either supplies or generates all other application directories.

Creating an Application and Source Code Directory using the CLI

Create one directory for your application and another for the application’s source code; this makes it easier to organize directories and files in the structure that the kernel expects.

Before You Begin

The environment variable must be set for each console terminal using Setting Environment Variables.

Steps

Create an application directory structure outside of the kernel’s installation directory tree. Often this is your workspace directory.

In a Linux console, navigate to a location where you want your applications to reside.

Create the application’s directory, enter:
$ mkdir application_name
Note

This directory and the path to it, are referred to in the documentation as ~/appDir.

Create a source code directory in your ~/appDir, enter:
```
$ mkdir src
```
The source code directory ~/appDir/src is created.
```
-- appDir
   |-- src
```

Creating an Application Makefile

Create an application Makefile to define basic information such as the kernel type, microkernel or nanokernel, and the board configuration used by the application. The build system uses the Makefile to build an image with both the application and the kernel libraries called either microkernel.elf or nanokernel.elf.

Before You Begin

Be familiar with the standard GNU Make language.
Be familiar with the board configuration used for your application and, if it is a custom board configuration, where it is located.
Set the environment variable for each console terminal using Setting Environment Variables.

Steps

In the appDir directory, create a Makefile. Enter:
```
$ touch Makefile
```
Open the Makefile and add the following mandatory entries using any standard text editor.

Note

Ensure that there is a space after each =.
1. Add the kernel type on a new line:
```
KERNEL_TYPE = micro|nano
```
  Either micro or nano, short for microkernel or nanokernel respectively.
2. Add the name of the board configuration for your application on a new line:
```
BOARD ?= board_configuration_name
```
  The supported boards can be found in Supported Boards.
3. Add the name of the default kernel configuration file for your application on a new line:
```
CONF_FILE = prj.conf
```
  The default name is prj.conf. If you are not using the default name, this entry must match the filename of the .conf file you are using.
4. For microkernel applications, add the name of the MDEF for your application:
```
MDEF_FILE = prj.mdef
```
  The default name is prj.mdef. If you are not using the default name, this entry must match the filename of the .mdef file you are using.
5. Include the mandatory Makefile fragments on a new line:
```
include ${ZEPHYR_BASE}/Makefile.inc
```
Save and close the Makefile.

Example Makefile

KERNEL_TYPE = micro
BOARD ?= qemu_x86
CONF_FILE = prj.conf
MDEF_FILE = prj.mdef
include ${ZEPHYR_BASE}/Makefile.inc