.. _build_custom_app:

Build Custom C/C++ App
######################

This guide provides step-by-step instructions for creating a custom C application and building it for the SiMa DevKit using the Palette SDKs. It covers developing a simple "Hello World" program, configuring it for cross-compilation, and using the SDK’s tools for building. 

.. note:: 

    While cross-compilation is the standard approach for both platforms, **Modalix (eLxr)** also supports **On-Device compilation** directly on the hardware. For more details on building directly on Modalix, see the :ref:`On-Device Compilation <on_device_compilation>` section.

Before you run the following commands, ensure you have followed the :ref:`cross compilation setup <cross_compilation_setup>` for your target platform (Yocto or eLxr).

.. dropdown:: Step 1. Create the Application Source Code
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    First, write a simple C program as your custom application.

    1. Create a project directory and navigate to it:

    .. code-block:: bash

        user@palette-container-id:/home/docker/$mkdir ~/myproject
        user@palette-container-id:/home/docker/$cd ~/myproject

    2. Create a file named ``hello.c`` with the following content:

    .. code-block:: c

        #include <stdio.h>

        int main() {
            printf("Hello, SiMa DevKit!\n");
            return 0;
        }

    This basic program prints a greeting when executed.

.. dropdown:: Step 2. Compile the Application Using the SDK
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    To compile the program for the target architecture, you must be inside the correct SDK container and have the environment activated.

    1. Compile the program:

    .. code-block:: bash

        user@palette-container-id:/home/docker/myproject$ $CC hello.c -o hello

    2. Verify the build:

    .. code-block:: bash

        user@palette-container-id:/home/docker/myproject$ file hello

    Output should resemble:
    ``hello: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1, ...``

.. dropdown:: Step 3. Deploy the Application to the DevKit
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    To run the application, transfer it to the SiMa DevKit and execute it.

    1. Copy the executable to the DevKit (e.g., via ``scp`` if networked):

        .. code-block:: bash

            user@palette-container-id:/home/docker/myproject$ scp hello sima@devkit-ip:~/

        Replace ``user@devkit-ip`` with your DevKit’s SSH credentials and IP address.

    2. Connect to the DevKit via SSH and run the application:

        .. code-block:: bash

            user@palette-container-id:/home/docker/myproject$ssh sima@devkit-ip "./hello"

        Expected output: ``Hello, SiMa DevKit!``