Developing Apps

Apps are written in MicroPython and installed in /apps/. See Filesystem Layout for the app directory structure.

Here we'll go over how to create and install a simple HelloWorld app.

More advanced examples are available in the source code repository.

Structure

Create the following file and folder structure:

com.micropythonos.helloworld/
├── assets/
│   └── hello.py
├── META-INF/
│   └── MANIFEST.JSON
└── res/
    └── mipmap-mdpi/
        └── icon_64x64.png

App code

In hello.py, put:

from mpos.apps import Activity

class Hello(Activity):

    def onCreate(self):
        screen = lv.obj()
        label = lv.label(screen)
        label.set_text('Hello World!')
        label.center()
        self.setContentView(screen)

The code above creates a new screen, adds a label, sets the label text, centers the label and activates the screen.

Manifest

In MANIFEST.JSON, put:

{
"name": "HelloWorld",
"publisher": "MicroPythonOS",
"short_description": "Minimal app",
"long_description": "Demonstrates the simplest app.",
"fullname": "com.micropythonos.helloworld",
"version": "0.0.2",
"category": "development",
"activities": [
    {
      "entrypoint": "assets/hello.py",
      "classname": "Hello",
      "intent_filters": [
        {
          "action": "main",
          "category": "launcher"
        }
      ]
    }
  ]
}

Icon

The icon is a simple 64x64 pixel PNG image, which you can create with any tool, such as GIMP.

It's recommended to keep it as small as possible by setting compression level to 9 and not storing any metadata such as background color, resolution, creation time, comments, Exif data, XMP data, thumbnail or color profile.

The size will be somewhere between 3 and 7KB.

Installing the App

The app can be installed by copying the top-level folder com.micropythonos.helloworld/ (and its contents) to the /apps/ folder.

On Desktop

You probably already have a clone of the internal_filesystem that you're using to run MicroPythonOS on desktop.

Just copy or move your the top-level folder com.micropythonos.helloworld/ (and its contents) to internal_filesystem/apps/ and you're good to go!

On ESP32

On the ESP32, you can use MicroPython tools such as mpremote.py to copy files and folders from-to your device using the MicroPython REPL.

Then connect your device with a cable and install your app using:

/path/to/mpremote.py fs cp -r com.micropythonos.helloworld/ :/apps/

Take a look at scripts/install.sh for convenient "install everything" or "install one app" scripting.

There might also exist MicroPython File Managers with a graphical user interface, if you prefer.

Starting your App

If the app is installed into the /apps/ folder, it should show up in the launcher after refreshing it.

You can also launch it manually by typing this in the MicroPython REPL:

import mpos.apps; mpos.apps.start_app('apps/com.micropythonos.helloworld/')