Adding a new interface can be straightforward if you are familiar with the extension system. This page expands on the concepts outlined in the extension developer docs focusing on the interfaces.

Creating an Interface

Lets look at adding an interface for a sensor to a counter example extension. The file should be named after the namespace for the extension we are providing an interface for. In this example a file named is created under a counter extension folder.

This counter extension directory would look like the following:

└── extensions
   └── counter
      └── extension.json

An interface needs to extend from the BaseInterface class at minimum. The interface must be named Interface so that MudPi can easily locate the class dynamically.

The interface requires a load() method that accepts a config dict in which it needs to process. The load() method needs to return True if successful. This dict of data will already have been passed to the interface's validate() method to be checked for configuration errors.

If the interface is adding a component it should do so by passing the instantiated component to the add_component method.

Here is what the file for the counter extension could look like:

from mudpi.extensions import BaseInterface
from mudpi.extensions.sensor import Sensor

class Interface(BaseInterface):

    def load(self, config):
        sensor = CounterSensor(self.mudpi, config)
        return True

    def validate(self, config):
        if not config[self.namespace].get('start_count'):
            raise ConfigError('Missing `start_count` in hello configs.')

        return config

class CounterSensor(Sensor):
    def state(self):
        return self._state

    def init(self):
        self._state = self.config.get('start_count', 0)

    def update(self):
        return True

The interface will load() a CounterSensor which in this case just increments each time it updates. If you want to learn more on components specifically read the developer component docs.

You could then use the following config to load the sensor through this interface:

"sensor": [{
    "key": "counter_1",
    "interface": "counter",
    "start_count": 0

Additional Resources

A good place to start if you are looking to create an interface is the example extension. This extension is focused on simple interfaces for testing each of the core components that support interface. There you can find some references on how to get started with your own interface up.