63 lines
3.5 KiB
Markdown
63 lines
3.5 KiB
Markdown
---
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layout: page
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title: "Adding support for a new platform"
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description: "Hints and tips for when you're adding a new platform to Home Assistant."
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date: 2014-12-21 13:27
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sidebar: false
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comments: false
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sharing: true
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footer: true
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---
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Components that interact with devices are structured in core- and platform logic. This allows the same logic to be used for different platforms.
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For example, the built-in `switch` component consists of the following files in [`homeassistant/components/switch/`](https://github.com/balloob/home-assistant/tree/master/homeassistant/components/switch):
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| File | Description |
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| ---- | ----------- |
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| \_\_init\_\_.py | Contains the Switch core logic.|
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| wemo.py | WeMo platform logic. Included if in config `platform=wemo`. |
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| tellstick.py | Tellstick platform logic. Included if in config `platform=tellstick`. |
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If you are planning to add support for a new type of device to an existing component, you can get away with only writing platform logic. Have a look at how the component works with other platforms and create a similar file for the platform that you would like to add.
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<p class='note'>
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Platform logic should not interface directly with the devices but use a third-party Python 3 library that speaks the actual API.
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</p>
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<a name='discovery'></a>
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## {% linkable_title Allowing your platform to be discovered %}
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Home Assistant has a discovery service running in the background to discover new devices. Whenever a new device is discovered, an `SERVICE_DISCOVERED` event will be fired with the found service and the information. The `discovery` component has some knowledge about which components handle which type of services and will ensure those are loaded and listening before firing the `SERVICE_DISCOVERED` event.
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### {% linkable_title Add discovery instructions %}
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Device discovery for Home Assistant has been extracted into an external library called [NetDisco](https://github.com/balloob/netdisco). This library is integrated using [the `discovery` component](https://github.com/balloob/home-assistant/blob/dev/homeassistant/components/discovery.py) and scans the network in intervals for uPnP and zeroconf/mDNS services.
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To have your device be discovered, you will have to extend the NetDisco library to be able to find your device. This is done by adding a new discoverable. [See the repository for examples of existing discoverables.](https://github.com/balloob/netdisco/tree/master/netdisco/discoverables)
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### {% linkable_title Listening to `SERVICE_DISCOVERED` events %}
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From your component, you will have to set up the listening for specific services. Below an example how one would listen for discovered Chromecasts:
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```python
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from homeassistant.loader import get_component
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def setup(hass, config):
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discovery = get_component('discovery')
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def chromecast_discovered(service, info):
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""" Called when a Chromecast has been discovered. """
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print("Discovered a new Chromecast: {}".format(info))
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discovery.listen(
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hass, discovery.services.GOOGLE_CAST, chromecast_discovered)
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```
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### {% linkable_title Auto-loading your component upon discovery %}
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The Discovery component is capable of setting up your components before firing the `SERVICE_DISCOVERD` event. To do this you will have to update the [`SERVICE_HANDLERS`](https://github.com/balloob/home-assistant/blob/dev/homeassistant/components/discovery.py#L29) constant in [the `discovery` component](https://github.com/balloob/home-assistant/blob/dev/homeassistant/components/discovery.py).
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<p class='note warning'>
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This option is currently limited to built-in components.
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</p>
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