NfcIntentProxy

WARNING: This app is currently a prototype. It does only the minimal stuff and no edge cases / unaccounted for scenarios are handled. Use at your own risk.

What is this?

TL;DR: This enables using existing supported read-only NFC tags as regular tags for automation with Home Assistant companion on Android.

Slightly longer version:

Home Assistant's Tags support is awesome, but requires writable NFC tags. This little app enables the use of read-only NFC tags for the same purpose. Currently only tags that contain a specific URL (that no one probably cares about) are supported. That is so the app doesn't eat intents that are meant for other apps / the browser.

Supported tags

• Philips Sonicare brush heads with NFC chips that publish these URLs:
  • https://www.philips.com/nfcbrushheadtap
  • https://www.philips.com

Why?

Because recycling existing read-only NFC tags is awesome. It doesn't matter that writable tags are cheap.

Also, I don't have any writable NFC tags and ordering a whole package just for those didn't sound good. When I was throwing out my old toothbrush head and tearing it apart to separate the materials, I came upon the idea for this small thing.

Also, I have no prior experience with mobile / Android / Kotlin development or NFC so I thought this would be a fun one-day project. -- René

How do I use it?

1. Your Home Assistant Android companion version must be at least 2021.2.1.
2. Install this app. Compile yourself or use an .apk from the Releases page.
3. Go to your HASS companion app settings and in sensors, in Last Update Sensor settings, add the intent cz.renekliment.nfcintentproxy.TAG_READ.
4. Restart your HASS companion app.
5. Now after you scan one of the supported NFC tags with your unlocked phone, the proper android.intent_received event should be received in your Home Assistant instance. You might have to select the app in a pop-up when multiple apps register the same kind of NDEF (URL). You can select to always use this app to handle these intents and then the pop-up should not appear anymore. Selecting to always use this app is safe because it only registers for specific URLs and you can always reset it in your phone settings. You can subscribe to the event in Developer Settings / Events for debug. The event will have the tag_id attribute that you can use to identify the tag. You can use this event directly in your automations.

Integrating with Tags in Home Assistant if you like things fancy

If you would like your tags to appear in Configuration/Tags and create automations with them, you can follow these steps:

For each tag:

1. Find out the tag ID from the android.intent_received event.
2. Create a tag manually with that ID.

Once: Create an automation that creates a proper tag_scanned event from the android.intent_received event:

Trigger:

platform: event
event_type: android.intent_received
event_data:
  intent: cz.renekliment.nfcintentproxy.TAG_READ

Action:

event: tag_scanned
event_data:
  tag_id: '{{ trigger.event.data.tag_id }}'
  device_id: '{{ trigger.event.data.device_id }}'