Auto Launch Webpages full screen on Android

While waiting for Amazon to get round to reviewing my Node-RED Alexa Smart Home Skill I’ve needed something to hack on.

I’ve been keeping an eye on what folk have been doing with Node-RED Dashboard and a common use case keeps coming up. That is running the UI on a Android tablet mounted on a wall as a way to keep track of and control things around the house. This got me thinking about how to set something like this up.

Icon

For the best results you really want to run this totally full screen, there are ways to get this to happen with Chrome, but it’s a bit convoluted. Sure you can add it as a shortcut on the home screen but I thought there had to be a easier/better way.

So I started to have a bit of a play and came up with a new app. It’s basically just a full screen Activity with a WebView, with a few of extra features.

Settings
Settings
  • Set URL – Pick a URL to load when the phone boots, or the app is launched.
  • Launch on boot – The app can be configured to start up as soon as the phone finishes booting.
  • Take Screen Lock – This prevents the screen from powering off or locking so the page is always visible.

You can change the URL by swiping from the left hand edge of the screen, this will cause the action bar to appear, from this you can select “Settings”.

Set URL to Load
Set URL to Load

The app is in the Google Play store here, the code is on Github here

Google Home

Having got hold of a Amazon Echo Dot just over a week ago, I was eager to get my hands on a Google Home to compare. Luckily a I had a colleague in the US on release day who very kindly brought me one back.

Google Home

It looks like the developer program will not be opening up until December, which is just as well as I need to get the my Alexa project finished first.

My initial impression from a couple of hours of playing is it’s very similar to the Echo, but knows a lot more about me out of the box (due Google already knowing all my secrets), I really do like the Chromecast integration for things like Youtube. I need to try the Echo with my FireTV stick to see if it can do anything similar. It’s still early days for the Google Home and it has only been released in the US so it wouldn’t be totally fair compare them too closely just yet.

I’ll keep this brief for now until I can get into the developer tools. It’s going to be fun time working out just what I can get these two devices to do.

Alexa Home Skill for Node-RED

Following on from my last post this time I’m looking at how to implement Alexa Home Skills for use with Node-RED.

Home Skills provide ON/OFF, Temperature, Percentage control for devices which should map to most home automation tasks.

To implement a Home Skill there are several parts that need to created.

Skill Endpoint

Unlike normal skills which can be implemented as either HTTP or Lambda endpoints, Home Skills can only be implemented as a Lambda function. The Lambda function can be written in one of three languages, Javascript, Python and Java. I’ve chosen to implement mine in Javascript.

For Home Skills the request is passed in a JSON object and can be one of three types of message:

  • Discovery
  • Control
  • System

Discovery

These messages are triggered when you say “Alexa, discover devices”. The reply this message is when the skill has the chance to tell the Echo what devices are available to control and what sort of actions they support. Each device section includes it’s name and a description to be shown in the Alexa phone/tablet application.

The full list of supported actions:

  • setTargetTemperature
  • incrementTargetTemperature
  • decrementTargetTemperature
  • setPercentage
  • incrementPercentage
  • decrementPercentage
  • turnOff
  • turnOn

Control

These are the actual control messages, triggered by something like “Alexa, set the bedroom lights to 20%”. It contains one of the actions listed earlier and the on/off or value of the change.

System

This is the Echo system checking that the skill is all healthy.

Linking Accounts

In order for the skill to know who’s echo is connecting we have to arrange a way to link an Echo to an account in the Skill. To do this we have to implement a oAuth 2.0 system. There is a nice tutorial on using passport to provide oAuth 2.0 services here, I used this to add the required HTTP endpoints needed.

Since there is a need to set up oAuth and to create accounts in order to authorise the oAuth requests this means that is makes sense to only do this once and to run it as a shared service for everybody (just got to work out where to host it and how to pay for it).

A Link to the Device

For this the device is actually Node-RED which is probably going to be running on people’s home network. This means something that can connect out to the Skill is probably best to allow or traversing NAT routers. This sounds like a good usecase for MQTT (come on, you knew it was coming). Rather than just use the built in MQTT nodes we have a custom set of nodes that make use of some of the earlier sections.

Firstly a config node that uses the same authentication details as account linking system to create oAuth token to be used to publish device details to the database and to authenticate with the MQTT broker.

Secondly a input node that pairs with the config node. In the input node settings a device is defined and the actions it can handle are listed.

Hooking it all together

At this point the end to end flow looks something like this:

Alexa -> Lambda -> HTTP to Web app -> MQTT to broker -> MQTT to Node-RED

At this point I’ve left the HTTP app in the middle, but I’m looking at adding direct database access to the Lambda function so it can publish control messages directly via MQTT.

Enough talk, how do I get hold of it!

I’m beta testing it with a small group at the moment, but I’ll be opening it up to everybody in a few days. In the mean time the code is all on github, the web side of all of this can be found here, the Lambda function is here and the Node-RED node is here, I’ll put it on npm as soon as the skill is public.