Automating the Elgato Key Light

Jason Hee — Wed, 26 May 2021 10:42:24 +0000

As video conference calls are now part of my daily life, I decided to investigate how I can look better in front of my webcam. After some research, I bought an Elgato Key Light Air to help illuminate my face better.

So far, I'm delighted with the purchase. The key light has definitely improved how I look on video calls. But having to turn it on every time I have a video call and then turn it off when the call ends is a pain.

I considered leaving the light on throughout the work day, but the light can be quite searing to my eyes when it's shining at me for an extended period of time.

I then put on my software engineering hat and wondered, "Can I automate this inconvenience away?". As it turns out, I can.

Elgato Key Light REST API

The Elgato Key Light and Key Light Air devices actually have a web server (listening on port 9123) built in. The web server exposes a REST API:

GET /elgato/lights

This endpoint returns the status of the key light.

Sample Response

{
    "numberOfLights": 1,
    "lights": [
        {
            "on": 1,
            "brightness": 9,
            "temperature": 262
        }
    ]
}

For updating the key light, there's a PUT action endpoint:

PUT /elgato/lights

Content-Type: 'application/json'
--data-raw '{
  "Lights": [
    {
      "Temperature": 344,
      "Brightness": 100,
      "On": 1
    }
  ]
}'

This endpoint allows you to set the attributes of the key light. You can set the brightness and temperature, including turning it on or off.

This means that I can turn the Elgato Key Light off and on by interfacing with its REST API endpoints.

A Node.js script

I created a Node.js script that toggles on and off the Elgato Key Light. I then bound the execution of the script to a keyboard macro. So now, I can tap a key to turn the Key Light on and off. :D

Conclusion

It is relatively easy for one to interface with an Elgato Key Light or Key Light Air using its built-in REST API. You can even integrate it into your smart home via something like Homebridge .

How to use YAML Aliases

Jason Hee — Tue, 18 May 2021 13:07:06 +0000

Have you ever had to copy and paste duplicate content in a YAML file and wondered if it is possible to DRY that up? As it turns out, YAML allows you to repeat nodes via aliases.

YAML Aliases allow you to assign a name to a value or block of data and recall the assigned data by its name in the YAML file. Aliases should work for any file written in YAML.

Simple Example

hello: &hello 'hello'
greeting:
  audience: 'world'
  hello: *hello  #greeting.hello has the string value of 'hello'
new_greeting:
  audience: 'room'
  hello: *hello  #new_greeting.hello has the string value of 'hello'

Aliasing blocks of data

Besides string or number values, you can alias a block of data as well:

foo:
  bar: &bar
    qux: 'quxqux'
    baz: 'bazbaz'
greeting:
  audience: 'world'
  bar: *bar  #greeting.bar has the same values as foo.bar.
             #So greeting.bar.baz is 'bazbaz'

Modifying a section of an alias

You can copy an alias and modify a section of it by using the merge key (<<:):

bar: &bar
  qux: 'quxqux'
  baz: 'bazbaz'
greeting:
  audience: 'world'
  bar:
    <<: *bar       # greeting.bar.qux is 'quxqux'
    baz: 'notbaz'  # greeting.bar.baz is 'notbaz'

Defining aliases from modified aliases

You can even modify a section of an alias and define that as a new alias:

bar: &bar
  qux: 'quxqux'
  baz: 'bazbaz'
greeting:
  audience: 'world'
  bar: &newalias
    <<: *bar
    baz: 'notbaz'
new_greeting:
  audience: 'room'
  bar: *newalias  #new_greeting.bar.baz is 'notbaz'

YAML specification

Alias nodes are described in the YAML specification here

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