ArduCastControl

Chromecast control library for platformio/arduino. It supports requesting some information of the casting (e.g. artist and title), as well as a minimal control (pause, previous, next, seek and volume).

Dependencies

The library depends on ArduinoJson and nanopb. This is already set for platformio.

It has a significant RAM footprint, which is usually not an issue for wifi capable boards. It was only tested on ESP8266.

References

• Node-castv2 has a great readme describing the protocol.
• pychromecast was used as a reference when implementing this
• CastVolumeKnob is a similar project in micropython, but it only targets volume control.
• Google's documentation on protocol buffers

Flow of connection

Understanding how the CASTV2/chromecast protocols work took me a while, so here's a quick summary on what this library does.

1. TCP/TLS connection is opened to the device. Self-signed certificates are sufficient
2. An application layer connection to the device itself ("receiver-0") is established
3. Status is requested from the device with GET_STATUS messages on the receiver namespace
   1. Reported status include volume information
4. When something casts to the device, chromecast reports an application is running with a sessionId
5. An application layer connection to the application (sessionid) is established
6. Status is requested from the application with GET_STATUS messages on the media namespace
   1. Reported status includes all sort of information of the currently playing track
   2. As well as a mediaSessionId, which is changed with every track change
7. Control messages can be sent to the application on the media namespace using a specified mediaSessionId

Useful values saved

All of the following are public fields of the class, which are updated when the class' loop() function is called on a given status.

• volume - The volume set on the device, between 0 and 1
• isMuted - True if the device is muted
• displayName - Typically the application casting, like "Spotify"
• statusText - A short status, e.g. "Casting: Whole Lotta Love"
• playerState - State of playback, e.g. "PLAYING"
• title - Title of the current song, e.g. "Whole Lotta Love"
• artist - Artist of the current song, e.g. "Led Zeppelin"
• duration - Duration of the current song in seconds, e.g. 333.89
• currentTime - Current time in the song in seconds, e.g. 2.27

This list can be easily extended by saving more when processing MEDIA_STATUS or RECEIVER_STATUS.

Control methods

The following controls are accessible as methods in the class:

• play() - Plays (resumes) the current song
• pause() - Pauses/Resumes the current song
• prev() - Previous track
• next() - Next track
• seek() - Seeks in song
• setVolume() - Volume control
• setMute() - Mute control

I think this covers all possible controls except casting and playlist features. However, extending it should be fairly easy, using the play() or setVolume() method as a template (for media/device commands respectively)

Further documentation

For further documentation, please refer to the comments in ArduCastControl.h and the example, which demonstrates the main features.

Further developement

Don't expect any new features/bugfixes, as I'm quite happy with the featureset as is. However, I do accept pull requests.