Scratch Link
INFO
This section will be expanded in the future, but it remains incomplete for now. Other sections such as Ideas, Runtime, and Palette are a higher priority to write at the moment, and writing this section well (such that it provides accurate and useful information) will require lots of research and effort.
In the meantime, here are some resources that may be useful if one would like to learn more about Scratch Link's inner workings and protocols:
Feel free to offer insight!
Scratch 3.0 is able to connect to supported programmable hardware components through the use of an external application called Scratch Link. When installed on a user's device, it interfaces with the Scratch runtime to allow certain hardware extension blocks to connect with and control connected devices. Its protocols and functionality are documented here to provide the full functionality of Scratch as a programming language.