Everybody knows that scratch 1.4 has a custom module for WeDo projects with custom blocks for starting a motor, detection the tilt sensor, etc, but… How about creating your custom module???

For anyone who have wondered how a module in scratch is created, probably the first step is going into google and type something about custom blocks for scratch. Then you'll find a lot of information of the real-actual blocks of Scratch 2.0 (the web version), more on custom blocks (made in scratch) for this platform but nothing for creating a block with new funcionalities.

For all those who have wondered how to do this, I put here my notes about the issue.

My first discover is a WeDoModule.c (in C) that exposes to the virtual machine of scratch (squeak) the information about WeDo:

http://squeakvm.org/cgi-bin/viewvc.cgi/squeak/trunk/src/plugins/WeDoPlugin/

Other point of information is the own source code of scratch:

There is a github repository: https://github.com/LLK/Scratch_1.4

and you can download it:

http://wiki.scratch.mit.edu/wiki/Scratch_1.4_Source_Code#Download

Investigating the download

After downloading the source code and unpacking it, you'll find a strange “image” file that (supposedly) contains the source code. Trying to open it with the command squeak ScratchSourceCode.1.4.image doesn't work (apparently after a long wait).

Investigating github

In github, you'll find the same big “image” file and some C files for some plugins (camera pluging, WeDo plugin). It seems that the core of the issue is in this *.image file, and the MIT doesn't help with this much.