In my article for the Raspberry Pi Handbook, I walk through the steps necessary to make Scratch aware of the GPIO (general purpose input/output) pins and create a proof of concept program and circuit.

Scratch by itself is a great tool to teach program development and design. However, sometimes we want to teach our kids more, such as basic circuit design. Using Scratch and Raspberry Pi, we can create applications that have tangible components, such as LEDs. Or we can create external circuits to control sprites in Scratch, such as using a switch to start and stop a sprite.

The full article can be found in the Raspberry Pi Handbook.