THE GENERAL PURPOSE INPUT OUTPUT (GPIO) pins on the Raspberry Pi are what make it really special. The behaviour of these pins can be controlled or programmed—by you! You can use the pins to sense and control physical objects in the real world, like lights and switches. The pins are located on the main board of the Raspberry Pi, shown in Figure 8-1.
In this adventure, you’ll learn some basics of electronics and then discover how to output to a light-emitting diode (LED), making it light up using your Raspberry Pi. For the final project in the adventure, you’ll hook up a marshmallow (yes, a real marshmallow) to input a signal to your Raspberry Pi to play a Scratch marshmallow game that senses the press of a button.