Each of the following connections provides additional interfaces for Raspberry Pi:

• 20 x 2 GPIO pin header (Model A+, B+, 2 B, 3 B, and Pi Zero): This is the main 40-pin GPIO header of Raspberry Pi used for interfacing directly with hardware components. We use this connection in Chapters 6, Detecting Edges and Contours in Images, Chapter 7, Creating 3D Graphics, Chapter 9, Using Python to Drive Hardware, and Chapter 10, Sensing and Displaying Real-world Data. The recipes in this book are also compatible with older models of Raspberry Pi that have a 13 x 2 GPIO pin header.
• P5 8 x 2 GPIO pin header (Model 1 B revision 2.0 only): We do not use this in the book.
• Reset connection: This is present on later models (no pins fitted). A reset is triggered when Pin 1 (reset) and Pin 2 (GND) are connected together. We use this in the A controlled shutdown button recipe in Chapter 9, Using Python to Drive Hardware.
• GPU/LAN JTAG: The Joint Test Action Group (JTAG) is a programming and debugging interface used to configure and test processors. These are present on newer models as surface pads. A specialist JTAG device is required to use this interface. We do not use this in the book.
• Direct camera CSI: This connection supports Raspberry Pi Camera Module. Note that the Pi Zero has a smaller CSI connector than the other models, so it requires a different ribbon connector.
• Direct Display DSI: This connection supports a directly connected display, such as a 7-inch 800 x 600 capacitive touch screen.