Identifying Your Board Revision; Gpio Pinout Diagrams - Raspberry Pi A User Manual

220
THE RASPBERRY PI'S
the printed circuit board, labelled P1. It's a 26-pin port, fitted with two rows of 13 male 2.54
mm headers at the factory. The spacing of these headers is particularly important: 2.54 mm
pin spacing (0.1 inches in imperial measurements) is a very common sight in electronics and
is the standard spacing for prototyping platforms that include stripboards and breadboards.

Identifying Your Board Revision

The pin layout of the Raspberry Pi's GPIO port differs slightly depending on what revision of
the board you own. All Model As and recent Model Bs have a common pin layout; the origi-
nal Model B, however, has a slightly different layout.
Before using the GPIO port for a hardware project, be sure you know which model of Raspberry
Pi you have. If you have a Model A, you can use the first diagram in this chapter; if you have a
Model B, you will need to use the first diagram—unless it's an original Revision 1 model.
The easiest way to spot a Model B Revision 1 board is to look at the top side of the board, just
underneath the GPIO pins themselves: where a Revision 2 board has two rows of four copper-
plated holes, the Revision 1 is solid. Another method is to see how much memory is available:
the Model B Revision 1 had just 256 MB of memory, compared to 512MB on Revision 2 boards.
For more details on the board revisions and how to tell them apart, see Chapter 1, "Meet the
Raspberry Pi".

GPIO Pinout Diagrams

Each pin of the GPIO port has its own purpose, with several pins working together to form
particular circuits. The layout of the GPIO port can be seen in Figure 14-1.
The GPIO port is the same across both the Raspberry Pi Model A and the Model B Revision 2.
If you have one of the original Raspberry Pi Model B Revision 1 boards—and if you do, con-
gratulations on having a collector's item—then the pins available on the GPIO port are subtly
different. These details can be seen in Figure 14-2.
If you're not sure which revision of the Raspberry Pi you have, and thus which pinout applies
TIP
to your board, load IDLE and type import RPi.GPIO as GPIO followed by GPIO.RPI_
REVISION to return the revision number.
Pin numbers for the GPIO port are split into two rows, with the bottom row taking the odd
numbers and the top row the even numbers. It's important to keep this in mind when working
with the Pi's GPIO port: most other devices use a different system for numbering pins, and
because there are no markings on the Pi itself, it's easy to get confused as to which pin is which.
P A R T I V H A R D W A R E H A C K I N G
general-purpose input-output (GPIO) port is located on the top-left of