User Guide

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or jacks. Unlike the designers of other development boards, the
Raspberry Pi Foundation use male pins for the GPIO headers on
the Pi. To connect the Pi to a solderless breadboard, you can
either use:
• A 40-pin female-to-female ribbon cable; or
• Individual female-to-male jumper wires.
If you use a female-to-female ribbon cable, you need to use
regular male-to-male jumper wires or a Raspberry Pi GPIO
breakout board to connect the socket on the cable to holes on
the breadboard.
7.3 The GPIO Header
The 40-pin GPIO header is located in the top-left of the Pi. The
pins are numbered from left to right, but odd-numbered pins are
on the lower row and even-numbered pins are on the top-row.
Figure 3. Location of the GPIO header (left), and the power and ground connections
(right)
You can configure most of the GPIO pins as inputs or outputs
and control them. But some have additional uses:
Pin # Name Description
3 GPIO2 Input/output. Or I2C wire SDA (I2C1_SDA).
5 GPIO3 Input/output. Or I2C wire SCL (I2C1_SCL).