Hardware Reference
In-Depth Information
GPIO Headers
GPIO is the next set of headers you will find on the Raspberry Pi. The 26-pin header is known as the GPIO connector
(P1); while strictly not all pins are GPIO in the pure sense of the meaning the collective set of pins is called GPIO by
the community.
When referring to a pin on the GPIO connectors, use the convention of “P1-XX” where XX is the pin number of
the GPIO pins. This is done to avoid confusion with Broadcom's naming convention for the GPIO pins on the system
on chip (SoC). When you look at the Pi you will see a label near the bottom of the PCB called “P1”: this indicates pin
1 of the GPIO, or P1-01. Opposite to that is P1-02. The pin at the opposite end of P1-01 is P1-25 and the pin at the
opposite end of P1-02 is P1-26. Some pins are labeled as “NC” or DNC”: that means “no connect” or “do not connect”
and you should not be connecting anything to these pins. They will either be physically or logically not connected to
anything or reserved for future use.
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Before we talk about the functions of each of the GpIO pins, I wish to offer you a small but highly important
warning. The GPIO pins on the Raspberry Pi are not tolerant of 3.3 V and above: the GpIO are purely 3.3 v only.
Warning
With that out of the way, let's take a look into the pins and what each pin can do. I've made a nice table that lays
out all the GPIO pin functions and their alternate functions if available. Refer to Table
1-1
to see what each pin can do.
Some notes on these pins. P1-01 has a maximum current draw of 50 mA. Like I have said, it's best to power
your heavy projects externally rather than via the Pi. P1-02 is a 5 V input: you can use this to power the Pi rather
than the micro USB port. I highly suggest you use some type of protection circuit when you power the Pi via the
GPIO power pins.
