PI GPIO reference board on a Rasperry Pi Rev 1"PI GPIO reference board on a Rasperry Pi Rev 1" by Low Voltage Labs is licensed under CC BY-SA 2.0

A powerful feature of the Raspberry Pi is the row of GPIO (general-purpose input/output) pins along the top edge of the board. A 40-pin GPIO header is found on all current Raspberry Pi boards (unpopulated on Pi Zero and Pi Zero W). Prior to the Pi 1 Model B+ (2014), boards comprised a shorter 26-pin header. Any of the GPIO pins can be designated (in software) as an input or output pin and used for a wide range of purposes.

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