This library uses GPIOX as reference where X is the number of the pin (e.g. pinMode(X, mode)). This library doesn’t use the Physical pin numbering as those numbers are a reference of the PCB and not of the Broadcom BCM283x SoC.
Raspberry Pi 40-pin GPIO connector
Raspberry Pi 26-pin GPIO connector
By Jorge Garza , Updated on: Aug 5, 2016