An Adafruit HAT with the PWM modification
Classic: Early forms of this library had this as default mapping, mostly derived from the 26 GPIO-header version so that it also can work on 40 Pin GPIO headers with more parallel chains. Not used anymore.
Classic pin-out for Rev-A Raspberry Pi.
The regular hardware mapping described in the wiring.md and used by the adapter PCBs.
The regular pin-out, but for Raspberry Pi1. The very first Pi1 Rev1 uses the same pin for GPIO-21 as later Pis use GPIO-27. Make it work for both.
This is used if you have an Adafruit HAT in the default configuration