AF_SEL_SET=no
GPIO Alternate Function Selectset. Writing a 1 to one or more bits in this register sets the bits in the same positions in GPIO_EN1 to 1, without affecting other bits in that register.
AF_SEL_SET | Mask of all of the pins on the port. 0 (no): No effect. 1 (set): Set the corresponding bit in GPIO_AF_SEL register. |