From Terasic Wiki

This demonstration shows how to control the users LED and KEY by accessing the register of GPIO controller through the memory-mapped device driver. The memory-mapped device driver allows developer to access the system physical memory.

Function Block Diagram

Figure 3-1 shows the function block diagram of this demonstration. The users LED and KEY are connected to the GPIO1 controller in HPS. The behavior of GPIO controller is controlled by the register in GPIO controller. The registers can be accessed by application software through the memory-mapped device driver, which is built into Intel SoC Linux.

Figure 3-1 Block diagram of GPIO demonstration