nrf24l01 transceiver on altera board de2-115
The DE2-115 FPGA board does not have any hardware dedicated to SPI (actually, it does for loading its configuration from flash, but not for other uses), so the SPI logic must be synthesized using the FPGA fabric.

There are a few different options as to how the SPI logic will interface with other system components. In the end, all choices end up using GPIO for output. One would select four pins to use (clk, mosi, miso, and cs) and assign your module's ports to those pins.

But, there are a few different choices you have for how to interface your controlling logic with the SPI core:


Use a "normal" verilog module
Use a SPI component (Altera provides one for their Avalon bus architecture)
Instantiate a CPU (such as NIOS) and use bit-banging to construct the SPI signals using a 4-bit "conduit".


If you're using an Avalon bus already, I'd suggest that method #2 would be the simplest. But, if you are not using SoC design techniques, you may want to investigate writing (or buying or downloading) a pre-written SPI-interface module.