I am a new to FPGA design, I am now playing a simple LED flow example. I am using Quartus 15.1 and Cyclone V.
I firstly write a verilog code and then go to setup the pins. In the Pin Planner, for a new Node, I give the name "dk_50M", then I try to set it to be as input. But when I click the "Direction", I get a pop-up "This is a read-only item".
My question is how to set this pin as input pin ?
You don't set I/O direction in the Pin Planner. The direction is based off your design. If you're trying to create I/O pins before you've actually created your design, you're limited in what you can do in the Pin Planner. Create your design, then run Analysis & Elaboration. You'll then be able to make I/O-related assignments for the top-level I/O in your design.
Sstreal is correct! Need to have blackbox module or entity with ports or IO's declared. So that, you can see the direction's in the pin assignments.
Your design file is the input for the Pin Planner.