Tutorial: FPGA Programming

This tutorial shows how to do basic FPGA programming with Cloud V.

Currently, the following FPGA boards are supported:

• Lattice iCEStick Evaluation Kit
• Lattice iCE40-HX8K Breakout Board
• NANDLand GoBoard (Untested)
• Olimex iCE40HX1K-EVB (Untested)

Cloud V runs the open source icestorm toolchain under the hood.

Setting up your project

To synthesize an FPGA bitstream on Cloud V, you need:

• A valid Verilog top module
• A pin constraints file

Creating the Verilog top module

In the Workspace, create a new Verilog module and set it as a top module by right clicking your module from the drop down list in the Verilog file:

Here is the code for the example top module shown here:

module LightUp (clk, ledArray);
    input clk;
    output [7:0] ledArray;
    reg [31:0] counter = 32'b0;

    assign ledArray[7:0] = counter[25:18];
    
    always @ (posedge clk) begin
        counter <= counter + 1;
    end
endmodule

Luckily, icestorm supports initialization in the manner shown above, so there is no need for a reset signal. You can also use an initial begin block if that's your cup of tea.

Next, you need to create a pin constraints file. You need a pinout of the board for this:

• For the iCEStick, the lovely people over at pighixxx.com have already mapped a pinout here.
• For the Breakout Board, conveniently, the names on the board are the names you want! The LEDs, however, do share pins with the GPIO (from left to right): B5, B4, A2, A1, C5, C4, B3, C3. Oh, and the clock is at J3.

Creating the file is straightforward. First you pick your board...

...then you specify the pins.

And voila. Your project is ready.

Generating a Bitstream

From the top menu, Project > Generate Bitstream.

From here, you can pick a constraints file (you could have multiple per project for multiple boards or whatever the case may be) and just press generate.

In the "build (read-only)" folder of your repository, a file called .bin should have been generated. Right click it and download it.

Programming

(In progress.)