This lab and the next lab work together to build a Pong game on the VGA display. In this lab you will create two modules, a ball drawer and a vertical line drawer.

• Exercise 1: Designing a BallDrawer state machine on paper.
• Exercise 2: Implementing the BallDrawer state machine in SystemVerilog, and verify with simulation.
• Exercise 3: Testing that your BallDrawer state machine correctly displays a ball on the VGA display.
• Exercise 4: Create a VLineDrawer module that draws vertical lines, simulate, and test with the VGA display.

• Learn how to implement state machines using behavioral SystemVerilog.

In this lab you will again be using the BitmapToVga module. Make sure you remember how this module works.

What 3-bit binary value would you provide to the module to set the color of a pixel to cyan? Provide your answer in SystemVerilog literal form (ex 3'b000).

What is the minimum number of cycles required to change the entire image to blue? How many microseconds would this take, given your system clock?

Design a state machine (on paper) that can be used to draw a ball. The module behavior is described below:

The state machine should wait for the start signal before starting to draw a ball. For each pixel that needs to be drawn, the state machine should output an (x,y) coordinate using the x_out and y_out outputs, and assert the draw_enable signal. The done signal should be asserted when the ball is done being drawn. The state machine should wait for the start signal to go low before waiting for it to go back high to draw another ball.

The following shows a diagram of a ball with 5 pixels, and a possible corresponding waveform for drawing this ball at (100,50).

Here are some other ball shapes you can use, or you can design your own. Your ball needs to have at least 4 pixels.

Exercise #1 Pass-off: Show the TA your state machine and describe how you verified that it meets the requirements described above.

Create the BallDrawer SystemVerilog module that implements your state machine.

module BallDrawer (
    input wire logic            clk,
    input wire logic            reset,
    input wire logic            start,
    output logic                draw,
    output logic                done,    
    input wire logic    [8:0]   x_in,
    input wire logic    [7:0]   y_in,
    output logic        [8:0]   x_out,
    output logic        [7:0]   y_out
);
 
endmodule

Simulate your BallDrawer module. Make sure your simulation tests drawing a ball in one location, then drawing a ball in another location. Use non-zero values for x_in and y_in.

Include a copy of your TCL file in your lab report.

Exercise #2 Pass-off: Show the TA a simulation of your BallDrawer module and explain how you tested its functionality.

In this exercise you will verify that your BallDrawer module works correctly, by drawing a ball to the VGA display. The following top-level module can be used. Look it over and make sure you understand it.

The module works by connecting up the appropriate signals from your BallDrawer module to the BitmapToVga module. You shouldn't have to change this file to get it to work properly; however, you may decide to change it later to modify the ball location or color.

top_object_drawer.sv

Add the above file to your Vivado project and make sure it is configured as the top-level module. Add a constraints file to your project that is configured appropriately.

Exercise #3 Pass-Off: Show your display to the TA. The TA will verify that you are successfully drawing a ball on the screen.

Now that you have created a module to draw a ball, you will follow the same process to create a module that can draw vertical lines of arbitrary height.

Create the following module. Use a state machine to implement the described behavior.

The module should output (x_out, y_out) coordinates to write to, starting with the cycle immediately following the assertion of the start signal, and continue each cycle until complete. The done signal should be asserted during the cycle of the last pixel.

The following shows a diagram of a line 6 pixels tall, and the corresponding waveform for drawing this line at (100, 50).

Simulate your VLineDrawer module to ensure it is working correctly. Then modify the top-level from the last exercise to draw a vertical line instead of a ball.

Exercise #4 Pass-off: Show the TA the simulation of your VLineDrawer module and the line drawing correctly on the monitor.

Submit your final lab report on Learning Suite.