Lab 3 - Bouncing Ball I

Introduction:

In this lab, we will program the FPGA on the Nexys2 board to display a “bouncing ball” on a 640 x 480 VGA monitor connected to the VGA interface on the board. This will requires us to generate the required sync and video signals consistent with the VGA standard.

VGA Display :

How a VGA Display works:

• Default VGA resolution: 640x480
• Raster Scanning (Figure 1)
  • Scanning, each horizontal row left to right, top to bottom, and then resetting to the top once the scanner hits the bottom (Starts in pixel (0,0) moves to the right to (639,0), resetting to (1,0) then moving to the right to (1,639), repeating to the bottom to row 479)

Steps:

Hardware Setup :

1. Plug in the monitor to the VGA port of the Nexys 2 Board

Initial Project Setup :

1. Start the Vivado program
   • This group used Vivado 2018.3
2. Create a New Project and name is 'VGAball'
   1. File -> New Project
   2. Leave Project type as RTL and do not specify sources as this time
   3. Default part is XC7A100TCSG324
      • This team chose XC7A100TCSG324-1 as the default part
3. Now create a new VHDL source
   1. File -> Add Sources
   2. Select "Add or create design sources" and Next
   3. Click the "+" and then "Create File"
   4. Ensure the File Type is set to VHDL and name the file "vga_sync"
   5. Replace the default code with the code in Figure 2

Configure FPGA :

1. Using the same project settings from Labs 1 and 2, create a new project titles 'VGAball'.
   • Shown in Initial Project Setup
2. Create a new source titled 'vga_sync'
   • Shown in Initial Project Setup
3. Create another source titled 'ball'
   • Use the code from Figure 3
4. Create another source titled 'vga_top'
   • Use the code from Figure 4
5. Right click on the module 'vga_top' in the Hierarchy window and select Set as Top Module (if it's not already)
6. Add an Implementation Constraint source file 'vga_top.xdc'
   • Use the code from Figure 5
7. Highlight the 'vga_top' module in the Hierarchy window and run Synthesis and Implementation
8. Generate Bitstream

10. Plug in the device if it is not already and Vivado should detect the board

11. Click Program Device and load the generated bitstream onto the board

1. If you cannot click Program Device, click Open Target first

You should now see a ball bouncing vertically in the middle of the screen. Feel free to modify the code to change the size, color, shape, etc. of the ball (hint: modify the ball.vhd file).

Note: There may be a problem with the aspect ratio/resolution of the display you are using, so if you are not seeingthe bouncing ball try another monitor

Note: You can set the clock rate of board to either 25 MHz or 50 MHz, both work but at 50Mhz the image will look less choppy because more images will be shown per second on the monitor/projector (unless the board can compute images faster than the monitor/projector refresh rate at the lower processor clock rate).

Helpful Resources:

How to set up the bitstream:

http://users.wpi.edu/~rjduck/Nexys4DDR%20Vivado%20VHDL%20Decoder%20Tutorial.pdf

How to Connect The Nexys A7 to your computer:

https://github.com/Digilent/Nexys-A7-100T-GPIO

Dr. Ackland's Lab Manual:

http://personal.stevens.edu/~backland/Courses/Course487_Spring_18_files/Labs/Lab3.pdf

GitHub:

https://github.com/kevinwlu/dsd