1. EEL 3705 / 3705L Digital Logic Design
Spring 2007 Instructor: Dr. Michael Frank Modules #90-99 (Extra Slides): Design Examples Module #93: Animated VGA Graphics– Ping-Pong Video Game
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

2. Ping-Pong Videogame Example
Dynamic Display Generation, Layered Graphics, Controlled Paddle Motion
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

3. Real-World Ping-Pong Table
Image credit: Wikipedia
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

4. Ping-Pong Game Display
Mocked-up here as a Powerpoint animation
Ball
Left paddle
Right paddle
“Midline”
“Net”
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

5. M. Frank, EEL3705 Digital Logic, Fall 2006
Plan for Game Controls
Left pushbutton FLEX_PB1 will control left player’s paddle
Held down = move down, released = move up
Right button controls right paddle similarly
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

6. Plan for game’s “physics”
When the ball hits a wall, it bounces elastically
Horizontal or vertical velocity will change sign
When the ball hits a paddle…
Its vertical velocity (vy) will increase or decrease depending on which direction paddle is moving
Paddle moving up  vertical velocity decreases
Paddle moving down  vertical velocity increases
Its horizontal velocity (vx) will change sign (bounce)
Its absolute value will increase if the ball hits near the center of the paddle (a “good hit”)
Its absolute value will decrease if the ball hits near the edge of the paddle (a “glancing blow”)
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

7. Prioritized Color Layer Combiner
Allows one graphics object to override another…
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

8. Table Surface Stipple Color Layer Generator
Pure green makes for an overly bright table surface, so instead we use an XOR gate to create a green-on-black checkerboard stipple pattern
implemented by this circuit
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

9. Game Display Generator (top half)
Note we use two instances of the color_mixer module to combine the outputs of the table, midline, and net renderers
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

10. Paddle Renderer (only left paddle so far)
Left paddle is rendered as a 10×50 pixel blue rectangle starting at y coordinate lpy (input)
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

11. Entire Ping-Pong Display Renderer (so far)
Altogether we’re using three of our color_mixer modules in order to correctly combine the graphics on the playing surface, midline, net, and paddle layers.
(default black background)
green stipple
Increasing graphics layer priority
white midline
black net
blue paddle
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

12. Left Paddle Controller Circuit
Comparator allows paddle y to be updated iff its new value is in the range [0,480−50] = [0,430]
Adder increments/ decrements paddle y coordinate in direction determined by pushbutton #1
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

13. Top-Level Circuit for Ping-Pong Game (so far)
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

14. Demonstration of Game Display (so far)
We can hook up the board directly to the lecture hall video projector in order to demonstrate the left paddle’s live functionality to the class…
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

15. Ping-Pong Ball Sprite Design
Planning the bitmap 1
Approx. on-screen appearance
DEPTH = 10;
WIDTH = 10;
ADDRESS_RADIX = HEX;
DATA_RADIX = BIN;
CONTENT
BEGIN
0 : ;
1 : ;
2 : ;
3 : ;
4 : ;
5 : ;
6 : ;
7 : ;
8 : ;
9 : ;
END;
ball_sprite.mif
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006

16. Still to do on ping-pong game…
You might like to try some of these yourself!
Add 2nd, red paddle on right, controlled by PB2
Create a ball object, implement game physics
Adjust movement speeds for best playability
Add a scoreboard using the 7-segment display
Hook up an external speaker to the expansion bus
and generate “beep” sounds when the ball bounces off a wall or a paddle or goes out of bounds
Done except for red paddle movement
11/10/2018
M. Frank, EEL3705 Digital Logic, Fall 2006