EE 231
Lab 11: Protoboard Ping-Pong

Prelab 11

Design and build a circuit that allows two people (LEFT and RIGHT) to play ping-pong using eight LEDs in a row to display the moving ball and two push buttons for paddles. A single lit LED represents the ball, which moves from left to right or from right to left. Here are the rules:

• The circuit powers up with the ball in the leftmost position, ready for LEFT to serve.
• The balance of the rules are symmetric for the two players, L (LEFT) and R (RIGHT).
• The circuit knows whose turn is next, L or R.
• When it is L's turn, L hits the left paddle button (LPB), and starts the ball moving from left to right. The LPB is ignored while the ball is moving from left to right.
• When the ball is moving from left to right, R must push the right paddle button (RPB) when the ball is in the right most position. If R pushes RPB at this time, the direction of the ball changes, and it then moves from right to left. Then it is up to L to press LPB at the proper time to "return the volley'' when the ball reaches the left end, etc...
• If R pushes RPB before the ball is in the rightmost position, or fails to push it the before the ball "falls off the end,'' then the turn ends, L gets a point, and it is L's turn next, to serve.
• When L scores a point, an output will go high. When L serves, the output will go back low. (Adding a score counter is not a required part of this lab.)
• If R scores a point (L failed to hit the ball at the proper time), the ball will go and sit at the rightmost position so that R can serve.

Implement and test your circuit. Use the debounced pushbuttons on your breadboard as paddles.

Bonus Question: Implement some method of keeping track of and displaying the score (5% extra)..

October 2000
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