A Tale of Two (three) Pongs

Created 2 April 2009, updated 1 Nov 2020

When I start learning a new  platform, I have a simple rule: If you don’t know what to do with it, make pong. What I love about pong is that it’s a simple rule set, easy to understand, and implementable on just about anything with a pixel display.  You can generally implement it in a day or less on any platform. And it’s a great example of engaging interaction.  People understand what’s going on right away, and, when implemented well, it’s just challenging enough to keep you engaged for several minutes at least.  That’s good interaction, to me.

I’m a big believer in starting with the application rather than the platform.  I think you do better work when the tools serve the need rather than the other way around.  But sometimes you get stuck with the assignment to learn a particular platform or tool, and you have to make up a project on the spot.  When that happens, make pong.

As an example of this, I built pong for two platforms yesterday [1 April 2009]: an Arduino Mega with 2 8×8 LED matrices (based on my earlier post), and Processing.  Since Arduino’s programming syntax was based closely on Processing’s, I figured it should be possible to port the code from one to the other pretty quickly. It took about ten minutes to go from Arduino to Processing.  In 2020, I updated this exercise to write the program in p5.js as well. Following, I’ll describe the thought process of putting the game together for all three, as a hopeful aid to beginning programmers.

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8×8 LED matrix control on an Arduino Mega

Created 31 March 2009, edited 1 Nov 2020

Once you’ve mastered microcontroller programming, you might be tempted to control a lot of LEDs.  Lots of people have this desire once they master the basics. Many microcontrollers have a limited number of output pins, however, so you might think that limits how many LEDs you can control.  I’ve written about a few different methods around this before in chapter 14 of Physical Computing and in this blog.

By matrixing your LEDs, you can control many more than the number of pins you have.  For example, with the Arduino Uno and earlier models, you had up to 20 digital outputs (13 labeled digital I/O 0 through 13, plus the six analog outputs, which double as digital I/O 14 through 19).  With 16 of those, you can control an 8×8 matrix of LEDs.  That’s 64 LEDs.  With the Arduino Mega, you have 54 digital I/O pins, so you can control a lot more.  This example uses 32 of them to control 2 8×8 matrices, for a total of 128 LEDs from one controller.

To make this example, you’ll need:

  • Arduino Mega
  • Breadboard or prototyping shield. 
  • 8×8 LED matrix.  I got mine in a surplus shop in China, but you can also get them from most electronics retailers
  • male pin headers
  • female pin headers
  • Wires

Step 1: Figure out the LED Matrix pins

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