The still-working led_matrix.

According to early pages in my notebook, I built this in 2006. I'm pretty sure this was my first microcontroller project (excluding of course blinking an LED). Back then I didn't have good back-up habits and had never even heard of git, so the code I wrote is gone forever (maybe for the best).

The enclosure is a translucent blue plastic so I can see some of the internals. I'm not willing to open it up though - I can see a birds-nest of wiring and I expect that after openeing, it may never work again. I was surprised it still works at all!

The matrix runs in two modes:

  1. Clock mode. By default it displays hours and minutes but you can "scroll" right to show seconds. There is a neat vertical scrolling animation when a digit changes. There is no battery back-up of any kind so the clock resets to 12:00 every time it switches on. It also keeps awful time - loses a few minutes each hour. Pretty sure I was relying on the internal oscillator and whatever scaling got me closest to a one-second interrupt trigger.
  2. Text mode. By default it scrolls the text "GAME OVER..." but you can change the text by scrolling through the alphabet for each character.

From my notes and from what I can see through the case, I know this much: