Tiny Charlieplexed Display

Electronics is a domain which entices not only engineers but hobbyists as well. This is a hobby project from another tech geek. The project is called Tiny Charlieplexed display using microcontroller. Charlieplexing is a technique proposed in early 1995 by Charlie Allen at Maxim Integrated Products for driving a multiplexed display in which relatively few I/O pins on a microcontroller are used to drive an array of LEDs. In other words, it means controlling many Leds with only a few pins.

The microcontroller used here is ATTiny85. It is an 8 pin processor from Atmel with 8K of program space, 6I/O lines, and 4 channel 8-bit ADC. The project uses 5 of the 8 output pins on the controller for designing a charlieplexed display of 20 Leds. Since 20 Leds are controlled here using only 5 output pins on the controller, this is a charlieplexed display.

The Leds are arranged in a grid of order 4×5 in a fashion that they are aligned in the same direction and run a game called Conway’s Game of Life. This game is a simple simulation of cellular life. By turning on a set of random LEDs, you can let the “colony” evolve based on a set of rules, and see how long it lasts. Sometimes the colonies die off quickly; sometimes the right configuration will get into a loop and survive forever. It’s a bit abstract, but interesting to watch.

The source code is written in VB.net. Programming software for the game includes writing some special routines like lighting specific Leds, storing the current grid, calculating the next generation and software PWM for fading of Leds. Another important aspect of programming was to detect the time for resetting the simulation. For this purpose, the next grid is compared with the current grid every certain interval of time. If a match is found, the simulation is reset.

Try making this interesting project yourself.