Some of the people love the “blink, blink things” and they just can’t help themselves when they discover this kind of stuff! Well, if you’re one of them, then you should try to develop this LED matrix – Blinkomat!
You would need to use an Atmega16 Microcontroller by Atmel that running at 16MHz for controlling the LEDs. It has 16KB of Flash memory, 1KB of SDRAM and 512 Bytes of EEPROM. Since it has 32 I/O lines, you only have to choose 12 and the others as dimensions for the LED matrix. As a result, it has 12 rows and 20 columns making 240 LEDs totally, where you can drive directly through the 32 I/O lines easily. The only problem that you’re going to face here is no I/O line left for input purpose.
The LEDs can be switched on and off line by line by using time multiplexing. Honestly, this can be done via a timer interrupt. Hence, every time when the interrupt occurs, you will need to switch to the next line of LEDs. By the way, those sixteen “greystomes” are possible for each LED by driving them using Pulse Width Modulation (PWM).