Blinkenrocket is a rocket-shaped accessory with an 8x8 LED matrix display and the ability to show user-defined texts and animations. However, unlike most such devices, users do not need an AVR programmer or USB-TTL converter to upload new patterns. Instead, they are flashed via a website and a standard 3.5mm audio cable. Hardware support is not limited to computers, but includes any device which is able to play audio at a decent volume (such as most tablets and smartphones).
It was a group project by Chaosdorf and shackspace people; I had the pleasure of writing the firmware for the ATTiny88 microcontroller powering the device. Parts of it have since been modified to make audio transmissions more robust.
Key features are:
- 8 MHz ATTiny88 microcontroller with direct (and slightly out-of-spec) LED matrix connection
- 8 kB I²C EEPROM for animation storage; supports up to 248 different animations.
- 3.5mm audio modem with forward error correction (utilizing David Cook's Hamming FEC implementation)
Here is an early modem demonstration with a not-yet-ideal error correction setup.