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Circuit Diagram & Source

I use a USBTinyISP from It works just fine, however you need an adapter to program the SOIC ATTiny26L out of socket.

All source code is written for WinAVR C compiler. It's a simple infinite loop that bit-bangs a PWM output to each of the 6 LED's. Cycle times are random. Each time you re-apply power, new random patters are chosen, so if you don't like the resulting pattern, try power cycling again!

Here's the simple circuit diagram. There's not much to it!

Charleplex firefly circuit

Charleplex firefly circuit

FireFly source code.

If you want to try your hand at the FireFly bottle, I do have some of the LED's and bottles left. I can also supply a pre-programmed SOIC ATTiny26L, just drop me a note at