I created this badge hack after the conference was already over, but I felt it would be extremely useful if somebody wanted to reuse their badge. The QR Code is generated on the fly and can work with a string up to 80 characters (2 lines of text wrapped), though it could be modified for longer strings without too much trouble. As the complexity of the QR Code increases, the size of the code is updated so that it always fits on the screen. Whenever a string is changed, it is automatically updated in non-volatile memory and loaded when the program starts even after the badge is reset so you don't need to keep typing it in. It took me about a day to write this and it has all of the enhancements I wanted to add.
I originally had placed a delay in the code because it was redrawing the QR code every cycle and looked weird. However, I had already updated it so the QR code is only redrawn on load or by changing the string. I went ahead and removed the delay because when typing quickly, sometimes characters were missed since there isn't any kind of keyboard buffer.