Toy cash register hack to add real bar code scanner.

My daughter was disappointed that the scanner in her toy cash register didn't really work. I solved this by interfacing an old PS/2 CueCat bar code scanner to a PIC and output the data to a serial port in ASCII format. The original cash register display is accessed by hacking the keypad through a couple of M74HC4051 multiplexers. The display can be cleared and the first 8 digits of the bar code displayed. All 8 characters can be reliably written to the display in less than 250 ms.