Here’s an old but quite clever approach app note from Microchip on utilizing microcontroller I/O’s to handle multiple display and switches with only few pins.
This application note demonstrates the capability of the PIC16C71 and has been broken down into four subsections:• Multiplexing Four 7-Segment LED Displays• Multiplexing Four 7-Segment LED Displays and Scanning a 4×4 Keypad• Multiplexing Four 7-Segment LED Displays and the A/D Channel 0• Multiplexing Four 7-Segment LED Displays with a 4×4 Keypad and 4 A/D Channels
I think this is good idea. Some days ago I’m just thinking about do same thing with LCD displays.