A PUSHBUTTON MULTIPLEXING TECHNIQUE TO ADD DATA TRANSFER CAPABILITY
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Aug-22
As portable communication equipment designs get smaller and smaller, there is an ever-increasing need to multiplex functions to maintain ease of access to buttons and controls. This design provides a technique for multiplexing existing pushbutton designs to provide data entry capability. This elimi- nates the need for additional pins for programming or other data entry. The invention consists of the modification to a typical conductive pushbutton (a typical configuration is shown in Figure 1). This typical pushbutton configuration is common on con- ductive rubber keypad designs as perfected by Shin- etsu Corp. and other silicone rubber molders. The typical application uses a conductive pad or pill on the underside of the button that shorts two adjacent lines on the interfacing board to close a switch sens- ing circuit (see Figure 1). In this design; however, the whole key is molded of the conductive material. This approach is fully feasible as verified by discus- sions with numberous silicone molders. This fully conductive button, when actuated, may be used to close a circuit on its mating circuit board or apply a force to a metal snapdome that will close a circuit on a mating circuit board just as in a typical applica- tion. Since the whole button is conductive it can further be used to conduct low current level infor- mation such as programming data for a radio etc. The microprocessor that reads the button circuit must be programmed to properly multiplex this cir- cuit. One example of a practical application for this design would be to add a programming interface to a portable radio without adding additional contacts or buttons. An existing silicone pushbutton could be converted to the new design by simply changing the conductivity of the base silicone material.