An infrared touch input system is taught. Briefly stated, the system comprises a four-sided frame having an infrared transparent bezel along the inside thereof and having infrared emitters along the top and one side of the frame with infrared detectors along the sides opposite the emitters. Darlington transitor arrays are used as source and sink drivers for driving the LED's in an array. The I/O lines of a microprocessor in conjunction with the source and sink drivers are used to selectively energize each LED. Additional I/O lines of the microprocessor in conjunction with BCD decoders are used to selectively energize corresponding infrared detecting phototransistors before, during and after LED turn-on. A host computer supplies a clocking signal for the microprocessor with programming in the microprocessor thereby automatically performing the selection and deselection of emitters and detectors. A serial data stream is outputted from the microprocessor which indicates to the host computer the location of any broken light beams thereby indicating a stylus hit.
Touch input device