Detecting phantom keys of keyboard using firmware - using diagnostic program during keyboard polling to detect when phantom conditions occur due to simultaneous operation of keys

摘要

The phantom key detection method involves using a single chip micro computer with a built-in diagnostic program to detect the so called phantom key state conditions when one or more keys are operated together. The keyboard arrangement has a matrix of 8 keys per row and 16 lines creating a matrix of 128 keys. The lines are polled every 8 ms using firmware. When only a single key is actuated only one column is 0 and the others 1 and the keyboard is free of phantom effects. For more than one key at a time the diagnostic process identifies more than one column being 0 and a phantom condition is identified. If phantom condition then stops accepting keyboard input and indicates condition via audio signal. USE/ADVANTAGE - Avoids problem of phantom key operations by rapid detection of this condition. Saves memory space by using firmware.