Data acquisition in a multi-function keyboard system which corrects for

Abstract

Data acquisition in a multi-function keyboard system includes both acquiring typing data by conventional keyboard scanning techniques and, simultaneously, acquiring pointing data by sampling force sensors coupled to the multi-function pointing key. The keyboard system periodically samples the force sensors to determine bias values defining a null point, and updates the bias values by a moving average calculation to compensate for manufacturing tolerance and long term drift. In response to a start pointing command from the host processor, the keyboard system transmits bias values and then pointing values, the latter being responsive to forces applied to the pointing key by the user for cursor control. The sensor values are encoded so as to pass through to the host processor in a manner transparent to application software. The system scans the force sensors periodically to acquire successive pointing values, and transmits them to the host, as long as pointing mode persists. Concurrently, the keyboard system scans the keyboard to detect other key changes and forwards them to the host as well. The keyswitch data may be interpreted as a pointing event (analogous to a mouse button action), or as an indication to change to typing mode.