Dual protocol remote control

Abstract

Methods and apparatus for use in communication between a remote control and a receiving unit provide power saving modes of operation and enable remote control use of high data generating devices, such as a trackball. A pulse position modulation protocol is provided in which the position of a single pulse, such as an infrared pulse is located in time in one of three or more locations. In the preferred embodiment, the pulse is provided at least in one of eight states, and more preferably in one of sixteen states. In the latter arrangement, a single bit provides for a hex data output by a single pulse. In this way, a single pulse may substitute for what otherwise would have been multiple pulses in a binary protocol. Power savings may be achieved through this method. A time base compensation method is provided in which the remote control provides two detectable events separated by a predetermined time as measured by the remote control time base or clock. The receiving unit measures the time difference between the two events as determined by the receiver's time base or clock. A correction factor is then applied to subsequent detections of time differences between events as sent by the remote control. In the preferred embodiment, a multiplicative factor is applied. Dual protocol remote control devices may be provided wherein a first protocol is utilized in conjunction with a second protocol comprising the pulse position modulated system, such as the hex based system. In this manner, a binary protocol may be utilized for lower channel or lower data transfer arrangements and the pulse position modulation protocol may be utilized for relatively high data generating devices, such as a trackball. The protocol is advantageously utilized with high key identification numbers, such as those above 255.