Apple Inc.
Method for stylus touch-down and lift-off noise mitigation

Abstract:

Active styli, methods and non-transitory computer readable storage media can be used for mitigating noise coupling from an active stylus to a touch sensing system. An active stylus can include a force sensor that can be used to detect stylus touch-down and lift-off events. Based on a touch-down and lift-off events, the stylus can generate stimulation signals and ramp up or ramp down the amplitude of the stimulation signals. Additionally or alternatively, an active stylus can receive information to synchronize the active stylus with a touch-sensitive device. Based on the information, the stylus can synchronize generation of stimulation signals with the stylus scan performed by the touch-sensitive device. The stimulation signals can be ramped up during a guard band period before a stylus scan and can be ramped down during a guard band period after the stylus scan.