Communication Between Active Stylus and Touch Sensor

摘要

In certain embodiments, a method includes wirelessly receiving, by an electrode of a stylus, a signal sent from a touch sensor of a computing device. The received signal includes a data bit and is based on a predefined code sequence. The method also includes producing, by the electrode of the stylus, a derivative signal from the received signal, the derivative signal corresponding to a derivative with respect to time of the received signal. The method further includes performing, by the stylus, a cross-correlation of the derivative signal and an expected-signal pattern, the expected-signal pattern based on a derivative with respect to time of the predefined code sequence, where the cross-correlation produces a cross-correlation signal including one or more cross-correlation pulses. The method also includes determining, by the stylus, based on the cross-correlation signal, that the received signal is associated with the predefined code sequence.

主权项

1. A method comprising:
wirelessly receiving, by an electrode of a stylus, a signal sent from a touch sensor of a computing device, the received signal comprising a data bit and being based on a predefined code sequence; producing, by the electrode of the stylus, a derivative signal derived from the received signal, the derivative signal corresponding to a derivative with respect to time of the received signal; performing, by the stylus, a cross-correlation of the derivative signal and an expected-signal pattern, the expected-signal pattern based on a derivative with respect to time of the predefined code sequence, wherein the cross-correlation produces a cross-correlation signal comprising one or more cross-correlation pulses; determining, by the stylus, based on the cross-correlation signal, that the received signal is associated with the predefined code sequence; and determining, by the stylus, a value of the data bit sent by the computing device based at least in part on an amplitude of the cross-correlation pulses.