Active stylus synchronization with multiple communication protocols

A method for operating an active stylus for use with one or more touch-sensitive display devices, the method comprising:

• driving a stylus electrode of the active stylus with a stylus-initiated synchronization waveform as part of a first repeated touch-sensing frame, the stylus-initiated synchronization waveform being configured to enable, via capacitive coupling with one or more electrodes of a capacitance-based touch sensor of a first display device, the first display device to become time synchronized with the active stylus, such synchronization mechanism being referred to as a stylus-initiated synchronization mode;
• receiving, on the stylus electrode, a response caused by a display-initiated synchronization waveform driven on one or more electrodes of a capacitance-based touch sensor of a second display device as part of a second repeated touch-sensing frame that is arranged differently than the first repeated touch-sensing frame;
• and
• interpreting the response on the stylus electrode to cause the active stylus to become time synchronized with the second display device, such synchronization mechanism being referred to as a display-initiated synchronization mode.

An active stylus for use with one or more touch-sensitive display devices, comprising:

• a stylus electrode configured to electrostatically couple with one or more electrodes of a display device having a capacitance-based touch sensor;
• transmit logic configured to drive the stylus electrode with a first synchronization waveform that is configured, via interpreting a response on one or more electrodes of a first display device, to enable the first display device to become time synchronized with the active stylus, where the first synchronization waveform is driven on the stylus electrode as part of a first repeated touch-sensing frame, this mechanism of synchronization being referred to as a stylus-initiated synchronization mode;
• receive logic configured to interpret a response on the stylus electrode caused by a second synchronization waveform being driven on one or more electrodes of a second display device, such interpretation configured to enable the active stylus to become time synchronized with the second display device, where the second synchronization waveform is driven on the one or more electrodes of the second display device as part of a second repeated touch-sensing frame that is arranged differently than the first repeated touch-sensing frame, this mechanism of synchronization being referred to as a display-initiated synchronization mode;
• and
• a controller configured to cause the active stylus to operate in the stylus-initiated synchronization mode as a default mode of operation of the active stylus, and wherein the controller is configured to cause the active stylus to switch to operation in the display-initiated synchronization mode in response to receiving the second synchronization waveform from the second display device or determining that active stylus is less than a threshold distance from the second display device.