Timing synchronization of active stylus and touch sensor
In one embodiment, a stylus includes one or more electrodes included in a tip, and a computer-readable non-transitory storage medium embodying logic that is configured when executed to receive, by the one or more electrodes and an analog front end, signals transmitted from a touch sensor coupled to a touch-sensor controller, and convert the signals into sequences of digital signals. The logic is further configured when executed to feed the sequences of digital signals received in different periods into a memory; correlate each of the sequences of digital signals with a digital data defined by a wide-band code to generate multiple correlations; and transmit a transmission signal to the touch-sensor controller according to a synchronization timing determined based at least in part on one or more of the multiple correlations.
1. A flexible printed circuit (FPC), comprising:
multiple touch-sensor controllers,
wherein the touch-sensor controllers include integrated circuits, which are general-purpose microprocessors, microcontrollers, programmable logic devices or arrays, or application-specific integrated circuits (ASICs), and which include analog circuitry, digital logic, and digital non-volatile memory;
wherein the multiple touch-sensor controllers are disposed on the FPC, which is bonded to a substrate of a touch sensor;
wherein the FPC is active or passive;
wherein the multiple touch-sensor controllers are configured to generate synchronization signals based on digital data, wherein the synchronization signals include one or more synchronization parameters indicative of a duty cycle of the synchronization signals; and
wherein the synchronization signals are configured to be converted, by a stylus, into sequences, which are correlated with the digital data to generate multiple correlations, and the multiple correlations are used by the stylus to synchronize communication timing with the touch sensor controllers.
2. The FPC according to claim 1 , wherein each of the touch-sensor controllers includes a processor unit, a drive unit, a sense unit, and a storage unit.
3. The FPC according to claim 2 , wherein the drive unit is configured to supply drive signals to drive electrodes of the touch sensor.
4. The FPC according to claim 3 , wherein the processor unit is configured to control supply of the drive signals by the drive unit.
5. The FPC according to claim 2 , wherein the sense unit is configured to sense charge at capacitive nodes of the touch sensor and provide measurement signals to the processor unit representing capacitances at the capacitive nodes.
6. The FPC according to claim 5 , wherein the processor unit is configured to process the measurement signals from the sense unit to detect and process the presence and location of a touch or proximity input within a touch-sensitive area of the touch sensor.
7. The FPC according to claim 1 , wherein the touch-sensor controllers are configured to transmit signals defined by a wide-band code via the touch sensor.
8. The FPC according to claim 7 , wherein the wide-band code includes ones and zeros with properties that are related at least to noise margin or synchronization.
9. The FPC according to claim 7 , wherein the signals include a pattern of one of ones and zeroes, highs and lows, or pulses and offs, corresponding to the wide-band code.
10. The FPC according to claim 7 , wherein the signals embed synchronization data to form the synchronization signals.
11. The FPC according to claim 7 , wherein the synchronization data additionally indicate at least one of a data rate, a frequency, a period, or a phase of the signals.