Touch controller synchronization with the downlink signal of stylus

1 . A system for synchronizing a stylus-enabled device with a stylus, the stylus-enabled device comprising a touch controller configured to:

transmit an uplink signal to the stylus;

receive a downlink signal from the stylus;

determine a timing offset between the uplink signal and the downlink signal;

determine a phase shift of the downlink signal; and

adjust a synchronization timing based on the determined timing offset and the determined phase shift.

2 . The system of claim 1 , wherein the touch controller is further configured to:

sample the downlink signal using an analog-to-digital converter (ADC);

segment the sampled downlink signal into a plurality of segments; and

determine the timing offset based on the segmented downlink signal.

3 . The system of claim 2 , wherein the touch controller is configured to:

determine a magnitude for each segment of the plurality of segments;

compare the magnitude of each segment to a predetermined threshold; and

identify valid segments based on the comparison.

4 . The system of claim 3 , wherein the touch controller is configured to:

calculate a length of the downlink signal based on the identified valid segments; and

determine the timing offset based on the calculated length of the downlink signal.

5 . The system of claim 1 , wherein the touch controller comprises an In-phase and Quadrature (I/Q) demodulator configured to extract magnitude and phase information from the downlink signal.

6 . The system of claim 5 , wherein the touch controller is configured to:

calculate the phase shift based on the extracted phase information; and

convert the calculated phase shift into a timing shift.

7 . The system of claim 1 , wherein the touch controller is configured to:

apply the determined timing offset as a coarse adjustment to the synchronization timing; and

apply the determined phase shift as a fine adjustment to the synchronization timing.

8 . A method for synchronizing a stylus-enabled device with a stylus, the method comprising:

transmitting, by a touch controller of the stylus-enabled device, an uplink signal to the stylus;

receiving, by the touch controller, a downlink signal from the stylus;

determining a timing offset between the uplink signal and the downlink signal;

determining a phase shift of the downlink signal; and

adjusting a synchronization timing based on the determined timing offset and the determined phase shift.

9 . The method of claim 8 , further comprising:

sampling the downlink signal using an analog-to-digital converter (ADC);

segmenting the sampled downlink signal into a plurality of segments; and

determining the timing offset based on the segmented downlink signal.

10 . The method of claim 9 , further comprising:

determining a magnitude for each segment of the plurality of segments;

comparing the magnitude of each segment to a predetermined threshold; and

identifying valid segments based on the comparison.

11 . The method of claim 10 , further comprising:

calculating a length of the downlink signal based on the identified valid segments; and

determining the timing offset based on the calculated length of the downlink signal.

12 . The method of claim 8 , further comprising extracting magnitude and phase information from the downlink signal using an In-phase and Quadrature (I/Q) demodulator.

13 . The method of claim 12 , further comprising:

calculating the phase shift based on the extracted phase information; and

converting the calculated phase shift into a timing shift.

14 . The method of claim 8 , further comprising:

applying the determined timing offset as a coarse adjustment to the synchronization timing; and

applying the determined phase shift as a fine adjustment to the synchronization timing.

15 . A touch controller for synchronizing a synchronizing a stylus-enabled device with a stylus, the touch controller comprising:

an analog-to-digital converter (ADC) configured to sample a downlink signal received from the stylus;

an In-phase and Quadrature (I/Q) demodulator configured to extract magnitude and phase information from the sampled downlink signal;

a processor configured to:

determine a timing offset between an uplink signal transmitted to the stylus and the downlink signal,

determine a phase shift of the downlink signal based on the extracted phase information, and

adjust a synchronization timing based on the determined timing offset and the determined phase shift; and

a timing generator circuit configured to apply the adjusted synchronization timing to subsequent communications with the stylus.

16 . The touch controller of claim 15 , wherein the processor is further configured to:

segment the sampled downlink signal into a plurality of segments;

determine a magnitude for each segment of the plurality of segments;

compare the magnitude of each segment to a predetermined threshold; and

identify valid segments based on the comparison.

17 . The touch controller of claim 16 , wherein the processor is configured to:

calculate a length of the downlink signal based on the identified valid segments; and

determine the timing offset based on the calculated length of the downlink signal.

18 . The touch controller of claim 15 , wherein the processor is configured to:

calculate the phase shift based on the extracted phase information; and

convert the calculated phase shift into a timing shift.

19 . The touch controller of claim 15 , wherein the processor is configured to:

apply the determined timing offset as a coarse adjustment to the synchronization timing; and

apply the determined phase shift as a fine adjustment to the synchronization timing.

20 . The touch controller of claim 15 , further comprising a modulating circuit configured to generate the uplink signal for transmission to the stylus, wherein the uplink signal is used as a reference for determining the timing offset.