WO2025023929A1

WO2025023929A1 - Method and device for clock synchronization in a touch sensing system

Info

Publication number: WO2025023929A1
Application number: PCT/US2023/028487
Authority: WO
Inventors: Hu-Chi Chang; Chengliang QIAN; Premal Parekh
Original assignee: Google LLC
Current assignee: Google LLC
Priority date: 2023-07-24
Filing date: 2023-07-24
Publication date: 2025-01-30
Anticipated expiration: 2026-01-24

Abstract

A method and a touch display device for clock synchronization in a touch sensing system. Touch driving circuitry of the touch display device receives a current first synchronization signal used by display driving circuity of the touch display device to drive a display panel of the touch display device. In response to a previous first synchronization signal being received before the current first synchronization signal is received, the touch driving circuitry determines whether a second synchronization signal has been sent or is going to be sent within a first predefined period. The second synchronization signal is used for clock synchronization between the touch driving circuitry and a stylus that cooperates with the touch display device. The touch driving circuitry determines a time delay of a next second synchronization signal based on whether the second synchronization signal has been sent or is going to be sent within the first predefined period.

Description

METHOD AND DEVICE FOR CLOCK SYNCHRONIZATION IN A TOUCH SENSING SYSTEM

TECHNICAL FIELD

[0001] The present disclosure relates to a touch sensing system, and more specifically, to clock synchronization between a stylus and a touch display device in the touch sensing system.

BACKGROUND

[0002] A touch display device can allow a user to input information or commands by using a finger, a stylus (or a pen), and the like. When the stylus is close to a display panel (or a touchscreen) of the touch display device, the touch display device can detect the stylus and setup a communication (e.g., a bidirectional communication) with the stylus.

SUMMARY

[0003] Aspects of the disclosure provide a touch display device for clock synchronization in a touch sensing system including the touch display device and a stylus that cooperates with the touch display device. Touch driving circuitry of the touch display device receives a current first synchronization signal that is used by display driving circuity of the touch display device to drive a display panel of the touch display device. In response to a previous first synchronization signal being received by the touch driving circuitry before the current first synchronization signal is received, the touch driving circuitry determines whether there is a second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within a first predefined period of receiving the current first synchronization signal. The second synchronization signal is used for clock synchronization between the touch driving circuitry and the stylus that cooperates with the touch display device. The touch driving circuitry determines a time delay of a next second synchronization signal based on whether there is the second synchronization signal that has been sent or is going to be sent within the first predefined period.

[0004] In an embodiment, in response to the previous first synchronization signal not being received by the touch driving circuitry before the current first synchronization signal is received, the touch driving circuitry determines a first time delay as the time delay of the next second synchronization signal. The first time delay is an inverse value of a maximum frequency of the first synchronization signal. [0005] In an embodiment, in response to a determination that there is the second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the touch driving circuitry determines a second time delay as the time delay of the next second synchronization signal. The second time delay is twice the length of time of the first time delay.

[0006] In an embodiment, in response to a determination that there is no second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the touch driving circuitry determines the first time delay as the time delay of the next second synchronization signal.

[0007] In an embodiment, the touch driving circuitry sends the next second synchronization signal to the stylus based on the determined time delay of the next second synchronization signal.

[0008] In an embodiment, the touch driving circuitry determines whether a next first synchronization signal is received by the touch driving circuitry within a second predefined period after the next second synchronization signal is sent. The second predefined period is twice the length of time of the first time delay. In response to the next first synchronization signal not being received by the touch driving circuitry within the second predefined period after the next second synchronization signal is sent, the touch driving circuitry continuously sends the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the touch driving circuitry. The predefined frequency is an inverse value of the second predefined period.

[0009] In an embodiment, the first synchronization signal is a vertical synchronization signal.

[0010] In an embodiment, the first synchronization signal is used for an image display function of the touch display device.

[0011] In an embodiment, the second synchronization signal is used for a touch sensing function of the touch display device.

[0012] Aspects of the disclosure provide a method for clock synchronization in a touch sensing system including a touch display device and a stylus that cooperates with the touch display device. The method includes receiving, by touch driving circuitry of the touch display device, a current first synchronization signal that is used by display driving circuity of the touch display device to drive a display panel of the touch display device. In response to a previous first synchronization signal being received by the touch driving circuitry before the current first synchronization signal is received, the method further includes determining, by the touch driving circuitry, whether there is a second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within a first predefined period of receiving the current first synchronization signal. The second synchronization signal is used for clock synchronization between the touch driving circuitry and the stylus that cooperates with the touch display device. The method further includes determining, by the touch driving circuitry, a time delay of a next second synchronization signal based on whether there is the second synchronization signal that has been sent or is going to be sent within the first predefined period.

[0013] In an embodiment, in response to the previous first synchronization signal not being received by the touch driving circuitry before the current first synchronization signal is received, the method includes determining, by the touch driving circuitry, a first time delay as the time delay of the next second synchronization signal. The first time delay is an inverse value of a maximum frequency of the first synchronization signal.

[0014] In an embodiment, in response to a determination that there is the second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the method includes determining, by the touch driving circuitry, a second time delay as the time delay of the next second synchronization signal. The second time delay is twice the length of time the first time delay.

[0015] In an embodiment, in response to a determination that there is no second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the method includes determining, by the touch driving circuitry, the first time delay as the time delay of the next second synchronization signal.

[0016] In an embodiment, the method includes sending, from the touch driving circuitry to the stylus, the next second synchronization signal based on the determined time delay of the next second synchronization signal.

[0017] In an embodiment, the method includes determining, by the touch driving circuitry, whether a next first synchronization signal is received by the touch driving circuitry within a second predefined period after the next second synchronization signal is sent. The second predefined period is twice the length of time of the first time delay. In response to the next first synchronization signal not being received by the touch driving circuitry within the second predefined period after the next second synchronization signal is sent, the method includes continuously sending, by the touch driving circuitry, the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the touch driving circuitry, the predefined frequency being an inverse value of the second predefined period.

[0018] In an embodiment, the first synchronization signal is a vertical synchronization signal.

[0019] In an embodiment, the first synchronization signal is used for an image display function of the touch display device.

[0020] In an embodiment, the second synchronization signal is used for a touch sensing function of the touch display device.

[0021] Aspects of the disclosure provide a non-transitory computer-readable medium storing instructions which when executed by an apparatus cause the apparatus to perform any one or a combination of the above methods.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various embodiments of this disclosure that are proposed as examples will be described in detail with reference to the following figures, wherein like numerals reference like elements, and wherein:

[0023] FIG. 1 shows an exemplary touch sensing system according to embodiments of the disclosure;

[0024] FIG. 2 shows an exemplary timing diagram illustrating how a beacon is arranged into a display driving period according to embodiments of the disclosure;

[0025] FIG. 3 shows two exemplary timing diagrams and illustrating how a beacon cadence break occurs according to embodiments of the disclosure;

[0026] FIGS. 4-11 show various exemplary timing diagrams illustrating how a fixed beacon cadence is maintained according to embodiments of the disclosure;

[0027] FIG. 12 shows a flowchart outlining a process according to embodiments of the disclosure; and

[0028] FIG. 13 shows a computer system according to embodiments of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS [0029] The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing an understanding of various concepts. However, these concepts may be practiced without these specific details.

[0030] Several aspects of a touch sensing system will now be presented with reference to various apparatuses and methods. These apparatuses and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

[0031] FIG. 1 shows an exemplary touch sensing system 100 according to embodiments of the disclosure. The touch sensing system 100 can include a touch display device 110 and a stylus 120 that cooperates with the touch display device 110. The touch display device 110 can provide an image (or video) display function to display an image (or video) and a touch sensing function to receive input information or commands from a finger, the stylus 120, or the like. The touch display device 110 can be, for example, a television (TV), a monitor, or a mobile device such as a tablet or a smart phone.

[0032] According to aspects of the disclosure, the touch display device 110 can include a display panel (or touch panel) 130, a display driver integrated circuit (DDIC) (or display driving circuitry) 140, a touch integrated circuit (TIC) (or touch driving circuitry) 150, and a host system (or processing circuitry) 160.

[0033] The display panel 130 can be any type of display panels such as a light-emitting diode (LED) display panel, an organic LCD (OLED) display panel, an active-matrix OLED (AMOLED) display panel, a liquid crystal display (LCD) panel, a field emission display (FED) panel, a plasma display panel (PDP), an electrophoretic display (EPD) panel, or the like. The display panel 130 can include a capacitive touchscreen that senses a touch input through a plurality of capacitance touch sensors. The touch input is not limited to a direct contact of a conductive object (e.g., a user's finger, a user's palm, a touch pen, a stylus pen, an active pen, etc.) on the touchscreen and may further include a conductive object being in proximity of the touchscreen.

[0034] To perform the image display function, the DDIC 140 can receive data of an input image from the host system 160 and send a display driving signal DD to the display panel 130 during a display driving period.

[0035] To perform the touch sensing function, the TIC 150 can send a touch driving signal TD during a touch driving period to the touchscreen and receive a touch sensing signal TS to sense charge variations of the plurality of touch sensors of the touchscreen. By analyzing the charge variations of the plurality of touch sensors, the TIC 150 can determine presence or absence of a touch input and calculate coordinates of the touch input if present. The coordinates of the touch input can be sent back to the host system 160 for further processing.

[0036] The touch driving signal TD and the display driving signal DD need to be synchronized with each other in order to avoid a flicker issue of the display panel 130. The display driving signal DD can include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, and the like. Accordingly, the touch driving signal TD needs to be synchronized with the vertical synchronization signal Vsync for example.

[0037] According to aspects of the disclosure, the TIC 150 can bidirectionally communicate with the stylus 120. For example, a signal provided from the TIC 150 to the stylus 120 can be referred to as an uplink signal, and a signal provided from the stylus 120 to the TIC 150 can be referred to as a downlink signal. The bidirectional communication can be performed through a capacitive coupling for example.

[0038] The uplink signal can include a beacon for clock synchronization between the TIC 150 and the stylus 120. A signal strength of the beacon can be strong enough to cause a flicker issue of the touchscreen. Accordingly, in order to avoid the flicker issue, the beacon should be sent from the TIC 150 to the stylus 120 during a period that the display panel 130 does not update data.

[0039] FIG. 2 shows an exemplary timing diagram 200 illustrating how a beacon is arranged into a display driving period according to embodiments of the disclosure. In the timing diagram 200, T_FP and T_BP represent a front porch time and a back porch time of a vertical synchronization signal Vsync, and T_D represents a display time of the display panel 130. Within the front porch time and back porch time, the display panel 130 does not display data, and thus the beacon can be sent during such a period. Accordingly, a beacon period T_B of the beacon should be set to be less than the display porch time (T_Fp+T_BP) of the display panel 130. In addition, the display time T_D can include a data update time T_DU and a display self-scan time T_DS. The display panel 130 updates data to be displayed during the data update time T_DU and performs a self-scan during the display self-scan time T_DS. Since the display panel 130 does not update data to be displayed during the display self-scan time T_Ds, the beacon can be sent during the display self-scan time T_DS. It is noted that when the display self-scan time T_DS is zero, the Vsync operates at a maximum frequency.

[0040] For example, the beacon can be delayed 0ms from the Vsync when the Vsync is at a maximum frequency (e.g., 120Hz), or can be delayed at a certain period (e.g., 8.3ms) from the Vsync when the Vsync frequency is below the maximum frequency.

[0041] The beacon, as a synchronization signal for synchronizing operations of the TIC 150 and the stylus 120, is sent at a fixed frequency (e.g., 60Hz). That is, a beacon cadence of the beacon should be fixed. However, the Vsync frequency can be varied due to a varied refresh rate of the display panel 130. For example, the Vsync frequency can be reduced to save a power or can be increased to improve a display quality. When the Vsync frequency varies, the beacon cadence may not be fixed. That is, a beacon cadence break can occur, leading to a connection failure of the stylus 120 to the touch display device 110.

[0042] FIG. 3 shows two exemplary timing diagrams 300 and 350 illustrating how a beacon cadence break occurs according to embodiments of the disclosure. In both timing diagrams 300 and 350, the beacon cadence is preset as 60Hz, and a maximum frequency of the Vsync is 120Hz. When the Vsync operates at the maximum frequency, the beacon is set to be delayed 0ms from a beginning Vsync that the TIC 150 can detect, and then the beacon operates according to the preset beacon cadence. When the Vsync operates at a frequency below the maximum frequency, and each time when the TIC 150 detects a Vsync, the beacon is set to be delayed 8.3ms from the detected Vsync, and then the beacon operates according to the preset beacon cadence.

[0043] In the first timing diagram 300, the Vsync frequency first keeps at 120Hz and then changes from 120Hz to 40Hz and keeps at 40Hz afterwards. During the period that the Vsync frequency keeps at 120Hz, a first beacon 301 is delayed 0ms from a beginning Vsync that the TIC 150 can detect, and then a second beacon 302 and a third beacon 303 are sent at a frequency of 60Hz according to the preset beacon cadence. After the third beacon 303 is sent, the stylus 120 may be moved far away from the display panel 130 so that the TIC 150 loses a connection with the stylus 120 and stops sending the beacon. Since no input data is detected, the host 160 may determine to reduce the refresh rate of the display panel 130 to save the power. Accordingly, the Vsync changes from 120Hz to 40Hz. After a certain period, the TIC 150 detects that the stylus 120 again is close enough to the display panel 130 and then starts sending the beacon again. Since the Vsync frequency now keeps at 40Hz that is below the maximum frequency (120Hz), each time when the TIC 150 detects the Vsync, the TIC 150 delays 8.3ms to send the beacon (e.g., the beacon 304 or 305). In addition, the TIC 150 still sends the beacon (e.g., the beacon 306 or 307) at a frequency of 60Hz according to the preset beacon cadence. Accordingly, it can be seen that the frequency change of the Vsync causes a beacon cadence break, for example, between the beacons 303 and 304, or between the beacons 305 and 306. That is, the time delay between the beacons 303 and 304 (or between the beacons 305 and 306) is not l/60s.

[0044] In the second timing diagram 350, the Vsync frequency first keeps at 60Hz and then changes from 60Hz to 40Hz and keeps at 40Hz afterwards. During the period that the Vsync frequency keeps at 60Hz, each time when a Vsync is detected, a beacon (e.g., beacon 351 or 352) is delayed 8.3ms from the detected Vsync, and the beacon 353 also keeps at 60Hz according to the preset beacon cadence. After the Vsync frequency changes to 40Hz, each time when a Vsync is detected, a beacon (e.g., beacon 354 or 356) is delayed 8.3ms from the detected Vsync. In addition, the TIC 150 still sends the beacon (e.g., beacon 355 or 357) at a frequency of 60Hz according to the preset beacon cadence. Accordingly, it can be seen that the frequency change of the Vsync causes the beacon cadence break, for example, between the beacons 353 and 354, or between the beacons 355 and 356. That is, the time delay between the beacons 353 and 354 (or between the beacons 355 and 356) is not l/60s.

[0045] The beacon cadence break can lead to a malfunction of the stylus 120, such as a connection failure between the stylus 120 and the display device 110. Therefore, it is desired to design a synchronization mechanism to maintain a fixed beacon cadence. This disclosure provides methods and embodiments for maintaining a fixed beacon cadence. In a method, a delay time between a next beacon and a current Vsync can be dynamically changed based on counting a gap (i.e., time difference) between the current Vsync and a last scheduled beacon that has been sent or is going to be sent.

[0046] Specifically, for a beginning (or first) Vsync that the TIC 150 detects (or receives) after the TIC 150 awakes, the TIC 150 can schedule to send a beacon with a first time delay that is an inverse value of a maximum frequency of the Vsync. For example, if the maximum frequency of the Vsync is 120Hz, then the first time delay is about 8.3ms, and the TIC 150 can schedule to delay 8.3ms to send a beacon when a beginning Vsync is detected by the TIC 150. For other Vsync such as any Vsync after the beginning Vsync, each time when the TIC 150 detects (or receives) a Vsync, the TIC 150 determines if a last scheduled beacon has been sent or is going to be sent within a first predefined period (e.g., 0.5ms) of detecting (or receiving) the Vsync. A sending (or transmitting) time of the last scheduled beacon is scheduled by the TIC 150 before the Vsync is detected, so that when the TIC 150 detects the Vsync, the TIC 150 can calculate a time difference between the sending time of the last scheduled beacon and the receiving time of the Vsync. It is noted that the last scheduled beacon can be sent before or after the Vsync is received. If the TIC 150 determines that the time difference is less than the first predefined period, the TIC 150 determines that the last scheduled beacon has been sent or is going to be sent within the first predefined period, and the TIC 150 can schedule to send a next beacon with a second time delay that is twice the length of time of the first time delay. Otherwise, the TIC 150 can schedule to send the next beacon with the first time delay.

[0047] For example, if the first time delay is 8.3ms, then the second time delay is 16.6ms. Each time when the TIC 150 detects a Vsync, the TIC 150 determines whether a time difference between a sending time of a last scheduled beacon and a receiving time of the Vsync is less than the first predefined period. If the time difference is less than first predefined period, the TIC 150 can schedule to delay 16.6ms to send a next beacon. Otherwise, the TIC 150 can schedule to delay 8.3ms to send the next beacon.

[0048] In addition, after a second predefined period after a beacon is sent, the TIC 150 determines whether a Vsync is detected (or received) in the past second predefined period. If there is not any Vsync being detected in the past second predefined period, the TIC 150 can immediately send a next beacon in order to keep a fixed beacon cadence (e.g., 60Hz if the second predefined period is 16.6ms) and continuously send beacons at the fixed beacon cadence until a Vsync is detected. [0049] FIGS. 4-11 show various exemplary timing diagrams illustrating how a fixed beacon cadence is maintained according to embodiments of the disclosure. It is noted that in the timing diagrams of FIGS. 4-11, the maximum frequency of the Vsync is set as 120Hz, so that the first time delay is set as 8.3ms and the second timing delay is set as 16.6ms. The beacon cadence is fixed at 60Hz. In addition, the first predefined period is set as 0.5ms and the second predefined period is set as 16.6ms.

[0050] FIG. 4 shows three exemplary timing diagrams 400, 430, and 460 illustrating how a fixed beacon cadence is maintained for different Vsync frequencies according to embodiments of the disclosure.

[0051] In the timing diagram 400, the Vsync frequency keeps at 120Hz. When the TIC 150 awakes and detects a first Vsync 411, the TIC 150 delays 8.3ms to send a first beacon 421. Then, each time when the TIC 150 detects a Vsync, the TIC 150 can count (or determine) if a beacon has been sent or is going to be sent within the first predefined period. For example, when the TIC 150 detects a second Vsync 412, the TIC 150 determines that the first beacon 421 is within the first predefined period and then delays 16.6ms to send a second beacon 422. When the TIC 150 detects a third Vsync 413, the TIC 150 determines that there is no beacon within the first predefined period and then delays 8.3ms to send a next beacon, which is still the second beacon 422. When the TIC 150 detects a fourth Vsync 414, the TIC 150 determines that the second beacon 422 is within the first predefined period and then delays 16.6ms to send a third beacon 423. Other beacons such as a fourth beacon 424 can be sent in a similar pattern.

[0052] In the timing diagram 430, the Vsync frequency keeps at 60Hz. When the TIC 150 awakes and detects a first Vsync 441, the TIC 150 delays 8.3ms to send a first beacon 451. Then, each time when the TIC 150 detects a Vsync, the TIC 150 can count if a beacon has been sent or is going to be sent within the first predefined period. For example, when the TIC 150 detects a second Vsync 442, the TIC 150 determines that there is no beacon within the first predefined period and then delay 8.3ms to send a second beacon 452. Other beacons such as a third beacon 453 and a fourth beacon 454 can be sent in a similar pattern.

[0053] In the timing diagram 460, the Vsync frequency keeps at 17.2Hz. When the TIC 150 awakes and detects a first Vsync 471, the TIC 150 delays 8.3ms to send a first beacon 481. Then, after the second predefined period (16.6ms) after the first beacon 481 is sent, the TIC 150 determines that there is not any Vsync being received in the past second predefined period, and immediately sends a second beacon 482. The TIC 150 keeps sending beacons 483-484 at a frequency of 60Hz until a second Vsync 472 is detected. When the TIC 150 detects the second Vsync 472, the TIC 150 delays 16.6ms to send a next beacon 485.

[0054] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 400, 430, and 460, no matter what the Vsync frequency is.

[0055] FIG. 5 shows two exemplary timing diagrams 500 and 550 illustrating how a fixed beacon cadence is maintained when the Vsync frequency reduces from 120Hz to 60Hz according to embodiments of the disclosure.

[0056] In the timing diagram 500, the Vsync first keeps at 120Hz, and a first beacon 521 overlaps with a first Vsync 511. That is, the first beacon 521 is sent within the first predefined period of the first Vsync 511. Accordingly, a second beacon 522 is delayed 16.6ms from the first Vsync 511. When the TIC 150 detects a second Vsync 512, the TIC 150 determines to delay 8.3ms to send a next beacon, which is still the second beacon 522. The second beacon 522 overlaps with a third Vsync 513, so that a third beacon 523 is delayed 16.6ms from the third Vsync 513. The third beacon 523 is also delayed 8.3ms from a fourth Vsync 514 because there is no beacon within the first predefined period of the fourth Vsync 514. After the fourth Vsync 514 is detected, the Vsync frequency reduces from 120Hz to 60Hz, and thus a time delay between the fourth Vsync 514 and a fifth Vsync 515 is 16.6ms. When the TIC 150 detects the fifth Vsync 515, the TIC determines that there is no beacon within the first predefined period of the fifth Vsync 515, and delays 8.3ms to send a fourth beacon 524. Similarly, a fifth beacon 525 is delayed 8.3ms from a sixth Vsync 516.

[0057] In the timing diagram 550, since a first beacon 571 overlaps with a first Vsync 561, a second beacon 572, which is delayed 16.6ms from the first Vsync 561, overlaps with a third Vsync 563, at which the Vsync frequency keeps at 120Hz. After the third Vsync 563 is detected, the Vsync frequency reduces from 120Hz to 60Hz, so that a third beacon 573, which is delayed 16.6ms from the third Vsync 563, overlaps with a fourth Vsync 564, from which the Vsync frequency keeps at 60Hz. Similarly, a fourth beacon 574 overlaps with a fifth Vsync 565, and a fifth beacon 575 overlaps with a sixth Vsync 566.

[0058] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 500 and 550, no matter how the Vsync frequency reduces from 120Hz to 60Hz. [0059] FIG. 6 shows two exemplary timing diagrams 600 and 650 illustrating how a fixed beacon cadence is maintained when the Vsync frequency reduces from 120Hz to 40Hz according to embodiments of the disclosure.

[0060] In the timing diagram 600, the Vsync frequency first keeps at 120Hz, and a first beacon 621 overlaps with a first Vsync 611, so that a second beacon 622 overlaps with a third Vsync 613. After a fourth Vsync 614 is detected, the Vsync frequency reduces from 120Hz to 40Hz. A third beacon 623 is delayed 16.6ms from the third Vsync 613 and 8.3ms from the fourth Vsync 614. After the second predefined period (16.6.ms) after the third beacon 623 is sent, the TIC 150 determines that there is no Vsync in the past second predefined period, and thus immediately sends a fourth beacon 624. The fourth beacon 624 overlaps with a fifth Vsync 615 from which the Vsync frequency keeps at 40Hz. Accordingly, a fifth beacon 625 is delayed 16.6ms from the fifth Vsync 615, and a sixth beacon 626 is delayed 8.3ms from a sixth Vsync 616.

[0061] In the timing diagram 650, the Vsync frequency first keeps at 120Hz, and a first beacon 671 overlaps with a first Vsync 661, so that a second beacon 672 overlaps with a third Vsync 663. After the third Vsync 663 is detected, the Vsync frequency reduces from 120Hz to 40Hz. A third beacon 673 is delayed 16.6ms from the third Vsync 663 because of the overlapping between the third Vsync 663 and the second beacon 672. A fourth beacon 674 is delayed 8.3ms from a fourth Vsync 664 from which the Vsync frequency keeps at 40Hz. After the second predefined period (16.6.ms) after the fourth beacon 674 is sent, the TIC 150 determines that there is no Vsync in the past second predefined period, and thus immediately sends a fifth beacon 675. The fifth beacon 675 overlaps with a fifth Vsync 665, so that a sixth beacon 676 is delayed 16.6ms from the fifth Vsync 665.

[0062] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 600 and 650, no matter how the Vsync frequency reduces from 120Hz to 40Hz.

[0063] FIG. 7 shows two exemplary timing diagrams 700 and 750 illustrating how a fixed beacon cadence is maintained when the Vsync frequency reduces from 120Hz to 17.2Hz according to embodiments of the disclosure.

[0064] In the timing diagram 700, the Vsync frequency first keeps at 120Hz, and a first beacon 721 overlaps with a first Vsync 711, so that a second beacon 722 overlaps with a third Vsync 713. After a fourth Vsync 714 is detected, the Vsync frequency reduces from 120Hz to 17.2Hz. A third beacon 723 is delayed 16.6ms from the third Vsync 713 and 8.3ms from the fourth Vsync 714. After the second predefined period (16.6.ms) after the third beacon 723 is sent, the TIC 150 determines that there is no Vsync in the past second predefined period, and thus immediately sends a fourth beacon 724. The TIC 150 keeps sending a fifth beacon 725 and a sixth beacon 726 each with a delay of 16.6ms until a fifth Vsync 715 is detected. Since the sixth beacon 726 overlaps with the fifth Vsync 715 from which the Vsync frequency keeps at 17.2Hz, a seventh beacon 727 is delayed 16.6ms from the fifth Vsync 715.

[0065] In the timing diagram 750, the Vsync frequency first keeps at 120Hz, and a first beacon 771 overlaps with a first Vsync 761, so that a second beacon 772 overlaps with a third Vsync 763. After the third Vsync 763 is detected, the Vsync frequency reduces from 120Hz to 17.2Hz. A third beacon 773 is delayed 16.6ms from the third Vsync 763 because of the overlapping between the third Vsync 763 and the second beacon 772. After the second predefined period (16.6. ms) after the third beacon 773 is sent, the TIC 150 determines that there is no Vsync in the past second predefined period, and thus immediately sends a fourth beacon 774. The TIC 150 keeps sending a fifth beacon 775 which is delayed 16.6ms from the fourth beacon 774, until the TIC 150 detects a fourth Vsync 764. Then, a sixth beacon 776 is delayed 8.3ms from the fourth Vsync 764 from which the Vsync frequency keeps at 17.2Hz.

[0066] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 700 and 750, no matter how the Vsync frequency reduces from 120Hz to 17.2Hz.

[0067] FIG. 8 shows two exemplary timing diagrams 800 and 850 illustrating how a fixed beacon cadence is maintained when the Vsync frequency increases from 60Hz to 120Hz according to embodiments of the disclosure.

[0068] In the timing diagram 800, the Vsync frequency first keeps at 60Hz. When the TIC 150 awakes and detects a first Vsync 811, the TIC 150 delays 8.3ms to send a first beacon 821. Similarly, the TIC 150 detects a second Vsync 812 and delays 8.3ms to send a second beacon 822. After the second Vsync 812 is detected, the Vsync frequency increases from 60Hz to 120Hz, so that the second beacon 822 overlaps with a third Vsync 813. A third beacon 823 is delayed 16.6ms from the third Vsync 813 and 8.3ms from a fourth Vsync 814, and overlaps with a fifth Vsync 815. A fourth beacon 824 is delayed 16.6ms from the fifth Vsync 815 and 8.3ms from a sixth Vsync 816, and overlaps with a seventh Vsync 817.

[0069] In the timing diagram 850, the Vsync frequency first keeps at 60Hz. When the TIC 150 awakes and detects a first Vsync 861, the TIC 150 delays 8.3ms to send a first beacon 871. Similarly, the TIC 150 detects a second Vsync 862 and delays 8.3ms to send a second beacon 872. After the second beacon 872 is sent, the Vsync frequency increases from 60Hz to 120Hz. The TIC 150 further detects a third Vsync 863 and delays 8.3ms to send a third beacon 873, which overlaps with a fourth Vsync 864. A fourth beacon 874 is delayed 16.6ms from the fourth Vsync 864 and 8.3ms from a fifth Vsync 865, and overlaps with a sixth Vsync 866. A fifth beacon 875 is delayed 16.6ms from the sixth Vsync 866 and a seventh Vsync 867, and overlaps with an eighth Vsync 868.

[0070] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 800 and 850, no matter how the Vsync frequency increases from 60Hz to 120Hz.

[0071] FIG. 9 shows two exemplary timing diagrams 900 and 950 illustrating how a fixed beacon cadence is maintained when the Vsync frequency increases from 60Hz to 120Hz according to embodiments of the disclosure.

[0072] In the timing diagram 900, the Vsync frequency keeps at 60Hz for first two Vsync 911-912 which overlap with beacons 921-922, respectively. Then, the Vsync frequency increases from 60Hz to 120Hz after the second Vsync 913 is detected, so that when the TIC 150 detects a fourth Vsync 914 that overlaps with a third beacon 923, the TIC 150 delays 8.3ms to send a fourth beacon 924. A fifth beacon 925 is delayed 16.6ms from a fifth Vsync 915 and 8.3ms from a sixth Vsync 916, and overlaps with a seventh Vsync 917.

[0073] In the timing diagram 950, the Vsync frequency keeps at 60Hz for first two Vsync 961-962 which overlap with beacons 971-972, respectively. Then, the Vsync frequency increases from 60Hz to 120Hz after the second Vsync 962 is detected, so that when the TIC 150 detects a third Vsync 963, the TIC 150 delays 8.3ms to send a third beacon 973, which overlaps with a fourth Vsync 964. A fourth beacon 974 is delayed 16.6ms from the fourth Vsync 964 and 8.3ms from a fifth Vsync 965, and overlaps with a sixth Vsync 966. A fifth beacon 975 is delayed 16.6ms from the sixth Vsync 966 and 8.3ms from a seventh Vsync 967, and overlaps with an eighth Vsync 968. [0074] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 900 and 950, no matter how the Vsync frequency increases from 60Hz to 120Hz.

[0075] FIG. 10 shows two exemplary timing diagrams 1000 and 1050 illustrating how a fixed beacon cadence is maintained when the Vsync frequency increases from 40Hz to 120Hz according to embodiments of the disclosure.

[0076] In the timing diagram 1000, the Vsync frequency keeps at 40Hz for first two Vsync 1011-1012. A first beacon 1021 overlaps with the first Vsync 1011 so that a second beacon 1022 is delayed 16.6ms from the first Vsync 1011. A third beacon 1023 is delayed 8.3ms from the second Vsync 1012. After the third beacon 1023 is sent, the Vsync frequency increases from 40Hz to 120Hz. Accordingly, a fourth beacon 1024 is delayed 8.3ms from a third Vsync 1013, from which the Vsync frequency keeps at 120Hz. A fifth beacon 1025 is delayed 16.6ms from a fourth Vsync 1014 because the fourth Vsync 1014 overlaps with the fourth beacon 1024, and is delayed 8.3ms from a fifth Vsync 1015 because there is no beacon within the first predefined period of the fifth Vsync 1015. The fifth beacon 1025 overlaps with a sixth Vsync 1016.

[0077] In the timing diagram 1050, the Vsync frequency keeps at 60Hz for first two Vsync 1061-1062. A first beacon 1071 overlaps with the first Vsync 1061 so that a second beacon 1072 is delayed 16.6ms from the first Vsync 1061. A third beacon 1073 is delayed 8.3ms from the second Vsync 1062. After the second Vsync 1062 is detected, the Vsync frequency increases from 40Hz to 120Hz. Accordingly, the third beacon 1073 overlaps with a third Vsync 1063, causing a fourth beacon 1074 to be delayed 16.6ms from the third Vsync 1063. The fourth beacon 1074 is also delayed 8.3ms from a fourth Vsync 1064, and overlaps with a fifth Vsync 1065. A fifth beacon 0175 is delayed 16.6ms from the fifth Vsync 1065 and 8.3ms from a sixth Vsync 1066, and overlaps with a seventh Vsync 1067.

[0078] Accordingly, it can be seen that a fixed beacon cadence (60Hz) can be maintained in each of the timing diagrams 1000 and 1050, no matter how the Vsync frequency increases from 40Hz to 120Hz.

[0079] FIG. 11 shows one exemplary timing diagram 1100 illustrating how a fixed beacon cadence is maintained when the Vsync frequency dynamically changes according to embodiments of the disclosure. [0080] In the timing diagram 1100, the Vsync frequency first keeps at 120Hz for first three Vsync 1101-1103. A first beacon 1121 overlaps with the first Vsync 1101, so a second beacon 1122 overlaps with the third Vsync 1103. After the third Vsync 1103 is detected, the Vsync frequency changes from 120Hz to 60Hz, so a third beacon 1123 overlaps with a fourth Vsync 1104, and a fourth beacon 1124 overlaps with a fifth Vsync 1105. The Vsync frequency keeps at 60Hz for the fourth Vsync 1104 and the fifth Vsync 1105. Then, the Vsync frequency changes from 60Hz to 40Hz. A fifth beacon 1125 is delayed 16.6ms from the fifth Vsync 1105 because the fourth beacon 1124 overlaps with the fifth Vsync 1105. A sixth beacon 1126 is delayed 8.3ms from a sixth Vsync 1106 where the Vsync frequency is 40Hz. Then, the Vsync frequency changes from 40Hz to 30Hz, causing that the TIC 150 does not detect a Vsync within 16.6ms after the sixth beacon 1126 is sent. Thus, the TIC 150 immediately sends a seventh beacon 1127 after 16.6ms after the sixth beacon 1126 is sent. When the TIC 150 detects a seventh Vsync 1107, an eighth beacon 1128 is delayed 8.3ms from the seventh Vsync 1107. After the eighth beacon 1128 is sent, the Vsync frequency changes from 30Hz to 120Hz. Accordingly, when TIC 150 detects an eighth Vsync 1108, a nineth beacon 1129 is delayed 8.3ms from the eighth Vsync 1108 and overlaps with a nineth Vsync 1109. After the nineth Vsync 1109 is detected, the Vsync frequency changes from 120Hz to 60Hz. A tenth beacon 1130 is delayed 16.6ms from the nineth Vsync 1109 because the nineth Vsync 1109 overlaps with the nineth beacon 1129. The tenth beacon overlaps with a tenth Vsync 1110 at which the Vsync frequency is 60Hz.

[0081] FIG. 12 shows a flowchart outlining a process 1200 according to embodiments of the disclosure. The process 1200 can be executed by the TIC 150 of the touch display device 110. The process 1200 may start at step S 1210.

[0082] At step S 1210, the process 1200 receives a current first synchronization signal (e.g., a first Vsync) that is used by the DDIC 140 of the touch display panel 110 to drive the display panel 130 of the touch display device 110. Then, the process 1200 proceeds to step S1220.

[0083] At step S1220, the process 1200 determines whether a previous first synchronization signal is received by the TIC 150 before the current first synchronization signal is received. In response to the previous first synchronization signal being received by the TIC 150 before the current first synchronization signal is received, the process 1200 proceeds to step S1230. Otherwise, the process 1200 proceeds to step S1240.

[0084] At step SI 230, the process 1200 determines whether there is a second synchronization signal (e.g., a beacon) that has been sent or is going to be sent by the TIC 150 within a first predefined period of receiving the current first synchronization signal. The second synchronization signal is used for clock synchronization between the TIC 150 and the stylus 120 that cooperates with the touch display device 110. In response to a determination that there is no second synchronization signal that has been sent to is going to be sent by the TIC 150 within the first predefined period, the process 1200 proceeds to step S1240. Otherwise, the process 1200 proceeds to step S1250.

[0085] At step S1240, the process 1200 determines a first time delay as a time delay of a next second synchronization signal. The first time delay is an inverse value of a maximum frequency of the first synchronization signal.

[0086] At step S1250, the process 1200 determines a second time delay as the time delay of the next second synchronization signal. The second time delay is twice the length of time of the first time delay.

[0087] After the time delay (either the first time delay or the second time delay) of the next second synchronization signal is determined, the process 1200 proceeds to step S1260.

[0088] At step S1260, the process 1200 sends the next second synchronization signal to the stylus 120 based on the determined time delay of the next second synchronization signal. Then, the process 1200 may terminate.

[0089] In an embodiment, the process 1200 determines whether a next first synchronization signal is received by the TIC 150 within a second predefined period after the next second synchronization signal is sent. The second predefined period is twice the length of time of the first time delay. In response to the next first synchronization signal not being received by the TIC 150 within the second predefined period after the next second synchronization signal is sent, the process 1200 keeps sending the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the TIC 150. In an example, the predefined frequency is an inverse value of the second predefined period.

[0090] In an embodiment, the first synchronization signal is a vertical synchronization signal. [0091] In an embodiment, the first synchronization signal is used for an image display function of the touch display device 110.

[0092] In an embodiment, the second synchronization signal is used for a touch sensing function of the touch display device 110.

[0093] Aspects of the disclosure provides a method of clock synchronization in a touch sensing system including a touch display device and a stylus that cooperates with the touch display device. The method includes receiving, by touch driving circuitry of the touch display device, a current first synchronization signal that is used by display driving circuity of the touch display device to drive a display panel of the touch display device. In response to a previous first synchronization signal being received by the touch driving circuitry before the current first synchronization signal is received, the method includes determining, by the touch driving circuitry, whether there is a second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within a first predefined period of receiving the current first synchronization signal. The second synchronization signal is used for clock synchronization between the touch driving circuitry and the stylus that cooperates with the touch display device. The method further includes determining, by the touch driving circuitry, a time delay of a next second synchronization signal based on whether there is the second synchronization signal that has been sent or is going to be sent within the first predefined period.

[0094] In an embodiment, in response to the previous first synchronization signal not being received by the touch driving circuitry before the current first synchronization signal is received, the method includes determining, by the touch driving circuitry, a first time delay as the time delay of the next second synchronization signal. The first time delay is an inverse value of a maximum frequency of the first synchronization signal.

[0095] In an embodiment, in response to a determination that there is the second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the method includes determining, by the touch driving circuitry, a second time delay as the time delay of the next second synchronization signal. The second time delay is twice the length of time the first time delay.

[0096] In an embodiment, in response to a determination that there is no second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the method includes determining, by the touch driving circuitry, the first time delay as the time delay of the next second synchronization signal.

[0097] In an embodiment, the method includes sending, from the touch driving circuitry to the stylus, the next second synchronization signal based on the determined time delay of the next second synchronization signal.

[0098] In an embodiment, the method includes determining, by the touch driving circuitry, whether a next first synchronization signal is received by the touch driving circuitry within a second predefined period after the next second synchronization signal is sent. The second predefined period is twice the length of time of the first time delay. In response to the next first synchronization signal not being received by the touch driving circuitry within the second predefined period after the next second synchronization signal is sent, the method includes continuously sending, by the touch driving circuitry, the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the touch driving circuitry, the predefined frequency being an inverse value of the second predefined period.

[0099] In an embodiment, the first synchronization signal is a vertical synchronization signal.

[0100] In an embodiment, the first synchronization signal is used for an image display function of the touch display device.

[0101] In an embodiment, the second synchronization signal is used for a touch sensing function of the touch display device.

[0102] Aspects of the disclosure provide a touch display device for clock synchronization in a touch sensing system including the touch display device and a stylus that cooperates with the touch display device. Touch driving circuitry of the touch display device receives a current first synchronization signal that is used by display driving circuity of the touch display device to drive a display panel of the touch display device. In response to a previous first synchronization signal being received by the touch driving circuitry before the current first synchronization signal is received, the touch driving circuitry determines whether there is a second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within a first predefined period of receiving the current first synchronization signal. The second synchronization signal is used for clock synchronization between the touch driving circuitry and the stylus that cooperates with the touch display device. The touch driving circuitry determines a time delay of a next second synchronization signal based on whether there is the second synchronization signal that has been sent or is going to be sent within the first predefined period.

[0103] In an embodiment, in response to the previous first synchronization signal not being received by the touch driving circuitry before the current first synchronization signal is received, the touch driving circuitry determines a first time delay as the time delay of the next second synchronization signal. The first time delay is an inverse value of a maximum frequency of the first synchronization signal.

[0104] In an embodiment, in response to a determination that there is the second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the touch driving circuitry determines a second time delay as the time delay of the next second synchronization signal. The second time delay is twice the length of time of the first time delay.

[0105] In an embodiment, in response to a determination that there is no second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, the touch driving circuitry determines the first time delay as the time delay of the next second synchronization signal.

[0106] In an embodiment, the touch driving circuitry sends the next second synchronization signal to the stylus based on the determined time delay of the next second synchronization signal.

[0107] In an embodiment, the touch driving circuitry determines whether a next first synchronization signal is received by the touch driving circuitry within a second predefined period after the next second synchronization signal is sent. The second predefined period is twice the length of time of the first time delay. In response to the next first synchronization signal not being received by the touch driving circuitry within the second predefined period after the next second synchronization signal is sent, the touch driving circuitry continuously sends the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the touch driving circuitry. The predefined frequency is an inverse value of the second predefined period.

[0108] In an embodiment, the first synchronization signal is a vertical synchronization signal. [0109] In an embodiment, the first synchronization signal is used for an image display function of the touch display device.

[0110] In an embodiment, the second synchronization signal is used for a touch sensing function of the touch display device.

[oni] The processes and functions described herein can be implemented as a computer program which, when executed by one or more processors (e.g., CPU 1341 of computer system 1300), can cause the one or more processors to perform the respective processes and functions. The computer program may be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with, or as part of, other hardware. The computer program may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. For example, the computer program can be obtained and loaded into an apparatus, including obtaining the computer program through physical medium or distributed system, including, for example, from a server connected to the Internet.

[0112] The computer program may be accessible from a computer-readable medium providing program instructions for use by or in connection with a computer or any instruction execution system. The computer readable medium may include any apparatus that stores, communicates, propagates, or transports the computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable medium can be magnetic, optical, electronic, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. The computer-readable medium may include a computer- readable non-transitory storage medium such as a semiconductor or solid-state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a magnetic disk and an optical disk, and the like. The computer-readable non- transitory storage medium can include all types of computer readable medium, including magnetic storage medium, optical storage medium, flash medium, and solid state storage medium.

[0113] FIG. 13 shows a computer system 1300, which can implement the processes or functions of the embodiments of the disclosure. The computer system 1300 may include certain human interface input devices. Such a human interface input device may be responsive to input by one or more human users through, for example, tactile input (such as: keystrokes, swipes, data glove movements), audio input (such as: voice, clapping), visual input (such as: gestures), olfactory input (not depicted). The human interface devices can also be used to capture certain media not necessarily directly related to conscious input by a human, such as audio (such as: speech, music, ambient sound), images (such as: scanned images, photographic images obtain from a still image camera), video (such as two-dimensional video, three-dimensional video including stereoscopic video).

[0114] Input human interface devices may include one or more of (only one of each depicted): keyboard 1301, mouse 1302, trackpad 1303, touchscreen 1310, data-glove (not shown), joystick 1305, microphone 1306, scanner 1307, and camera 1308.

[0115] The computer system 1300 may also include certain human interface output devices. Such human interface output devices may be stimulating the senses of one or more human users through, for example, tactile output, sound, light, and smell/taste. Such human interface output devices may include tactile output devices (for example tactile feedback by the touchscreen 1310, data-glove (not shown), or joystick 1305, but there can also be tactile feedback devices that do not serve as input devices), audio output devices (such as: speakers 1309, headphones (not depicted)), visual output devices (such as touchscreen 1310 to include CRT screens, LCD screens, plasma screens, OLED screens, each with or without touch-screen input capability, each with or without tactile feedback capability — some of which may be capable to output two dimensional visual output or more than three dimensional output through means such as stereographic output; virtual-reality glasses (not depicted), holographic displays and smoke tanks (not depicted)), and printers (not depicted). These visual output devices (such as touchscreen 1310) can be connected to a system bus 1348 through a graphics adapter 1350.

[0116] The computer system 1300 can also include human accessible storage devices and their associated media such as optical media including CD/DVD ROM/RW 1320 with CD/DVD or the like media 1321, thumb-drive 1322, removable hard drive or solid state drive 1323, legacy magnetic media such as tape and floppy disc (not depicted), specialized ROM/ASIC/PLD based devices such as security dongles (not depicted), and the like.

[0117] Those skilled in the art should also understand that term “computer readable media” as used in connection with the presently disclosed subject matter does not encompass transmission media, carrier waves, or other transitory signals. [0118] The computer system 1300 can also include a network interface 1354 to one or more communication networks 1355. The one or more communication networks 1355 can for example be wireless, wireline, optical. The one or more communication networks 1355 can further be local, wide-area, metropolitan, vehicular and industrial, real-time, delay -tolerant, and so on. Examples of the one or more communication networks 1355 include local area networks such as Ethernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TV wireline or wireless wide area digital networks to include cable TV, satellite TV, and terrestrial broadcast TV, vehicular and industrial to include CANBus, and so forth. Certain networks commonly require external network interface adapters that attached to certain general purpose data ports or peripheral buses 1349 (such as, for example USB ports of the computer system 1300); others are commonly integrated into the core of the computer system 1300 by attachment to a system bus as described below (for example Ethernet interface into a PC computer system or cellular network interface into a smartphone computer system). Using any of these networks, the computer system 1300 can communicate with other entities. Such communication can be uni-directional, receive only (for example, broadcast TV), uni-directional send-only (for example CANbus to certain CANbus devices), or bi-directional, for example to other computer systems using local or wide area digital networks. Certain protocols and protocol stacks can be used on each of those networks and network interfaces as described above.

[0119] Aforementioned human interface devices, human-accessible storage devices, and network interfaces can be attached to a core 1340 of the computer system 1300.

[0120] The core 1340 can include one or more Central Processing Units (CPU) 1341, Graphics Processing Units (GPU) 1342, specialized programmable processing units in the form of Field Programmable Gate Areas (FPGA) 1343, hardware accelerators for certain tasks 1344, graphics adapters 1350, and so forth. These devices, along with Read-only memory (ROM) 1345, Random-access memory 1346, internal mass storage 1347 such as internal non-user accessible hard drives, SSDs, and the like, may be connected through the system bus 1348. In some computer systems, the system bus 1348 can be accessible in the form of one or more physical plugs to enable extensions by additional CPL^Ts, GPU, and the like. The peripheral devices can be attached either directly to the core’s system bus 1348, or through a peripheral bus 1349. In an example, the screen 1310 can be connected to the graphics adapter 1350. Architectures for a peripheral bus include PCI, USB, and the like. [0121] CPUs 1341, GPUs 1342, FPGAs 1343, and accelerators 1344 can execute certain instructions that, in combination, can make up the aforementioned computer code. That computer code can be stored in ROM 1345 or RAM 1346. Transitional data can also be stored in RAM 1346, whereas permanent data can be stored for example, in the internal mass storage 1347. Fast storage and retrieve to any of the memory devices can be enabled through the use of cache memory, that can be closely associated with one or more CPU 1341, GPU 1342, mass storage 1347, ROM 1345, RAM 1346, and the like.

[0122] The computer readable media can have computer code thereon for performing various computer-implemented operations. The media and computer code can be those specially designed and constructed for the purposes of the present disclosure, or they can be of the kind well known and available to those having skill in the computer software arts.

[0123] As an example and not by way of limitation, the computer system having architecture 1300, and specifically the core 1340 can provide functionality as a result of processor(s) (including CPUs, GPUs, FPGA, accelerators, and the like) executing software embodied in one or more tangible, computer-readable media. Such computer-readable media can be media associated with user-accessible mass storage as introduced above, as well as certain storage of the core 1340 that are of non-transitory nature, such as core-internal mass storage 1347 or ROM 1345. The software implementing various embodiments of the present disclosure can be stored in such devices and executed by core 1340. A computer-readable medium can include one or more memory devices or chips, according to particular needs. The software can cause the core 1340 and specifically the processors therein (including CPU, GPU, FPGA, and the like) to execute particular processes or particular parts of particular processes described herein, including defining data structures stored in RAM 1346 and modifying such data structures according to the processes defined by the software. In addition or as an alternative, the computer system can provide functionality as a result of logic hardwired or otherwise embodied in a circuit (for example: accelerator 1344), which can operate in place of or together with software to execute particular processes or particular parts of particular processes described herein. Reference to software can encompass logic, and vice versa, where appropriate. Reference to a computer-readable media can encompass a circuit (such as an integrated circuit (IC)) storing software for execution, a circuit embodying logic for execution, or both, where appropriate. The present disclosure encompasses any suitable combination of hardware and software. [0124] It is understood that the specific order or hierarchy of blocks in the processes / flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes I flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order and are not meant to be limited to the specific order or hierarchy presented.

[0125] While this disclosure has described several exemplary embodiments, there are alterations, permutations, and various substitute equivalents, which fall within the scope of the disclosure. It will thus be appreciated that those skilled in the art will be able to devise numerous systems and methods which, although not explicitly shown or described herein, embody the principles of the disclosure and are thus within the spirit and scope thereof.

[0126] The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof’ include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “one or more of A, B, or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or any combination thereof’ may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module,” “mechanism,” “element,” “device,” and the like may not be a substitute for the word “means.” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”

Claims

WHAT IS CLAIMED IS:

1. A method of clock synchronization, comprising: receiving, by touch driving circuitry of a touch display device, a current first synchronization signal that is used by display driving circuity of the touch display device to drive a display panel of the touch display device; and in response to a previous first synchronization signal being received by the touch driving circuitry before the current first synchronization signal is received, determining, by the touch driving circuitry, whether there is a second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within a first predefined period of receiving the current first synchronization signal, the second synchronization signal being used for clock synchronization between the touch driving circuitry and a stylus that cooperates with the touch display device, and determining, by the touch driving circuitry, a time delay of a next second synchronization signal based on whether there is the second synchronization signal that has been sent or is going to be sent within the first predefined period.

2. The method of claim 1, further comprising: in response to the previous first synchronization signal not being received by the touch driving circuitry before the current first synchronization signal is received, determining, by the touch driving circuitry, a first time delay as the time delay of the next second synchronization signal, the first time delay being an inverse value of a maximum frequency of the first synchronization signal.

3. The method of claim 2, wherein the determining the time delay of the next second synchronization signal comprises: in response to a determination that there is the second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, determining, by the touch driving circuitry, a second time delay as the time delay of the next second synchronization signal, the second time delay being twice the length of time of the first time delay.

4. The method of claim 2, wherein the determining the time delay of the next second synchronization signal comprises: in response to a determination that there is no second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, determining, by the touch driving circuitry, the first time delay as the time delay of the next second synchronization signal.

5. The method of claim 2, further comprising: sending, from the touch driving circuitry to the stylus, the next second synchronization signal based on the determined time delay of the next second synchronization signal.

6. The method of claim 5, further comprising: determining, by the touch driving circuitry, whether a next first synchronization signal is received by the touch driving circuitry within a second predefined period after the next second synchronization signal is sent, the second predefined period being twice the length of time of the first time delay.

7. The method of claim 6, further comprising: in response to the next first synchronization signal not being received by the touch driving circuitry within the second predefined period after the next second synchronization signal is sent, continuously sending, by the touch driving circuitry, the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the touch driving circuitry, the predefined frequency being an inverse value of the second predefined period.

8. The method of claim 1, wherein the first synchronization signal is a vertical synchronization signal.

9. The method of claim 1, wherein the first synchronization signal is used for an image display function of the touch display device.

10. The method of claim 1, wherein the second synchronization signal is used for a touch sensing function of the touch display device.

11. A touch display device, comprising: touch driving circuitry configured to receive a current first synchronization signal that is used by display driving circuity of the touch display device to drive a display panel of the touch display device, and in response to a previous first synchronization signal being received by the touch driving circuitry before the current first synchronization signal is received, determine whether there is a second synchronization signal that has been sent or is going to be sent by the touch driving circuitry within a first predefined period of receiving the current first synchronization signal, the second synchronization signal being used for clock synchronization between the touch driving circuitry and a stylus that cooperates with the touch display device, and determine a time delay of a next second synchronization signal based on whether there is the second synchronization signal that has been sent or is going to be sent within the first predefined period.

12. The touch display device of claim 11, wherein the touch driving circuitry is further configured to: in response to the previous first synchronization signal not being received by the touch driving circuitry before the current first synchronization signal is received, determine a first time delay as the time delay of the next second synchronization signal, the first time delay being an inverse value of a maximum frequency of the first synchronization signal.

13. The touch display device of claim 12, wherein the touch driving circuitry is further configured to: in response to a determination that there is the second synchronization that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, determine a second time delay as the time delay of the next second synchronization signal, the second time delay being twice the length of time of the first time delay.

14. The touch display device of claim 12, wherein the touch driving circuitry is further configured to: in response to a determination that there is no second synchronization that has been sent or is going to be sent by the touch driving circuitry within the first predefined period, determine the first time delay as the time delay of the next second synchronization signal.

15. The touch display device of claim 12, wherein the touch driving circuitry is further configured to: send the next second synchronization signal to the stylus based on the determined time delay of the next second synchronization signal.

16. The touch display device of claim 15, wherein the touch driving circuitry is further configured to: determine whether a next first synchronization signal is received by the touch driving circuitry within a second predefined period after the next second synchronization signal is sent, the second predefined period being twice the length of time of the first time delay.

17. The touch display device of claim 16, wherein the touch driving circuitry is further configured to: in response to the next first synchronization signal not being received by the touch driving circuitry within the second predefined period after the next second synchronization signal is sent, continuously send the second synchronization signal at a predefined frequency until the next first synchronization signal is received by the touch driving circuitry, the predefined frequency being an inverse value of the second predefined period.

18. The touch display device of claim 11, wherein the first synchronization signal is a vertical synchronization signal.

19. The touch display device of claim 11, wherein the first synchronization signal is used for an image display function of the touch display device.

20. The touch display device of claim 11, wherein the second synchronization signal is used for a touch sensing function of the touch display device.