Clock synchronization between a stylus and a touch display device under uplink signal attenuation

Abstract

A stylus, a method, and a computer-readable medium that receive an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, obtain an uplink code from the uplink signal, the uplink code including a preamble code, and in response to a determination that the preamble code is a complementary code of a preset preamble code, performs a clock synchronization based on the Bluetooth connection of the touch display device, and sends touch input information of the stylus to the touch display device based on the clock synchronization.

Description

CLOCK SYNCHRONIZATION BETWEEN A STYLUS AND A TOUCH DISPLAY DEVICE UNDER UPLINK SIGNAL ATTENUATIONCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 616,107, filed on December 29, 2023, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] The present disclosure relates to a touch sensing system, and more specifically, to a clock synchronization between a stylus and a touch display device in the touch sensing system.BACKGROUND

[0003] 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

[0004] Aspects of the disclosure provide a stylus. Processing circuitry of the stylus is configured to receive an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtain an uplink code from the uplink signal. The uplink code includes a preamble code. In response to a determination that the preamble code is a complementary code of a preset preamble code, the process circuitry is configured to perform a clock synchronization based on the Bluetooth connection of the touch display device, and send touch input information of the stylus to the touch display device based on the clock synchronization.

[0005] In an embodiment, the processing circuitry is configured to perform the clock synchronization based on a timestamp of the Bluetooth connection of the touch display device.

[0006] In an embodiment, the processing circuitry is configured to send the touch input information of the stylus by sending a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes the touch input information of the stylus.

[0007] In an embodiment, the processing circuitry is further configured to determine whether the touch display device is a main device of the stylus. In response to determining thatthe touch display device is not a main device of the stylus, the processing circuitry is configured to assign the touch display device as the main device of the stylus.

[0008] In an embodiment, the processing circuitry is configured to determine whether the touch display device is the main device of the stylus by determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, the processing circuitry is configured to determine that the touch display device is the main device of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, the processing circuitry is configured to determine that the touch display device is not the main device of the stylus.

[0009] In an embodiment, the processing circuitry is configured to assign the touch display device as the main device of the stylus by assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

[0010] In an embodiment, the processing circuitry is configured to assign the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus by reducing a Bluetooth connection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

[0011] In an embodiment, the processing circuitry is further configured to receive another uplink signal from another touch display device that is in another Bluetooth connection with the stylus, and obtain another uplink code from the other uplink signal. The other uplink code includes another preamble code. In response to a determination that the other preamble code is the preset preamble code, the processing circuitry is configured to assign the other touch display device as a main device of the stylus, perform another clock synchronization based on the other Bluetooth connection of the other touch display device, and send other touch input information of the stylus to the other touch display device based on the other clock synchronization.

[0012] In an embodiment, the touch input information includes at least one of position information or tilt information of the stylus.

[0013] Aspects of the disclosure provide a method for a stylus to perform a clock synchronization with a touch display device. The method includes receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtaining an uplink code from the uplink signal. The uplink code includes a preamble code. In response to a determination that the preamble code is a complementary code of a preset preamble code, the method includes performing a clock synchronization based on the Bluetooth connection of the touch display device, and sending touch input information of the stylus to the touch display device based on the clock synchronization.

[0014] In an embodiment, the clock synchronization is performed based on a timestamp of the Bluetooth connection of the touch display device.

[0015] In an embodiment, the sending the touch input information of the stylus includes sending a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes the touch input information of the stylus.

[0016] In an embodiment, the method further includes determining whether the touch display device is a main device of the stylus. In response to determining that the touch display device is not a main device of the stylus, the method includes assigning the touch display device as the main device of the stylus.

[0017] In an embodiment, the determining whether the touch display device is the main device of the stylus includes determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, the method includes determining that the touch display device is the main device of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, the method includes determining that the touch display device is not the main device of the stylus.

[0018] In an embodiment, the assigning the touch display device as the main device of the stylus includes assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

[0019] In an embodiment, the assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus includes reducing a Bluetoothconnection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

[0020] In an embodiment, the method further includes receiving another uplink signal from another touch display device that is in another Bluetooth connection with the stylus, and obtaining another uplink code from the other uplink signal. The other uplink code includes another preamble code. In response to a determination that the other preamble code is the preset preamble code, the method includes assigning the other touch display device as a main device of the stylus, performing another clock synchronization based on the other Bluetooth connection of the other touch display device, and sending other touch input information of the stylus to the other touch display device based on the other clock synchronization.

[0021] In an embodiment, the touch input information includes at least one of position information or tilt information of the stylus.

[0022] 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 features.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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:

[0024] FIG. 1 shows a touch sensing system according to embodiments of the disclosure;

[0025] FIG. 2 shows a clock synchronization between a stylus and a touch display device according to embodiments of the disclosure;

[0026] FIG. 3A shows an example of attenuating an uplink signal according to embodiments of the disclosure;

[0027] FIG. 3B shows a simplified circuit schematic of the uplink signal transmission between a stylus and a touch display device when the uplink signal is not attenuated;

[0028] FIG. 3C shows a simplified circuit schematic of the uplink signal transmission between the stylus and the touch display device when the uplink signal is attenuated;

[0029] FIG. 3D shows another simplified circuit schematic of the uplink signal transmission between the stylus and the touch display device when the uplink signal is attenuated;

[0030] FIG. 4 shows an example of obtaining a correct device ID from an attenuated uplink signal according to embodiments of the disclosure;

[0031] FIGS. 5-8 show four different application scenarios according to embodiments of the disclosure; and

[0032] FIGS. 9-12 shows four flowcharts illustrating different processes according to embodiments of the disclosure.DETAILED DESCRIPTION OF EMBODIMENTS

[0033] 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.

[0034] 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.

[0035] FIG. 1 shows a touch sensing system 100 according to embodiments of the disclosure. The touch sensing system 100 can include a plurality of touch display devices (e.g., touch display devices 110-112) and a stylus 120. It is noted that a number of the plurality of touch display devices in the touch sensing system 100 is not limited in this disclosure, and three touch display devices 110-112 are shown in FIG. 1 for exemplary illustration. In the following description, the touch display device 110 is illustrated in detail as an example, and other touch display device(s) in this disclosure can be described in a similar manner.

[0036] 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 command information from a finger, a passive pen, an active pen such as 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.

[0037] According to aspects of the disclosure, the touch display device 110 can include a touchscreen 130, display driving circuitry 140, touch driving circuitry 150, processing circuitry 160, and Bluetooth circuitry 170. In an example, each circuitry can include a separate integrated circuit chip. For example, the display driving circuitry 140 can include a display driver integrated circuit (DDIC) chip, the touch driving circuitry 150 can include a touch integrated circuit (TIC) chip, the processing circuitry 160 can include a central processing unit (CPU) chip, and the Bluetooth circuitry 170 can include a Bluetooth integrated circuit chip. In an example, a subset or all of the circuitry can be implemented in a system-on-chip (SoC).

[0038] The touchscreen 130 can include a cover panel 131, a touch panel 132, and a display panel 133.

[0039] The cover panel 131 can include a transparent material and be used for protecting the touch panel 132 and the display panel 133. In an example, the cover panel 131 can include a glass or a plastic material.

[0040] The touch panel 132 can include a plurality of touch sensors that senses a touch input from a user. In an example, the plurality of touch sensors can be capacitive touch sensors. In an example, the touch input can be a direct contact of a conductive object (e.g., the user's finger, the user's palm, a touch pen, a passive pen, an active pen, and the like) on the touchscreen 130. In an example, the touch input can be an indirect contact of the conductive object that is in proximity of the touchscreen 130.

[0041] The display panel 133 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.

[0042] It is noted that a location of the touch panel 132 relative to the display panel 133 is not limited in this disclosure. In an example such as FIG. 1, the touch panel 132 can be on top of the display panel 133. In another example, the touch panel 132 can be underneath the display panel 133.

[0043] The display driving circuitry 140 can drive the display panel 133 to perform the image display function of the touch display device 100. The display driving circuitry 140 can receive a command signal from the processing circuitry 160 based on image data to be displayed and send a display driving signal DD to the display panel 133 during a display driving period.

[0044] The touch driving circuitry 150 can drive and sense the touch panel 132 to perform the touch sensing function of the touch display device 100. The touch driving circuitry 150 can send a touch driving signal TD during a touch driving period to the touch panel 132 and receive from the touch panel 132 a touch sensing signal TS that senses charge variations of the plurality of touch sensors of the touch panel 132. By analyzing the charge variations of the plurality of touch sensors, the touch driving circuitry 150 can determine presence or absence of a touch input and obtain touch input information (e.g., position information and / or tilt information) of the touch input if present. The touch input information of the touch input can be sent back to the processing circuitry 160 for further processing.

[0045] 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 133. The display driving signal DD can include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, and the like. In an example, the touch driving signal TD needs to be synchronized with the vertical synchronization signal Vsync.

[0046] The Bluetooth circuitry 170 can be used for pairing the touch display device 110 to the stylus 120 via a Bluetooth connection when the Bluetooth function of the touch display device 110 is turned on and the stylus 120 is within a Bluetooth connection range (e.g., around 10m) of the touch display device 110. After the Bluetooth pairing succeeds, the stylus 120 can store an identity of the touch display device 110, such as a media access control (MAC) address of the touch display device 110.

[0047] In an embodiment, stylus configuration information of the stylus 120 can be sent from the touch display device 110 to the stylus 120 via the Bluetooth connection. The stylus configuration information can include various settings (e.g., erase setting or ink setting) of the stylus 120.

[0048] In an embodiment, stylus status information of the stylus 120 can be sent from the stylus 120 to the touch display device 110 via the Bluetooth connection. The stylus status information can include battery information and pressure information of the stylus 120 for example.

[0049] According to aspects of the disclosure, the stylus 120 can include Bluetooth (BT) circuitry 121, processing (Proc) circuitry 122, transmitting / receiving (Tx / Rx) circuitry 123, and an electrode (ET) 124. In an example, each circuitry can include a separate integrated circuitchip. For example, the Bluetooth circuitry 121 can include a Bluetooth integrated circuit chip, the processing circuitry 122 can include a microcontroller (MCU) chip, and the transmitting / receiving circuitry 123 can include a communication integrated circuit chip. In an example, a subset or all of the circuitry can be implemented in a system-on-chip (SoC).

[0050] The Bluetooth circuitry 121 can be used for pairing the stylus 120 to the touch display device 110 or any other device having a Bluetooth function. In an embodiment, the stylus 120 can use a Bluetooth low energy (BLE) technology to pair with a device such as the touch display device 110.

[0051] The processing circuitry 122 can receive data from the Bluetooth circuitry 121 and / or the Tx / Rx circuitry 123, process the data, and send commands to the Bluetooth circuitry 121 and / or the Tx / Rx circuitry 123 based on the processed data.

[0052] The Tx / Rx circuitry 123 can set up (or establish) a bidirectional communication with touch driving circuitry of a touch display device (e.g., the touch driving circuitry 150 of the touch display device 110), when a distance between the stylus 120 and a touchscreen of the touch display device (e g., the touchscreen 130 of the touch display device 110) is within a communication range (e.g., within 3cm) of the bidirectional communication. The bidirectional communication can enable a cooperation between the stylus 120 and the touch display device 110. That is, the bidirectional communication can enable the stylus 120 and the touch display device 110 to enter a stylus operation mode and a stylus scan mode, respectively, so that the stylus 120 can cooperate / properly communicate with the touch display device 110. For example, in the stylus operation mode, the stylus 120 can cooperate with the touch display device 110 by sending a touch input to the touch display device 110. In the stylus scan mode, the touch display device 110 can cooperate with the stylus 120 by scanning for the touch input from the stylus 120.

[0053] In the bidirectional communication, a signal provided from the touch driving circuitry 150 of the touch display device 110 to the Rx circuitry of the Tx / Rx circuitry 123 of the stylus 120 can be referred to as an uplink signal, and a signal provided from the Tx circuitry of the Tx / Rx circuitry 123 of the stylus 120 to the touch driving circuitry 150 of the touch display device 110 can be referred to as a downlink signal. The uplink signal can include a beacon for clock synchronization between the touch driving circuitry 150 of the touch display device 110 and the Tx / Rx circuitry 123 of the stylus 120. The downlink signal can include touch input information (e.g., position information and / or tilt information) of a stylus tip of the stylus 120.

[0054] In an embodiment, the bidirectional communication can be performed through a capacitive coupling between the touch sensors of the touch panel 132 and the electrode 124 of the stylus 120. The uplink and downlink signals can be transmitted via the touch sensors of the touch panel 132 and the electrode 124 of the stylus 120. In an example, the electrode 124 can be located at the stylus tip of the stylus 120.

[0055] When the stylus 120 is moved out of the communication range of the bidirectional communication between the Tx / Rx circuitry 123 of the stylus 120 and the touch driving circuitry 150 of the touch display device 110, the touch display device 110 is not able to receive a touch input from the stylus 120. For example, when the stylus 120 is lifted up or moved away from the touchscreen 130 of the touch display device 110 (e.g., outside of the communication range), the touch display device 110 is not able to cooperate / properly communicate with the stylus 120. That is, the touch display device 110 is not able to receive the touch input information of the stylus tip of the stylus 120.

[0056] It is noted that the touch display device 110 and / or the stylus 120 can include other modules such as power circuitry, Wi-Fi circuitry, and various sensor circuitry (e.g., pressure sensor, inertial sensor, etc.). The wireless connection between the touch display device 110 and the stylus 120 is not limited to the Bluetooth connection in this disclosure, and can be Wi-Fi connection, near-field connection, or the like.

[0057] According to embodiments of the disclosure, a stylus (e.g., stylus 120) can pair with a touch display device (e.g., touch display device 110) via a Bluetooth connection when a Bluetooth function of the touch display device is turned on and the touch display device is within a Bluetooth connection range (e.g., 10m) of the stylus. In response to the Bluetooth connection being successful, the stylus can assign an uplink code (e.g., 01) to the touch display device via the Bluetooth connection. In an example, the uplink code can include 3 bits for a preamble, 2 bits for a device identification (ID), and 2 bits for a cyclic redundancy check (CRC). After assigning the uplink code, the stylus can enter a stylus scan mode (or stylus discovery mode) to scan for uplink signals from the touch display device.

[0058] In response to receiving the uplink code, the touch display device can start sending the uplink signals indicating the uplink code. The uplink signals can be sent from touch driving circuitry (e.g., touch driving circuitry 150) of the touch display device to Rx circuitry (e.g., Rx circuitry 123) of the stylus. In an example, a signal length of an uplink signal may notexceed 270ps, and can be placed within a blink time period, so the touch driving circuitry is able to trim a clock with Vsync.

[0059] When the stylus is close to the touch display device (e.g., a distance between the stylus and the touch display device is within a communication range (e.g., 3cm) of a bidirectional communication between the stylus and the touch display device), the stylus can receive the uplink signals sent from the touch display device. From the uplink signals, the stylus can detect the uplink code assigned to the touch display device. The stylus can determine whether the detected uplink code is effective based on a preamble of the detected uplink code. In an example, if the preamble of the detected uplink code matches a predetermined preamble or if the preamble of the detected uplink code is a complementary code of the predetermined preamble, the stylus can determine that the detected uplink code is effective. Otherwise, the stylus can determine that the detected uplink code is not effective. Based on the detected uplink code being determined to be effective, the stylus can perform a clock synchronization with the touch display device corresponding to the detected uplink code. If the stylus determines that the detected uplink code is not effective, the stylus does not know which touch display device corresponds to the detected uplink code and thus can ignore the detected uplink code. In such a case, the stylus does not perform the clock synchronization with the touch display device.

[0060] The clock synchronization between the stylus and the touch display device can be performed by using either beacons included in the uplink signals or a Bluetooth connection between the stylus and the touch display device.

[0061] In an embodiment, in addition to the uplink code, the stylus can detect the beacons included in the uplink signals. Based on the beacons included in the uplink signals, the stylus can perform the clock synchronization to synchronize a clock of the Tx / Rx circuitry of the stylus to a clock of the touch driving circuitry of the touch display device. Based on the clock synchronization, the stylus can send downlink signals to the touch display device. The downlink signals can include touch input information (e.g., position information and / or tilt information) of the stylus. From the downlink signals, the touch display device can obtain the touch input information of the stylus. Accordingly, a cooperation between the stylus and the touch display device can be enabled and performed. In the cooperation, the stylus can send a touch input to the touch display device and the touch display device can scan for the touch input.

[0062] In an embodiment, the stylus can obtain from the touch display device and via the Bluetooth connection, a downlink frequency of the downlink signals. The stylus can send back an acknowledge (ACK) signal to the touch display device and enter the stylus operation mode. The ACK signal can be sent, via a downlink signal with the downlink frequency, from Tx circuitry (e.g., Tx circuitry 123) of the stylus to the touch driving circuitry of the touch display device. In the stylus operation mode, the stylus can send, via the downlink signals, touch input information of the stylus to the touch display device.

[0063] In response to receiving the ACK signal, the touch display device can enter the stylus scan mode to scan for the downlink signals including the touch input information of the stylus. Accordingly, the bidirectional communication between the Tx / Rx circuitry of the stylus and the touch driving circuitry of the touch display device can be set up, and a cooperation between the stylus and the touch display device can be enabled and performed. During the cooperation, the touch display device can receive a touch input from the stylus so that a user can use the stylus, for example, to write, draw, and input a command on the touch display device.

[0064] It is noted that if the clock synchronization is not maintained during the cooperation between the stylus and the touch display device, the cooperation (e.g., the use of the stylus) may be affected or disturbed. In an example, an ink latency of the stylus, which is a time lag between a current position of the stylus and a digital ink being shown on the touchscreen of the touch display device, may be increased. In an example, a tapping of the stylus may not be detected by the touch display device.

[0065] FIG. 2 shows a clock synchronization 200 between a stylus (e.g., stylus 120) and a touch display device (e.g., touch display device 110) according to embodiments of the disclosure. In the clock synchronization 200, the stylus can be first in a stylus discovery mode to scan for uplink signals, as shown in the timing diagram 210. Then, once the stylus receives an uplink signal (e.g., uplink signal 230) or detects a pressure signal from the touch display device, the stylus can enter a stylus operation mode. In the stylus operation mode, the stylus can send downlink signals (e.g., downlink signals 240-249) to the touch display device based on the clock synchronization, as shown in the timing diagram 220. The downlink signals include touch input information (e.g., position information and / or tilt information) of the stylus. From the downlink signals, the touch display device can obtain the touch input information of the stylus. Accordingly, a cooperation between the stylus and the touch display device can be enabled andperformed. During the cooperation, the touch display device can receive a touch input from the stylus.

[0066] In FIG. 2, the clock synchronization can be performed via uplink signals (e.g., signals 230 and 231) or via the Bluetooth connection between the stylus and the touch display device. If the clock synchronization is performed via the uplink signals, the stylus can enter the stylus operation mode when the stylus detects an uplink signal from the touch display device. If the clock synchronization is performed via the Bluetooth connection between the stylus and the touch display device, the stylus can enter the stylus operation mode when the stylus detects a pressure signal from the touch display device. In an example, the stylus can use Bluetooth timestamp for the clock synchronization.

[0067] Compared to detecting the pressure signal, detecting the uplink signals can enable the stylus to enter the stylus operation mode in advance while the stylus is still hovering in the air (above, for example, the touchscreen 130 of the touch display device 110). That is, before the stylus detects the pressure signal by contacting the touch display device, the stylus can already be in the stylus operation mode by detecting the uplink signals from the touch display device, so that the ink latency of the stylus can be reduced.

[0068] However, when the stylus is hovering in the air to receive an uplink signal, the uplink signal may be significantly attenuated. For example, a user’s palm on the touch display device may cause a signal attenuation for the uplink signal. The signal attenuation may prevent the stylus from correctly receiving the uplink signal.

[0069] FIG. 3A shows an example of attenuating an uplink signal according to embodiments of the disclosure. In FIG. 3A, the stylus 120 is above the touch display device 110 to detect an uplink signal from the touch display device 110. The stylus 120 can detect the uplink signal because of a first capacitive coupling between the electrode 124 of the stylus 120 and the touch sensor of the touch display device 110. The first capacitive coupling can be represented by a capacitor Ci in FIGS. 3A-3D.

[0070] FIG. 3B shows a simplified circuit schematic of the uplink signal transmission between the stylus 120 and the touch display device 110 when the uplink signal is not attenuated (e.g., when a user’s palm 310 is not on the touch display device 110). In FIG. 3B, the touch display device 110 and the stylus 120 can be represented by the circuits 320 and 330, respectively. Due to the first capacitive coupling (i.e., the capacitor Ci), the uplink signalCi t>ecoupled to the electrode 124 of the stylus 120, and can be amplified as — ~ Vpp

[0071] However, when a conductive object (e.g., the user’s palm 310) is on the touch display device 110, the uplink signal may be attenuated because of a second capacitive coupling between the conductive object and the stylus 120, as shown in FIG. 3A. The second capacitive coupling can be represented by a capacitor CPaim_to_pen_GND in FIGS. 3A, 3C, and 3D.

[0072] It is noted that the palm 310 is used to illustrate the uplink signal attenuation issue and should not be limited in this disclosure, as any conductive material on the touch display device 110 may cause the performance degradation of the uplink signals.

[0073] FIG. 3C shows a simplified circuit schematic of the uplink signal transmission between the stylus 120 and the touch display device 110 when the uplink signal is attenuated (e.g., when a user’s palm 310 is on the touch display device 110). In FIG. 3C, due to the second capacitive coupling (i.e., the capacitor Cpaim-t0_pen-GND), the uplink signal VPPup|inkcan be coupled to the electrical ground plane (Pen GND) of the stylus 120, and can be amplified asgly, the effective uplink signal can be represented as —

[0074] When the stylus 120 is right above the user’s palm 310, Ci can be assumed to be extremely low, and thus the detected uplink signal can be representedas shown in FIG. 3D, and this scenario can be considered as a significant attenuation. That is, the uplink signal attenuation can cause the uplink signal transmitted by the touch display device 110 and the effective uplink signal received by the stylus 120 to be out of phase.

[0075] Further, if the stylus 120 performs the clock synchronization with the touch display device 110 via the Bluetooth connection between the stylus 120 and the touch display device 110, the uplink signal attenuation can still affect the clock synchronization. This is because the stylus 120 may not be able to obtain a correct device ID from the received effective uplink signal that is out of phase from the transmitted uplink signal. Without obtaining a correct device ID, the stylus 120 is not able to choose a correct Bluetooth timestamp for the clock synchronization.

[0076] In order to solve these issues, this disclosure provides methods of performing a clock synchronization under the uplink signal attenuation.

[0077] As described above, under the uplink signal attenuation, a received effective uplink signal received by a stylus (e.g., stylus 120) can be out of phase from a transmitted uplink signal transmitted by a touch display device (e.g., touch display device 110), indicating that an uplink code (or a received uplink code) included in the received effective uplink signal can be a complementary code of an uplink code (or a transmitted uplink code) included in the transmitted uplink signal. For example, under the uplink signal attenuation, the transmitted uplink code is 01 while the received uplink code is 10.

[0078] Accordingly, in a method, the stylus can determine whether the received uplink code is the complementary code of the transmitted uplink code by determining whether a preamble of the received uplink code is a complementary code of a preamble of the transmitted uplink code. The preamble of the transmitted uplink code can be a predetermined preamble. Accordingly, when the stylus determines that the preamble of the received uplink code is the complementary code of the predetermined preamble, the stylus determines that the received uplink code is the complementary code of the transmitted uplink code. Then, in an embodiment, the stylus can generate a complementary code of the received uplink code and thus obtain a correct device ID from the complementary code of the received uplink code. In an embodiment, the stylus can obtain the device ID code from the received uplink code and generate a complementary code of the device ID code as the correct device ID. Based on the correct device ID, the stylus can choose a correct touch display device to perform the clock synchronization.

[0079] Accordingly, by using the method, the clock synchronization between the stylus and the touch display device can still be performed accurately under the uplink signal attenuation, so that the stylus and the touch display device can properly communicate with each other based on the accurate clock synchronization.

[0080] FIG. 4 shows an example of obtaining a correct device ID from an attenuated uplink signal according to embodiments of the disclosure. In FIG. 4, a timing diagram 400 shows digital (or pre-modulated) waveforms of uplink signals transmitted by the touch display device 110, and a timing diagram 450 shows digital (or demodulated) waveforms of the uplink signal received by the stylus 120. As shown in FIG. 3C, the uplink signals obtained through the first capacitive coupling and the second capacitive coupling are out of phase. Thus, in the timingdiagram 450, the demodulated waveforms of the uplink signals obtained through the first capacitive coupling and the second capacitive coupling can be below and above a reference voltage (e.g., a reference voltage of an analog-to-digital converter), respectively, indicating that the uplink codes included in the uplink signals obtained through the first capacitive coupling and the second capacitive coupling are complementary to each other.

[0081] For example, for a transmitted uplink signal 410, the demodulated waveform 420 Ci represents the uplink signal — ^VPpuplinkobtained through the first capacitive coupling, and the demodulated waveform 430 represents the uplink signalPalm-t°-Pen-through the second capacitive coupling. It can be seen that the demodulated uplink signals 420 and 430 are below and above a reference voltage ADC ref of an analog-to-digital converter (ADC), respectively. In an example, the reference voltage ADC_ref can be set as a half of power supply rail VDD rail. Thus, the demodulated waveform 440 represents the detected uplink signalwhen an amplitude of the demodulated uplink signal 430 is greater than an amplitude of the demodulated uplink signal 420.

[0082] In this disclosure, it is assumed that an uplink code included in the uplink signal obtained through the first capacitive coupling is the same as an uplink code included in the uplink signal transmitted by the touch display device 110. For example, the transmitted uplink signal 410 includes an uplink code 1, so the uplink code included in the demodulated uplink signal 420 is 1. As described above, the uplink codes included in the demodulated uplink signals 420 and 430 are complementary to each other. Accordingly, the uplink code included in the demodulated signal 430 is 0. Since the amplitude of the demodulated uplink signal 430 is greater than the amplitude of the demodulated uplink signal 420, the detected uplink signal 440 is above the reference voltage ADC ref, and thus the uplink code included in the detected uplink signal 440 is 0.

[0083] In FIG. 4, a transmitted uplink code 411 can be represented as 1011011, wherein the first three-bits 101 represents a preamble code, the following two-bits 10 represents a device ID, and the last two-bits 11 represents a CRC. A received uplink code 421, which is obtained through the first capacitive coupling, can be the same as the transmitted uplink code 411. A received uplink code 431, which is obtained through the second capacitive coupling, can becomplementary to the transmitted uplink code 411 and represented as 0100100. Accordingly, a detected uplink code 441 can be represented as 0100100, wherein the first three-bits 010 represents a preamble code, the following two-bits 01 represents a device ID, and the last two- bits 00 represents a CRC.

[0084] From the detected uplink code 441, the stylus 120 can obtain the preamble code 010 and determine that the preamble code 010 is complementary to the preamble code 101 of the transmitted uplink code 411. It is noted that the preamble code 101 of the transmitted uplink code 411 is predetermined and known to the stylus 120. Accordingly, the stylus 120 can determine that the detected uplink code 411 is complementary to the transmitted uplink code 411.

[0085] In an embodiment, the stylus 120 can generate a complementary code of the detected uplink code 441. The complementary code of the detected uplink code 441 is the same as the transmitted uplink code 411. Based on the complementary code of the detected uplink code 441, the stylus 120 can obtain the correct device ID 10.

[0086] In an embodiment, the stylus 120 can first obtain the device ID 01 from the detected uplink code 441, and generate a complementary code of the device ID 01. The complementary code of the device ID 01 is 10. Thus, the stylus 120 can obtain the correct device ID 10 from the complementary code of the device ID 01.

[0087] Based on the correct device ID, the stylus 120 can select a correct touch display device to perform the clock synchronization. For example, the stylus 120 can determine whether the selected touch display device is a main device which has a highest priority of Bluetooth communication of the stylus 120. If the selected touch display device is not the main device of the stylus 120, the stylus 120 can set the selected touch display device as the main device. In an embodiment, the stylus 120 can set a priority of the Bluetooth connection of the selected touch display device to be the highest priority for the Bluetooth communication of the stylus 120. In an embodiment, the stylus 120 can set a connection interval (CI) of the Bluetooth connection of the selected touch display device to be the shortest for the Bluetooth communication of the stylus 120. A Bluetooth CI is a time period between two data transfer events of a Bluetooth connection between two devices.

[0088] FIGS. 5-8 show four different application scenarios according to embodiments of the disclosure. In each scenario, the stylus 120 can be in Bluetooth connections with both touchdisplay devices A 110 and B 111. Through the Bluetooth connections, the stylus 120 can assign the devices A 110 and B 111 as the main and auxiliary devices of the stylus 120, respectively.

[0089] Specifically, in the application scenario of FIG. 5, there is no uplink signal attenuation. As shown in diagram 500, the stylus 120 is in a stylus discovery mode and hovering above the device A 110. When the stylus 120 approaches the device A 110, the stylus 120 can detect an uplink signal from the device A 110. Based on the uplink signal, the stylus 120 can obtain an uplink code 01 indicating that the device A 110 is the main device of the stylus 120. Accordingly, the stylus 120 can enter a stylus operation mode and perform a clock synchronization based on the uplink signal, as shown in the diagram 550. When the stylus 120 lands on the device A 110, the stylus 120 can detect a pressure signal from the device A 110.

[0090] In the application scenario of FIG. 6, a user’s palm 640 is on the touch display device A 110, causing a signal attenuation for an uplink signal 610 transmitted from the device A 110. As shown in diagram 600, the stylus 120 is in a stylus discovery mode and hovering above the device 110. When the stylus 120 approaches the device A 110, the stylus 120 can detect the attenuated uplink signal 610 from the device A 110. Once detecting the attenuated uplink signal 610, the stylus 120 can determine whether a preamble of the attenuated uplink signal 610 is a complementary code of a predetermined preamble. The predetermined preamble is a preamble of an unattenuated uplink signal (e.g., uplink signal 510, 520, or 620).

[0091] When the stylus 120 determines that the preamble of the attenuated uplink signal 610 is the complementary code of the predetermined preamble, the stylus 120 can determine a device ID of the device A 110 from the attenuated uplink signal 610. Based on the device ID, the stylus 120 can confirm that the device A 110 is the main device of the stylus 120 for the clock synchronization.

[0092] As shown in diagram 650, when the stylus 120 lands on the device A 110, the stylus 120 can detect a pressure signal 630 from the device A 110. In response to detecting the pressure signal 630, the stylus 120 can enter the stylus operation mode. In the stylus operation mode, the stylus 120 can perform the clock synchronization via the Bluetooth connection between the stylus 120 and the main device of the stylus 120, which is the device A 110. Based on the clock synchronization, the stylus 120 can properly cooperate or communicate with the device A 110. For example, when the stylus 120 sends a touch input to the device A 110, thedevice A 110 can correctly receive the touch input, since the stylus 120 and the device A 110 are now clock synchronized.

[0093] In the application scenario of FIG. 7, a user’s palm 740 is on the touch display device B i l l, causing a signal attenuation for an uplink signal 720 transmitted from the device B 111. As shown in diagram 700, the stylus 120 is hovering above and between the device A 110 to the device B i l l. For example, the stylus 120 is moving from the device A 110 to the device B i l l. The stylus 120 can detect an unattenuated uplink signal 710 from the device A 110 and the attenuated uplink signal 720 from the device B i l l. Once detecting the attenuated uplink signal 720, the stylus 120 can determine whether a preamble of the attenuated uplink signal 720 is the complementary of the predetermined preamble.

[0094] When the stylus 120 determines that the preamble of the attenuated uplink signal 720 is the complementary code of the predetermined preamble, the stylus 120 can determine a device ID of the device B i l l from the attenuated uplink signal 720. Based on the device ID, the stylus 120 can confirm that the device B 111 is the auxiliary device of the stylus 120. Then, the stylus 120 can set the device B 111 as the main device of the stylus 120 for the clock synchronization. The stylus 120 can upgrade a priority of Bluetooth connection of the device B 111 to be the highest priority for the Bluetooth communication of the stylus 120. The stylus 120 can reduce a Bluetooth CI of the device B 111 to the shortest Bluetooth CI for the Bluetooth communication of the stylus 120. The stylus 120 can also set the device A 110 as the auxiliary device of the stylus 120. The stylus 120 can downgrade a priority of Bluetooth connection of device A 110 to be the non-highest priority for the Bluetooth communication of the stylus 120. The stylus 120 can increase a Bluetooth CI of the device A 110 to the non-shortest Bluetooth CI for the Bluetooth communication of the stylus 120.

[0095] As shown in diagram 750, when the stylus 120 lands on the device B i l l, the stylus 120 can detect a pressure signal 730 from the device B i l l. In response to detecting the pressure signal 730, the stylus 120 can enter the stylus operation mode. In the stylus operation mode, the stylus 120 can perform the clock synchronization via the Bluetooth connection between the stylus 120 and the main device of the stylus 120, which is the device B i l l now. Based on the clock synchronization, the stylus 120 can properly cooperate or communicate with the device B i l l. For example, when the stylus 120 sends a touch input to the device B i l l, thedevice B 111 can correctly receive the touch input, since the stylus 120 and the device B 111 are now clock synchronized.

[0096] In the application scenario of FIG. 8, a user’s palm 840 is on the touch display device B i l l, causing a signal attenuation for an uplink signal 820 transmitted from the device B 111. As shown in diagram 800, the stylus 120 is hovering above and between the device A 110 and the device B i l l. For example, the stylus 120 is moving from the device B 111 to the device A 110. The stylus 120 can detect an unattenuated uplink signal 810 from the device A110 and the attenuated uplink signal 820 from the device B i l l. Once detecting the attenuated uplink signal 820, the stylus 120 can determine whether a preamble of the attenuated uplink signal 820 is the complementary of the predetermined preamble.

[0097] When the stylus 120 determines that the preamble of the attenuated uplink signal 820 is the complementary code of the predetermined preamble, the stylus 820 can determine a device ID of the device B i l l from the attenuated uplink signal 820. Based on the device ID, the stylus 120 can confirm that the device B 111 is the auxiliary device of the stylus 820. Then, the stylus 120 can set the device B 111 as the main device of the stylus 120 for the clock synchronization. The stylus 120 can upgrade a priority of Bluetooth connection of the device B111 to be the highest priority for the Bluetooth communication of the stylus 120. The stylus 120 can reduce a Bluetooth CI of the device B 111 to the shortest Bluetooth CI for the Bluetooth communication of the stylus 120. The stylus 120 can also set the device A 110 as the auxiliary device of the stylus 120. The stylus 120 can downgrade a priority of Bluetooth connection of device A 110 to be the non-highest priority for the Bluetooth communication of the stylus 120. The stylus 120 can increase a Bluetooth CI of the device A 110 to the non-shortest Bluetooth CI for the Bluetooth communication of the stylus 120.

[0098] As shown in diagram 850, when the stylus 120 lands on the device A 110, the stylus 120 can detect a pressure signal 830 from the device A 110. In response to detecting the pressure signal 830, the stylus 120 can determine whether an unattenuated uplink signal is received. Since there is no user’s palm on the device A 110, the stylus 120 can still receive the unattenuated uplink signal 810 from the device A 110. Accordingly, in response to receiving the unattenuated uplink signal 810 after detecting the pressure signal 830, the stylus 120 can obtain the device ID of the device A 110 from the unattenuated uplink signal and set the device A 110 as the main device of the stylus 120 for the clock synchronization. The stylus 120 can upgradethe priority of Bluetooth connection of the device A 110 to be the highest priority for the Bluetooth communication of the stylus 120. The stylus 120 can reduce the Bluetooth CI of the device A 110 to the shortest Bluetooth CI for the Bluetooth communication of the stylus 120. The stylus 120 can also set the device B 111 as the auxiliary device of the stylus 120. The stylus 120 can downgrade the priority of Bluetooth connection of device B 111 to be the non-highest priority for the Bluetooth communication of the stylus 120. The stylus 120 can increase the Bluetooth CI of the device A 111 to the non-shortest Bluetooth CI for the Bluetooth communication of the stylus 120.

[0099] Then, the stylus 120 can enter the stylus operation mode. In the stylus operation mode, the stylus 120 can perform the clock synchronization via the Bluetooth connection between the stylus 120 and the main device of the stylus 120, which is the device A l l i now. Based on the clock synchronization, the stylus 120 can properly cooperate or communicate with the device A 110. For example, when the stylus 120 sends a touch input to the device A 110, the device A 110 can correctly receive the touch input, since the stylus 120 and the device A 110 are now clock synchronized.

[0100] FIG. 9 shows a flowchart illustrating a process 900 of determining whether an uplink signal is an attenuated uplink signal according to embodiments of the disclosure. The process 900 can be implemented by processing circuitry (e.g., processing circuitry 122) of a stylus (e.g., stylus 120). The process 900 can be implemented as instructions stored in a non- transitory computer-readable medium. When executed by for example processing circuitry of an apparatus (e.g., stylus 120), the instructions can cause the apparatus to perform the process 900. The process 900 may start at step S901.

[0101] At step S901, the process 900 can receive an uplink signal from a touch display device (e.g., touch display device A 110). Then, the process 900 can proceed to step S902.

[0102] At step S902, the process 900 can obtain a preamble of the uplink signal. Then, the process 900 can proceed to step S903.

[0103] At step S903, the process 900 can determine whether the preamble is a predetermined preamble. If the preamble of the uplink signal is the predetermined preamble, the process 900 can proceed to step S904. Otherwise, the process 900 can proceed to step S905.

[0104] At step S904, in response to the preamble of the uplink signal being the predetermined preamble, the process 900 can determine that the uplink signal is an unattenuated uplink signal.

[0105] At step S905, in response to the preamble of the uplink signal not being the predetermined preamble, the process 900 can determine whether the preamble is a complementary code of the predetermined preamble. If the preamble of the uplink signal is the complementary code of the predetermined preamble, the process 900 can proceed to step S906.

[0106] At step S906, in response to the preamble of the uplink signal being the complementary code of the predetermined preamble, the process 900 can determine that the uplink signal is an attenuated uplink signal.

[0107] Then, the process 900 can terminate.

[0108] FIG. 10 shows a flowchart illustrating a process 1000 of determining a correct device ID from an attenuated uplink signal according to embodiments of the disclosure. The process 1000 can be implemented by processing circuitry (e.g., processing circuitry 122) of a stylus (e.g., stylus 120). The process 1000 can be implemented as instructions stored in a non- transitory computer-readable medium. When executed by for example processing circuitry of an apparatus (e.g., stylus 120), the instructions can cause the apparatus to perform the process 1000. The process 1000 may start at step SI 001.

[0109] At step SI 001, the process 1000 can receive an attenuated uplink signal. Then, the process 1000 can proceed to step SI 002.

[0110] At step SI 002, the process 1000 can obtain an uplink code included in the attenuated uplink signal. For example, in FIG. 4, the uplink code 441 can be obtained from the detected uplink signal. Then, the process 1000 can proceed to step SI 003.[OlH] At step SI 003, the process 1000 can generate a complementary code of the uplink code. In FIG. 4, the uplink code 441 is 0100100, so the complementary code of the uplink code 441 is 1011011, which is the same as the uplink code 411 included the uplink signal transmitted by the touch display device. Then, the process 1000 can proceed to step SI 004.

[0112] At step SI 004, the process 1000 can determine a correct device ID based on the complementary code. Still referencing back to FIG. 4, the device ID of the complementary code 1011011 is 10, which is the same as the correct device ID included in the uplink code 411. Thus,the correct device ID can be obtained from the complementary code of the uplink code included in the attenuated uplink signal.

[0113] Then, the process 1000 can terminate.

[0114] FIG. 11 shows a flowchart illustrating a process 1100 of determining a correct device ID from an attenuated uplink signal according to embodiments of the disclosure. The process 1100 can be implemented by processing circuitry (e.g., processing circuitry 122) of a stylus (e g., stylus 120). The process 1100 can be implemented as instructions stored in a non- transitory computer-readable medium. When executed by for example processing circuitry of an apparatus (e.g., stylus 120), the instructions can cause the apparatus to perform the process 1100. The process 1100 may start at step SI 101.

[0115] At step SI 101, the process 1100 can receive an attenuated uplink signal. Then, the process 1100 can proceed to step SI 102.

[0116] At step SI 102, the process 1100 can obtain an uplink code included in the attenuated uplink signal. For example, in FIG. 4, the uplink code 441 can be obtained from the detected uplink signal. Then, the process 1100 can proceed to step SI 103.

[0117] At step SI 103, the process 1100 can obtain a device ID from the uplink code. In FIG. 4, the uplink code 441 is 0100100, so the device ID of the uplink code 441 is 01, which is complementary to the correct device ID in the uplink code 411 included the uplink signal transmitted by the touch display device. Then, the process 1100 can proceed to step SI 104.

[0118] At step SI 104, the process 1100 can generate a complementary code of the device ID as a correct device ID. Still referencing back to FIG. 4, the device ID of the uplink code 411 is 01, so the complementary code of the device ID is 10, which is the same as the correct device ID included in the uplink code 411. Thus, the correct device ID can be obtained from the complementary code of the device ID of the uplink code included in the attenuated uplink signal.

[0119] Then, the process 1100 can terminate.

[0120] FIG. 12 shows a flowchart illustrating a process 1200 of performing a clock synchronization when receiving an attenuated uplink signal according to embodiments of the disclosure. The process 1200 can be implemented by processing circuitry (e.g., processing circuitry 122) of a stylus (e.g., stylus 120). The process 1200 can be implemented as instructions stored in a non-transitory computer-readable medium. When executed by for exampleprocessing circuitry of an apparatus (e.g., stylus 120), the instructions can cause the apparatus to perform the process 1200. The process 1200 may start at step S 1201.

[0121] At step SI 201, the process 1200 can receive an attenuated uplink signal from a first touch display device (e.g., touch display device A 110). Then, the process 1200 can proceed to step S1202.

[0122] At step S1202, the process 1200 can determine whether the first touch display device is a main device of the stylus. If the first touch display device is the main device, the process 1200 can proceed to step S1204. Otherwise, the process 1200 can proceed to step S1203.

[0123] At step S1203, the process 1200 can assign the first touch display device as the main device. Then, the process 1200 can proceed to step S1204.

[0124] At step S1204, the process 1200 can receive a pressure signal. In response to receiving the pressure signal, the process 1200 can proceed to step S1205.

[0125] At step SI 205, the process 1200 can determine whether an unattenuated uplink signal is received from a second touch display device (e g., touch display device B 111). If the process 1200 determines that the unattenuated uplink signal is received from the second touch display device, the process 1200 can proceed to step S1208. Otherwise, the process 1200 can proceed to step SI 206.

[0126] At step SI 206, the process 1200 can perform a first clock synchronization based on a first Bluetooth connection between the stylus and the first touch display device. Then, the process 1200 can proceed to step SI 207.

[0127] At step SI 207, the process 1200 can send first touch input information of the stylus to the first touch display device based on the first clock synchronization.

[0128] At step S1208, the process 1200 can assign the second touch display device as the main device. Then, the process 1200 can proceed to step S1209.

[0129] At step SI 209, the process 1200 can perform a second clock synchronization based on a second Bluetooth connection between the stylus and the second touch display device. Then, the process 1200 can proceed to step S1210.

[0130] At step S1210, the process 1200 can send second touch input information of the stylus to the second touch display device based on the second clock synchronization.

[0131] Then, the process 1200 can terminate.

[0132] Methods provided in this disclosure can effectively reduce the impact of a conductive object on a touch display device, so that a stylus can still perform an accurate clock synchronization with the touch display device even under a significant uplink signal attenuation caused by the conductive object. By the methods, the stylus is able to obtain a correct device ID no matter an attenuated uplink signal or an unattenuated uplink signal is received. For example, in a method, once receiving an uplink signal, the stylus can determine whether a preamble of an uplink code included in the uplink signal is a predetermined preamble (or a complementary code of the predetermined preamble). Once the stylus determines that the preamble of the uplink code included in the uplink signal is the predetermined preamble (or the complementary code of the predetermined preamble), the stylus can obtain a correct device ID based on the uplink code. The correct device ID corresponds to a correct touch display device that stylus needs to cooperate with. Based on the correct device ID, the stylus can perform a clock synchronization with the correct touch display device based on a Bluetooth connection between the stylus and the correct touch display device.

[0133] Aspects of the disclosure provide a stylus. Processing circuitry of the stylus is configured to receive an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtain an uplink code from the uplink signal. The uplink code includes a preamble code. In response to a determination that the preamble code is a complementary code of a preset preamble code, the process circuitry is configured to perform a clock synchronization based on the Bluetooth connection of the touch display device, and send touch input information of the stylus to the touch display device based on the clock synchronization.

[0134] In an embodiment, the processing circuitry is configured to perform the clock synchronization based on a timestamp of the Bluetooth connection of the touch display device.

[0135] In an embodiment, the processing circuitry is configured to send the touch input information of the stylus by sending a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes the touch input information of the stylus.

[0136] In an embodiment, the processing circuitry is further configured to determine whether the touch display device is a main device of the stylus. In response to determining that the touch display device is not a main device of the stylus, the processing circuitry is configured to assign the touch display device as the main device of the stylus.

[0137] In an embodiment, the processing circuitry is configured to determine whether the touch display device is the main device of the stylus by determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, the processing circuitry is configured to determine that the touch display device is the main device of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, the processing circuitry is configured to determine that the touch display device is not the main device of the stylus.

[0138] In an embodiment, the processing circuitry is configured to assign the touch display device as the main device of the stylus by assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

[0139] In an embodiment, the processing circuitry is configured to assign the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus by reducing a Bluetooth connection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

[0140] In an embodiment, the processing circuitry is further configured to receive another uplink signal from another touch display device that is in another Bluetooth connection with the stylus, and obtain another uplink code from the other uplink signal. The other uplink code includes another preamble code. In response to a determination that the other preamble code is the preset preamble code, the processing circuitry is configured to assign the other touch display device as a main device of the stylus, perform another clock synchronization based on the other Bluetooth connection of the other touch display device, and send other touch input information of the stylus to the other touch display device based on the other clock synchronization.

[0141] In an embodiment, the touch input information includes at least one of position information or tilt information of the stylus.

[0142] Aspects of the disclosure provide a method for a stylus to perform a clock synchronization with a touch display device. The method includes receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtaining anuplink code from the uplink signal. The uplink code includes a preamble code. In response to a determination that the preamble code is a complementary code of a preset preamble code, the method includes performing a clock synchronization based on the Bluetooth connection of the touch display device, and sending touch input information of the stylus to the touch display device based on the clock synchronization.

[0143] In an embodiment, the clock synchronization is performed based on a timestamp of the Bluetooth connection of the touch display device.

[0144] In an embodiment, the sending the touch input information of the stylus includes sending a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes the touch input information of the stylus.

[0145] In an embodiment, the method further includes determining whether the touch display device is a main device of the stylus. In response to determining that the touch display device is not a main device of the stylus, the method includes assigning the touch display device as the main device of the stylus.

[0146] In an embodiment, the determining whether the touch display device is the main device of the stylus includes determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, the method includes determining that the touch display device is the main device of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, the method includes determining that the touch display device is not the main device of the stylus.

[0147] In an embodiment, the assigning the touch display device as the main device of the stylus includes assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

[0148] In an embodiment, the assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus includes reducing a Bluetooth connection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

[0149] In an embodiment, the method further includes receiving another uplink signal from another touch display device that is in another Bluetooth connection with the stylus, and obtaining another uplink code from the other uplink signal. The other uplink code includes another preamble code. In response to a determination that the other preamble code is the preset preamble code, the method includes assigning the other touch display device as a main device of the stylus, performing another clock synchronization based on the other Bluetooth connection of the other touch display device, and sending other touch input information of the stylus to the other touch display device based on the other clock synchronization.

[0150] In an embodiment, the touch input information includes at least one of position information or tilt information of the stylus.

[0151] Aspects of the disclosure provide a non-transitory computer-readable storage medium including computer executable instructions, wherein the instructions, when executed by a stylus, cause the stylus to perform a method. The method includes receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtaining an uplink code from the uplink signal. The uplink code includes a preamble code. In response to a determination that the preamble code is a complementary code of a preset preamble code, the method includes performing a clock synchronization based on the Bluetooth connection of the touch display device, and sending touch input information of the stylus to the touch display device based on the clock synchronization.

[0152] In an embodiment, the clock synchronization is performed based on a timestamp of the Bluetooth connection of the touch display device.

[0153] In an embodiment, the sending the touch input information of the stylus includes sending a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes the touch input information of the stylus.

[0154] In an embodiment, the method further includes determining whether the touch display device is a main device of the stylus. In response to determining that the touch display device is not a main device of the stylus, the method includes assigning the touch display device as the main device of the stylus.

[0155] In an embodiment, the determining whether the touch display device is the main device of the stylus includes determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus. In responseto determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, the method includes determining that the touch display device is the main device of the stylus. In response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, the method includes determining that the touch display device is not the main device of the stylus.

[0156] In an embodiment, the assigning the touch display device as the main device of the stylus includes assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

[0157] In an embodiment, the assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus includes reducing a Bluetooth connection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

[0158] In an embodiment, the method further includes receiving another uplink signal from another touch display device that is in another Bluetooth connection with the stylus, and obtaining another uplink code from the other uplink signal. The other uplink code includes another preamble code. In response to a determination that the other preamble code is the preset preamble code, the method includes assigning the other touch display device as a main device of the stylus, performing another clock synchronization based on the other Bluetooth connection of the other touch display device, and sending other touch input information of the stylus to the other touch display device based on the other clock synchronization.

[0159] In an embodiment, the touch input information includes at least one of position information or tilt information of the stylus.

[0160] Aspects of the disclosure provide a stylus. Processing circuitry of the stylus is configured to receive an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtain an uplink code from the uplink signal. The uplink code includes a preamble code. The processing circuitry is configured to determine that the preamble code is a complementary code of a preset preamble code. The processing circuitry is configured to perform a clock synchronization using the Bluetooth connection of the touch display device based on the preamble code being the complementary code of the preset preamble code. Theprocessing circuitry is configured to send touch input information of the stylus to the touch display device based on the clock synchronization.

[0161] Aspects of the disclosure provide a method for a stylus to perform a clock synchronization with a touch display device. The method includes receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtaining an uplink code from the uplink signal. The uplink code includes a preamble code. The method includes determining that the preamble code is a complementary code of a preset preamble code. The method includes performing a clock synchronization using the Bluetooth connection of the touch display device based on the preamble code being the complementary code of the preset preamble code. The method includes sending touch input information of the stylus to the touch display device based on the clock synchronization.

[0162] Aspects of the disclosure provide a non-transitory computer-readable storage medium including computer executable instructions, wherein the instructions, when executed by a stylus, cause the stylus to perform a method. The method includes receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, and obtaining an uplink code from the uplink signal. The uplink code includes a preamble code. The method includes determining that the preamble code is a complementary code of a preset preamble code. The method includes performing a clock synchronization using the Bluetooth connection of the touch display device based on the preamble code being the complementary code of the preset preamble code. The method includes sending touch input information of the stylus to the touch display device based on the clock synchronization..

[0163] 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.

Claims

WHAT IS CLAIMED IS:

1. A stylus, comprising: processing circuitry configured to receive an uplink signal from a touch display device that is in a Bluetooth connection with the stylus, obtain an uplink code from the uplink signal, the uplink code including a preamble code, and in response to a determination that the preamble code is a complementary code of a preset preamble code, perform a clock synchronization based on the Bluetooth connection of the touch display device, and send touch input information of the stylus to the touch display device based on the clock synchronization.

2. The stylus of claim 1, wherein the processing circuitry is configured to perform the clock synchronization based on a timestamp of the Bluetooth connection of the touch display device.

3. The stylus of claim 1, wherein the processing circuitry is configured to send the touch input information of the stylus by sending a downlink signal to the touch display device based on the clock synchronization, the downlink signal including the touch input information of the stylus.

4. The stylus of claim 1, wherein the processing circuitry is further configured to determine whether the touch display device is a main device of the stylus, and in response to determining that the touch display device is not a main device of the stylus, assign the touch display device as the main device of the stylus.

5. The stylus of claim 4, wherein the processing circuitry is configured todetermine whether the touch display device is the main device of the stylus by determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus, and in response to determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, determine that the touch display device is the main device of the stylus, and in response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, determine that the touch display device is not the main device of the stylus.

6. The stylus of claim 5, wherein the processing circuitry is configured to assign the touch display device as the main device of the stylus by assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

7. The stylus of claim 6, wherein the processing circuitry is configured to assign the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus by reducing a Bluetooth connection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

8. The stylus of claim 1, wherein the processing circuitry is further configured to receive another uplink signal from another touch display device that is in anotherBluetooth connection with the stylus, obtain another uplink code from the other uplink signal, the other uplink code including another preamble code, and in response to a determination that the other preamble code is the preset preamble code, assign the other touch display device as a main device of the stylus, perform another clock synchronization based on the other Bluetooth connection of the other touch display device, and send other touch input information of the stylus to the other touch display device based on the other clock synchronization.

9. The stylus of claim 1, wherein the touch input information includes at least one of position information or tilt information of the stylus.

10. A method for a stylus to perform a clock synchronization with a touch display device, the method comprising: receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus; obtaining an uplink code from the uplink signal, the uplink code including a preamble code; and in response to a determination that the preamble code is a complementary code of a preset preamble code, performing a clock synchronization based on the Bluetooth connection of the touch display device, and sending touch input information of the stylus to the touch display device based on the clock synchronization.

11. The method of claim 10, wherein the clock synchronization is performed based on a timestamp of the Bluetooth connection of the touch display device.

12. The method of claim 10, wherein the sending the touch input information of the stylus comprises sending a downlink signal to the touch display device based on the clock synchronization, the downlink signal including the touch input information of the stylus.

13. The method of claim 10, further comprising: determining whether the touch display device is a main device of the stylus, and in response to determining that the touch display device is not a main device of the stylus, assigning the touch display device as the main device of the stylus.

14. The method of claim 13, whereinthe determining whether the touch display device is the main device of the stylus comprises determining whether a priority of the Bluetooth connection of the touch display device is a highest priority for Bluetooth communication of the stylus; and in response to determining that the priority of the Bluetooth connection of the touch display device is the highest priority for the Bluetooth communication of the stylus, determining that the touch display device is the main device of the stylus, and in response to determining that the priority of the Bluetooth connection of the touch display device is not the highest priority for the Bluetooth communication of the stylus, determining that the touch display device is not the main device of the stylus.

15. The method of claim 14, wherein the assigning the touch display device as the main device of the stylus comprises assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus.

16. The method of claim 15, wherein the assigning the priority of the Bluetooth connection to be the highest priority for the Bluetooth communication of the stylus comprises reducing a Bluetooth connection interval of the Bluetooth connection to a shortest connection interval for the Bluetooth communication of the stylus.

17. The method of claim 10, further comprising: receiving another uplink signal from another touch display device that is in another Bluetooth connection with the stylus; obtaining another uplink code from the other uplink signal, the other uplink code including another preamble code; and in response to a determination that the other preamble code is the preset preamble code, assigning the other touch display device as a main device of the stylus, performing another clock synchronization based on the other Bluetooth connection of the other touch display device, and sending other touch input information of the stylus to the other touch display device based on the other clock synchronization.

18. The method of claim 10, wherein the touch input information includes at least one of position information or tilt information of the stylus.

19. A non-transitory computer-readable storage medium including computer executable instructions, wherein the instructions, when executed by a stylus, cause the stylus to perform a method, the method comprising: receiving an uplink signal from a touch display device that is in a Bluetooth connection with the stylus; obtaining an uplink code from the uplink signal, the uplink code including a preamble code; and in response to a determination that the preamble code is a complementary code of a preset preamble code, performing a clock synchronization based on the Bluetooth connection of the touch display device, and sending touch input information of the stylus to the touch display device based on the clock synchronization.

20. The non-transitory computer-readable storage medium of claim 19, wherein the clock synchronization is performed based on a timestamp of the Bluetooth connection of the touch display device.

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