Clock synchronization between a stylus and a touch display device

Abstract

A stylus, a method, and a computer-readable medium that perform, within a time period, a clock synchronization of the stylus with a touch display device based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus, perform, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus, and send a downlink signal to the touch display device based on the clock synchronization, the downlink signal including touch input information of the stylus.

Description

CLOCK SYNCHRONIZATION BETWEEN A STYLUS AND A TOUCH DISPLAY DEVICECROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 616,101, 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 perform, within a time period, a clock synchronization of the stylus with a touch display device based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus. The processing circuitry is configured to perform, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus. The processing circuitry is configured to also send a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes touch input information of the stylus.

[0005] In an embodiment, the uplink signal indicates a device identification of the touch display device, and the processing circuitry is configured to determine the time period based on the device identification of the touch display device.

[0006] In an embodiment, the time period is predetermined.

[0007] In an embodiment, the processing circuitry is configured to determine whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus. If the processing circuitry determines that the Bluetooth connection of the touch display device has the highest priority for the Bluetooth communicationof the stylus, the processing circuitry is configured to determine the time period as a first time period. If the processing circuitry determines that the Bluetooth connection of the touch display device does not have the highest priority for the Bluetooth communication of the stylus, the processing circuitry is configured to assign a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determines the time period as a second time period. In an example, the second time period is longer than the first time period. In an example, the processing circuitry is configured to assign the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

[0008] In an embodiment, the processing circuitry is configured to determine whether uplink signals are continuously received within the time period from the touch display device. If the processing circuitry determines that the uplink signals are not continuously received within the time period, the processing circuitry is configured to set the stylus to be in a stylus discovery mode to scan for the uplink signals.

[0009] In an embodiment, the processing circuitry is configured to determine a signal strength of the Bluetooth connection. If the signal strength is greater than or equal to a first signal strength threshold, the processing circuitry is configured to instruct the touch display device to start sending the uplink signal. If the signal strength is less than or equal to a second signal strength threshold, the processing circuitry is configured to instruct the touch display device to stop sending the uplink signal. In an example, the first signal strength threshold is greater than the second signal strength threshold.

[0010] In an embodiment, the processing circuitry is configured to instruct one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus.

[0011] Aspects of the disclosure provide a method for a stylus to perform a clock synchronization with a touch display device. The method includes performing, within a time period, the clock synchronization based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus. The method includes performing, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus. The method includes sending a downlink signal to the touchdisplay device based on the clock synchronization. The downlink signal includes touch input information of the stylus.

[0012] In an embodiment, the uplink signal indicates a device identification of the touch display device, and the method includes determining the time period based on the device identification of the touch display device.

[0013] In an embodiment, the time period is predetermined.

[0014] In an embodiment, the method includes determining whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus. In response to a determination that the Bluetooth connection of the touch display device has the highest priority for the Bluetooth communication of the stylus, the method includes determining the time period as a first time period. In response to a determination that the Bluetooth connection of the touch display device does not have the highest priority for the Bluetooth communication of the stylus, the method includes assigning a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determining the time period as a second time period. In an example, the second time period is longer than the first time period. In an example, the method includes assigning the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

[0015] In an embodiment, the method includes determining whether uplink signals are continuously received within the time period from the touch display device. In response to a determination that the uplink signals are not continuously received within the time period, the method includes setting the stylus to be in a stylus discovery mode to scan for the uplink signals.

[0016] In an embodiment, the method includes determining a signal strength of the Bluetooth connection. If the signal strength is greater than or equal to a first signal strength threshold, the method includes instructing the touch display device to start sending the uplink signal. If the signal strength is less than or equal to a second signal strength threshold, the method includes instructing the touch display device to stop sending the uplink signal. In an example, the first signal strength threshold is greater than the second signal strength threshold.

[0017] In an embodiment, the method includes instructing one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus.

[0018] 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

[0019] 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:

[0020] FIG. 1 shows a touch sensing system according to embodiments of the disclosure;

[0021] FIG. 2 shows a clock synchronization between a stylus and a touch display device according to embodiments of the disclosure;

[0022] FIG. 3 shows an example of a palm rejection issue according to embodiments of the disclosure;

[0023] FIG. 4 shows a flowchart illustrating a process of performing a clock synchronization using both uplink signals and Bluetooth connection according to embodiments of the disclosure;

[0024] FIG. 5 shows a timing diagram illustrating Bluetooth connection interval (CI) changes of devices A and B each in a respective Bluetooth connection with a stylus according to embodiments of the disclosure;

[0025] FIG. 6 shows an example of start / stop sending uplink signals according to embodiments of the disclosure;

[0026] FIG. 7 shows a diagram of coverage areas of a stylus according to embodiments of the disclosure;

[0027] FIG. 8 shows an example of switching from a stylus discovery mode to a stylus operation mode when a stylus approaches a main device of a stylus according to embodiments of the disclosure;

[0028] FIG. 9 shows an example of switching from a stylus discovery mode to a stylus operation mode when a stylus approaches an auxiliary device of the stylus according to embodiments of the disclosure;

[0029] FIG. 10 shows an example of requesting a device to start / stop sending uplink signals to a stylus according to embodiments of the disclosure;

[0030] FIG. 11 shows an example of stopping sending uplink signals by a device itself when a Bluetooth connection between the device and a stylus is lost according to embodiments of the disclosure;

[0031] FIG. 12 shows an example of how a stylus enters a stylus operation mode according to embodiments of the disclosure:

[0032] FIG. 13 shows a flowchart illustrating a process 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 thelike. 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 canreceive 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 1 10 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 circuit chip. 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 1 10), 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 forclock 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 not exceed 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. In addition to the uplink code, the stylus can detect beacons included in the uplink signals. Based on the beacons included in the uplink signals, the stylus can perform a 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.

[0060] 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.

[0061] 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 cooperationbetween 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.

[0062] 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.

[0063] 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 and performed. During the cooperation, the touch display device can receive a touch input from the stylus.

[0064] 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.

[0065] 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. However, a palm rejection issue may occur if the clock synchronization is performed only via the uplink signals.

[0066] FIG. 3 shows an example of a palm rejection issue according to embodiments of the disclosure. In FIG. 3, a clock synchronization between a touch display device 310 and a stylus 320 is performed only via uplink signals that are sent from the touch display device 310 to the stylus 320. A palm 330 on a touchscreen of the touch display device 310 can degrade the signal strength of the uplink signals so that the stylus 320 may not correctly receive the uplink signals and the clock synchronization may not be correctly performed. Accordingly, the cooperation between the touch display device 310 and the stylus 320 may be affected or disturbed. It is noted that the palm 330 is used to illustrate the palm rejection issue and should not be limited in this disclosure, as any conductive material on the touch display device 320 may cause the performance degradation of the uplink signals.

[0067] In order to resolve the palm rejection issue, this disclosure provides methods of the clock synchronization. In a method, the clock synchronization can be performed first via the uplink signals and then via the Bluetooth connection between the touch display device and the stylus. This method addresses the palm rejection issue without losing the benefit of using the uplink signals for the clock synchronization. That is, by using the method, both the palm rejection issue and the ink latency of the stylus can be minimized. Accordingly, the clock synchronization can be well maintained even when the palm 330 is on the touchscreen of the touch display device 310, and the cooperation between the stylus 320 and the touch display device 310 can be performed based on the well-maintained clock synchronization.

[0068] FIG. 4 shows a flowchart illustrating a process 400 of performing a clock synchronization using both uplink signals and Bluetooth connection according to embodiments of the disclosure. The process 400 can be implemented by processing circuitry (e.g., processing circuitry 122) of a stylus (e.g., stylus 120). The process 400 can be implemented as instructions stored in a non-transitory computer-readable medium. When executed by an apparatus (e.g., stylus 120), the instructions can cause the apparatus to perform the process 400. The process 400 may start at step S410.

[0069] At step S410, the process 400 can set the stylus to be in a stylus discovery mode to scan for uplink signals from one or more touch display devices that are Bluetooth connected to the stylus. When the stylus receives an uplink signal from one device (e.g., touch display device 110) of the one or more touch display devices, the stylus can proceed to step S420.

[0070] At step S420, the process 400 can determine whether the touch display device is a main device of the stylus. The main device has the highest Bluetooth communication priority with the stylus among all the one or more devices that are Bluetooth connected to the stylus. That is, a Bluetooth connection between the main device and the stylus has the highest priority among the Bluetooth connections between the stylus and all the one or more devices that are Bluetooth connected to the stylus. A connection interval (CI) of the Bluetooth connection between the main device and the stylus is the shortest among the Cis of the Bluetooth connections between the stylus and all one or more devices that are Bluetooth connected to the stylus. A Bluetooth CI is a time period between two data transfer events of a Bluetooth connection between two devices.

[0071] In an embodiment, the uplink signal can indicate an uplink code that is assigned by the stylus to the touch display device. Based on the uplink code, the stylus can obtain a device ID of the touch display device and determine whether the touch display device is the main device of the stylus based on the device ID of the touch display device.

[0072] At step S430, in response to a determination that the touch display device is the main device of the stylus, the process 400 can perform a clock synchronization with the touch display device via the uplink signals for a first time period and enter a stylus operation mode. Then, the process 400 can proceed to step S450.

[0073] At step S440, in response to a determination that the touch display device is not the main device of the stylus, the process 400 can set the touch display device as the main device of the stylus, perform a clock synchronization with the touch display device via the uplink signals for a second time period, and enter the stylus operation mode. Then, the process 400 can proceed to step S460.

[0074] In an embodiment, the first time period can be shorter than the second time period. For example, the first and second time periods can be 1 frame and 50 frames of uplink signal, respectively.

[0075] In an embodiment, one or both of the first and second time periods can be predetermined. In an example, the first and second time periods can be predetermined to be 1 frame and 50 frames of uplink signals, respectively. In an example, the first time period can be predetermined to be 1 frame of uplink signal, and the second time period can vary depending on the Bluetooth CI of the touch display device. For example, the second time period for the touch display device B 111 in FIG. 1 can be different from that for the touch display device C 112 in FIG. 1, although none of the touch display devices B i l l and C 112 is the main device of the stylus.

[0076] At step S450, the process 400 can determine, within the first time period, whether the uplink signals are continuously received from the touch display device. If the uplink signals are not continuously received within the first time period, the process 400 can proceed to step S410. Otherwise, the process 400 can determine whether the first time period is exceeded. If the first time period is exceeded, the process 400 can proceed to step S470.

[0077] At step S460, the process 400 can determine, within the second time period, whether the uplink signals are continuously received from the touch display device. If the uplink signals are not continuously received within the second time period, the process 400 can proceed to step S410. Otherwise, the process 400 can determine whether the second time period is exceeded. If the second time period is exceeded, the process 400 can proceed to step S470.

[0078] At step S470, the process 400 can switch the clock synchronization via the uplink signals to the clock synchronization via a Bluetooth connection between the stylus and the touch display device. Then, the process 400 can proceed to step S480.

[0079] In an embodiment, the process 400 can perform the clock synchronization using Bluetooth timestamps of the Bluetooth connection.

[0080] At step S480, the process 400 can determine whether an uplink signal or a pressure signal is received from the touch display device. If the uplink signal or the pressure signal is received, the process 400 can proceed to step S490. Otherwise, the process 400 can proceed to step S410.

[0081] At step S490, in response to a determination that the uplink signal or the pressure signal is received, the process 400 can determine that the stylus remains in the stylus operation mode and proceed to step S480 in order to continuously monitor the uplink signal or the pressure signal.

[0082] It can be seen that by first using the uplink signals and then using the Bluetooth connection, the clock synchronization can be correctly performed even with the palm rejection issue during the cooperation between the stylus and the touch display device.

[0083] Further, the methods provided in this disclosure can be used for seamlessly switching a cooperation of stylus among multiple touch display devices.

[0084] In the related art, switching a cooperation of a stylus from a first touch display device to a second touch display device is performed by a manual unpairing and pairing. That is, if a user wants a stylus that is currently cooperated with a first touch display device to cooperate with a second touch display device, the user has to first manually unpair the stylus from the first touch display device and then pair the stylus to the second touch display device. This manual operation limits the seamless cooperation of the stylus among multiple touch display devices.

[0085] According to aspects of the disclosure, a stylus can Bluetooth connect to multiple touch display devices and one of the multiple touch display devices can be selected by the stylus as a main device of the stylus. Other touch display device(s) can be assigned by the stylus as auxiliary (or secondary) device(s). The main device of the stylus can have the highest Bluetooth communication priority and the shortest Bluetooth CI among the multiple touch display devices. The Bluetooth Cis of other touch display devices can be the same or different.

[0086] In an embodiment, when the stylus starts to perform a clock synchronization with a touch display device, depending on a Bluetooth CI of the touch display device, the stylus can determine a number of frames of uplink signals used for the clock synchronization via the uplink signals. After performing the clock synchronization via the number of frames of uplink signals, the stylus can perform the clock synchronization via a Bluetooth connection between the stylus and the touch display device. For example, the stylus can use Bluetooth timestamps for the clock synchronization.

[0087] FIG. 5 shows a timing diagram 500 illustrating Bluetooth CI changes of devices A and B each in a respective Bluetooth connection with a stylus according to embodiments of the disclosure.

[0088] At timestamp tO, the stylus (e.g., stylus 120) can begin a cooperation with device A (e.g., touch display device 110) by assigning devices A and B (e.g., touch display device 111) as main and auxiliary devices, respectively. A Bluetooth CI of a main device is shorter than a Bluetooth CI of an auxiliary device. Accordingly, the Bluetooth Cis of devices A and B are setas T1 and T2, respectively, wherein T1 is less than T2. In an example, T1 and T2 can be 16.6ms and 400ms, respectively.

[0089] At timestamp tl, the stylus can move close to device B (e.g., within the communication range) and receive an uplink signal from device B. The stylus can determine a number of frames of uplink signals based on the Bluetooth CI T2, and perform a clock synchronization with device B within a time period of the number of frames of uplink signals.

[0090] For example, based on the Bluetooth CI T2, the stylus can calculate a timestamp t2 for transmitting a next Bluetooth signal to device B, and calculate a time difference At between the timestamps t2 and tl . Based on the time difference At and the frequency of the uplink signal, the stylus can calculate the number of frames of uplink signals for the clock synchronization via the uplink signals.

[0091] At timestamp t2, the stylus can set devices A and B as the auxiliary and main devices, respectively. The stylus can adjust the Bluetooth Cis of devices A and B as T2 and Tl, respectively.

[0092] It is noted that the stylus can also be in a Bluetooth connection with device C (e.g., touch display device 112) while being in the Bluetooth connections with devices A and B. The stylus can assign device C as an auxiliary device and set a Bluetooth CI of device C as T2 or T3, wherein T3 is greater than Tl and different from T2.

[0093] According to an embodiment of the disclosure, the stylus can request a touch display device to start / stop sending uplink signals, in order to save power for the touch display device.

[0094] FIG. 6 shows an example of start / stop sending uplink signals according to embodiments of the disclosure. FIG. 6 presents a process 600 for a stylus (e.g., stylus 120) to request a touch display device (e.g., touch display device 110) to turn on / off the sending of uplink signals based on a signal strength of the touch display device. For example, the signal strength can be received signal strength indicator (RSSI) of the touch display device. The process 600 can be implemented by processing circuitry (e.g., processing circuitry 122) of the stylus.

[0095] The process 600 may start at step S610, at which the process 600 can detect the RSSI of the touch display device.

[0096] If the touch display device is not sending the uplink signals, the process 600 can determine whether the RSSI of the touch display device is greater than or equal to a first signal strength threshold N. In response to a determination that the RSSI of the touch display device is greater than or equal to the first signal strength threshold N, the stylus can request the touch display device to turn on the sending of the uplink signals, at step S620.

[0097] If the touch display device is sending the uplink signals, the process 600 can determine whether the RSSI of the touch display device is less than or equal to a second signal strength threshold M. In response to a determination that the RSSI of the touch display device is less than or equal to the second signal strength threshold M, the stylus can request the touch display device to turn off the sending of the uplink signals, at step S630.

[0098] As shown in the diagram 650, the first signal strength threshold N is greater than the second signal strength threshold M.

[0099] In an embodiment, after confirming that the touch display device turns off the sending of the uplink signals, the stylus can increase a Bluetooth CI of the touch display device for power saving.

[0100] It is noted that the RSSI is only for illustration and is not limited in this disclosure. The signal strength can include, but is not limited to, reference signal received power (RSRP) or reference signal received quality (RSRQ).

[0101] FIG. 7 shows a diagram illustrating coverage areas of a stylus 701 (e.g., stylus 120) according to embodiments of the disclosure. In FIG. 7, the stylus 701 can have three coverage areas 710, 720, and 730, each having a solid round shape for example. A first coverage area 710 is included by a second coverage area 720, and both are included by a third coverage area 730.

[0102] In an embodiment, if a touch display device (e.g., touch display device A 702 or B 703) is in the first coverage area 710, a signal strength (e.g., RSSI) of the touch display device can be considered to be greater than or equal to the first signal strength threshold N as shown in FIG. 6, and then the stylus 701 can require the touch display device to start sending uplink signals.

[0103] In an embodiment, if a touch display device (e.g., touch display device D 705) is outside the second coverage area 720, the signal strength of the touch display device can beconsidered to be less than or equal to the second signal strength threshold M as shown in FIG. 6, and then the stylus 701 can require the touch display device to stop sending uplink signals.

[0104] In an embodiment, if the touch display device (e.g., touch display device E 706) is outside the third coverage area 730, the Bluetooth connection between the touch display device and the stylus 701 can be considered to be lost, and the touch display device can be considered as offline for the stylus 701. If the touch display device (e.g., touch display device D 705) is in the third coverage area 730, the Bluetooth connection between the touch display device and the stylus 701 can be considered to be maintained, and the touch display device can be considered as online for the stylus 701.

[0105] In FIG. 7, touch display devices A 702 and B 703 (e.g., touch display devices 110 and 111) are inside the first coverage area 710 of the stylus 701. In the first coverage area 710, an RSSI of a touch display device can be considered to be greater than or equal to the first signal strength threshold N. A touch display device C 704 (e.g., touch display devices 112) is outside the first coverage area 710 and inside a second coverage area 720 of the stylus 701. In the second coverage area 720, an RSSI of a touch display device can be considered to be greater than or equal to the second signal strength threshold M. A touch display device D 705 is outside the second coverage area 720 and inside a third coverage area 730 of the stylus 701 . In the third coverage area 730, a Bluetooth connection can be maintained. That is, a touch display device E 706, which is outside the third coverage area 730, loses a Bluetooth connection with the stylus 701 and thus can be considered as offline.

[0106] In an embodiment, radiuses of the three coverage areas 710-730 can be Im, 4m, and 10m, respectively.

[0107] In FIG. 7, once a touch display device is Bluetooth connected to the stylus 701, the stylus 701 can assign an uplink code to the touch display device via the Bluetooth connection between the stylus and the touch display device. The uplink code can correspond to a device ID of the touch display device. Accordingly, the stylus 701 can assign a different uplink code to each of the touch display devices A-D and instruct the touch display devices A-D to start sending uplink signals, based on the touch display devices A-D being located inside the third coverage area 730. The stylus 701 can measure the RSSIs of the touch display devices A-D and instruct the touch display device D 705 to turn off the sending of the uplink signals based on the touch display device D 705 being located outside the second coverage area 720.

[0108] In an embodiment, in response to the touch display device C 704 being moved out of the second coverage area 720, the stylus 701 can instruct the touch display device C 704 to turn off the sending of the uplink signals.

[0109] In an embodiment, the stylus 701 can set the touch display device A 702 as a main device of the stylus 701, and then can be moved close to the touch display device B 703. When the stylus 701 detects an uplink signal from the touch display device B 703, the stylus 701 can perform, within a time period (e.g., 50 frames of uplink signal), a clock synchronization with the touch display device B 703 via uplink signals sent from the touch display device B 703 to the stylus 701, and enter a stylus operation mode. After the time period, the stylus 701 can switch to use Bluetooth timestamps for performing the following clock synchronization.

[0110] In an embodiment, based on the status of the stylus, for example when the stylus 701 is idle or charging, the stylus 701 can instruct all connecting devices to turn off the sending of the uplink signals in order to preserve battery power.[OHl] FIG. 8 shows an example of switching from a stylus discovery mode to a stylus operation mode when a stylus (e.g., stylus 120) approaches a main device of the stylus according to embodiments of the disclosure. In FIG. 8, the stylus 120 can Bluetooth connect to three touch display devices A-C 1 10-112 and assign uplink codes 01 , 10, and 11 to the devices A-C 1 10-112, respectively.

[0112] First, as shown in the diagram 800, the stylus 120 can be in a stylus discovery mode. The device A 110 can be a main device of the stylus 120 and a Bluetooth CI of the device A 110 can be set to be the shortest Bluetooth CI (e.g., 16.6ms) among the devices A-C 110-112. The devices B 111 and C 112 are auxiliary devices of the stylus 120, and Bluetooth Cis of the devices B i l l and Cl 12 can be set to 400ms, for example. The stylus 120 can keep receiving Bluetooth timestamps from all devices. Each device can send uplink signals with its own device ID.

[0113] Then, as shown in the diagram 850, the stylus 120 can approach the device A 110 and detect the uplink signals from the device A 110, perform a clock synchronization with the device A 110 via the uplink signals, and enter a stylus operation mode. The stylus 120 can detect a device ID of the device A 110 from the uplink code 01 assigned to the device A 110 and determine that the device A 110 is the main device. After a first time period such as 1 frame ofuplink signal, the stylus 120 can switch to use timestamps of the Bluetooth connection with the device A 110 directly for performing the following clock synchronization.

[0114] FIG. 9 shows an example of switching from a stylus discovery mode to a stylus operation mode when a stylus (e.g., stylus 120) approaches an auxiliary device of the stylus according to embodiments of the disclosure. In FIG. 9, the stylus 120 can Bluetooth connect to three touch display devices A-C 110-112 and assign uplink codes 01, 10, and 11 to the devices A-C 110-112, respectively.

[0115] First, as shown in the diagram 900, the stylus 120 can be in a stylus discovery mode. The device A 110 can be a main device of the stylus 120 and a Bluetooth CI of the device A 110 can be set to be the shortest Bluetooth CI (e.g., 16.6ms) among the devices A-C 110-112. The devices B i l l and C 112 are auxiliary devices of the stylus 120, and Bluetooth Cis of the devices B i l l and Cl 12 can be set to 400ms, for example. The stylus 120 can keep receiving Bluetooth timestamps from all devices. Each device can send uplink signals with its own device ID.

[0116] Then, as shown in the diagram 950, the stylus 120 can approach the device B i l l and detect the uplink signals from the device B i l l, perform a clock synchronization with the device B i l l via the uplink signals, and enter a stylus operation mode. The stylus 120 can detect a device ID of the device B i l l from the uplink code 10 assigned to the device B i l l and determine that the device B 111 is not the main device. Thus, the stylus 120 can set the device B 111 as the main device by rising a Bluetooth communication priority of the device B 111 to the highest priority and by changing the Bluetooth CI of the device B 111 to the shortest Bluetooth CI (e.g., 16.6ms). During this time period, the stylus 120 can keep using uplink signals from the device B 111 for clock synchronization. Once the Bluetooth CI of the device B 111 is set to 16ms, then the stylus 120 can switch to use timestamps of the Bluetooth connection with the device B 111 for performing the following clock synchronization. In an embodiment, the whole switching process can be done within 50 frames of the uplink signals. Then, the stylus 120 can set the device A 110 as the auxiliary device.

[0117] FIG. 10 shows an example of requesting a device to start / stop sending uplink signals to a stylus (e.g., stylus 120) according to embodiments of the disclosure. Based on a Bluetooth RSSI of the device, the stylus 120 can request the device to turn on / off the sending of the uplink signals for saving power.

[0118] First, as shown in the diagram 1000, the stylus 120 can be in a stylus discovery mode. The device A 110 can be a main device (with an uplink code 01) of the stylus 120 and a Bluetooth CI of the device A 110 can be set to be the shortest Bluetooth CI (e.g., 16.6ms) among the devices A-C 110-112. The devices B i l l and C 112 are auxiliary devices of the stylus 120, and Bluetooth Cis of the devices B i l l and Cl 12 can be set to 400ms for example. The stylus 120 can keep receiving Bluetooth timestamps from all devices. The devices B i l l and C 112 can be far away (e.g., 5? 5 m away) from the stylus 120 (e.g., the devices B i l l and C 112 are outside of the second coverage area 720 in FIG. 7), and thus the Bluetooth RSSIs of the devices B i l l and C 112 are below the second signal strength threshold M (as shown in FIG. 6). The stylus 120 can request the devices B i l l and C 112 to turn off the sending of the uplink signals.

[0119] Then, as shown in the diagram 1050, the device B i l l can be moved close to (e g., Im close) the stylus 120 (e.g., the device B 111 is in the first coverage area 710 in FIG. 7), and the stylus 120 can determine that the Bluetooth RS SI of the device B 111 is high enough and above the first signal strength threshold N (as shown in FIG. 6). The stylus 120 can assign a device ID (corresponding to an uplink code 10) to the device B 111 via the Bluetooth connection between the stylus 120 and the device B i l l and request the device B 111 to turn on the sending of uplink signals. The uplink signals can include the uplink code 10 indicating the device ID of the device B i l l.

[0120] FIG. 11 shows an example of stopping the sending of uplink signals by a device itself, when a Bluetooth connection between the device and a stylus (e.g., stylus 120) is lost according to embodiments of the disclosure.

[0121] First, as shown in the diagram 1100, a Bluetooth connection between the stylus 120 and the device B i l l somehow breaks / is disrupted, and the device B I l l is still sending uplink signals. Then, as shown in the diagram 1150, the device B i l l can instruct (or inform) its touch driving circuitry to turn off the sending of uplink signals if the Bluetooth connection is not recovered within a time period threshold (e.g., 5s).

[0122] FIG. 12 shows an example of how a stylus (e.g., stylus 120) enters a stylus operation mode according to embodiments of the disclosure. In FIG, 12, as long as the stylus 120 detects an uplink signal or a pressure signal from its pressure sensor, then the stylus 120 can enter a stylus operation mode. The device A 110 is the main device of the stylus 120.

[0123] In the diagram 1200, the stylus 120 can detect both the pressure and uplink signals, and then the stylus 120 can enter the stylus operation mode.

[0124] In the diagram 1210, due to the palm rejection issue, the stylus 120 loses the uplink signal and only detects the pressure signal, and then the stylus 120 can enter the stylus operation mode. The stylus 120 can use the Bluetooth timestamps for the clock synchronization.

[0125] In the diagram 1220, the stylus 120 can detect the uplink signal and not detect the pressure signal, and then the stylus 120 can enter the stylus operation mode. Due to the device A 110 being the main device, the stylus 120 can perform the clock synchronization via the uplink signal for the first frame and then switch to use the Bluetooth timestamps for performing the following clock synchronization.

[0126] FIG. 13 shows a flowchart illustrating a process 1300 according to embodiments of the disclosure discussed above. The process 1300 can be implemented by processing circuitry (e.g., processing circuitry 122) of a stylus (e.g., stylus 120). The process 1300 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 1300. The process 1300 may start at step S1310.

[0127] At step SI 310, the process 1300 scans for uplink signals. Then, the process 1300 proceeds to step SI 320.

[0128] At step S1320, the process 1300 determines whether the stylus receives an uplink signal from a touch display device (e.g., touch display device 110) that is in a Bluetooth connection with the stylus. If the process 1300 determines that the stylus receives the uplink signal from the touch display device, the process 1300 proceeds to step S 1330. Otherwise, the process 1300 proceeds to step S1310.

[0129] At step S1330, the process 1300 determines a time period for a clock synchronization between the stylus and the touch display device. Then, the process 1300 proceeds to step SI 340.

[0130] In an embodiment, the uplink signal indicates a device identification of the touch display device, and the process 1300 determines the time period based on the device identification of the touch display device.

[0131] In an embodiment, however, the time period can be a predetermined time period that is set in advance.

[0132] In an embodiment, the process 1300 determines whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus. If the process 1300 determines that the Bluetooth connection of the touch display device has the highest priority for the Bluetooth communication of the stylus, the process 1300 determines the time period as a first time period. Otherwise, the process 1300 assigns a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determines the time period as a second time period. In an example, the second time period is longer than the first time period. In an example, the process 1300 assigns the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

[0133] At step S1340, the process 1300 performs, within the time period, the clock synchronization based on the uplink signal received from the touch display device. Then, the process 1300 proceeds to step S135O.

[0134] At step S1350, the process 1300 determines whether uplink signals are continuously received within the time period from the touch display device. If the process 1300 determines that the uplink signals are continuously received within the time period, the process 1300 proceeds to step SI 360. Otherwise, the process 1300 proceeds to step S1310 to set the stylus to be in a stylus discovery mode to scan for the uplink signals.

[0135] At step S1360, the process 1300 performs, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus. Then, the process 1300 proceeds to step S1370.

[0136] At step S1370, the process 1300 sends a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes touch input information of the stylus.

[0137] In an embodiment, the process 1300 determines a signal strength of the Bluetooth connection. If the signal strength is greater than or equal to a first signal strength threshold, the process 1300 informs (or instructs) the touch display device to start sending the uplink signal. If the signal strength is less than or equal to a second signal strength threshold, the process 1300 informs the touch display device to stop sending the uplink signal. In an example, the first signal strength threshold is greater than the second signal strength threshold.

[0138] In an embodiment, the process 1300 informs one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus. In an example, the status of the stylus indicates that the stylus is in a sleep mode, an idle mode, or a charging mode.

[0139] Aspects of the disclosure provide a stylus (e.g., stylus 120). Processing circuitry (e.g., processing circuitry 122) of the stylus is configured to perform, within a time period, a clock synchronization of the stylus with a touch display device (e.g., touch display device 110) based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus. The processing circuitry is configured to perform, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus. The processing circuitry is configured to send a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes touch input information of the stylus.

[0140] In an embodiment, the uplink signal indicates a device identification of the touch display device, and the processing circuitry is configured to determine the time period based on the device identification of the touch display device.

[0141] In an embodiment, the time period is predetermined.

[0142] In an embodiment, the processing circuitry is configured to determine whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus. If the processing circuitry determines that the Bluetooth connection of the touch display device has the highest priority for the Bluetooth communication of the stylus, the processing circuitry is configured to determine the time period as a first time period. Otherwise, the processing circuitry is configured to assign a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determine the time period as a second time period. In an example, the second time period is longer than the first time period. In an example, the processing circuitry is configured to assign the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

[0143] In an embodiment, the processing circuitry is configured to determine whether uplink signals are continuously received within the time period from the touch display device. If the processing circuitry determines that the uplink signals are not continuously received withinthe time period, the processing circuitry is configured to set the stylus to be in a stylus discovery mode to scan for the uplink signals.

[0144] In an embodiment, the processing circuitry is configured to determine a signal strength of the Bluetooth connection. If the signal strength is greater than or equal to a first signal strength threshold, the processing circuitry is configured to instruct the touch display device to start sending the uplink signal. If the signal strength is less than or equal to a second signal strength threshold, the processing circuitry is configured to instruct the touch display device to stop sending the uplink signal. In an example, the first signal strength threshold is greater than the second signal strength threshold.

[0145] In an embodiment, the processing circuitry is configured to instruct one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus. In an example, the status of the stylus indicates that the stylus is in a sleep mode, an idle mode, or a charging mode.

[0146] Aspects of the disclosure provide a method for a stylus to perform a clock synchronization with a touch display device. The method includes performing, within a time period, the clock synchronization based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus. The method includes performing, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus. The method includes sending a downlink signal to the touch display device based on the clock synchronization. The downlink signal includes touch input information of the stylus.

[0147] In an embodiment, the uplink signal indicates a device identification of the touch display device, and the method includes determining the time period based on the device identification of the touch display device.

[0148] In an embodiment, the time period is predetermined.

[0149] In an embodiment, the method includes determining whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus. In response to a determination that the Bluetooth connection of the touch display device has the highest priority for the Bluetooth communication of the stylus, the method includes determining the time period as a first time period. In response to a determination that the Bluetooth connection of the touch display device does not have the highest priority for theBluetooth communication of the stylus, the method includes assigning a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determining the time period as a second time period. In an example, the second time period is longer than the first time period. In an example, the method includes assigning the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

[0150] In an embodiment, the method includes determining whether uplink signals are continuously received within the time period from the touch display device. In response to a determination that the uplink signals are not continuously received within the time period, the method includes setting the stylus to be in a stylus discovery mode to scan for the uplink signals.

[0151] In an embodiment, the method includes determining a signal strength of the Bluetooth connection. If the signal strength is greater than or equal to a first signal strength threshold, the method includes instructing the touch display device to start sending the uplink signal. If the signal strength is less than or equal to a second signal strength threshold, the method includes instructing the touch display device to stop sending the uplink signal. In an embodiment, the first signal strength threshold is greater than the second signal strength threshold.

[0152] In an embodiment, the method includes instructing one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus. In an example, the status of the stylus indicates that the stylus is in a sleep mode, an idle mode, or a charging mode.

[0153] Aspects of the disclosure provide a non-transitory computer-readable storage medium including computer executable instructions. The instructions, when executed by a stylus, cause the stylus to perform a method. The method includes performing, within a time period, a clock synchronization based on an uplink signal received from a touch display device that is in a Bluetooth connection with the stylus. The method includes performing, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus. The method includes sending a downlink signal to the touch display device based on the clock synchronization, the downlink signal including touch input information of the stylus.

[0154] In an embodiment, the uplink signal indicates a device identification of the touch display device, and the method includes determining the time period based on the device identification of the touch display device.

[0155] In an embodiment, the time period is predetermined.

[0156] In an embodiment, the method includes determining whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus. In response to a determination that the Bluetooth connection of the touch display device has the highest priority for the Bluetooth communication of the stylus, the method includes determining the time period as a first time period. In response to a determination that the Bluetooth connection of the touch display device does not have the highest priority for the Bluetooth communication of the stylus, the method includes assigning a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determining the time period as a second time period. In an example, the second time period is longer than the first time period. In an example, the method includes assigning the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

[0157] In an embodiment, the method includes determining whether uplink signals are continuously received within the time period from the touch display device. In response to a determination that the uplink signals are not continuously received within the time period, the method includes setting the stylus to be in a stylus discovery mode to scan for the uplink signals.

[0158] In an embodiment, the method includes determining a signal strength of the Bluetooth connection. If the signal strength is greater than or equal to a first signal strength threshold, the method includes instructing the touch display device to start sending the uplink signal. If the signal strength is less than or equal to a second signal strength threshold, the method includes instructing the touch display device to stop sending the uplink signal. In an embodiment, the first signal strength threshold is greater than the second signal strength threshold.

[0159] In an embodiment, the method includes instructing one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus. In an example, the status of the stylus indicates that the stylus is in a sleep mode, an idle mode, or a charging mode.

[0160] 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 perform, within a time period, a clock synchronization of the stylus with a touch display device based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus, perform, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus, and send a downlink signal to the touch display device based on the clock synchronization, the downlink signal including touch input information of the stylus.

2. The stylus of claim 1, wherein the uplink signal indicates a device identification of the touch display device, and the processing circuitry is configured to determine the time period based on the device identification of the touch display device.

3. The stylus of claim 1 , wherein the time period is predetermined.

4. The stylus of claim 1, wherein the processing circuitry is configured to: determine whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus, in response to the Bluetooth connection of the touch display device having the highest priority for the Bluetooth communication of the stylus, determine the time period as a first time period, and in response to the Bluetooth connection of the touch display device not having the highest priority for the Bluetooth communication of the stylus, assign a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determine the time period as a second time period.

5. The stylus of claim 4, wherein the second time period is longer than the first time period.

6. The stylus of claim 4, wherein the processing circuitry is configured to assign the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

7. The stylus of claim 1, wherein the processing circuitry is configured to: determine whether uplink signals are continuously received within the time period from the touch display device, and in response to a determination that the uplink signals are not continuously received within the time period, set the stylus to be in a stylus discovery mode to scan for the uplink signals.

8. The stylus of claim 1, wherein the processing circuitry is configured to: determine a signal strength of the Bluetooth connection, in response to the signal strength being greater than or equal to a first signal strength threshold, instruct the touch display device to start sending the uplink signal, and in response to the signal strength being less than or equal to a second signal strength threshold, instruct the touch display device to stop sending the uplink signal.

9. The stylus of claim 8, wherein the first signal strength threshold is greater than the second signal strength threshold.

10. The stylus of claim 1, wherein the processing circuitry is configured to instruct one or more touch display devices that are Bluetooth connected to the stylus to stop sending uplink signals based on a status of the stylus.

11. A method for a stylus to perform a clock synchronization with a touch display device, the method comprising: performing, within a time period, the clock synchronization based on an uplink signal received from the touch display device that is in a Bluetooth connection with the stylus; performing, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus; andsending a downlink signal to the touch display device based on the clock synchronization, the downlink signal including touch input information of the stylus.

12. The method of claim 11, wherein the uplink signal indicates a device identification of the touch display device, and the method further comprises determining the time period based on the device identification of the touch display device.

13. The method of claim 11, wherein the time period is predetermined.

14. The method of claim 11, further comprising: determining whether the Bluetooth connection of the touch display device has a highest priority for Bluetooth communication of the stylus; in response to the Bluetooth connection of the touch display device having the highest priority for the Bluetooth communication of the stylus, determining the time period as a first time period; and in response to the Bluetooth connection of the touch display device not having the highest priority for the Bluetooth communication of the stylus, assigning a priority of the Bluetooth connection of the touch display device to be the highest priority for the Bluetooth communication of the stylus, and determining the time period as a second time period.

15. The method of claim 14, wherein the second time period is longer than the first time period.

16. The method of claim 14, wherein the assigning assigns the priority of the Bluetooth connection by reducing a Bluetooth connection interval of the Bluetooth connection.

17. The method of claim 11, further comprising: determining whether uplink signals are continuously received within the time period from the touch display device; andin response to a determination that the uplink signals are not continuously received within the time period, setting the stylus to be in a stylus discovery mode to scan for the uplink signals.

18. The method of claim 11, further comprising: determining a signal strength of the Bluetooth connection; in response to the signal strength being greater than or equal to a first signal strength threshold, instructing the touch display device to start sending the uplink signal; and in response to the signal strength being less than or equal to a second signal strength threshold, instructing the touch display device to stop sending the uplink signal.

19. The method of claim 18, wherein the first signal strength threshold is greater than the second signal strength threshold.

20. 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: performing, within a time period, a clock synchronization based on an uplink signal received from a touch display device that is in a Bluetooth connection with the stylus; performing, after the time period, the clock synchronization based on the Bluetooth connection between the touch display device and the stylus; and sending a downlink signal to the touch display device based on the clock synchronization, the downlink signal including touch input information of the stylus.

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