System and detection circuit based on DOCKING keyboard of tablet computer

Abstract

The utility model discloses a system and detection circuit based on a DOCKING keyboard of a tablet personal computer, and the detection circuit comprises a first detection module for detecting whether the keyboard is inserted or not, a first power supply, a control unit, a first resistor, a second resistor, a third resistor and a second detection module, the first detection module is respectively connected with a first end of the first resistor and a first end of the second resistor, a second end of the first resistor is connected with a first power supply, a second end of the second resistor is connected with the control unit, the second detection module is connected with GND through the third resistor, and the first detection module transmits a detected first detection result to the control unit. Compared with the prior art, when the tablet computer is in contact with the keyboard, whether the DOCKING keyboard is inserted or not is judged through an intermediate voltage value, and the problem of short circuit caused by wrong judgment due to short circuit of a detection pin and a ground pin is solved.

Description

Technical Field

[0001] The utility model relates to the field of tablet computer expansion equipment detection, in particular to a system and a detection circuit based on a tablet computer DOCKING keyboard. Background Art

[0002] The application scope of two-in-one tablet PC is very wide, which also means that the use environment is diverse and complex. Business people can use two-in-one tablet PC to check information, write documents, send emails, etc.; educational institutions can use it for online teaching, courseware display, student examinations, etc.; and ordinary users can also use it to browse the web, watch videos, play games and other security activities.

[0003] At present, the tablet module and DOCKING keyboard of the mainstream two-in-one tablet PC on the market are connected by POGO PIN connectors. There are five exposed metal contacts on the tablet end, and five elastic ejector pins on the DOCKING keyboard end. When the tablet and DOCKING keyboard are close to each other, the metal contacts and elastic ejector pins are in point-to-point contact through magnetic attraction and mechanical positioning slots, thus completing the physical connection of the two modules. After that, the tablet needs to perform electronic detection on the DOCKING keyboard to complete the tablet's recognition of the keyboard.

[0004] Currently, the more common detection method is: there is a metal contact with a high level on the tablet end, and the corresponding elastic pin on the DOCKING keyboard is a ground (GND) signal. When the two are in contact, the high level on the tablet end will be pulled down by the ground signal of the DOCKING keyboard. At this time, the tablet thinks that the keyboard is inserted, and then other contacts provide 5V power and USB (Universal Serial Bus) signals for the keyboard.

[0005] Since two-in-one tablet PCs have a wide range of application scenarios, in complex actual use, the metal contacts of the tablet are exposed outside the casing. When metal iron sheets or conductive liquids come into contact with multiple metal contacts (detection and ground) on the tablet end, the tablet will be triggered by error and release a 5V voltage that shorts with GND, thereby rendering the USB interface function ineffective and even damaging the PC. Utility Model Content

[0006] In view of the above technical problems, the utility model provides a system and a detection circuit based on a tablet computer DOCKING keyboard to avoid the above erroneous judgment caused by the short circuit between the detection pin and the ground pin.

[0007] The first embodiment of the utility model provides a detection circuit based on a DOCKING keyboard of a tablet computer, the detection circuit comprising a first detection module for detecting whether the keyboard is inserted, a first power supply, a control unit, a first resistor, a second resistor, a third resistor and a second detection module, the first detection module is respectively connected to the first end of the first resistor and the first end of the second resistor, the second end of the first resistor is connected to the first power supply, the second end of the second resistor is connected to the control unit, the second detection module is connected to GND through the third resistor, the first detection module transmits the detected first detection result to the control unit, and the control unit determines whether to power the keyboard according to the first detection result.

[0008] Optionally, the detection circuit also includes a second power supply and a power switch connected to the second power supply. When the control unit determines that the first detection result meets a preset condition, the control unit controls the power switch to turn on, and the second power supply supplies power to the keyboard.

[0009] Optionally, the control unit includes an analog-to-digital converter acquisition module, which is used to convert the acquired analog signal into a digital signal.

[0010] Optionally, a correspondence table between the first detection result and the numerical symbol is pre-stored in the control unit, and the preset condition is that the numerical symbol is within a preset range.

[0011] Optionally, the first detection module is a USB-DOCK-DET# pin located on the tablet computer.

[0012] Optionally, the second detection module is a DOCK_DET# pin located on the keyboard.

[0013] Optionally, the DOCK_DET# pin is connected to a GND terminal on the keyboard via a third resistor.

[0014] Optionally, the first resistor and the third resistor have equal resistance values.

[0015] A second embodiment of the utility model provides a system based on a tablet computer DOCKING keyboard, the system comprising a keyboard and a tablet computer, the tablet computer being provided with a second power supply, the second power supply being used to power the keyboard when the tablet computer detects that the keyboard is inserted, the system further comprising a data transmission module for data transmission between the keyboard and the tablet computer, and a signal detection circuit, the signal detection circuit comprising any of the above detection circuits based on the tablet computer DOCKING keyboard.

[0016] Optionally, the data transmission module is a USB_DN terminal and a USB_DP terminal located on the keyboard, and a USB_DN terminal and a USB_DP terminal located on the tablet computer.

[0017] In the technical solution provided by the embodiment of the utility model, the first detection module is respectively connected to the first end of the first resistor and the first end of the second resistor, the second end of the first resistor is connected to the first power supply, the second end of the second resistor is connected to the control unit, the second detection module is connected to GND through the third resistor, the first detection module transmits the detected first detection result to the control unit, and the control unit determines whether to power the keyboard according to the first detection result. Compared with the prior art, when the tablet computer and the keyboard are in contact, the detection signal of the tablet computer no longer changes from a high level to a low level, but uses an intermediate voltage value to determine whether the DOCKING keyboard is inserted, so as to avoid the problem of short circuit caused by erroneous judgment due to the short circuit between the detection pin and the ground pin. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the detection circuit based on the DOCKING keyboard of a tablet computer in the utility model;

[0019] Figure 2 It is a partial circuit diagram of the detection circuit of the tablet computer DOCKING keyboard based on the utility model;

[0020] Figure 3 This is another circuit diagram of the detection circuit of the tablet computer DOCKING keyboard based on the utility model. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0022] A two-in-one tablet PC is a device that can realize the full-featured applications of a traditional PC and the entertainment experience of a tablet PC. One device has the characteristics of both types of products. A two-in-one tablet PC usually consists of two parts: a tablet and a DOCKING keyboard (detachable keyboard). The DOCKING keyboard refers to an extended keyboard that can be quickly connected to a tablet by magnetic attraction. It is one of the components of a two-in-one tablet PC. This component can quickly switch the tablet into a notebook form to meet the needs of customer work scenarios.

[0023] POGO PIN is a kind of precision connector widely used in electronic products such as tablets, mobile phones, and electronic watches, which plays a connecting role. POGO PIN is a spring-type probe formed by riveting and pre-pressing three basic components: needle shaft, spring, and needle tube. It has a precise spring structure inside. GPIO is the abbreviation of general-purpose input / output. Its function is similar to the P0-P3 pins of 8051. Its pins can be freely used by users through program control. PIN pins can be used as general-purpose input (GPI) or general-purpose output (GPO) or general-purpose input and output (GPIO) according to practical considerations, such as clkgenerator, chip select, etc.

[0024] There are five metal contacts on the outside of the tablet case, and five elastic pins on the DOCKING keyboard. When the tablet is used as a PC, the five metal contacts will connect with the five POGO PINs of the DOCKING keyboard. When the tablet and the DOCKING keyboard are close, the metal contacts and the elastic pins will make point-to-point contact through magnetic attraction and mechanical positioning slots, thus completing the physical connection between the two modules. After that, the tablet needs to perform electronic detection on the DOCKING keyboard to complete the tablet's recognition of the keyboard.

[0025] See also Figure 1 As shown, the utility model provides a detection circuit based on a tablet computer Docking keyboard, the detection circuit includes a first detection module for detecting whether the keyboard is inserted, a first power supply, a control unit, a first resistor R6, a second resistor R7, a third resistor and a second detection module, the first detection module is preferably Figure 1 The USB-DOCK-DET# pin is connected to the first end of the first resistor and the first end of the second resistor respectively, the second end of the first resistor is connected to the first power supply, the second end of the second resistor is connected to the control unit, and the second detection module is connected to GND through a third resistor. Preferably, the second detection module is the DOCK_DET# pin, and the first detection module transmits the first detection result to the control unit, and the control unit determines whether to power the keyboard according to the first detection result.

[0026] In one embodiment of the present invention, please refer to Figure 2As shown, the detection circuit also includes a second power supply, which is preferably a 5V_USB pin located on the tablet computer, and the 5V_USB pin is connected to the power switch U1. When the control unit determines that the first detection result meets the preset condition, the control unit controls the power switch U1 to turn on, and 5V_USB supplies power to the keyboard. The control unit includes an analog-to-digital converter acquisition module, which is used to convert the collected analog signal into a digital signal.

[0027] Please refer to Figure 2 As shown, the EN end of the power switch U1 is connected to the fourth resistor R4 and the fifth resistor R2 respectively, the other end of the fourth resistor R4 is grounded, and the other end of the fifth resistor R2 is connected to the DOCKING_DET_EC pin of the control unit. The fourth resistor R4 is used to control the default no-voltage output of the 5V_USB power supply at the moment of startup. After the control unit is initialized, the output enable is controlled by the DOCKING_PWR_EN_EC signal.

[0028] In one embodiment of the present invention, a correspondence table between the first detection result and the numerical symbol is pre-stored in the control unit, and the preset condition is that the numerical symbol is within a preset range.

[0029] Specifically, the USB_DOCK_DET# pin on the tablet is used to detect whether a DOCKING keyboard is inserted. The signal is controlled by the GPIO of the control unit (MCU) and is set as an input pin, with two states of detecting high level (binary symbol 1) and low level (binary symbol 0). One end of the USB_DOCK_DET# pin is connected to the first end of the first resistor R6 and the first end of the second resistor R7. The second end of the first resistor R6 is connected to 3V3_SYS. The first resistor R6 is a pull-up resistor. The default high level notifies the control unit that DOCKING is not detected. The second end of the second resistor R7 is connected to the DOCKING_DET_EC pin of the control unit for suppressing ESD. The control unit includes an analog-to-digital converter acquisition module ADC. If the resolution of the ADC is 8 bits, the GPIO can measure 2 8 = 256 analog values. Assuming that VSIG is a signal with a maximum level of 3.3V, the minimum voltage change unit that the 8-bit ADC can receive is 3.3V / 256=0.012890625V, "0"=0V~0.012890625V, "1"=0.012890626V~2*0.012890625V, ..., "127"=1.637109375V~1.65V, ..., "255"=3.287109375V~3.3V. According to the above relationship, the corresponding relationship table between the first detection result and the numerical symbol can be obtained, which is as follows:

[0030]

[0031]

[0032] It should be noted that the Symbol in the above table stores the corresponding binary code in the MCU code. For the convenience of expression, this application uses digital Symbol instead; the 8-bit ADC module circuit of the MCU can convert the detected analog quantity 0~3.3V into an 8-bit binary number and store it in the register.

[0033] Please refer to Figure 3 As shown, the DOCK_DET# pin of the DOCKING keyboard is connected to GND through the third resistor R8. Preferably, the resistance value of the third resistor R8 is the same as the resistance value of the first resistor R6. This embodiment takes the resistance value of the third resistor R8 as 100KΩ as an example. In this way, when the tablet computer is connected to the DOCKING keyboard, the detection result of the USB_DOCK_DET# pin of the tablet computer will be changed from the original 3.3V to 1.65V through the voltage division of the first resistor R6 and the third resistor R8, and the calculation is as follows:

[0034] V USB_DOCK_DET# =V 3V3_SYS X{R8 / (R6+R8)}

[0035] =3.3VX{100K / (100K+100K)}

[0036] =1.65V

[0037] The above 1.65V is the theoretical value when the tablet computer and the DOCKING keyboard are connected. In actual operation, due to the fluctuation of the power supply and the error of the resistor, 1.65V can take an error value of ±5%, that is, 1.485V~1.815V. The code corresponding to 1.485 is "115" (1.65 / 0.012890625=115.2), and the code corresponding to 1.815V is "140" (1.815 / 0.012890625=140.8). In this way, when the MCU detects that the first detection result meets the preset condition, that is, the code between "115" and "140", it can be considered that the DOCKING keyboard has been connected to the tablet computer, and then controls the power switch to close to provide 5V power and USB signal to the keyboard.

[0038] It can be seen from the above embodiments that when the tablet computer is not plugged into a DOCKING keyboard, the signal of the USB_DOCK_DET# pin is pulled up to 3.3V through the first resistor R6, which is a high level 3.3V (3V3_SYS), and the MCU determines that the tablet computer has not detected the DOCKING keyboard.

[0039] When the DOCKING keyboard is inserted, the USB_DOCK_DET# pin on the tablet computer contacts the DOCK_DET# pin of the DOCKING keyboard. The first detection result of the USB_DOCK_DET# pin of the tablet computer is transmitted to the MCU. When the MCU determines that the first detection result is within a preset range (e.g., 115-140) according to the pre-stored correspondence table between the first detection result and the numerical symbol, it can be considered that the DOCKING keyboard has been connected to the tablet computer. The MCU controls DOCKING_PWR_EN_EC to become a high level, so that the power switch IC U1 is turned on (i.e., 5V_SYS and 5V_USB) to supply power to the USB interface.

[0040] Compared with the prior art, when the tablet computer and the keyboard are in contact, the detection signal of the tablet computer no longer changes from a high level to a low level, but instead uses an intermediate voltage value to determine whether the DOCKING keyboard is inserted. This can avoid the problem of short circuit caused by erroneous judgment due to the short circuit between the detection pin and the ground pin.

[0041] The utility model also provides a system based on a tablet computer docking keyboard, the system includes a keyboard and a tablet computer, the tablet computer is provided with a second power supply, when the tablet computer detects that the keyboard is inserted, the second power supply is used to power the keyboard, the system also includes a data transmission module, used for data transmission between the keyboard and the tablet computer, a signal detection circuit, the signal detection circuit includes the detection circuit based on the tablet computer docking keyboard described in any of the above embodiments. Wherein, the data transmission module is a USB_DN terminal and a USB_DP terminal located on the keyboard, and a USB_DN terminal and a USB_DP terminal located on the tablet computer.

[0042] The above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit them; the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Although the utility model has been described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the utility model.

Claims

1. A detection circuit based on a tablet computer DOCKING keyboard, characterized in that: The detection circuit includes a first detection module for detecting whether the keyboard is inserted, a first power supply, a control unit, a first resistor, a second resistor, a third resistor and a second detection module, the first detection module is respectively connected to the first end of the first resistor and the first end of the second resistor, the second end of the first resistor is connected to the first power supply, the second end of the second resistor is connected to the control unit, the second detection module is connected to GND through the third resistor, the first detection module transmits the detected first detection result to the control unit, and the control unit determines whether to power the keyboard according to the first detection result.

2. The detection circuit according to claim 1, characterized in that: The detection circuit also includes a second power supply and a power switch connected to the second power supply. When the control unit determines that the first detection result meets the preset condition, the control unit controls the power switch to be turned on, and the second power supply supplies power to the keyboard.

3. The detection circuit according to claim 2, characterized in that: The control unit comprises an analog-to-digital converter acquisition module, which is used to convert the acquired analog signal into a digital signal.

4. The detection circuit according to claim 3, characterized in that: A correspondence table between the first detection result and the numerical symbol is pre-stored in the control unit, and the preset condition is that the numerical symbol is within a preset range.

5. The detection circuit according to claim 1, characterized in that: The first detection module is a USB-DOCK-DET# pin located on the tablet computer.

6. The detection circuit according to claim 1, characterized in that: The second detection module is a DOCK_DET# pin located on the keyboard.

7. The detection circuit according to claim 6, characterized in that: The DOCK_DET# pin is connected to the GND terminal on the keyboard through a third resistor.

8. The detection circuit according to claim 1, characterized in that: The resistance values ​​of the first resistor and the third resistor are equal.

9. A system based on a tablet computer DOCKING keyboard, characterized in that: The system includes a keyboard and a tablet computer, wherein the tablet computer is provided with a second power supply, and the second power supply is used to power the keyboard when the tablet computer detects that the keyboard is inserted. The system also includes a data transmission module for data transmission between the keyboard and the tablet computer, and a signal detection circuit, wherein the signal detection circuit includes the detection circuit based on the tablet computer DOCKING keyboard as described in any one of claims 1 to 8 above.

10. The system based on tablet computer DOCKING keyboard according to claim 9, characterized in that: The data transmission module is a USB_DN terminal and a USB_DP terminal located on the keyboard, and a USB_DN terminal and a USB_DP terminal located on the tablet computer.

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