A timing detection circuit for a vehicle-mounted split touch screen

Abstract

A timing detection circuit for a vehicle-mounted split touch screen includes a CPU module, a touch screen controller, a serializer and a deserializer, wherein data transparent transmission is realized between the CPU module and the touch screen controller through the serializer and the deserializer; further includes a first switching module, a second switching module, a power supply module and a signal generating module; the first switching module is connected to the power supply module and the touch screen controller; the second switching module is connected between the deserializer and the touch screen controller; the signal generator is connected to the power supply module to generate a fixed frequency when the power is turned on; the touch screen controller is connected to the signal generator; the CPU module determines the working state of the touch screen according to the waveform signal, and outputs the corresponding control signal to the deserializer; the deserializer is also connected to the first switching module to control the states of the first switching module and the second switching module according to the control signal. The circuit structure of the present invention is simple, easy to implement, low in cost and highly versatile.

Description

Technical Field

[0001] The invention relates to the field of vehicle-mounted equipment, in particular to a timing detection circuit of a vehicle-mounted split touch screen. Background Art

[0002] With the development of touch technology, touch screens are increasingly used in the automotive field. Currently, almost all in-vehicle central control displays have built-in touch functions to achieve better human-computer interaction. However, customers' requirements for human-computer interaction functions are also constantly increasing, and the use of capacitive touch screens in the automotive field is gradually becoming the mainstream.

[0003] In actual use, due to the limitation of the installation size on the vehicle, when designing the product, the touch screen will follow the central control display screen and adopt a split design, and will be separated from the host (the capacitive touch screen and the display screen are fully bonded or frame-bonded). This split design makes the central control display screen consist of a host controller and a remote touch display screen (including the capacitive touch screen and the display screen). In order to meet the requirements of high resolution and high speed of the display screen, the communication between the host controller and the remote touch display screen adopts the FPD-Link serializer / deserializer method for remote high-speed data transmission and touch screen remote control.

[0004] At present, the more mature solutions such as Maxim or TI use twisted pair or coaxial line as the transmission medium between the serializer and the deserializer to achieve high-speed signal transmission and remote control of the touch screen, so that the remote touch screen can be several meters away from the host controller, which is suitable for installation in special environments on the vehicle. During operation, since the remote touch screen is controlled by the host controller, during the power-on process, the deserializer of the remote touch screen is initialized, and the CPU of the host controller needs to configure the relevant registers, and the initialization of the remote deserializer is realized by transparent transmission through the serializer, thereby realizing the initialization of the touch screen. Only in this way can the remote touch screen work normally.

[0005] However, in vehicle applications, the electrostatic test requirements for touch screens are relatively stringent. According to the relevant provisions of ISO 10605, air discharge is ±15KV and contact discharge is ±8KV. If the touch screen is not properly handled in this electrostatic test environment, the control chip inside the touch screen will often fail before other peripheral chips and circuits fail. If the touch screen cannot be restored immediately, it will cause the touch screen to malfunction for a long time. Due to the uncertainty of electrostatic testing, the failure of the control chip inside the touch screen may be partial failure or complete failure. For example, the host can actively access the I2C of the touch screen, but the interrupt pin of the touch screen remains in the default high state. When the touch screen is clicked, the interrupt pin does not pull down (under normal circumstances, the interrupt pin is always high. If the touch screen is touched, the interrupt pin will be pulled down), indicating that the touch screen has no interrupt output, and the host cannot respond to the touch action. In this case, the host has to actively access multiple status registers inside the touch screen at regular intervals to analyze and determine whether the touch screen is in an abnormal state, and then perform self-recovery. This will inevitably occupy the I2C bus data resources (under normal circumstances, the host will access the I2C of the touch screen to read relevant data only when an interrupt signal arrives from the touch screen), and increase the difficulty and cost of software development.

[0006] In addition, for electrostatic testers, if the touch screen fails functionally during the test, it is impossible to determine whether the touch screen fails without a click operation, which increases the trouble for the testers. Summary of the invention

[0007] The main purpose of the present invention is to overcome the above defects in the prior art and to provide a timing detection circuit for a vehicle-mounted split touch screen, which has low cost and is easy to use.

[0008] The present invention adopts the following technical solution:

[0009] A timing detection circuit for a vehicle-mounted split touch screen comprises a CPU module, a touch screen controller, a serializer and a deserializer, wherein data transparent transmission is realized between the CPU module and the touch screen controller through the serializer and the deserializer; the circuit is characterized in that: it also comprises a first switching module, a second switching module, a power supply module and a signal generating module; the first switching module is connected to the power supply module and the touch screen controller to control the on and off of the power supply of the touch screen; the second switching module is connected between the deserializer and the touch screen controller to control the on and off of the signal transmission; the signal generator is connected to the power supply module to generate a fixed frequency when the power supply is turned on; the touch screen controller is connected to the signal generating module to transparently transmit the waveform signal of the fixed frequency to the CPU module via the deserializer; the CPU module determines the working state of the touch screen according to the waveform signal, and outputs the corresponding control signal to be transparently transmitted to the deserializer; the deserializer is also connected to the first switching module to control the states of the first switching module and the second switching module according to the control signal.

[0010] Preferably, it further comprises a resistor R8 and a light emitting diode D1, wherein one end of the resistor R8 is connected to the waveform signal output end of the touch screen controller, and the other end is connected to the light emitting diode D1.

[0011] Preferably, the signal generating module includes an active crystal oscillator, a magnetic bead, a resistor R3, a resistor R4, a capacitor C1, a capacitor C2 and a frequency dividing unit; one end of the magnetic bead is connected to the output end of the power supply module, and the other end is connected to one end of the resistor R3 and the capacitor C1; the other end of the resistor R3 is connected to the input end of the active crystal oscillator, the output end of the active crystal oscillator is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the capacitor C2 and the input end of the frequency dividing unit, and the output end of the frequency dividing unit is connected to the touch screen controller.

[0012] Preferably, the frequency division unit includes a transistor Q1, a resistor R6, a resistor R7 and a binary counter, the base of the transistor Q1 is connected to the other end of the resistor R4, the collector is connected to one end of the resistor R7 and the CL pin of the binary counter, the emitter is connected to one end of the resistor R6, the other end of the resistor R6 is connected to the R pin of the binary counter, and the output end of the binary counter is connected to the input end of the touch screen controller.

[0013] Preferably, the first switching module includes a switch K1, a capacitor C3 and a capacitor C4; the control end of the switch K1 is connected to the output end of the power supply module, one static end thereof is connected to one end of the capacitor C4, and the other static end is connected to one end of the capacitor C3 and the power supply end of the touch screen controller.

[0014] Preferably, the second switching module includes a switch K2, a resistor R9, a resistor R10 and a resistor R5; the control end of the switch K2 is connected to one end of the resistor R5 and the output end of the deserializer, the first moving end and the second moving end of the switch K2 are connected to the two signal ends of the deserializer, a first static end is connected to one end of the resistor R9, a second static end is connected to one end of the resistor R10, and the other end of the resistor R9 and the other end of the resistor R8 are respectively connected to the two signal ends of the touch screen controller.

[0015] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The circuit of the present invention is provided with a first switching module, a second switching module, a power supply module and a signal generating module, etc. The signal sending module can generate a fixed frequency when the touch screen works normally. The CPU module judges the working state of the touch screen by detecting the waveform signal of the fixed frequency, and outputs a corresponding control signal to control the first switching module and the second switching module, so as to realize the timing detection of the touch screen and the self-recovery control in the abnormal state, which is convenient for electrostatic testing and abnormality troubleshooting. The circuit structure is simple, easy to realize, low cost and strong versatility.

[0017] 2. The present invention can reduce the extra burden of the CPU caused by frequent CPU detection. The fixed low-frequency signal detection method saves more CPU resources than the pure software I2C bus communication polling method, thereby reducing the difficulty of software development; further, the risk of being interfered by static electricity is reduced, and the frequency range of static noise interference is avoided.

[0018] 3. The present invention cooperates with the use of light-emitting diodes to facilitate the observation of the working status of the touch screen by naked eyes, and has an abnormal reminder function.

[0019] 4. The present invention utilizes the frequency characteristics of an active crystal oscillator, the frequency division characteristics of a binary counter, and the control characteristics of an electronic analog switch; at the same time, it adopts the detection control technology of an I / O port, and the transparent transmission control technology of an FPD-Link serializer / deserializer to realize the timing detection of a vehicle-mounted split touch screen, as well as the abnormal self-recovery and abnormal reminder functions after an electrostatic test.

[0020] 5. The circuit of the present invention is actually applied to a vehicle-mounted remote touch screen with a separate host and touch screen, and is used to solve the problem that the remote touch screen fails and cannot restore touch control normally; it is convenient for relevant testers to conduct electrostatic test experiments on the remote touch screen and self-check and troubleshoot the touch screen in daily use. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural diagram of the present invention;

[0022] Figure 2It is the work flow chart of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described below through specific implementation modes.

[0024] Reference Figure 1 A timing detection circuit for a vehicle-mounted split touch screen includes a CPU module, a touch screen controller, a serializer, a deserializer, a first switching module, a second switching module, a power supply module, and a signal generation module. Data transparent transmission is achieved between the CPU module and the touch screen controller through the serializer and the deserializer.

[0025] The first switching module is connected to the power supply module and the touch screen controller to control the power supply on and off of the touch screen. The first switching module can be implemented by a single-pole double-throw switch, a MOS tube, or a relay.

[0026] Specifically, the first switching module includes a switch K1, a capacitor C3 and a capacitor C4. The control end of the switch K1 is connected to an output end VOUT1 of the power supply module, a static end thereof is connected to one end of the capacitor C4, and the other end is connected to one end of the capacitor C3 and the VCC end of the touch screen controller, i.e., the power supply end, and the other ends of the capacitors C3 and C4 are grounded. The internal default state of the switch K1 is that the moving end A1 is connected to a static end B1. The control end S1 is low by default, and the control end S1 is connected to the GPIO5_REG port of the power supply module U4, and the C1 pin of KI is connected to the power supply end VCC3.3 of the touch screen controller U5. Capacitors C3 and C4 are power supply filter capacitors.

[0027] The second switching module is connected between the deserializer and the touch screen controller to control the on and off of signal transmission. The first switching module can be implemented by a double-pole double-throw switch or an analog switch (such as SGM3002).

[0028] The second switching module includes a switch K2, a resistor R9, a resistor R10 and a resistor R5. The control end of the switch K2 is connected to one end of the resistor R5 and the output end of the deserializer, the first moving end and the second moving end of the switch K2 are connected to the two signal ends of the deserializer, a first static end is connected to one end of the resistor R9, a second static end is connected to one end of the resistor R10, and the other end of the resistor R9 and the other end of the resistor R10 are respectively connected to the two signal ends of the touch screen controller. R5 is a pull-down resistor to ensure that the GPIO5_REG of the deserializer U4 is low at the moment of power-on.

[0029] See also Figure 1The double-pole double-throw switch has a control terminal S which is low by default, and the control terminal S is connected to the GPIO5_REG port of the deserializer U4. The first moving terminal D is connected to a first static terminal D1 by default, and the first moving terminal D is connected to the I2C clock signal SCL of the deserializer U4. The other first static terminal D2 is connected to the I2C clock signal SCL1 pin of the touch screen controller U5 through a resistor R9.

[0030] The second moving terminal E is connected to a second static terminal E1, and the second static terminal E is connected to the data signal SDA of the I2C of the deserializer U4. Another second static terminal E2 is connected to the data signal SDA1 pin of the I2C of U5 through R10. The switch K2 control is added to prevent the touch screen controller U5 from being unable to reset normally during the reset and power-off process due to the I2C of the deserializer U4 connecting to U5. The pull-up resistor corresponding to I2C is not drawn in the figure. Resistors R9 and R10 are matching resistors to reduce the overshoot of the I2C signal, and generally take 22 ohms.

[0031] The signal generator and the power supply module generate a fixed frequency when the power is turned on, which includes an active crystal oscillator, a magnetic bead, a resistor R3, a resistor R4, a capacitor C1, a capacitor C2 and a frequency division unit. One end of the magnetic bead L1 is connected to the other output terminal VOUT2 of the power supply module, and the other end is connected to one end of the resistor R3 and the capacitor C1. The magnetic bead is used to eliminate high-frequency interference. The other end of the resistor R3 is connected to the input end of the active crystal oscillator, and the output end of the active crystal oscillator is connected to one end of the resistor R4. The active crystal oscillator Y1 outputs a fixed frequency of F1, which can be 32.768KHZ in practice. The other end of the resistor R4 is connected to the capacitor C2 and the input end of the frequency division unit, and the output end of the frequency division unit is connected to the touch screen controller. Among them, R4 is a matching resistor, capacitor C2 is a high-frequency filter capacitor, R3 is a current limiting resistor, and capacitor C1 is a power supply filter capacitor.

[0032] The frequency division unit includes a transistor Q1, a resistor R6, a resistor R7 and a binary counter. The base of the transistor Q1 is connected to the other end of the resistor R4, the collector is connected to one end of the resistor R7 and the CL pin of the binary counter, the emitter is connected to one end of the resistor R6, the other end of the resistor R6 is connected to the R pin of the binary counter, and the output end of the binary counter is connected to the input end of the touch screen controller. U7 is a binary counter, such as CD4020BE in actual use, to achieve the frequency division function.

[0033] The frequency output by the active crystal oscillator Y1 is set to the waveform of F1, and the waveform after frequency division by U7 is F2. The frequency of F2 is required to be less than 20HZ (because the human eye cannot distinguish the flicker at frequencies above 50HZ, and at the same time to avoid the audio signal range of 20HZ-20KHZ that can be distinguished by the human ear to prevent audio interference). Low-frequency signals are used to reduce the CPU burden caused by frequent detection and the risk of electrostatic interference, because electrostatic interference is high-frequency signal interference. In actual application, F2 should be as small as possible, such as 2HZ.

[0034] The pin R of U7 is the clear terminal, which is grounded through the resistor R6. The pin CL of U7 is the clock input terminal; Q1, Q2 to Qn are the counter pulse output terminals (n represents an n-bit binary counter, which can realize 2 n Resistor R7 is a pull-up resistor, which is pulled up to VCC2, which is generally 3.3V. Q1 is an NPN transistor.

[0035] The touch screen controller U5 is connected to the signal generator to transmit the fixed frequency waveform signal to the CPU module through the deserializer. The touch screen controller U5 is the control IC of the touch screen, such as ATMXT1189T in actual application. When customizing the touch screen, you can choose according to your needs.

[0036] The CPU module U1 determines the working state of the touch screen according to the waveform signal, and outputs the corresponding control signal to the deserializer. U1 is the core system module, which contains CPU, DDR3, EMMC, PMIC, etc. It has audio and video encoding and decoding functions, including dual-channel LVDS interface, HDMI interface, MIPI interface, and combination circuits including WIFI, Bluetooth, GPS, etc. It actually runs on the Android platform. I / O1; I / O2 are the internal GPIO ports of U1, and I / O1 and I / O2 are configured as input ports. The input ports I / O1 and I / O2 of the CPU module U1 are connected to pull-up resistors R1 and R2 at one end, and the pull-up resistors R1 and R2 are connected to VCC1 and VCC2 respectively. I / O1 and I / O2 of U1 are high level by default.

[0037] The serializer U2 can use an FPD-Link serializer (such as TI's DS90UB949Q-Q1), and the CPU module U1 and the serializer U2 internally perform I2C communication and HDMI signal communication; during power-on initialization, the CPU module U1 configures relevant registers through I2C, configures the GPIO1 and GPIO2 ports of the serializer U2 as output ports, and connects them to the I / O1 and I / O2 of the CPU module U1, respectively.

[0038] The deserializer U4 is also connected to the first switching module to control the states of the first switching module and the second switching module according to the control signal. The deserializer can be an FPD-Link deserializer (such as TI's DS90UB948Q-Q1), and the touch screen controller U5 can be a touch screen control chip. The deserializer U4 and the touch screen controller U5 communicate via I2C, the input pin GPIO2 of U4 is connected to the interrupt output pin INT of U5, the output pin GPIO6_REG of U4 is connected to the reset pin RST of U5, and the input pin GPIO1 of U4 is connected to the output pin I / O_1 of U5.

[0039] The present invention also includes a resistor R8 and a light emitting diode D1, one end of the resistor R8 is connected to the output pin I / O_1 of the touch screen controller, and the other end is connected to the positive electrode of the light emitting diode D1, and the negative electrode of the light emitting diode D1 is grounded. R8 is a current limiting resistor.

[0040] The power supply module U6 of the present invention is a power supply module for a remote touch screen, which may include DCDC and LDO, and may be powered by a DC-DC module U3 at the end where the CPU module U1 is located, and the DC-DC module U3 may output a 12 V voltage. The power supply module U6 includes an input terminal VIN and two output terminals VOUT1 and VOUT2.

[0041] AB represents the connection line between the host and the remote touch screen, which is a twisted pair inside and contains the required differential signal line, power line, and ground line. The VOUT of the DC-DC module is generally 12V, which is connected to the power input terminal VIN of the power supply module U6 by the AB line, and is converted into VOUT1 by the power supply module U6 and controlled by the switch K1 to provide power to the touch screen controller U5. At the same time, there is a power supply VOUT2 to power the active crystal oscillator Y1; U4, K2 and other power supply networks are not drawn in the figure. VCC1 represents the pull-up voltage of the internal GPIO of the CPU (U1), which is generally 3.3V.

[0042] See also Figure 2 When the present invention is powered on and initialized, U1 configures its own I / O1 and I / O2 as interrupt inputs. At the same time, U1 configures the corresponding registers of U2 and U4 through I2C, so that the serializer U2 and the deserializer U4 are initialized and establish high-speed communication, and U2 transparently transmits it to U4, and configures the GPIO1 and GPIO2 ports of U4 as input ports, and configures the GPIO5_REG and GPIO6_REG ports as output pins. At the same time, the touch screen controller U5 is initialized and configured with related registers, so that the touch screen can be used normally. After the touch screen controller is initialized, the I / O_2 port of U5 is configured as an input pin that is triggered by both the rising edge and the falling edge. Each time it is triggered, the level jumps once; the I / O_1 port of U5 is configured as an output pin, and the output waveform of I / O_1 changes with the input waveform of I / O_2.

[0043] When the GPIO5_REG output of U4 is high, the A1 and C1 pins inside K1 will be turned on, and the VOUT1 power supply will be directly supplied to the touch screen controller. At the same time, D and D2, E and E2 inside K2 will be turned on, so that the I2C of U5 and U4 are connected normally. After the touch screen works normally, if a human body touches the touch screen, the interrupt output pin INT of U5 will generate a low interrupt signal input to the GPIO2 of U4, and finally transmitted to the I / O2 of U1 through the serial deserializer. After receiving the interrupt signal, U1 reads the relevant register value through I2C to determine the touch coordinates and finally executes the relevant application.

[0044] When the remote touch screen is working normally, the active crystal oscillator Y1 will output a fixed frequency F1, which will be divided by U7 to obtain a waveform with a frequency of F2, and input to the I / O_2 port of U5. After internal software processing, U5 will output the F2 waveform with the same frequency from the I / O_1 port to the GPIO1 of U4. At this time, D1 will flash at the frequency of F2. Then, using the FPD-Link serializer / deserializer technology, the deserializer U4 will transmit the GPIO1 signal to the GPIO1 of U2, and finally input it to the I / O1 of U1. U1 detects the level change of I / O1 and confirms whether the waveform is F2 to determine whether the remote touch screen is in normal working condition.

[0045] When the touch screen is disturbed by static electricity, if the touch screen controller U5 fails, then U5's I / O_2 will not be able to detect the waveform with a frequency of F2 sent by U7, and U5's I / O_1 will not be able to output the F2 waveform to U4. After transparent transmission through the serial / deserializer, U1's I / O1 will also be unable to detect the F2 waveform, and D1 will not flicker. At this time, the touch screen is considered to have failed, and U1 will use the transparent transmission of U2 and U4 to simultaneously pull down U4's GPIO5_REG and GPIO6_REG, and then pull them up at the same time after time T1, and reconfigure the relevant registers of the I2C of the touch screen controller to reinitialize the touch screen. At this time, the touch screen returns to normal and D1 will continue to flicker.

[0046] The present invention utilizes the frequency characteristics of the active crystal oscillator and the frequency division characteristics of the binary counter to generate a low-frequency signal below 20HZ that is stable, reliable and easy to detect. With the use of light-emitting diodes, it is convenient for the naked eye to observe the working status of the touch screen, and has an abnormal reminder function. At the same time, it avoids the audio signal range of 20HZ-20KHZ that can be distinguished by the human ear, and prevents unnecessary audio noise interference; secondly, it reduces the extra burden of the CPU caused by frequent CPU detection. The fixed low-frequency signal detection method saves more CPU resources than the pure software I2C bus communication polling method, thereby reducing the difficulty of software development; and further reduces the risk of being interfered by static electricity, avoiding the frequency range of static noise interference. The present invention uses analog switch isolation control between I2Cs to prevent the problem of normal reset caused by cross-current between chips.

[0047] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A timing detection circuit for a vehicle-mounted split touch screen, comprising a CPU module, a touch screen controller, a serializer and a deserializer, wherein data transparent transmission is realized between the CPU module and the touch screen controller through the serializer and the deserializer; Features: It also includes a first switching module, a second switching module, a power supply module and a signal generating module; the first switching module is connected to the power supply module and the touch screen controller to control the on and off of the power supply of the touch screen; the second switching module is connected between the deserializer and the touch screen controller to control the on and off of the signal transmission; the signal generating module is connected to the power supply module to generate a fixed frequency when the power is turned on; the touch screen controller is connected to the signal generator to transmit the waveform signal of the fixed frequency to the CPU module through the deserializer; the CPU module determines the working state of the touch screen according to the waveform signal, and outputs the corresponding control signal to the deserializer; the deserializer is also connected to the first switching module to control the states of the first switching module and the second switching module according to the control signal.

2. A timing detection circuit for a vehicle-mounted split touch screen as claimed in claim 1, Features: It also includes a resistor R8 and a light emitting diode D1. One end of the resistor R8 is connected to the waveform signal output end of the touch screen controller, and the other end is connected to the light emitting diode D1.

3. The timing detection circuit of a vehicle-mounted split touch screen as claimed in claim 1, Features: The signal generating module comprises an active crystal oscillator, a magnetic bead, a resistor R3, a resistor R4, a capacitor C1, a capacitor C2 and a frequency dividing unit; one end of the magnetic bead is connected to the output end of the power supply module, and the other end is connected to one end of the resistor R3 and the capacitor C1; the other end of the resistor R3 is connected to the input end of the active crystal oscillator, the output end of the active crystal oscillator is connected to one end of the resistor R4, the other end of the resistor R4 is connected to the capacitor C2 and the input end of the frequency dividing unit, and the output end of the frequency dividing unit is connected to the touch screen controller.

4. A timing detection circuit for a vehicle-mounted split touch screen as claimed in claim 3, Features: The frequency division unit includes a transistor Q1, a resistor R6, a resistor R7 and a binary counter. The base of the transistor Q1 is connected to the other end of the resistor R4, the collector is connected to one end of the resistor R7 and the CL pin of the binary counter, the emitter is connected to one end of the resistor R6, the other end of the resistor R6 is connected to the R pin of the binary counter, and the output end of the binary counter is connected to the input end of the touch screen controller.

5. The timing detection circuit of a vehicle-mounted split touch screen as claimed in claim 1, Features: The first switching module includes a switch K1, a capacitor C3 and a capacitor C4; the control end of the switch K1 is connected to the output end of the power supply module, one static end is connected to one end of the capacitor C4, and the other static end is connected to one end of the capacitor C3 and the power supply end of the touch screen controller.

6. A timing detection circuit for a vehicle-mounted split touch screen as claimed in claim 1, Features: The second switching module includes a switch K2, a resistor R9, a resistor R10 and a resistor R5; the control end of the switch K2 is connected to one end of the resistor R5 and the output end of the deserializer, the first moving end and the second moving end of the switch K2 are connected to the two signal ends of the deserializer, a first static end is connected to one end of the resistor R9, a second static end is connected to one end of the resistor R10, and the other end of the resistor R9 and the other end of the resistor R8 are respectively connected to the two signal ends of the touch screen controller.

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