A highway sign having a control module

Abstract

The utility model discloses a highway signboard with control module, include: signboard body, signboard body includes control module, and control module includes: power -on reset reference circuit, analog switch, DTR signal processing circuit, RTS signal processing circuit, including second current -limiting resistance, PNP triode, pull -down resistance and damping resistance, and one end of second current -limiting resistance connects RTS signal, and the other end connects the base of PNP triode, and the emitter of PNP triode connects power supply, and the collector passes through damping resistance and connects BOOT0 pin, and pull -down resistance is connected between the base of PNP triode and power supply, wherein the input and output of analog switch are connected signal passage of DTR signal processing circuit and RTS signal processing circuit respectively. This highway signboard with control module has power protection, strong anti -interference ability, remote maintenance is convenient, stable and reliable characteristics.

Description

Technical Field

[0001] This utility model relates to a highway sign with a control module. Background Technology

[0002] With the rapid development of intelligent transportation systems, road signs have evolved from simple static display devices into intelligent devices with multiple functions such as dynamic information display, remote control, and environmental monitoring. These intelligent road signs are typically installed along roads to display traffic information, warning information, and guidance information, playing a vital role in ensuring road safety and improving traffic efficiency. In the control system of intelligent road signs, the microcontroller (MCU) is the core processing unit, and its firmware updates and maintenance are crucial for ensuring the normal operation of the equipment.

[0003] Currently, firmware updates for highway sign controllers mainly take the following forms: direct on-site replacement of the memory chip, firmware updates via a dedicated programmer, and remote firmware updates via serial port. Among these, remote firmware updates via serial port are increasingly popular due to their ease of operation and low maintenance costs. When using serial port for firmware updates, it is necessary to control the MCU's reset signal (NRST) and boot mode selection signal (BOOT0) to put the MCU into bootloader mode and receive new firmware data.

[0004] Traditional serial port automatic download circuits typically connect the DTR# and RTS# handshake signals of the serial port directly to the NRST and BOOT0 pins of the MCU via transistors or other switching circuits. When download mode is required, the MCU is controlled by controlling the DTR# and RTS# signals. This traditional solution works well in ideal environments, but it has the following main problems in special application scenarios such as highway signs:

[0005] First, highway signs are typically installed outdoors, making them susceptible to interference from complex electromagnetic environments. Traditional serial port automatic download circuits lack isolation mechanisms against external interference signals during power-up. Noise and electrostatic interference on the serial line can easily cause the MCU to be mistakenly triggered into download mode during startup, preventing the system from booting properly. This problem is particularly pronounced in thunderstorms or environments with heavy vehicle traffic.

[0006] Secondly, during remote maintenance, the signal quality deteriorates due to the long-distance communication lines connecting the highway sign controller to the maintenance terminal, leading to unstable download timing and making firmware update processes prone to failure. Especially when the system requires multiple restarts, traditional circuits lack special handling for power-off restart processes, making protection mechanisms susceptible to failure.

[0007] Third, existing serial port automatic download circuits usually require specific download tools or dedicated drivers, which increases the training costs for maintenance personnel and equipment dependence, and is not conducive to rapid response and emergency maintenance.

[0008] Fourth, highway sign controllers operate in a wide temperature range (-20℃ to +70℃), requiring the circuit to have good temperature adaptability and stability. However, traditional circuits are often designed for general indoor environments and lack the ability to adapt to harsh environments. Utility Model Content

[0009] The purpose of this invention is to provide a highway sign with a control module. This highway sign with a control module features power-on protection, strong anti-interference capability, convenient remote maintenance, and stable reliability.

[0010] The above-mentioned technical objective of this utility model is achieved through the following technical solution:

[0011] A highway sign with a control module includes: a sign body, the control module being disposed within the sign body, the control module including: a power-on reset reference circuit, comprising a resistor (R78), a capacitor (C44), and a diode (D13) connected in parallel across the resistor (R78), one end of the resistor (R78) being connected to a power supply, and the other end being connected to one end of the capacitor (C44) to form an RC node, the other end of the capacitor (C44) being grounded; an analog switch (U15), the enable terminal (E) of which is connected to the RC node; and a DTR# signal processing circuit, comprising a first current-limiting resistor (R74), an NPN transistor (Q16), and a pull-up resistor (R73), one end of the first current-limiting resistor (R74) being connected to the DTR# signal, and the other end being connected to the base of the NPN transistor (Q16), the collector of the NPN transistor (Q16) being... The NRST pin is connected to one end of the pull-up resistor (R73), and the other end of the pull-up resistor (R73) is connected to the power supply; the RTS# signal processing circuit includes a second current-limiting resistor (R75), a PNP transistor (Q17), a pull-down resistor (R79), and a damping resistor (R76). One end of the second current-limiting resistor (R75) is connected to the RTS# signal, and the other end is connected to the base of the PNP transistor (Q17). The emitter of the PNP transistor (Q17) is connected to the power supply, and the collector is connected to the BOOT0 pin through the damping resistor (R76). The pull-down resistor (R79) is connected between the base of the PNP transistor (Q17) and the power supply; the input and output terminals of the analog switch (U15) are respectively connected to the signal paths of the DTR# signal processing circuit and the RTS# signal processing circuit.

[0012] The present invention is further configured such that the time constant formed by the resistor (R78) and the capacitor (C44) is used to set the shielding time of the external control signal after power-on.

[0013] The present invention is further configured such that the diode (D13) provides a fast discharge path for the capacitor (C44) after power failure, preventing false reset caused by repeated short power-on cycles.

[0014] The present invention is further configured such that the NPN transistor (Q16) is used to convert the low-level active DTR# signal into a low-level reset signal.

[0015] The present invention is further configured such that the PNP transistor (Q17) is used to convert the low-level active RTS# signal into a low-level Boot mode enable signal.

[0016] The present invention is further configured such that: the analog switch (U15) remains in the off state during the initial power-on phase to prevent the input of external control signals, and turns on after the voltage at the RC node rises to the threshold level to allow the transmission of external control signals.

[0017] The present invention is further configured such that the damping resistor (R76) is used to form a slight RC filter with the distributed capacitor to suppress interference on the BOOT0 signal line.

[0018] The present invention is further configured such that the resistance of the resistor (R78) is 820kΩ and the capacitance of the capacitor (C44) is 10μF, forming a time constant of approximately 8.2 seconds.

[0019] The present invention is further configured such that the analog switch (U15) is a 74HC1G66 single-channel analog switch.

[0020] The present invention is further configured such that: the resistance of the first current-limiting resistor (R74) is 2.7kΩ, the resistance of the second current-limiting resistor (R75) is 1kΩ, and the resistance of the damping resistor (R76) is 1kΩ.

[0021] In summary, this utility model has the following beneficial effects:

[0022] Power-on protection window mechanism: This invention creates a power-on protection window through an RC network formed by a resistor (R78) and a capacitor (C44), and a corresponding analog switch (U15). During the initial power-on phase, the analog switch is in the off state, completely isolating external DTR# and RTS# signals to prevent these signals from interfering with the MCU's NRST and BOOT0 pins before the system stabilizes.

[0023] Fast Discharge Path Design: This invention incorporates a diode (D13) connected in parallel across the resistor (R78) in the RC network, providing a fast discharge path for the capacitor (C44). When the system is powered off, the capacitor can discharge rapidly through the diode, ensuring that the RC network can be charged from zero upon the next power-on, generating a complete protection window. This design solves the problem of weakened or failed protection functions caused by residual charge in capacitors during frequent power outages and restarts in traditional circuits.

[0024] Complementary Transistor Signal Conversion: This invention employs a complementary structure of NPN transistor (Q16) and PNP transistor (Q17) to convert the low-activity serial handshake signals DTR# and RTS# into the control levels required by the MCU. This design not only simplifies the circuit structure, eliminating the need for additional logic inverters and reducing the number of components and cost, but also improves the reliability and speed of signal conversion.

[0025] Anti-interference design: This invention incorporates a damping resistor (R76) in series in the BOOT0 signal path, forming a slight RC filter with the distributed trace capacitors, effectively suppressing high-frequency interference. Simultaneously, the first current-limiting resistor (R74) and the second current-limiting resistor (R75) not only protect the transistor from overcurrent damage but also form an additional filtering network with the transistor's input capacitor.

[0026] The adaptability of parametric design: By adjusting the values ​​of resistor (R78) and capacitor (C44), the time constant of the power-on protection window can be easily changed to adapt to the needs of different control boards. The standard configuration of an 820kΩ resistor and a 10μF capacitor creates a time constant of approximately 8.2 seconds, far exceeding the startup time requirements of conventional MCUs, providing ample stabilization time for the system. This parametric design allows the same circuit to be adapted to different application scenarios through simple component value adjustments, reducing development and maintenance costs.

[0027] Compatible with standard serial port tools: This design is compatible with the standard DTR# and RTS# handshake signals of over 95% of USB-to-serial converters on the market, requiring no dedicated downloader or special driver. Maintenance personnel can perform remote firmware updates using only standard serial port tools, significantly reducing maintenance costs and training requirements. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of this utility model;

[0029] Figure 2 This is the overall circuit schematic diagram of this utility model. Detailed Implementation

[0030] In the description of this utility model, it should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0031] like Figure 1 , Figure 2 As shown, this utility model provides a highway sign with a control module, including a sign body 1. The sign body 1 is equipped with a control module. The control module is used to convert the two lines of UART DTR# / RTS# into MCU NRST / BOOT0 control, and at the same time provides power-on reset timing and anti-interference protection.

[0032] This module consists of the following parts: power-on reset reference circuit, analog switch, DTR# signal processing circuit, and RTS# signal processing circuit.

[0033] The power-on reset reference circuit includes a resistor (R78), a capacitor (C44), and a diode (D13). The resistor (R78) is a standard surface-mount resistor with a resistance of 820kΩ. One end is connected to a 3V3 power supply, and the other end is connected to one end of the capacitor (C44) to form an RC node. The capacitor (C44) is a surface-mount capacitor with a capacitance of 10μF, and the other end is grounded. The diode (D13) is a small surface-mount diode of model 1N4148WS, connected in parallel across the resistor (R78). The anode is connected to the junction of the resistor (R78) and the capacitor (C44), and the cathode is connected to the power supply terminal. These three components are arranged closely together to form a power-on delay reference source with a time constant set to approximately 8.2 seconds.

[0034] The analog switch (U15) uses a 74HC1G66 single-channel analog switch, packaged in a small package such as SOT-23-5 or TSSOP-5. Its enable terminal (E) is connected to the aforementioned RC node. A controllable switch is formed between the Y and Z terminals of U15. When E is high, Y and Z are connected, allowing external control signals to be transmitted; when E is low, Y and Z are disconnected, preventing external signals from interfering with the MCU.

[0035] The DTR# signal processing circuit includes a first current-limiting resistor (R74), an NPN transistor (Q16), and a pull-up resistor (R73). The first current-limiting resistor (R74) is a surface-mount resistor with a resistance of 2.7kΩ. One end is connected to the DTR# signal, and the other end is connected to the base of the NPN transistor (Q16). The NPN transistor (Q16) is an S8050W model, with its collector connected to the Z-terminal and one end of the pull-up resistor (R73), and its emitter grounded. The pull-up resistor (R73) is a surface-mount resistor with a resistance of 10kΩ, and the other end is connected to a 3V3 power supply.

[0036] The RTS# signal processing circuit includes a second current-limiting resistor (R75), a PNP transistor (Q17), a pull-down resistor (R79), and a damping resistor (R76). The second current-limiting resistor (R75) is a surface-mount resistor with a resistance of 1kΩ. One end is connected to the RTS# signal, and the other end is connected to the base of the PNP transistor (Q17). The PNP transistor (Q17) is an S8550W model, with its emitter connected to a 3V3 power supply, and its collector connected to the MCU's BOOT0 pin via the damping resistor (R76). The damping resistor (R76) is also a surface-mount resistor with a resistance of 1kΩ. The pull-down resistor (R79) is a surface-mount resistor with a resistance of 10kΩ, connected between the base of the PNP transistor (Q17) and the 3V3 power supply.

[0037] The input and output terminals of the analog switch (U15) are connected to the signal paths of the DTR# signal processing circuit and the RTS# signal processing circuit, respectively. Specifically, U15 can control whether the DTR# signal can be transmitted to the base of Q16 and whether the RTS# signal can be transmitted to the base of Q17.

[0038] During system power-up, once the 3V3 power supply stabilizes, capacitor (C44) begins charging, and the RC node voltage gradually rises. Since the initial capacitor voltage is zero, the emitter (E) terminal of analog switch (U15) is at a low level, disconnecting Y and Z. During this period, even if interference or abnormal levels occur in the DTR# or RTS# signals, they cannot be transmitted to the base of Q16 or Q17, thus protecting the NRST and BOOT0 pins from interference. As capacitor (C44) charges, when the RC node voltage rises to the threshold level of the emitter (E) terminal of U15 (approximately 1.5V), the analog switch turns on, allowing the DTR# and RTS# signals to control NRST and BOOT0.

[0039] When power is interrupted and then restored, the presence of diode (D13) allows capacitor (C44) to discharge rapidly, ensuring that the RC node starts charging from zero voltage upon the next power-on, thus creating a complete protection window. This solves the problem of insufficient protection time caused by incomplete capacitor discharge in traditional circuits during rapid power-off and restart scenarios.

[0040] During firmware download, when entering download mode is required, the RTS# signal is first pulled low, which pulls the BOOT0 pin low via Q17, setting the MCU to bootloader mode. Then, the DTR# signal is briefly pulled low, generating a low pulse via Q16 and applying it to the Z terminal, then to the NRST pin, triggering an MCU reset. When NRST returns to high, the MCU detects that BOOT0 is low and enters bootloader mode, ready to receive new firmware data. After the firmware transfer is complete, RTS# returns to high, BOOT0 returns to its default high-level state, and after triggering NRST reset again, the MCU will start operating normally from the new firmware.

[0041] The working principle of this utility model is as follows:

[0042] Power-on phase: After the 3V3 power supply is connected, the RC network formed by resistor (R78) and capacitor (C44) begins to charge. Initially, the voltage at the RC nodes is low, keeping the analog switch (U15) off and isolating external control signals. This period lasts approximately 3-5 seconds, which is sufficient for the MCU and surrounding circuits to stabilize.

[0043] Normal operation phase: After the RC network is fully charged, the analog switch is turned on, allowing external control signals to be transmitted. At this time, the system is in normal operation, NRST remains high, and BOOT0 remains in its default state according to the system configuration (usually high, indicating booting from main flash memory).

[0044] Firmware update phase: When a firmware update is required, the download tool first pulls RTS# low, and then pulls BOOT0 low via Q17; then it briefly pulls DTR# low, and generates a reset pulse via Q16; after the MCU resets, it detects that BOOT0 is low and enters bootloader mode; after the download is completed, RTS# is restored to high, BOOT0 returns to the default state, and after another reset, the MCU boots from the new firmware.

[0045] Power failure and restart phase: When the system is powered off, the capacitor (C44) discharges rapidly through the diode (D13); when the power is restored next time, the capacitor starts charging from zero, ensuring a complete protection window.

[0046] In practical applications, this module can be integrated onto the mainboard of the highway sign controller, located between the serial interface and the MCU. The DTR# and RTS# signals typically originate from the RS232 interface or a USB-to-serial converter, while the NRST and BOOT0 signals are connected to the corresponding pins of the MCU. All components of the module are surface-mount, resulting in a small PCB footprint and easy integration.

[0047] This module is suitable for various highway sign controllers, including variable message signs, speed limit signs, and warning signs. Due to its excellent anti-interference capabilities and reliable protection mechanisms, it is particularly suitable for installation in complex electromagnetic environments and under limited maintenance conditions, such as along highways. By simply adjusting the parameters of key components, it can also adapt to the specific needs of different controller models, improving the versatility and adaptability of the design.

[0048] This utility model of a highway sign with a control module constructs a power-on protection window through an RC network and analog switches. Combined with a fast discharge path and a complementary transistor structure, it solves the reliability problem of automatic serial port download in outdoor environments, realizes high-reliability self-starting and convenient remote firmware updates for the highway sign controller, and has good application value.

[0049] The effectiveness of the technical solution of this application is verified through the following experiments:

[0050] 1. Verification employs a comparative testing method, comparing this solution with a traditional serial port automatic download circuit. The experiment is conducted under simulated real-world working conditions for highway signs, including electromagnetic interference simulation, power-off restart sequences, firmware update operations, and extreme temperature cycling tests. The test platform includes identical MCU control boards, each equipped with download / reset circuits from both solutions, and uses an oscilloscope, EMI generator, and ambient temperature chamber to assist in testing, ensuring the accuracy and comparability of the data acquisition.

[0051] 2. Technical Effect Comparison Table

[0052]

[0053] 3. Verification Conclusion

[0054] Through systematic comparative testing, the highway sign with control module of this invention significantly outperforms traditional technologies in terms of performance indicators. Especially in terms of power-on protection and anti-interference, the RC+analog switch gating structure of this solution successfully solves the starting problem of the highway sign controller in complex electromagnetic environments, increasing starting reliability from 60% to over 95%. This is crucial for ensuring reliable self-starting of the highway sign after power failure.

[0055] The diode fast discharge path design solves the protection failure problem of traditional solutions in scenarios with frequent power outages and restarts. Experiments have shown that this solution can still maintain nearly 100% protection effectiveness under repeated power-on intervals of 1-5 seconds, greatly improving the reliability during field maintenance.

[0056] The complementary transistor signal conversion structure not only simplifies circuit design and reduces the number of components by approximately 40%, but also increases signal conversion speed by approximately 50%, making firmware updates more efficient and reliable. The slight RC filtering formed by the damping resistor and distributed capacitance also significantly improves the system's anti-interference capability, maintaining stable operation even under ±8kV ESD testing, meeting the requirements of harsh outdoor environments.

[0057] Comprehensive evaluation shows that this solution, while maintaining high compatibility with standard serial port tools, significantly improves the self-starting reliability and remote maintenance efficiency of highway sign controllers, and has broad application prospects.

Claims

1. A highway sign with a control module, characterized in that, include: The sign body contains a control module, which includes: The power-on reset reference circuit includes a resistor (R78), a capacitor (C44), and a diode (D13) connected in parallel across the resistor (R78). One end of the resistor (R78) is connected to the power supply, and the other end is connected to one end of the capacitor (C44) to form an RC node. The other end of the capacitor (C44) is grounded. An analog switch (U15) has its enable terminal (E) connected to the RC node; The DTR# signal processing circuit includes a first current-limiting resistor (R74), an NPN transistor (Q16), and a pull-up resistor (R73). One end of the first current-limiting resistor (R74) is connected to the DTR# signal, and the other end is connected to the base of the NPN transistor (Q16). The collector of the NPN transistor (Q16) is connected to the NRST pin and one end of the pull-up resistor (R73). The other end of the pull-up resistor (R73) is connected to the power supply. The RTS# signal processing circuit includes a second current-limiting resistor (R75), a PNP transistor (Q17), a pull-down resistor (R79), and a damping resistor (R76). One end of the second current-limiting resistor (R75) is connected to the RTS# signal, and the other end is connected to the base of the PNP transistor (Q17). The emitter of the PNP transistor (Q17) is connected to the power supply, and the collector is connected to the BOOT0 pin through the damping resistor (R76). The pull-down resistor (R79) is connected between the base of the PNP transistor (Q17) and the power supply. The input and output terminals of the analog switch (U15) are respectively connected to the signal paths of the DTR# signal processing circuit and the RTS# signal processing circuit.

2. The highway sign with a control module according to claim 1, characterized in that, The time constant formed by the resistor (R78) and the capacitor (C44) is used to set the shielding time of external control signals after power-on.

3. The highway sign with a control module according to claim 1, characterized in that, The damping resistor (R76) is used to form a slight RC filter with the distributed capacitance to suppress interference on the BOOT0 signal line.

4. The highway sign with a control module according to claim 1, characterized in that, The resistor (R78) has a resistance of 820kΩ and the capacitor (C44) has a capacitance of 10μF, forming a time constant of approximately 8.2 seconds.

5. The highway sign with a control module according to claim 1, characterized in that, The analog switch (U15) is a 74HC1G66 single-channel analog switch.

6. The highway sign with a control module according to claim 1, characterized in that, The first current-limiting resistor (R74) has a resistance of 2.7kΩ, the second current-limiting resistor (R75) has a resistance of 1kΩ, and the damping resistor (R76) has a resistance of 1kΩ.

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