Controller watchdog function self-checking circuit

Abstract

The utility model relates to the technical field of electronic circuits, in particular to a self-checking circuit for a watchdog function of a controller, which comprises a power supply, a microprocessor, a resistor and a capacitor. A power supply and a watchdog reset function are provided for an electric power steering system controller board level, charging and discharging of a resistor and a capacitor are adopted, safety self-checking is carried out on the watchdog function, the corresponding function safety requirement is met, and meanwhile the requirement for relatively economical cost is met.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, specifically a circuit for self-testing the watchdog function of a controller. Background Technology

[0002] Electric power steering systems are considered safety components in automobiles, requiring a high level of functional safety. The motor controller in the power steering control system must also be designed based on functional safety requirements, ensuring both functionality and reliability. Specifically, the controller's watchdog function needs to have appropriate safety mechanisms for safety monitoring.

[0003] To implement security testing for watchdog functionality, a relatively simple approach is to select a highly integrated power supply chip with watchdog self-test capabilities.

[0004] However, the cost of using highly integrated power chips is high, which cannot meet the requirements of today's fiercely competitive market.

[0005] Therefore, it is necessary to design a circuit for the self-testing of the controller watchdog function, and to meet the self-testing requirements of the control system watchdog function in a low-cost manner. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a circuit for self-testing the watchdog function of a controller, which satisfies the self-testing of the watchdog function of the control system in a low-cost manner.

[0007] To achieve the above objectives, this utility model provides a self-test circuit for a controller watchdog function, comprising a power supply, a microprocessor, resistors, and capacitors. The power supply's input pin is connected in two paths to the positive terminal of an external power source and one end of capacitor one, respectively. The power supply's delay pin is connected to one end of capacitor two. The power supply's output pin is connected in six paths to one end of capacitor three, one end of capacitor five, one end of resistor one, one end of resistor two, the 3.3V power supply terminal, and the microprocessor's VDD pin, respectively. The other end of resistor one is connected in two paths to the power supply's reset pin and one end of resistor three, respectively. The other end of resistor three is connected to the microprocessor's Reset pin. A resistor four is connected in series between the power supply's watchdog input pin and the microprocessor's I / O 3 pin. The power supply's watchdog enable pin is connected in series with resistor five, and then in two paths to the other end of resistor two and the microprocessor's I / O 4 pin, respectively. The microprocessor's I / O 1 pin is connected in three paths to one end of resistor six, one end of resistor seven, and one end of capacitor four, respectively. The other end of resistor six is ​​connected to the microprocessor's I / O 4 pin. The two pins are connected as follows: the other end of capacitor 1, the other end of capacitor 2, the other end of capacitor 3, the other end of capacitor 4, the other end of capacitor 5, the other end of resistor 7, the ground pin of the power supply, and the VSS pin of the microprocessor.

[0008] The power supply is a board-level power supply with a watchdog module.

[0009] The external power source is an external storage battery.

[0010] The capacitance of capacitor four is 100nF, and the resistance of resistor seven is 5MΩ.

[0011] Compared with the prior art, this utility model adopts a relatively low-cost power supply with built-in watchdog function to provide power and watchdog reset function for the electric power steering system controller board. It also uses the charging and discharging of resistors and capacitors to perform safety self-testing of the watchdog function to achieve the corresponding functional safety requirements, while ensuring the need for relatively economical cost. Attached Figure Description

[0012] Figure 1 This is the circuit diagram of this utility model. Detailed Implementation

[0013] The present invention will now be further described with reference to the accompanying drawings.

[0014] See Figure 1This utility model relates to a self-test circuit for a controller watchdog function, comprising a power supply, a microprocessor, resistors, and capacitors. The power input pin of the power supply LDO is connected in two paths to the positive terminal of an external power supply and one end of capacitor C1. The delay pin of the power supply LDO is connected to one end of capacitor C2. The power output pin of the power supply LDO is connected in six paths to one end of capacitor C3, one end of capacitor C5, one end of resistor R1, one end of resistor R2, the 3.3V power supply terminal, and the VDD pin of the microprocessor. The other end of resistor R1 is connected in two paths to the reset pin of the power supply LDO and one end of resistor R3. The other end of resistor R3 is connected to the Reset pin of the microprocessor. A resistor R4 is connected in series between the watchdog input pin of the power supply LDO and the I / O 3 pin of the microprocessor. The watchdog enable pin of the power supply LDO is connected in series with resistor R5, and then in two paths to the other end of resistor R2 and the I / O 4 pin of the microprocessor. Pin 1 is divided into three paths and connected to one end of resistor R6, one end of resistor R7, and one end of capacitor C4 respectively. The other end of resistor R6 is connected to the I / O 2 pin of the microprocessor. The other ends of capacitors C1, C2, C3, C4, C5, and R7, the ground pin of the power supply LDO, and the VSS pin of the microprocessor are grounded.

[0015] The external power supply is an external battery, and the power supply LDO is a board-level power supply with a watchdog module. The power supply LDO provides low-voltage power supply and watchdog reset function for the system.

[0016] Microprocessors provide functions such as system control, calculation, storage, communication, input, output, and self-testing.

[0017] Capacitors primarily function as filters and voltage regulators. Resistors primarily function as current limiters.

[0018] To prevent program crashes in the microprocessor, the watchdog timer function requires the program to periodically "feed" the watchdog. If feeding fails, the system is reset. The watchdog self-test function involves the microprocessor simulating a feeding failure signal to the watchdog timer. The watchdog timer returns a flag indicating that the feeding failure signal has been received, thus verifying the watchdog timer function is working correctly. Typically, an LDO power supply with a watchdog function will immediately output a reset signal to reset the microprocessor after a feeding failure. In this case, the microprocessor cannot receive the feeding failure signal and therefore cannot determine whether the watchdog feeding action was completed.

[0019] When this utility model is working, the positive terminal of the external battery supplies power to the power input pin of the LDO power supply, and the negative terminal of the external battery is grounded. After the LDO power supply is powered on, it outputs a 3.3V voltage on the power output pin. The 3.3V voltage is regulated by capacitor C3 and filtered by capacitor C5 before it supplies power to the microprocessor.

[0020] After the microprocessor powers on, I / O 1 and I / O 2 are in a high-impedance state, initialized as output and input functions respectively. The microprocessor reads the state of I / O 2 and determines its level. I / O 4 is initialized as a low-level output, so the watchdog enable pin is low, enabling the watchdog function of the LDO power supply.

[0021] When I / O 2 pin = 0, the system determines that the watchdog timer is not performing a self-test, and I / O 1 pin outputs a high level.

[0022] Read the status of I / O 2 pin again and make the following judgments: 1) If the level of I / O 2 pin is low, the system determines that the watchdog self-test mechanism is not normal, enters the OS scheduling, and reports a watchdog self-test mechanism fault DEM; 2) If the level of I / O 2 pin is high, the watchdog self-test function is started, and the I / O 3 pin outputs a low level to the watchdog input pin of the power supply LDO to simulate the watchdog feed failure signal.

[0023] Waiting for system reset time: 1) If the reset pin of the power supply LDO outputs a low level, the microprocessor will reset and return to the microprocessor initialization state, repeating the above steps; 2) If the system reset time has elapsed and the microprocessor has not reset, the program will continue to run sequentially, then enter the OS scheduling and report the watchdog self-test mechanism fault DEM.

[0024] When I / O 2 pin = 1, the system determines that the watchdog function self-test has been completed, I / O 1 pin outputs a low level, the program enters the OS scheduling, and the system runs normally.

[0025] The capacitor C4 and resistor R7 form an RC discharge delay circuit. In this invention, the capacitance of capacitor C4 is set to 100nF and the resistance of resistor R7 is set to 5MΩ. The time from microprocessor reset to the start of the watchdog self-test program is approximately 100ms.

[0026] Within this 100ms period, when the microprocessor's I / O 1 pin outputs a high level, capacitor C4 charges. Since the impedance between the I / O 1 pin and capacitor C4 is very small and negligible, capacitor C4 is immediately charged to approximately 3.3V. This facilitates immediate reading of the I / O 2 pin status and minimizes instruction execution time. After the microprocessor resets, capacitor C4 discharges through resistor R7. At the time of the watchdog self-test, the remaining voltage on capacitor C4 is approximately: V0 = = =2.7V, which is still greater than the high-level detection voltage of the microprocessor (3.3V × 0.7 = 2.31V). Therefore, the charge on capacitor C4 is sufficient to maintain the high level required from microprocessor reset to watchdog self-test, thus enabling the completion of the watchdog self-test function to be identified by the voltage on capacitor C4 upon power-up.

[0027] This invention utilizes the characteristic of RC discharge time delay to fully charge capacitor C4 just before the system performs watchdog timer feeding, and reads the level of the remaining charge on capacitor C4 after system reset, thereby confirming whether the watchdog function self-test program has been completed.

[0028] This utility model uses a relatively low-cost power supply with built-in watchdog function to provide power and watchdog reset function for the electric power steering system controller board. It also uses the charging and discharging of resistors and capacitors to perform safety self-testing of the watchdog function to meet the corresponding functional safety requirements while ensuring the need for relatively economical cost.

Claims

1. A circuit for self-testing the watchdog function of a controller, comprising a power supply, a microprocessor, resistors, and capacitors, characterized in that: The power input pin of the power supply (LDO) is connected in two paths to the positive terminal of the external power supply and one end of capacitor 1 (C1). The delay pin of the power supply (LDO) is connected to one end of capacitor 2 (C2). The power output pin of the power supply (LDO) is connected in six paths to one end of capacitor 3 (C3), one end of capacitor 5 (C5), one end of resistor 1 (R1), one end of resistor 2 (R2), the 3.3V power supply terminal, and the VDD pin of the microprocessor. The other end of resistor 1 (R1) is connected in two paths to the reset pin of the power supply (LDO) and one end of resistor 3 (R3). The other end of resistor 3 (R3) is connected to the Reset pin of the microprocessor. Resistor 4 (R4) is connected in series between the watchdog input pin of the power supply (LDO) and the I / O 3 pin of the microprocessor. The watchdog enable pin of the power supply (LDO) is connected in series with resistor 5 (R5), and then splits into two paths to the other end of resistor 2 (R2) and the I / O pin of the microprocessor. The 4-pin connection is as follows: the microprocessor's I / O 1 pin is connected to one end of resistor 6 (R6), one end of resistor 7 (R7), and one end of capacitor 4 (C4) respectively. The other end of resistor 6 (R6) is connected to the microprocessor's I / O 2 pin. The other ends of capacitor 1 (C1), capacitor 2 (C2), capacitor 3 (C3), capacitor 4 (C4), capacitor 5 (C5), resistor 7 (R7), the ground pin of the power supply (LDO), and the microprocessor's VSS pin are grounded.

2. The circuit for self-testing the watchdog function of a controller according to claim 1, characterized in that: The power supply (LDO) is a board-level power supply with a watchdog module.

3. The circuit for self-testing the watchdog function of a controller according to claim 1, characterized in that: The external power source is an external storage battery.

4. The circuit for self-testing the watchdog function of a controller according to claim 1, characterized in that: The capacitance of capacitor four (C4) is 100nF, and the resistance of resistor seven (R7) is 5MΩ.

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