Multi-mode high-precision PPS time service test system and method

Abstract

The invention discloses a multi-mode high-precision PPS time service test system and method, relates to the technical field of time synchronization of a satellite-borne system, and solves the problem that in the prior art, comprehensive time synchronization test is difficult to perform on a satellite-borne single machine in a ground environment. The test system comprises a GNSS receiving module, an SoC (System on Chip), a power management module and a differential output module; the power management module supplies power to each module; the SoC system on chip comprises a pulse per second generation module, a PPS output module, a message input module, a longitude and latitude reading module, a UTC time updating module and a message output module. The testing system is provided with an external time system and an internal time system, external GNSS signals and internal system timing can be received at the same time, and the stability of the time signals is ensured while the time precision is ensured. According to the invention, four sending modes are adopted, so that comprehensive testing of satellite-borne single-machine time synchronization precision is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of time synchronization of satellite systems, and in particular to a high-precision PPS timing test system and method under multiple modes. Background Art

[0002] High-precision time synchronization is crucial to onboard systems. It is the prerequisite for ensuring that each onboard unit works in coordination with other systems (such as the inertial navigation system), improving measurement accuracy, and ensuring the stable operation of spacecraft in complex environments. Therefore, ground testing of onboard units requires strict time synchronization in order to verify the time accuracy of the unit and the data association with other systems.

[0003] The Global Navigation Satellite System, or GNSS, uses multiple satellites to transmit signals to the ground, and the receiver performs triangulation to determine its own longitude, latitude, and other information. The positioning signal using GNSS can provide high-precision time and location information for the above-mentioned fields.

[0004] When conducting time synchronization ground tests on satellite-borne single machines, on the one hand, it is necessary to provide high-precision and high-reliability time information; on the other hand, it is necessary to simulate various situations that may occur on the satellite. This requires the ground test system to ensure the reliability and accuracy of the output information while designing multiple error conditions, but the existing technology lacks the ability to meet both requirements at the same time. Summary of the invention

[0005] The present invention solves the problem that it is difficult to conduct a comprehensive time synchronization test on a satellite-borne single machine in a ground environment in the prior art, and provides a high-precision PPS timing test system and method in multiple modes. The test system of the present invention has two sets of time systems, an external time system and an internal time system, which can simultaneously receive external GNSS signals and internal system timing, and ensure the stability of the time signal while ensuring the time accuracy. In addition, the present invention designs four transmission modes to achieve a comprehensive test of the time synchronization accuracy of the satellite-borne single machine.

[0006] A multi-mode high-precision PPS timing test system, the test system includes a GNSS receiving module, a SoC system-on-chip, a power management module and a differential output module; the power management module supplies power to each module; the SoC system-on-chip includes a second pulse generation module, a PPS output module, a message input module, a latitude and longitude reading module, a UTC time update module and a message output module;

[0007] The GNSS receiving module acquires a GNSS signal, wherein the GNSS signal includes an external PPS pulse per second and satellite positioning information;

[0008] The second pulse generation module generates second pulses by using the external constant temperature crystal oscillator of the SoC system on chip, and receives the external PPS second pulses at the same time, and uses the external PPS second pulses as the absolute time reference of the test system; the second pulse generation module transmits the generated second pulses to the PPS output module, the UTC time update module and the message output module;

[0009] The PPS output module expands the received second pulse to multiple channels for synchronous timing test of multiple devices, and selects whether to send a PPS signal according to the output mode of the current PPS output module;

[0010] The message input module receives the satellite positioning information in the GNSS signal, and parses the longitude and latitude information and the UTC time information and transmits them to the longitude and latitude reading module and the UTC time updating module respectively;

[0011] The latitude and longitude reading module obtains the latitude and longitude information and transmits it to the message output module;

[0012] The UTC time update module realizes local timing and message time update at the same time; the UTC time update module is started when the rising edge of the second pulse of the second pulse generation module is received; it is judged whether the UTC time information received by the message input module is valid, if the UTC time information is valid, the read UTC time information will overwrite the local UTC time of the system; if the UTC time information is invalid, the internal time system is started;

[0013] The message output module sends the current latitude and longitude information and UTC time information to the differential output module according to the current output mode and the communication protocol;

[0014] The differential output module outputs UTC time information and PPS second pulses through a variety of communication methods.

[0015] The present invention also provides a multi-mode high-precision PPS timing test method, which is implemented by the multi-mode high-precision PPS timing test system, and the method is implemented by the following steps:

[0016] Step 1: Connect the GNSS receiving module, differential output module and the interface of the SOC chip system correctly; initialize the system;

[0017] Step 2: The message input module of the SOC system-on-chip determines whether the message data is received. If the message data is not received, it continues to wait; if the message data is received, it stores the message data in a buffer row by row, and reads the UTC time information and the longitude and latitude information;

[0018] The SOC system-on-chip also determines whether an F2P interrupt is generated. If so, execute step 3; otherwise, continue to wait for the F2P interrupt;

[0019] Step 3: Delay 100ms and execute step 4; at the same time, determine the PPS output mode of the PPS output module; execute step 5;

[0020] Step 4: After the delay is completed, determine the output mode of the message output module. If the output mode is sending, send the UTC time information and longitude and latitude information. Otherwise, continue to determine.

[0021] Step 5: If the PPS output mode is sending, the PPS output module sends information, otherwise, continue to judge.

[0022] Beneficial effects of the present invention:

[0023] The test system of the present invention includes a complete hardware system for satellite signal reception, data processing and synchronous time output. The system has high system integration, high time accuracy, is easy to program, and can be set in multiple modes. It can provide time synchronization information to multiple satellite-borne units at the same time, providing a simple and reliable time synchronization system for ground testing of satellite-borne units.

[0024] The test equipment of the present invention includes two time systems, an external time system and an internal time system. The external time system relies on GNSS satellite signals to obtain accurate full second pulse time and current time position information for alignment with the internal time system; the internal time system relies on a constant temperature crystal oscillator to generate accurate second information. When the external time system is unavailable, the device can also stably output PPS second pulses and time information; when the external time system is available and the information is valid, the internal time system is aligned, eliminating the time error of the crystal oscillator and obtaining accurate position information. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention provides a schematic diagram of a high-precision PPS timing test system in multiple modes.

[0026] Figure 2 It is the schematic diagram of SoC system on chip;

[0027] Figure 3 The present invention provides a flow chart of a high-precision PPS timing test method under multiple modes. DETAILED DESCRIPTION

[0028] Specific implementation method 1. Combination Figure 1 and Figure 2 The present embodiment is described as a high-precision PPS timing test system in multiple modes, the system comprising a GNSS receiving module, a SoC system-on-chip, a power management module, a differential output module, a button group and an LED light group;

[0029] In this implementation, the SoC system-on-chip, power management module, differential output module, button group and LED group are integrated on a set of circuit boards, and the GNSS receiving module is connected to the circuit board via a connection interface.

[0030] The GNSS receiving module includes an antenna and a GNSS receiver chip, which is used to obtain external PPS pulses and satellite positioning information of the NMEA-0183 protocol, and the obtained external PPS second pulse is used as the absolute time reference of the system;

[0031] The differential output module includes a CAN differential output chip, an RS422 differential output chip and a PPS differential output chip;

[0032] The SoC system-on-chip refers to a fully programmable system-on-chip (APSoC), which integrates an ARM processor and a programmable logic (FPGA) to achieve programmable integration of software and hardware. The SoC system-on-chip mainly consists of two parts: an ARM processor core (PS) module and a programmable FPGA (PL) module, in which:

[0033] The FPGA module includes a pulse per second generation module and a PPS output module;

[0034] The ARM module includes a message input module, a latitude and longitude reading module, a UTC time update module and a message output module;

[0035] In this implementation, the output configuration of the GNSS receiving module used is to output only the RMA sentence, and the data output mode is an asynchronous receiver-transmitter, i.e., UART;

[0036] The SoC system-on-chip uses UART to connect to the GNSS receiving module to obtain GNSS positioning information; the SoC system-on-chip uses CAN and another UART to connect to the CAN differential signal output chip and the RS422 differential output chip respectively; the SoC system-on-chip uses GPIO to connect to the PPS differential output chip. At the same time, the FPGA of the SoC system-on-chip is connected to the PPS pulse output interface of the GNSS receiver chip through an interface configured as an input pin to capture the rising edge of the PPS pulse; the SoC system-on-chip is connected to the key group through the GPIO port configured as the input to capture the signal of the key being pressed or released; the SoC system-on-chip is connected to the LED light group through the GPIO port configured as the output to control the on and off of the LED light.

[0037] In this embodiment, the chip used in the power management module is TPS7A7001. There are two power supply methods: one is to connect to a 5V DC power supply through the DE socket interface on the circuit board, and the DC power obtained is stepped down to 3.3V through the power management chip; the other is to connect to a 5V DC power supply through the TYPE-C port of the SoC system on chip.

[0038] In this embodiment, the GNSS receiving module is used to obtain GNSS signals, including receiving satellite positioning information and external PPS second pulses. The indicator light on the GNSS receiver indicates whether the signal is received. When there is no signal, the external PPS second pulse and satellite positioning information are not output. When a signal is received, the rising edge of the second pulse is used to represent the whole second, and the satellite positioning information encoded in the NMEA-0183 protocol is output through the serial port TX interface.

[0039] The SoC system-on-chip is used to receive GNSS signals, obtain and update UTC time information and longitude and latitude information by processing the received signals, update the time data within the system, generate a timestamp for the current time information, package and send the synchronization information according to the protocol, and realize time synchronization; specifically including.

[0040] In order to ensure the high-precision characteristics of PPS, the second pulse generation module is implemented in FPGA. FPGA counts 1 second through an external constant-temperature 50MHz crystal oscillator. When 1 second is reached, FPGA generates a high-level pulse edge, and this pulse rising edge is used as the stable output of the entire system. At the same time, FPGA receives the external PPS second pulse sent by the GNSS receiving module. The external PPS second pulse is only used to align the internal time system. The specific process is: when the external PPS second pulse is captured, the second pulse generation module stops counting and generates a second pulse at this moment. At this time, the internal second pulse is synchronized with the external PPS second pulse. After that, the crystal oscillator starts counting again to stably generate second pulses.

[0041] The message input module receives the satellite positioning information sent by the GNSS receiving module through the serial port. The positioning information is encoded in a fixed mode. Each message starts with the character "$" and ends with a line feed. By identifying the first and last characters of the message, the complete message is stored in the system buffer, and each field of the message is parsed, and the longitude and latitude and UTC time information (UTC time and date data) are read in the corresponding fields.

[0042] The latitude and longitude reading module reads the character data read in the message input module, including east / west longitude, south / north latitude and specific longitude and latitude data, wherein the specific longitude and latitude values ​​need to be changed from the format specified by the NMEA-0183 protocol to decimal floating point numbers, and the current east / west longitude and south / north latitude information is represented by the specified values.

[0043] The UTC time update module can simultaneously realize local timing and message time update. The UTC time update module will start the module only when it receives the rising edge pulse of the second pulse generation module, indicating that the whole second time has arrived. After the module is started, it first determines whether the UTC and date data obtained by the message input module are valid by receiving the flag bit. If the data is valid, the read time information will overwrite the local UTC and date of the system; if the data is invalid, it means that the GNSS signal is unavailable, and the internal time system needs to be used, that is, the plus 1 operation is performed on the internal UTC, indicating that the current time is increased by 1 second. After each time update, the current time is timestamped.

[0044] The message output module also needs to receive the rising edge of the second pulse generation module, which represents the arrival of a whole second. The system needs to send information outward, and the message output module is started. After the module is started, it first determines whether the receiving flag in the longitude and latitude reading module is valid. If it is valid, the longitude and latitude information is sent in multiple ways using RS422 and CAN bus in accordance with the communication protocol; if the data is invalid, the longitude and latitude information is not sent. Since the system can count stably under any circumstances and generate the current timestamp, the message output module obtains the current timestamp information in the UTC time update module, and sends it in multiple ways using RS422 and CAN bus in accordance with the communication protocol. The module sends the above information in the output message mode; the above information is not sent in the non-output message mode.

[0045] The PPS output module copies three second pulses generated by the second pulse generation module in the FPGA and connects them to the PPS differential output chip to output multiple second pulses with low latency, which can be used for timing tests of multiple satellite-borne single machines. The module sends second pulses in the output PPS mode and does not send second pulses in the non-output PPS mode.

[0046] The differential output module includes a PPS differential output chip, a CAN differential output chip, and an RS422 differential output chip, and outputs UCT time information and PPS pulses through multiple communication modes to improve the signal anti-interference capability.

[0047] This embodiment can simulate four conditions through the key group: sending a message signal and sending a PPS pulse, sending a message signal and not sending a PPS pulse, not sending a message signal and sending a PPS pulse, and not sending a message signal and not sending a PPS pulse.

[0048] In this implementation, the power management module is used for power supply voltage conversion to supply power to the system;

[0049] The button group is used to switch the system between four modes: sending message signal / not sending message signal mode / sending PPS pulse / not sending PPS pulse; the LED light group is used to indicate the current system mode.

[0050] Specific implementation method 2: Combination Figure 3 This embodiment is described as a test method for a high-precision PPS timing test system in multiple modes described in the first embodiment. The method is implemented by the following steps:

[0051] Step 1. Connect the GNSS receiving module, differential output module and the interface of the SOC system on chip correctly; turn on the system, the system enters initialization, the FPGA starts counting, and the LED light group is in the preset state, that is, the indicator light for not sending PPS pulses and messages is on, and the indicator light for sending PPS pulses and messages is off; wait for the GNSS receiver chip to enter the normal receiving state, that is, both LED lights on the GNSS receiver chip are on.

[0052] Step 2: The SoC system-on-chip starts to determine whether the serial port has received the message data. If the message data is not received, it waits for the message data. When the serial port RX port receives the message data, it stores the message information in the buffer by line, reads each field, finds and stores the UTC time information and the longitude and latitude information, and determines whether these data are valid. If the data is valid, the receiving flag position is set to 1; if the data is invalid, the receiving flag position is set to 0.

[0053] The system also determines whether an F2P interrupt is generated, that is, the rising edge of the second pulse generated by the FPGA. The determination of the F2P interrupt and the reception of the serial port signal are two simultaneous and independent steps. When the rising edge of the second pulse is not received, it means that the whole second has not arrived, and the system waits for the F2P interrupt; when the rising edge pulse is captured, the next step is entered.

[0054] Step 3: When the system generates an F2P interrupt, the FPGA copies and expands the pulse signal into three paths, and then determines the output mode of the PPS output module at this time. If the output mode is to send, it is output through the PPS differential output chip; otherwise, the PPS pulse is not sent.

[0055] When the system generates an F2P interrupt, it means the whole second has arrived. The system first delays for 100ms to wait for the GNSS receiver to send a message and process the internal data of the SoC system.

[0056] The system delay of 100ms and the determination of the PPS output mode are two steps that are performed simultaneously and independently of each other.

[0057] Step 4: After the delay is completed, the system starts to judge the message output mode, that is, whether the send signal button is pressed. If the button is not pressed, continue to judge; if the button is pressed to start sending information, execute step 5;

[0058] Step 5: The system sends UTC time information and longitude and latitude information;

[0059] In this implementation, when sending UTC time information, it is necessary to determine whether the receiving flag is 1. If it is 1, the UTC time received externally is output, and the current time is timestamped and packaged; if it is 0, the internal time system is enabled, that is, the internal UTC time + 1, and the updated time is timestamped and packaged and sent.

[0060] When sending longitude and latitude, it is also necessary to judge the receiving flag. If the receiving flag of the longitude and latitude signal is 1, it means that a valid position signal is received and the current longitude and latitude information is packaged and sent; if the receiving flag is 0, there is no valid position information and the current longitude and latitude information is empty.

[0061] In this embodiment, when the system is in output mode, the PPS differential output chip outputs three differential second pulses; the RS422 differential output chip outputs multiple differential serial port data that conform to the communication protocol; and the CAN differential output chip outputs multiple CAN bus data that conform to the communication protocol.

[0062] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0063] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-precision PPS timing test system in multiple modes, characterized by: The test system includes a GNSS receiving module, a SoC system-on-chip, a power management module and a differential output module; the power management module supplies power to each module; the SoC system-on-chip includes a pulse-per-second generation module, a PPS output module, a message input module, a latitude and longitude reading module, a UTC time update module and a message output module; The GNSS receiving module acquires a GNSS signal, wherein the GNSS signal includes an external PPS pulse per second and satellite positioning information; The second pulse generation module generates second pulses by using the external constant temperature crystal oscillator of the SoC system on chip, and receives the external PPS second pulses at the same time, and uses the external PPS second pulses as the absolute time reference of the test system; the second pulse generation module transmits the generated second pulses to the PPS output module, the UTC time update module and the message output module; The PPS output module expands the received second pulse to multiple channels for synchronous timing test of multiple devices, and selects whether to send a PPS signal according to the output mode of the current PPS output module; The message input module receives the satellite positioning information in the GNSS signal, and parses the longitude and latitude information and the UTC time information and transmits them to the longitude and latitude reading module and the UTC time updating module respectively; The latitude and longitude reading module obtains the latitude and longitude information and transmits it to the message output module; The UTC time update module realizes local timing and message time update at the same time; the UTC time update module is started when the rising edge of the second pulse of the second pulse generation module is received; it is judged whether the UTC time information received by the message input module is valid, if the UTC time information is valid, the read UTC time information will overwrite the local UTC time of the system; if the UTC time information is invalid, the internal time system is started; The message output module sends the current latitude and longitude information and UTC time information to the differential output module according to the current output mode and the communication protocol; The differential output module outputs UTC time information and PPS second pulses through a variety of communication methods.

2. A multi-mode high-precision PPS timing test system according to claim 1, characterized in that: The test system also includes a button group and an LED light group; the button group is used to switch the test system between four modes: sending message signals or not sending message signals, sending PPS pulses or not sending PPS pulses; the LED light group is used to indicate the current system mode.

3. A multi-mode high-precision PPS timing test system according to claim 1, characterized in that: The message output module receives the rising edge of the second pulse of the second pulse generating module, indicating that the whole second has arrived. The message output module determines whether the data in the longitude and latitude reading module is valid. If the data is valid, the longitude and latitude information is sent in the output message mode by using RS422 and CAN bus in accordance with the communication protocol. If the data is invalid, the longitude and latitude information will not be sent; the message output module obtains the current timestamp information in the UTC time update module, packages it according to the communication protocol, and sends it in the output message mode using RS422 and CAN bus.

4. A multi-mode high-precision PPS timing test system according to claim 1, characterized in that: The GNSS receiving module includes an antenna and a GNSS receiver chip, which is used to obtain external PPS pulses and satellite positioning information of the NMEA-0183 protocol, and uses the obtained external PPS second pulse as the absolute time reference of the test system.

5. A multi-mode high-precision PPS timing test system according to claim 1, characterized in that: The PPS output module copies three pulses of the second pulse generated by the pulse generation module and connects them to the PPS differential output chip to output multiple pulses of the second pulse under low latency for timing testing of multiple satellite-borne single machines; the PPS output module sends the pulse of the second pulse in the output PPS mode; In the non-PPS output mode, no second pulse is sent.

6. A multi-mode high-precision PPS timing test system according to claim 1, characterized in that: The differential output module includes a CAN differential output chip, an RS422 differential output chip and a PPS differential output chip; When the system is in output mode, the PPS differential output chip outputs three differential second pulses; The RS422 differential output chip outputs multiple channels of differential serial port data that conform to the communication protocol; The CAN differential output chip outputs multiple channels of CAN bus data that conform to the communication protocol.

7. A multi-mode high-precision PPS timing test method according to claim 1, characterized in that: The method is implemented by a multi-mode high-precision PPS timing test system as described in claims 1-6, and the specific process of the method is as follows: Step 1: Connect the GNSS receiving module, differential output module and the interface of the SOC chip system correctly; initialize the system; Step 2: The message input module of the SOC system-on-chip determines whether the message data is received. If the message data is not received, it continues to wait; if the message data is received, it stores the message data in a buffer row by row, and reads the UTC time information and the longitude and latitude information; The SOC system-on-chip also determines whether an F2P interrupt is generated. If so, execute step 3; otherwise, continue to wait for the F2P interrupt; Step 3: Delay 100ms and execute step 4; at the same time, determine the PPS output mode of the PPS output module; execute step 5; Step 4: After the delay is completed, determine the output mode of the message output module. If the output mode is sending, send the UTC time information and longitude and latitude information. Otherwise, continue to determine. Step 5: If the PPS output mode is sending, the PPS output module sends information, otherwise, continue to judge; 8. A multi-mode high-precision PPS timing test method according to claim 7, characterized in that: In step 2, after receiving the message data, it is determined whether the data is valid. If the data is valid, the receiving flag is set to 1; if the data is invalid, the receiving flag is set to 0.

9. A multi-mode high-precision PPS timing test method according to claim 7, characterized in that: In step 2, when an F2P interrupt occurs, the FPGA copies and expands the second pulse into three paths, and then determines the output mode of the PPS output module at this time. If the output mode is to send, it is output through the PPS differential output chip; otherwise, the PPS pulse is not sent.

10. A multi-mode high-precision PPS timing test method according to claim 7, characterized in that: In step 4, when the message output module sends UTC time information, it needs to determine whether the receiving flag of the received UTC time information is 1. If it is 1, the UTC time information received from the outside is output, and the current UTC time information is timestamped and packaged; if it is 0, the internal time system is enabled, that is, the internal UTC time + 1, and the updated time is timestamped and packaged for sending; When the message output module sends longitude and latitude information, it is necessary to judge the information reception flag. If the reception flag of the longitude and latitude information is 1, a valid position signal is received and the current longitude and latitude information is packaged and sent; if the reception information flag is 0, there is no valid position information and the current longitude and latitude information is empty.

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