USB to network port expansion circuit and implementation method for rail transit vehicle control box

Abstract

The present invention relates to a rail transit vehicle control box USB-to-network port expansion circuit and implementation method, belonging to the field of communication systems. A USB-formatted signal received from a vehicle control box device is transmitted to a network port expansion circuit via a set of transceiver data lines. The network port expansion circuit converts the USB-formatted signal transmitted via the data line into a network port-formatted signal, which is then transmitted to an isolation protection circuit via two sets of transceiver data lines. The generated network port-formatted signal, after being processed by the isolation protection circuit, is then transmitted to an RJ45 network port signal receiving circuit, also via two sets of transceiver data lines. The RJ45 network port signal receiving circuit transmits the signal to a PC via Ethernet, thereby achieving network port-formatted interactive communication with the vehicle control box device. The present invention converts USB data lines into network port data lines, expanding its application scope. The network port expansion circuit provides multiple layers of protection for data transmission, making transmission more stable and secure. Furthermore, the invention is compact, convenient, and low-cost.

Description

Technical Field

[0001] The present invention relates to the technical field of network port expansion, and in particular to a USB to network port expansion circuit for a rail transit vehicle control box and an implementation method thereof. Background Art

[0002] With the continuous advancement of communication technology, Ethernet has become the most widely used technology for network connectivity and data transmission. Ethernet communication has gradually become well-known due to its wide application, low cost, and high communication speed. Communication with TCMS, PIS, and other systems in the rail transit sector has also evolved from dry contacts and serial ports to digital network communication using Ethernet ports, which not only increases transmission speed but also improves stability. However, most vehicle control boxes used in rail transit have a limited number of Ethernet interfaces. The commonly used im6 core board even has only one Ethernet port, which is far from sufficient for multi-port communication with other devices. Therefore, to meet the needs of equipment for multi-port communication and faster and more stable transmission, it is imperative to design an Ethernet port expansion circuit to adapt to the development of communication technology in the rail transit sector. Summary of the Invention

[0003] In view of the shortcomings of the existing vehicle control box equipment, such as a single communication network port, slow and unstable transmission speed, the present invention provides a rail transit vehicle control box USB to network port expansion circuit and implementation method. By docking with the USB interface on the rail transit equipment, the original USB interface is converted into a more widely used network port for information transmission, making the transmission faster and more stable, and more easily meeting the needs of the changing on-site environment.

[0004] The technical solution adopted by the present invention is: a rail transit vehicle control box USB to network port expansion circuit, including a USB interface electrostatic protection circuit, a network port expansion circuit, an isolation protection circuit and an RJ45 network port signal receiving circuit; the USB interface electrostatic protection circuit is connected to the RJ45 network port signal receiving circuit through the network port expansion circuit and the isolation protection circuit in sequence; the USB interface electrostatic protection circuit is used to dock with the vehicle control box communication interface; the network port expansion circuit is used to convert and expand the USB-format data line transmitted by the USB interface electrostatic protection circuit into network port format data; the isolation protection circuit is used to isolate and protect the network port format data line transmitted by the network port expansion circuit; the RJ45 network port signal receiving circuit uses the received expanded network port format data line to connect to the external device interface for communication.

[0005] A method for implementing a USB-to-network port expansion circuit for a rail transit vehicle control box. During operation, a USB interface electrostatic protection circuit is connected to an external vehicle control box device, and an RJ45 network port signal receiving circuit is connected to a PC. When the vehicle control box device communicates with the PC, the USB interface electrostatic protection circuit receives a USB-formatted signal from the vehicle control box device and transmits it to the network port expansion circuit via a set of transceiver data lines. The network port expansion circuit converts the USB-formatted signal transmitted via the data line into a network port-formatted signal, which is transmitted to an isolation protection circuit via two sets of transceiver data lines. The generated network port-formatted signal is processed by the isolation protection circuit and then transmitted to the RJ45 network port signal receiving circuit via two sets of transceiver data lines. The RJ45 network port signal receiving circuit transmits the signal to the PC via Ethernet, thereby implementing network port-formatted interactive communication between the vehicle control box device and the vehicle PC.

[0006] When the PC communicates with the control box device, the PC will send a signal through Ethernet to the RJ45 network port signal receiving circuit. The RJ45 network port signal receiving circuit transmits the network port form signal to the isolation protection circuit through two sets of transceiver data lines. After the signal is processed by the isolation protection circuit, it is also transmitted to the network port expansion circuit through two sets of transceiver data lines. The network port expansion circuit converts the transmitted network port form signal into a USB form signal, and transmits it to the USB interface electrostatic protection circuit through a set of transceiver data lines. The USB interface electrostatic protection circuit transmits the USB form signal to the vehicle control box device, thereby realizing network port form interactive communication between the PC and the vehicle control box device.

[0007] The method for the network port expansion circuit to convert the USB format signal transmitted by the data cable into the network port format signal is as follows: the network port expansion chip U1 of the network port expansion circuit is connected to the external vehicle control box device through the USB interface electrostatic protection circuit, and the network port expansion circuit will be recognized as a USB device by the vehicle control box device. The network port expansion chip U1 contains an integrated USB to Ethernet bridge for processing the conversion between USB data packets and Ethernet. When the data is transmitted to the USB port of the network port expansion chip U1 through the data cable, the network port expansion chip U1 will encapsulate the transmitted data into an Ethernet frame format that complies with the IEEE 802.3 standard, thereby realizing the USB expansion of the network port. Similarly, when the data is transmitted to the network port expansion chip U1 through the Ethernet port, it can also be converted into USB format for external communication.

[0008] The two groups of transceiver data lines are transmitted to the isolation protection circuit, and the generated network port form signal is processed by the isolation protection circuit in the following manner: when the vehicle control box device communicates with the PC, the two groups of transceiver data lines TX_P, TX_N and RX_P, RX_N in the network port form transmitted by the network port expansion circuit are transmitted to the network transformer N1. The network transformer N1 contains a winding inside. The sending end winding is connected to the data line generated by the network port expansion circuit, and the receiving end winding is connected to the ESD protector N2. When the data line passes through the sending end, a changing magnetic field will be generated. The changing magnetic field will generate a corresponding current at the receiving end to transmit the data line to the ESD protector N2, thereby realizing the isolation of the data lines of the receiving end and the sending end. The isolated data line is transmitted to the rear ESD protector, which contains a diode inside. It maintains a high resistance state during normal operation. Once it is affected by external static electricity, it will quickly convert to a low resistance state to transfer energy, thereby realizing the isolation between the vehicle control box device and the PC. Signal isolation protection during PC communication; when the PC communicates with the vehicle control box device, the two sets of receiving and transmitting data lines TD_P, TD_N and RD_P, RD_N in the form of the network port transmitted by the RJ45 network port signal receiving circuit first pass through the ESD protector N2, and the data lines are first protected against static electricity by the diode inside the ESD protector N2. The protected data lines are transmitted to the network port transformer N1. The network transformer N1 contains a winding. At this time, the sending end winding is connected to the data line transmitted from one end of the ESD protector N2, and the receiving end winding is connected to the network port expansion chip U1 in the network port expansion circuit expansion. When the data line passes through the sending end, a changing magnetic field will be generated. The changing magnetic field generates a corresponding current at the receiving end, and the data line is transmitted to the network port expansion chip U1 in the network port expansion circuit expansion, realizing the isolation of the receiving and sending end data lines, and realizing the signal isolation protection when the PC communicates with the vehicle control box device.

[0009] The beneficial effects of the present invention are as follows: the present invention utilizes the LAN9500A chip in the network port expansion circuit to provide a fully functional bus-powered USB to Ethernet interface, and realizes the expansion of the network port by bridging the USB to the 10 / 100 Ethernet port. In addition, the RJ45 network port signal receiving circuit and the USB interface electrostatic protection circuit are used to provide Ethernet and USB ports, thereby realizing the expansion of the USB to the network port for data transmission, increasing the number of network ports available for communication in the vehicle control box equipment, and converting the USB interface into a more widely used network port for information transmission in this way. It can realize data transmission with other devices in the form of a network port, increasing the possibility of data transmission with other devices, which is not only low-cost, but also has a fast transmission speed and a longer transmission distance, and is more likely to meet the needs of the changing environment on site.

[0010] The present invention converts the USB data cable into a network port data cable communication with a wider range of applications, and provides layered protection for data transmission through the network port expansion circuit, making the transmission more stable and secure. It is also compact, convenient and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A connection diagram for realizing the network port expansion circuit of the present invention;

[0012] Figure 2 A circuit diagram for realizing the USB interface electrostatic protection circuit of the present invention;

[0013] Figure 3 A circuit diagram for implementing the USB to network port expansion circuit of the present invention;

[0014] Figure 4 A circuit diagram for realizing the isolation protection circuit of the present invention;

[0015] Figure 5 To implement the circuit diagram of the RJ45 network port signal receiving circuit of the present invention;

[0016] Figure 6 A schematic diagram of circuit connections for implementing an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1 As shown, a rail transit vehicle platform control box USB to network port expansion circuit includes a USB interface electrostatic protection circuit, a network port expansion circuit, an isolation protection circuit and an RJ45 network port signal receiving circuit; the USB interface electrostatic protection circuit is bidirectionally connected to the network port expansion circuit through a group of transceiver signal lines USBD_N and USBD_P, the network port expansion circuit is bidirectionally connected to the isolation protection circuit through two groups of transceiver data lines TX_P, TX_N and RX_P, RX_N, and the isolation protection circuit is connected to the RJ45 network port signal receiving circuit through two groups of transceiver data lines TD_P, TD_N and RD_P, RD_N.

[0019] like Figure 2As shown, the connection relationship of the USB interface electrostatic protection circuit is as follows: pin 1 of the USB interface P1 is connected to one end of the ferrite bead FB4 and pin 5 of the TVS diode VD1, the other end of the ferrite bead FB4 is connected to +5V and one end of the capacitor C22, and the other end of the capacitor C22 is connected to GND. Pin 2 of the USB interface P1 is connected to pin 6 of the TVS diode VD1 through the USBD_N network. Pin 3 of the USB interface P1 is connected to pin 1 of the TVS diode VD1 through the USBD_P network. Pin 4 of the USB interface P1 is connected to one end of the capacitor C20 and the resistor R10 in parallel to GND. Pin 0 of the USB interface P1 is connected to the other end of the capacitor C20 and the resistor R10 in parallel to EARTH. Pin 2 of the TVS diode VD1 is connected to GND. The model of the USB interface P1 is USB2.0 STD-A MALE, the model of the TVS diode VD1 is NUP4202W1T2G, and the model of the ferrite bead FB4 is CBG160808U121T.

[0020] like Figure 3As shown, the connection relationship of the network port expansion circuit is as follows: pin 2 of the network port expansion chip U1 is connected to the TX_N network, pin 3 is connected to the TX_P network, pin 5 is connected to the RX_N network, pin 6 is connected to the RX_P network, pin 26 is connected to the cathode of the light-emitting diode LED2 through the nFDX_LED / GPIO8 network, and the anode of the light-emitting diode LED2 is connected to +3.3V through the resistor R13. Pin 27 of the network port expansion chip U1 is connected to pin 9 of the network port J1 of the RJ45 network port signal receiving circuit through the nLNKA_LED / GPIO9 network, and pin 28 is connected to pin 11 of the network port J1 of the RJ45 network port receiving circuit through the nSPD_LED / GPIO10 network. Pin 11 of chip U1 is connected to the USBD_N network, pin 12 is connected to the USBD_P network, pin 20 is connected to one end of resistor R8 through the VBUS_DET network, and the other end of resistor R8 is connected to +3.3V. Pin 8 of the network port expansion chip U1 is connected to one end of resistor R5, pin 16 is connected to one end of resistor R6, and the other ends of resistor R5 and resistor R6 are connected to GND respectively. Pin 49 of the network port expansion chip U1 is connected to +3.3V, and pin 13 is connected to GND. Pin 18 of the network port expansion chip U1 is connected to resistor R7, one end of capacitor C19 and pin 2 of crystal oscillator G1, pin 19 is connected to resistor R7, the other end of capacitor C18 and pin 1 of crystal oscillator G1, and the other ends of capacitor C18 and capacitor C19 are connected to GND.Pin 57 of the network port expansion chip U1 is connected to GND, pins 33 and 34 of the network port expansion chip U1 are connected to test point TP2 and GND, pin 31 is connected to one end of resistor R16 through the EEDO / AUTOMDIX_EN network, and the other end of resistor R16 is connected to GND, pin 24 of the network port expansion chip U1 is connected to resistor R1, one end of capacitor C2 and test point TP1 through the nRESET network, and the other end of capacitor C2 is connected to GND, pin 56 of the network port expansion chip U1 is connected to one end of resistor R2, and the other ends of resistor R1 and resistor R2 are connected to +3.3V, pins 36, 38, 39 and Pin 40 is connected to +3.3V, pin 22 is connected to +3.3V through resistor R3 and light-emitting diode LED1 in sequence, pin 17 of network port expansion chip U1 is connected to capacitor C16 and one end of ferrite bead FB2, the other end of ferrite bead FB2 is connected to capacitor C12, capacitor C13, capacitor C14, capacitor C15, one end of ferrite bead FB3 and pin 21 and pin 50 of network port expansion chip U1, the other end of ferrite bead FB3 is connected to one end of capacitor C17 and pin 10 of network port expansion chip U1, the other ends of capacitors C12, capacitor C13, capacitor C14, capacitor C15, capacitor C16 and capacitor C17 are connected to GND, network port expansion chip U1 Pins 25, 35, 48, 51, and 52 of the LDO chip are connected to capacitors C9, C7, C5, C4, C3, C1, C28, and one end of C29, and pins 2 and 4 of the LDO chip N3, as well as +3.3V. Pin 1 of the LDO chip N3 is connected to one end of capacitors C25 and C26, as well as +5V. The other ends of capacitors C9, C7, C5, C4, C3, C1, C28, C29, C25, and C26, and pin 3 of the LDO chip N3 are connected to GND respectively. Pin 7 of the network port expansion chip U1 is connected to resistor R4. On one end, the 4th, 9th, and 15th pins of the network port expansion chip U1 and the other end of the resistor R4 are connected to capacitors C6, C8, C10, C11, one end of the ferrite bead FB1 and the isolation protection circuit resistor R9 respectively. The other ends of capacitors C6, C8, C10, and C11 are connected to GND, and the other end of the ferrite bead FB1 is connected to +3.3V; the model of the network port expansion chip U1 is LAN9500A, the models of the ferrite beads FB1, FB2, and FB3 are all CBG160808U121T, the model of the crystal oscillator G1 is 25MHZ, and the model of the LDO chip N3 is ASM1117.

[0021] like Figure 4 As shown, the connection relationship of the isolation protection circuit is as follows: Pin 1 of the network transformer N1 is connected to one end of R12 and the TX_P network, Pin 3 is connected to one end of the resistor R14 and the TX_N network, Pin 6 is connected to one end of the resistor R9 and the RX_P network, Pin 8 is connected to one end of the resistor R11 and the RX_N network, Pin 2 and Pin 7 are connected to the resistor R15 and one end of the capacitor C21 respectively.

[0022] The other ends of resistors R9, R11, R12, R14, and R15 are connected to pin 15 of the network port expansion circuit and network port expansion chip U1. The other end of capacitor C21 is connected to GND. Pin 9 of network transformer N1 is connected to pin 4 of ESD protector N2, pin 11 is connected to pin 3 of ESD protector N2, pin 14 is connected to pin 2 of ESD protector N2, and pin 16 is connected to pin 1 of ESD protector N2. Pin 10 of network transformer N1 is connected to one end of resistor R17, and pin 15 is connected to one end of resistor R18. The other ends of resistors R17 and R18 are connected to EARTH through capacitor C23. Pin 5 of ESD protector N2 is connected to RD_N network, pin 6 is connected to RD_P network, pin 7 is connected to TD_N network, and pin 8 is connected to TD_P network.

[0023] The network transformer N1 model is H1102, and the ESD protector N2 model is TLSD2.8K4B.

[0024] like Figure 5 As shown, the connection relationship of the RJ45 network port signal receiving circuit is as follows: Pin 1 of the network port J1 is connected to the TD_P network, Pin 2 is connected to the TD_N network, Pin 3 is connected to the RD_P network, Pin 6 is connected to the RD_N network, Pins 4 and 5 are connected to one end of the resistor R19, Pins 7 and 8 are connected to one end of the resistor R20, and the other ends of the resistors R19 and R20 are connected to EARTH through capacitor C24. Pin 9 of the network port J1 is connected to the network port expansion chip U1 in the USB to network port expansion circuit through the nLNKA_LED / GPIO9 network. Pin 27 is connected, pin 11 is connected to pin 28 of the network port expansion chip U1 in the USB to network port expansion circuit through the nSPD_LED / GPIO10 network, pin 10 of the network port J1 is connected to one end of the resistor R22, pin 12 is connected to one end of the resistor R23, the other end of the resistor R22 and the resistor R23 are connected to +3.3V, pin 0 of the network port J1 is connected to one end of the capacitor C27 and the resistor R21 and connected to EARTH, the other end of the capacitor C27 and the resistor R21 are connected to GND; the model of the network port J1 is MODULAR RJ45.

[0025] Example 1, a method for implementing a USB to network port expansion circuit for a rail transit vehicle control box, the environment and working state during the specific implementation of the present invention are as follows: Figure 6 As shown, the USB interface P1 of the USB interface electrostatic protection circuit in this network port expansion circuit is connected to the USB interface of the vehicle control box device, and the network port J1 of the RJ45 network port signal receiving circuit is connected to the PC through an Ethernet cable;

[0026] When the vehicle control box device communicates with the PC, the vehicle control box device and the USB interface electrostatic protection circuit communicate data in the form of USB. The USB signal from the vehicle control box device is protected by the TVS diode VD1 inside the USB interface electrostatic protection circuit. The USB signal from the vehicle control box device received by the USB interface P1 is transmitted to the network port expansion circuit through a set of transceiver signal lines USBD_N and USBD_P. The network port expansion chip U1 is used to provide a fully functional bus-powered USB to Ethernet interface. The network port is expanded by bridging the USB to the 10 / 100 Ethernet port, and the USB signal is converted into a network port signal. The network port signal generated by the expansion is then transmitted by two groups The transceiver data lines TX_P, TX_N and RX_P, RX_N are transmitted to the isolation protection circuit. Through the network transformer N1 and ESD protector N2 inside the isolation protection circuit, the winding inside the network transformer N1 and the diode-related components inside the ESD protector N2 are used to isolate and electrostatically protect the signals in the form of the network port composed of the two groups of transceiver data lines, so that they can be safely and stably transmitted to the RJ45 network port signal receiving circuit; finally, the two groups of transceiver data lines TD_P, TD_N and RD_P, RD_N in the form of the network port are transmitted to the RJ45 network port signal receiving circuit. Through the network port J1 inside the RJ45 network port signal receiving circuit as the medium for external interaction, the signal is transmitted to the PC via Ethernet, completing the communication between the vehicle control box device and the PC;

[0027] When the PC communicates with the vehicle-mounted control box device, the PC performs data transmission communication through Ethernet in the reverse manner of the communication between the above-mentioned vehicle control box device and the PC. The PC is connected to the internal network port J1 of the RJ45 network port signal receiving circuit through Ethernet. The RJ45 network port signal receiving circuit transmits the received network port signal from the PC through two groups of transceiver data lines TD_P, TD_N and RD_P, RD_N to the isolation protection circuit. Through the network transformer N1 and ESD protector N2 inside the isolation protection circuit, the winding inside the network transformer N1 and the diode related devices inside the ESD protector N2 are used to isolate and electrostatically protect the transmitted network port signal composed of the two groups of transceiver data lines. The protected signal is transmitted to the network port expansion circuit through two groups of transceiver data lines TX_P, TX_N and RX_P, RX_N, and is converted into a USB signal through the network port expansion chip U1 in the network port expansion circuit by utilizing the USB to Ethernet bridge integrated in the network port expansion chip U1. The converted USB signal is transmitted to the USB interface electrostatic protection circuit through a group of transceiver data lines USBD_N and USBD_P, and is protected by the TVS diode VD1 inside the USB interface electrostatic protection circuit before being transmitted to the vehicle control box device, thus completing the communication between the PC and the vehicle control box device. Through the above method, the PC and the vehicle control box are able to use the network port for fast, safe and stable information transmission and interaction.

Claims

1. A USB to network port expansion circuit for a rail transit vehicle control box, characterized by: Including USB interface electrostatic protection circuit, network port expansion circuit, isolation protection circuit and RJ45 network port signal receiving circuit; The USB interface electrostatic protection circuit is connected to the RJ45 network port signal receiving circuit through the network port expansion circuit and the isolation protection circuit in sequence; The USB interface electrostatic protection circuit is used to connect to the vehicle control box communication interface; The network port expansion circuit is used to convert and expand the USB data line transmitted by the USB interface electrostatic protection circuit into network port data; The isolation protection circuit is used to isolate and protect the data line in the form of the network port transmitted by the network port expansion circuit; The RJ45 network port signal receiving circuit uses the received data line in the form of an extended network port to connect to the external device interface for communication; The connection relationship of the network port expansion circuit is as follows: pin 2 of the network port expansion chip U1 is connected to the TX_N network, pin 3 is connected to the TX_P network, pin 5 is connected to the RX_N network, pin 6 is connected to the RX_P network, pin 26 is connected to the cathode of the light-emitting diode LED2 through the nFDX_LED / GPIO8 network, and the anode of the light-emitting diode LED2 is connected to +3.3V through the resistor R13; pin 27 of the network port expansion chip U1 is connected to pin 9 of the network port J1 of the RJ45 network port signal receiving circuit through the nLNKA_LED / GPIO9 network, and pin 28 is connected to pin 11 of the network port J1 of the RJ45 network port receiving circuit through the nSPD_LED / GPIO10 network. Pin 11 of chip U1 is connected to the USBD_N network, pin 12 is connected to the USBD_P network, pin 20 is connected to one end of resistor R8 through the VBUS_DET network, and the other end of resistor R8 is connected to +3.3V. Pin 8 of network port expansion chip U1 is connected to one end of resistor R5, pin 16 is connected to one end of resistor R6, and the other ends of resistor R5 and resistor R6 are respectively connected to GND. Pin 49 of network port expansion chip U1 is connected to +3.3V, pin 13 is connected to GND, pin 18 of network port expansion chip U1 is connected to resistor R7, one end of capacitor C19 and pin 2 of crystal oscillator G1, pin 19 is connected to resistor R7, the other end of capacitor C18 and pin 1 of crystal oscillator G1, and the other ends of capacitor C18 and capacitor C19 are connected to GND. Connect pin 57 of the network port expansion chip U1 to GND, pins 33 and 34 of the network port expansion chip U1 to test point TP2 and GND, and pin 31 to one end of resistor R16 through the EEDO / AUTOMDIX_EN network. The other end of resistor R16 is connected to GND. Pin 24 of the network port expansion chip U1 is connected to resistor R1, one end of capacitor C2, and test point TP1 through the nRESET network. The other end of capacitor C2 is connected to GND. Pin 56 of the network port expansion chip U1 is connected to one end of resistor R2. The other ends of resistors R1 and R2 are connected to +3.3V. Pins 36, 38, 39, and 40 of the network port expansion chip U1 are connected to +3.3V respectively. Pin 22 is connected to +3.3V through resistor R3 and light-emitting diode LED1 in sequence. Connect pin 17 of the network port expansion chip U1 to capacitor C16 and one end of the ferrite bead FB2. Connect the other end of the ferrite bead FB2 to capacitors C12, C13, C14, C15, one end of the ferrite bead FB3, and pins 21 and 50 of the network port expansion chip U1. Connect the other end of the ferrite bead FB3 to one end of capacitor C17 and pin 10 of the network port expansion chip U1. Connect the other ends of capacitors C12, C13, C14, C15, C16, and C17 to GND. Pins 25, 35, 48, 51, and 52 of the network port expansion chip U1 are connected to one end of capacitors C9, C7, C5, C4, C3, C1, C28, and C29, and pins 2 and 4 of the LDO chip N3 and +3.3V. Pin 1 of the LDO chip N3 is connected to one end of capacitors C25 and C26 and +5V. The other ends of capacitors C9, C7, C5, C4, C3, C1, C28, C29, C25, and C26, and pin 3 of the LDO chip N3 are connected to GND respectively. Connect pin 7 of the network port expansion chip U1 to one end of resistor R4. Connect pins 4, 9, and 15 of the network port expansion chip U1 and the other end of resistor R4 to capacitors C6, C8, C10, and C11, one end of the ferrite bead FB1, and the isolation protection circuit resistor R9, respectively. Connect the other ends of capacitors C6, C8, C10, and C11 to GND, and the other end of the ferrite bead FB1 to +3.3V. The network port expansion chip U1 is LAN9500A, the magnetic beads FB1, FB2, and FB3 are all CBG160808U121T, the crystal oscillator G1 is 25MHZ, and the LDO chip N3 is ASM1117.

2. The USB to network port expansion circuit for a rail transit vehicle control box according to claim 1, characterized in that: The connection relationship of the USB interface electrostatic protection circuit is as follows: Pin 1 of the USB interface P1 is connected to one end of the magnetic bead FB4 and the 5th pin of the TVS diode VD1, the other end of the magnetic bead FB4 is connected to +5V and one end of the capacitor C22, the other end of the capacitor C22 is connected to GND, Pin 2 of the USB interface P1 is connected to Pin 6 of the TVS diode VD1 through the USBD_N network, Pin 3 of the USB interface P1 is connected to Pin 1 of the TVS diode VD1 through the USBD_P network, Pin 4 of the USB interface P1 is connected to one end of the capacitor C20 and the resistor R10 and connected to GND, Pin 0 of the USB interface P1 is connected to the other end of the capacitor C20 and the resistor R10 and connected to EARTH, and Pin 2 of the TVS diode VD1 is connected to GND; The USB interface P1 model is USB2.0 STD-A MALE, the TVS diode VD1 model is NUP4202W1T2G, and the magnetic bead FB4 model is CBG160808U121T.

3. The USB to network port expansion circuit of the rail transit vehicle control box according to claim 1 is characterized in that: The connection relationship of the isolation protection circuit is as follows: pin 1 of the network transformer N1 is connected to one end of R12 and the TX_P network, pin 3 is connected to one end of the resistor R14 and the TX_N network, pin 6 is connected to one end of the resistor R9 and the RX_P network, pin 8 is connected to one end of the resistor R11 and the RX_N network, pins 2 and 7 are respectively connected to the resistor R15 and one end of the capacitor C21, the other ends of the resistors R9, R11, R12, R14 and R15 are connected to pin 15 of the network port expansion circuit network port expansion chip U1, and the other end of the capacitor C21 is connected to GND; Pin 9 of the network transformer N1 is connected to pin 4 of the ESD protector N2, pin 11 is connected to pin 3 of the ESD protector N2, pin 14 is connected to pin 2 of the ESD protector N2, and pin 16 is connected to pin 1 of the ESD protector N2. Pin 10 of the network transformer N1 is connected to one end of the resistor R17, and pin 15 is connected to one end of the resistor R18. The other ends of the resistors R17 and R18 are connected to EARTH through capacitor C23. Pin 5 of ESD protector N2 is connected to RD_N network, pin 6 is connected to RD_P network, pin 7 is connected to TD_N network, and pin 8 is connected to TD_P network; The network transformer N1 is model H1102, and the ESD protector N2 is model TLSD2.8K4B.

4. The rail transit vehicle control box USB to network port expansion circuit according to claim 1, characterized in that: The connection relationship of the RJ45 network port signal receiving circuit is as follows: pin 1 of the network port J1 is connected to the TD_P network, pin 2 is connected to the TD_N network, pin 3 is connected to the RD_P network, pin 6 is connected to the RD_N network, pins 4 and 5 are connected to one end of the resistor R19, pins 7 and 8 are connected to one end of the resistor R20, and the other ends of the resistors R19 and R20 are connected to EARTH through capacitor C24; Pin 9 of the network port J1 is connected to pin 27 of the network port expansion chip U1 in the USB-to-network port expansion circuit through the nLNKA_LED / GPIO9 network, and pin 11 is connected to pin 28 of the network port expansion chip U1 in the USB-to-network port expansion circuit through the nSPD_LED / GPIO10 network. Pin 10 of the network port J1 is connected to one end of resistor R22, pin 12 is connected to one end of resistor R23, the other ends of resistors R22 and R23 are connected to +3.3V, pin 0 of the network port J1 is connected to one end of capacitor C27 and resistor R21 and connected to EARTH, the other ends of capacitor C27 and resistor R21 are connected to GND; the model of the network port J1 is MODULAR RJ45.

5. A method for implementing the USB to network port expansion circuit of the rail transit vehicle control box according to claim 1, characterized in that: During operation, the USB interface electrostatic protection circuit is connected to the external vehicle control box device, and the RJ45 network port signal receiving circuit is connected to the PC. When the vehicle control box device communicates with the PC, the USB interface electrostatic protection circuit will receive the USB signal from the vehicle control box device, and transmit it to the network port expansion circuit through a set of transceiver data lines. The network port expansion circuit converts the USB signal from the data line into a network port signal, and transmits it to the isolation protection circuit through two sets of transceiver data lines. The generated network port signal is processed by the isolation protection circuit and then transmitted to the RJ45 network port signal receiving circuit through two sets of transceiver data lines. The RJ45 network port signal receiving circuit transmits the signal to the PC through Ethernet, thereby realizing network port interactive communication between the vehicle control box device and the vehicle PC. When the PC communicates with the control box device, the PC will send a signal through Ethernet to the RJ45 network port signal receiving circuit. The RJ45 network port signal receiving circuit transmits the network port form signal to the isolation protection circuit through two sets of transceiver data lines. After the signal is processed by the isolation protection circuit, it is transmitted to the network port expansion circuit with two sets of transceiver data lines. The network port expansion circuit converts the transmitted network port form signal into a USB form signal, and transmits it to the USB interface electrostatic protection circuit through a set of transceiver data lines. The USB interface electrostatic protection circuit transmits the USB form signal to the vehicle control box device, thereby realizing network port form interactive communication between the PC and the vehicle control box device.

6. The method for implementing the USB to network port expansion circuit of the rail transit vehicle control box according to claim 5, characterized in that: The method for the network port expansion circuit to convert the USB format signal transmitted by the data cable into the network port format signal is as follows: the network port expansion chip U1 of the network port expansion circuit is connected to the external vehicle control box device through the USB interface electrostatic protection circuit, and the network port expansion circuit will be recognized as a USB device by the vehicle control box device. The network port expansion chip U1 contains an integrated USB to Ethernet bridge for processing the conversion between USB data packets and Ethernet. When the data is transmitted to the USB port of the network port expansion chip U1 through the data cable, the network port expansion chip U1 will encapsulate the transmitted data into an Ethernet frame format that complies with the IEEE802.3 standard, thereby realizing the USB expansion of the network port. Similarly, when the data is transmitted to the network port expansion chip U1 through the Ethernet port, it can also be converted into USB format for external communication.

7. The method for implementing the USB to network port expansion circuit of the rail transit vehicle control box according to claim 5, characterized in that: The two groups of transceiver data lines are transmitted to the isolation protection circuit, and the generated network port form signal is processed by the isolation protection circuit in the following method: when the vehicle control box device communicates with the PC, the two groups of transceiver data lines TX_P, TX_N and RX_P, RX_N in the network port form transmitted by the network port expansion circuit are transmitted to the network transformer N1. The network transformer N1 contains a winding inside. The sending end winding is connected to the data line generated by the network port expansion circuit, and the receiving end winding is connected to the ESD protector N2. When the data line passes through the sending end, a changing magnetic field will be generated. The changing magnetic field generates a corresponding current at the receiving end to transmit the data line to the ESD protector N2, thereby realizing the isolation of the data lines of the receiving end and the sending end. The isolated data line is transmitted to the rear ESD protector, which contains a diode inside. It maintains a high resistance state during normal operation. Once it is affected by external static electricity, it will quickly convert to a low resistance state to transfer energy, thereby realizing the isolation between the vehicle control box device and the PC. The signal isolation protection function during communication between the C machine and the vehicle control box device; when the PC communicates with the vehicle control box device, the two sets of receiving and transmitting data lines TD_P, TD_N and RD_P, RD_N in the form of the network port transmitted by the RJ45 network port signal receiving circuit first pass through the ESD protector N2, and the data line is first protected against static electricity by the diode inside the ESD protector N2. The protected data line is transmitted to the network port transformer N1. The network transformer N1 contains a winding. At this time, the sending end winding is connected to the data line transmitted from one end of the ESD protector N2, and the receiving end winding is connected to the network port expansion chip U1 in the network port expansion circuit expansion. When the data line passes through the sending end, a changing magnetic field will be generated. The changing magnetic field generates a corresponding current at the receiving end, and the data line is transmitted to the network port expansion chip U1 in the network port expansion circuit expansion, realizing the isolation of the receiving and sending end data lines, thereby achieving the signal isolation protection function when the PC communicates with the vehicle control box device.

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