Patent Publication Number: US-2020304340-A1

Title: In-vehicle relay device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Patent Application No. PCT/JP2018/041572 filed on Nov. 9, 2018, which designated the U.S. and claims the benefit of priority from Japanese Patent Application No. 2017-236713 filed on Dec. 11, 2017. The entire disclosures of all of the above applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to an in-vehicle relay device. 
     BACKGROUND 
     A relay device used in an in-vehicle communication network has been proposed. The relay device includes a plurality of ports. When one of the plurality of ports inputs a signal, the signal is transmitted to another one of the plurality of ports connected to the same relay device and designated by a destination included in the signal. 
     SUMMARY 
     The present disclosure provides an in-vehicle relay device that includes a layer 2 relay unit and a layer 3 relay unit. A hardware circuit performs functions of a layer 1 to a layer 3. A microcomputer performs functions of a layer 4 and higher layers than the layer 4. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
         FIG. 1  is a diagram showing a configuration of an in-vehicle communication system; 
         FIG. 2  is a block diagram showing a configuration of a relay device; and 
         FIG. 3  is a block diagram showing a configuration of a relay device. 
     
    
    
     DETAILED DESCRIPTION 
     For example, in an in-vehicle ECU having a relay function, each of a physical layer and a data link layer in OSI reference model is provided by an 
     ASIC, and layers higher than the data link layer are provided by a microcomputer. Therefore, when the relay function is executed in a network layer which is the layer 3, the microcomputer executes the relay function by software. 
     However, the relay at the network layer requires a relay across the network, and thus has a high processing load. As a result, communication delay may occur even when a high-performance microcomputer is used. Further, since the processing load is high, heat generation may increase. 
     The present disclosure to provide an in-vehicle relay device that is less likely to cause a communication delay and can also reduce heat generation. 
     An exemplary embodiment of the present disclosure provides an in-vehicle relay device that includes a layer 2 relay unit and a layer 3 relay unit. A hardware circuit performs functions of a layer 1 to a layer 3. A microcomputer performs functions of a layer 4 and higher layers than the layer 4. 
     In the exemplary embodiment of the present disclosure, the hardware circuit performs the functions of the layer 1 to the layer 3, and thus the layer 3 relay unit is provided by a hardware circuit. The processing speed is increased by providing the layer 3 relay unit as a hardware circuit. Therefore, communication delay is less likely caused. In addition, heat generation can be reduced by using the hardware circuit. Furthermore, since the microcomputer executes the processing of the layer 4 and above, it is possible to use the microcomputer that is not so sophisticated in function. 
     (Embodiment) 
     (Entire Configuration) 
     Hereinafter, embodiments will be described with reference to the drawings.  FIG. 1  shows an exemplary configuration of an in-vehicle communication system  10 . The in-vehicle communication system  10  is configured according to the in-vehicle Ethernet standard. “Ethernet” is a registered trademark. The in-vehicle communication system  10  is mounted on a vehicle C. 
     The in-vehicle communication system  10  shown in  FIG. 1  includes six end ECUs  20  and one relay device  100 . The number of the end ECUs  20  is an example, and any number of the end ECUs  20  can be provided. 
     The end ECU  20  corresponds to a node connected to the relay device  100  via a cable  30 . The node may be a sensor or the like instead of the ECU. Alternatively, another relay device may be connected as a node. Each end ECU  20  directly communicates only with the relay device  100 . When transmitting a signal to another node, the end ECU  20  causes the signal to include an address of the destination node. This signal is output to the relay device  100  via the cable  30 . The cable  30  may be a twisted pair cable. 
     The relay device  100  divides a plurality of nodes connected to the relay device  100  into two VLANs (Virtual LANs)  40 ,  50 . It should be noted that the number of VLANs is an example, and the plurality of nodes may be divided into three or more VLANs  40 ,  50 . The relay device corresponds to an in-vehicle relay device. 
     (Configuration of Relay Device  100 ) 
     The configuration of the relay device  100  is shown in  FIG. 2 . The relay device  100  includes a power supply circuit  110 , a PHY  120 , an FPGA (field-programmable gate array)  130 , and a microcomputer  140 . 
     The power supply circuit  110  supplies power to the PHY  120 , the FPGA  130 , and the microcomputer  140 . 
     The PHY  120  includes a plurality of ports P. In  FIG. 1 , six ports P 1 , P 2 , 
     P 3 , P 4 , P 5 , P 6  are provided. When each of the six ports P 1 , P 2 , P 3 , P 4 , P 5 , P 6  is not distinguished, it is described as a port P. 
     One end of the cable  30  is connected to the port P. The other end of the cable  30  is connected to the end ECU  20 . 
     The PHY  120  converts the signal supplied from the FPGA  130  into an electric signal capable of being transmitted to the cable  30 .The PHY  120  also converts the signal supplied from the end ECU  20  via the cable  30  into a signal capable of being processed by the FPGA  130 . The PHY  120  corresponds to a physical layer in the OSI reference model, that is, a layer 1 L1. In addition to the above-described signal conversion, the PHY  120  also performs frame coding, serial/parallel conversion, signal waveform conversion, and the like. The PHY  120  is provided by an IC including an analog circuit, that is, a hardware circuit. In  FIG. 2 , one PHY  120  includes a plurality of ports P. Alternatively, the PHY  120  may be divided into a plurality of PHYs such as an independent configuration for each port P. 
     The FPGA  130  is programmed to execute the functions of a layer 2 L2 and a layer 3 L3 in the OSI reference model. 
     The layer 2 L2 is a data link layer and performs communication in the same VLAN  40 ,  50 . The layer 2 L2 also detects an error of the signal. The layer 2 L2 functions as a layer 2 relay unit  131 . The layer 2 relay unit is also referred to as a layer 2 relay. The layer 2 relay unit  131  performs communication in the same VLAN  40 ,  50 . The layer 2 relay unit  131  determines the node to which the signal is to be transmitted based on a MAC (Media Access Control) address. 
     The layer 3 L3 is a network layer and performs communication between different networks. In order to perform communication between networks, the layer 3 L3 functions as a layer 3 relay unit  132 . The layer 3 relay unit is also referred to as a layer 3 relay. The layer 3 relay unit  132  performs communication in the different VLAN  40 ,  50 . The layer 3 relay unit  132  determines the node to which the signal is to be transmitted based on an IP (Internet Protocol) address. 
     The microcomputer  140  is a computer including a CPU, a ROM, a RAM, an I/O, and a bus line for connecting these components. The ROM stores a program for causing a general-purpose computer to function as the microcomputer  140 . The microcomputer  140  functions as a layer 4 L4, a layer 5 L5, a layer 6 L6, and a layer 7 L7 by executing the program stored in the ROM while using the temporary storage function of the RAM. That is, the layer 4 L4, the layer 5 L5, the layer 6 L6, and the layer 7 L7 are realized by the software processing. It should be noted that a storage medium for storing the program executed by the CPU is not limited to the ROM. The program may be stored in a non-transitory tangible storage medium. 
     The layer 4 L4 is a transport layer and executes inter-program communication, data transfer guarantee, and the like. The layer 5 L5 is a session layer, the layer 6 L6 is a presentation layer, and the layer 7 L7 is an application layer. The layer 5 L5, the layer 6 L6, and the layer 7 L7 execute user authentication, data encoding and decoding, a user interface function, and the like. The relay device  100  having these functions can also be referred to as a switching hub ECU. The functions of the layer 2 relay unit  131  and the layer 3 relay unit  132  may be referred to as a switch. 
     (Summary of Embodiment) 
     In the relay device  100  of the present embodiment, the layer 2 L2 and the layer 3 L3 are provided by the FPGA  130  that is a hardware circuit, so the layer 3 relay unit  132  is provided by the hardware circuit. The processing speed is increased by providing the layer 3 relay unit  132  as the hardware circuit. Therefore, communication delay is less likely caused. In addition, heat generation can be reduced by using the hardware circuit. 
     Furthermore, since the microcomputer  140  executes the processing of the layer 4 L4 and above, it is possible to use the microcomputer  140  that is not so sophisticated in function. 
     Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modified examples described below are also included in the technical scope of the present disclosure. Furthermore, various modifications other than the following can be made without departing from the gist. In the following description, elements having the same reference numerals as those used so far are the same as elements having the same reference numerals in the previous embodiments, except when specifically mentioned. When only a part of the configuration is described, the embodiment described above can be applied to other parts of the configuration. 
     (First Modification) 
     In the relay device  100  of the embodiment, the layer 2 L2 and the layer 3 L3 are provided by the FPGA  130 . However, as shown in  FIG. 3 , a relay device  200  including an ASIC  230  instead of the FPGA  130  may be employed. 
     (Second Modification) 
     The PHY  120  may not be necessarily provided separately from the FPGA  130  or the ASIC  230 , and the FPGA  130  or the ASIC  230  may function as the PHY  120 . 
     (Third Modification) 
     A hardware circuit having the functions of the layer 1 L1 and the layer 2 L2 and a hardware circuit having the function of the layer 3 L3 may be separated.