JP2013126119A - Gateway unit and network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce delay in data transfer of a network as a whole.SOLUTION: A plurality of CAN buses 1, 2, 3 are connected with a gateway unit 5. The gateway unit 5 has a function for transferring a message from some CAN bus to other CAN bus. When transferring a message to the plurality of CAN buses, the gateway unit 5 performs transfer processing for each bus by software processing. According to a routing table 14, the order of transferring the message is determined by the time occupied by a CAN bus that is the transfer destination of a message having a transmission priority higher than that of a message to be transferred.

Description

  The present invention relates to a gateway apparatus that performs transfer processing for each bus when the same message is transferred to a plurality of buses on a network, and a network system including the gateway apparatus.

CAN (Controller Area Network) communication is widely used for in-vehicle networks. In CAN communication, the priority of transmission is set for each message to be transmitted by the ID number of the message, and when a transmission request is generated at the same time during bus transmission, arbitration is performed based on the priority and a message with a small ID number Sent from
When there are a plurality of buses, a gateway device that relays data between the buses is generally provided. When the gateway device receives the message, the gateway device performs transfer processing (routing processing) to the destination bus according to a routing table (provided by the gateway device) in which information of the reception / transmission bus is recorded.

JP 2008-306648 A

By the way, in a network provided with a plurality of CAN communication buses (CAN buses), the gateway device may transfer a message received from one bus (including buses other than the CAN bus) to two or more CAN buses.
In this case, if routing processing is performed by software processing, message transfer to a plurality of buses cannot be processed at the same time, and processing is performed for each bus. The slower the order, the longer the delay time in the gateway device.

In this case, the processing order is generally the order of CAN buses having the highest bus load factor (ratio of time during which the bus is used within a certain period).
However, since the distribution of ID numbers of messages to be transmitted is different for each CAN bus, the number of messages prior to the message transferred to a certain CAN bus by the gateway device and the bus load factor on the CAN bus. The order of processing in routing processing is the order in which the bus load factor is high, but it is not necessarily optimal for all messages from the viewpoint of early completion of data transfer of the entire system. There is a bug that there is no.
An object of the present invention is to make it possible to reduce data transfer delay as a whole network.

  (1) According to one aspect of the present invention, when the same message is transferred to a plurality of buses on a network, the gateway device performs transfer processing for each bus and transmits from any of the nodes connected to the bus. Receiving means for receiving the received message, and recording means for recording the order of transfer when the same message is transferred to the bus and a plurality of the buses to which the message is transferred for each identification display of the message Determining means for determining the transfer destination bus corresponding to the identification display with reference to the recording means for the identification display of the message received by the reception means, and the transfer destination determined by the determination means Transmitting means for transmitting a transfer message to the bus, wherein the recording means is a message to be transferred as the transfer order. Time higher priority transmission from di message occupies the bus serving as the transfer destination is recorded as a long bus order, it is a gateway apparatus according to claim.

(2) In this case, if the time for which a message having a higher priority of transmission than the message to be transferred occupies the transfer destination bus is the same for a plurality of buses, the recording means May be recorded so that data is transferred in the order of higher buses.
(3) According to another aspect of the present invention, in the network system in which a gateway device and a plurality of buses are connected on a network, the gateway device is the gateway device according to (1) or (2). This is a featured network system.

  According to the aspect of the present invention, the delay of data transfer can be reduced as a whole network.

1 is a block diagram showing an overall configuration of a network system according to an embodiment of the present invention. It is explanatory drawing of the routing table of the network system which is one embodiment of this invention. It is a flowchart of the transfer process of the message which the gateway apparatus of the network system which is one embodiment of this invention performs. It is explanatory drawing explaining an example of the message transmitted / received by the network system which is one embodiment of this invention. It is a timing chart explaining operation | movement of the gateway apparatus of the network system which is one embodiment of this invention. It is explanatory drawing explaining operation | movement of the gateway apparatus which is a comparative example. It is explanatory drawing explaining operation | movement of the gateway apparatus of the network system which is one embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described.
FIG. 1 is a block diagram showing the overall configuration of a network system according to an embodiment of the present invention. This network system is a system mounted on a vehicle, for example, and includes a plurality of buses 1, 2, and 3. In this example, each of the buses 1, 2, and 3 is a CAN bus that transmits and receives data by CAN (Controller Area Network) communication. Each CAN bus 1, 2, 3 is connected to the gateway device 5. Of course, the gateway device 5 may be connected to a bus that performs communication using a communication protocol other than CAN communication. One or more nodes 6 are connected to each CAN bus 1, 2, 3 respectively. Each node 6 is a control device such as an engine control unit (ECU), a sensor, or the like. In FIG. 1, the gateway device 5 in which the identification number of the node 6 is assigned to each node 6 is operated by the microcomputer, and the message receiving unit 11, the message transfer destination setting unit 12, and the message transmitting unit 13 are operated. Each function is realized and a routing table 14 is provided.

The message receiving unit 11 is a receiving unit that receives a message transmitted from any one of the nodes 6 of the CAN buses 1, 2, and 3.
As shown in FIG. 2, the routing table 14 specifies the CAN bus that is the transfer destination of the message and transfers the same message to a plurality of CAN buses for each ID number that is an identification display of the message exchanged in the network system 1. In this case, the recording means records the order of transfer between the CAN buses.

The message transfer destination setting unit 12 is a determining unit that determines a CAN bus that is a transfer destination of a message corresponding to the ID number by referring to the routing table 14 for the ID number of the message received by the message receiving unit 11.
The message transmission unit 13 is a transmission unit that transmits a message to be transferred to the transfer destination CAN bus determined by the message transfer destination setting unit 12.

  FIG. 2 is an explanatory diagram of the routing table 14. In the example of the routing table 14 shown in FIG. 2, for messages having ID numbers “100”, “150”, and “300”, the gateway device 5 is the CAN bus that should receive the message. “Transfer destination bus 1”, which is a CAN bus to which the message is to be transferred, and “transfer destination bus 2”, which is the CAN bus to which the message is to be transferred next, are recorded in association with each other (only the code is displayed on the CAN bus). For example, for the message with ID number “100”, the “reception bus” is the CAN bus 1, the “transfer destination bus 1” to which the message is to be transferred first is the CAN bus 3, and the “transfer destination bus” to which the message is to be transferred next. 2 ″ is the CAN bus 2.

  FIG. 3 is a flowchart of message transfer processing executed by the gateway device 5. The gateway device 5 executes message transfer processing (routing processing) by software processing. The processing of FIG. 3 is considered to be performed by periodic repetitive processing or by interrupt processing that is activated when a CAN controller (not shown) built in each node 6 receives a message. It is done. First, when a message is received by the message receiving means 11 (step S1), the ID number of the message is acquired, and routing information is searched from the routing table 14 by the ID number (step S2). Next, based on the information in the routing table 14, it is determined whether or not the message is transferred to a CAN bus other than the CAN bus that has received the message (step S3). If the message is a routing target message that needs to be transferred to a CAN bus other than the received CAN bus (Y in step S3), the transfer processing order to each CAN bus to which the message is to be transferred is set in the routing table 14. It is determined by the information (step S4). Of course, if there is one CAN bus to which a message is to be transferred, the message is transferred only to that CAN bus. Then, the data is stored in a transmission message box (not shown) of the CAN bus to be transferred and set for transmission (step S5). In this state, the message is waiting to be transmitted, and when the priority is acquired according to the arbitration in the CAN bus, the message is transferred to the target CAN bus.

Next, the message transfer process will be described in detail with a specific example. In CAN communication, the priority of transmission is set for each message to be transmitted by the ID number of the message. When transmission requests are generated simultaneously during bus transmission, arbitration is performed based on the priority, and the numerical value of the ID number is set. Sent from a small message.
The CAN communication protocol used here has the following characteristics.

(1) Multi-master: All nodes 6 can transmit messages if the CAN bus is free.
(2) Multicast: All nodes 6 receive messages simultaneously.
(3) System flexibility: The content of the message is defined by an ID number that is a unique identification display in the CAN bus associated with the message, and the sender and receiver devices are specified by this ID number.

(4) Collision detection method: The ID number added to the message also defines the priority on the network system, and when a plurality of nodes 6 try to send a message at the same time, the ID number (number is higher) due to bus arbitration. A message having a higher priority (the smaller the priority is) obtains the transmission right, and a message having an ID number with a lower priority is stopped.

  As described above, the process in FIG. 3 is performed by a cyclic process that is repeated and an interrupt process that is activated when a CAN controller (not shown) built in each node 6 receives a message. However, when it is carried out by periodic repetitive processing, a high priority is assigned to one having a short cycle.

  FIG. 4 is an explanatory diagram for explaining an example of a message transmitted and received in the network system. In FIG. 4, with respect to a plurality of messages, the “ID number”, “cycle (msec)” (cycle when the message is transmitted in a cyclic repetition process), and “data field” (how many bytes of data are transmitted) Indicates). Further, for each message on each of the CAN buses 1, 2, and 3, a transmission message, a gateway transfer message, and no transmission of these messages are indicated by a double circle, a single circle, and “−”. The transmission message is a message transmitted through the CAN bus 1, 2 or 3. The gateway transfer message is a message transferred to one or a plurality of CAN buses 1, 2, 3 by the gateway device 5. The number added in parentheses to the double circle of the transmission message is the node 6 from which the node 6 is transmitted (see FIG. 1). The values of 5%, 12.5%, and 15.5% in parentheses below the CAN bus 1, CAN bus 2, and CAN bus 3 characters indicate the bus load factor (the bus is In this example, the message length is 250 μsec. As described above, a message having a smaller ID number has a higher transmission priority. Furthermore, a message with a shorter period is assigned a higher priority. Therefore, in FIG. 4, the message displayed above has a higher transmission priority.

  First, the message of each ID number in FIG. 4 is transmitted to the CAN bus with a double circle. In this example, the number in parentheses in the double circle is the node 6 from which the node 6 is transmitted, so the ID number is “100”, “150”, “300”. In the message, the node numbers “11”, “12”, and “13” are transmitted from the node 6 to the CAN bus 1, and all are transferred by the gateway device 5 and transferred to the CAN bus 2 and the CAN bus 3. It will be.

  Since the message with the ID number “100” has the highest priority in this example, arbitration in each CAN bus always takes priority, and if the transfer destination CAN bus waits for transmission, another message is sent during transmission. The bus arbitration is won even when the message of the node 6 is waiting to be transmitted. Therefore, the transmission of the message whose ID number is “100” is started simultaneously with the completion of the transmission of the other message being transmitted.

  The message with the ID number “150” has the highest priority on the CAN bus 3 except for other messages transferred by the gateway device 5. Therefore, like the message with the ID number “100”, when waiting for transmission on the transfer destination CAN bus 3, if another message is being transmitted, the ID number is simultaneously with the completion of transmission of the other message being transmitted. The transmission of the message “150” is started. On the other hand, the CAN bus 2 has the lowest priority except for other messages transferred by the gateway device 5, so when a message from another node 6 waits for transmission start, it loses bus arbitration and starts transmission. If transmission of all the waiting messages is not completed, transmission is not started, and the transfer delay time in the gateway device 5 becomes long.

  Since such a situation occurs with a probability corresponding to the bus load factor, the delay of the gateway device 5 is reduced as the CAN bus has a higher probability of arbitration loss in the transfer of a message with a low priority in the CAN bus. It will be necessary.

  As described above, when the routing processing is performed by software processing, as shown in the timing chart of FIG. 5, since processing is sequentially performed for each CAN bus, a software delay occurs, and a CAN bus with a slower processing order. The delay time in the gateway device 5 becomes long. That is, in the example of FIG. 5, the gateway device 5 receives a message from the CAN bus (CAN bus 1 in this example) that transmits a message at the timing (1), and forwards the message at the timing (2). The transfer order is determined, and by this determination, the data is transmitted to the first CAN bus (CAN bus 3 in this example) at the timing (3), and then the second CAN bus ( In this example, it is transmitted to the CAN bus 2).

  Therefore, it is necessary to perform routing processing in the order of CAN buses that occupy the CAN bus of the transfer destination within a transmission cycle of a message transferred by a message having a higher priority than the message to be transferred. In the example of the routing table 14 shown in FIG. 2, settings are made so that such routing processing can be performed (in the case of messages with ID numbers “150” and “300”).

  A more specific example will be described. In the message with the ID number “150” in FIG. 4, the message is transmitted through the CAN bus 1, and the message is transferred to the CAN buses 2 and 3. The time during which a message having a higher priority than the message having the ID number “150” occupies the transfer destination CAN bus within 10 msec, which is the transmission cycle of the message to be transferred, is as follows. If the message length is 250 μsec, the CAN bus 2 has four high priority messages with a 10 msec cycle (four ID numbers “100” to “130”), so “250 × 4 = 1000 μsec”. . In the CAN bus 3, since there is only one high-priority message with a 10 msec period (one ID number is “100”), “250 × 1 = 250 μsec”. Therefore, even if the bus load factor is low, it is advantageous to perform message transfer processing by giving priority to the CAN bus 2 over the CAN bus 3.

  By adopting such a file transfer order, the message transfer delay time when another node 6 tries to start transmitting a message on the transfer destination CAN bus during the file transfer process in the gateway device 5 is set. Can be reduced.

  For example, when a message is transferred to two CAN buses, if a message transmission request with a high priority occurs in the transfer destination CAN bus during the transfer process of the message to the second CAN bus, the bus load When messages are transferred in the order of CAN buses with a high rate, the time required for transfer as a whole network system increases as shown in the comparative example of FIG. 6, but as compared with the messages to be transferred as in this embodiment. If the routing table 14 is set so that routing processing is performed in the order of CAN buses that occupy the transfer destination CAN bus within the transmission cycle of the messages transferred by the high priority message, for example, as shown in FIG. Thus, the total time required for transfer in the CAN bus 2 and the CAN bus 3 can be made smaller than the example of FIG.

  That is, the example of FIGS. 6 and 7 will be described in detail. First, the passage of time is shown in the horizontal direction. A message having an ID number of “150” is transmitted on the CAN bus 1 which is a “reception bus” for receiving the message. “Gateway processing time” indicates each processing time in the gateway device 5 as (1) to (4) corresponding to (1) to (4) in FIG. The time required for message transfer on the CAN buses 2 and 3 is indicated as “time required for transfer”.

  In the example of FIG. 6, immediately after “(3) transmission processing to the first transfer destination bus” is performed in the gateway device 5, the message with the ID number “150” in the CAN bus 3 with a high bus load factor is displayed. The transfer has started. Then, transmission of the message is started on the other node 6 of the CAN bus 2 as the transfer destination (the start time is indicated as “other node transmission request time”). In this case, messages with ID numbers “110”, “120”, and “130” are transmitted. These messages have ID numbers smaller than those with ID numbers “150”, and the priority of transmission is high. Is expensive. Therefore, even if the gateway device 5 performs “(4) transmission processing to the second transfer destination bus”, the transfer of the message with the ID number “150” is not started immediately, but “110”, “120”. , And started after transmission of a message having an ID number of “130”. For this reason, the “time required for transfer” of the message whose ID number is “150” is long.

  On the other hand, in the case of the present embodiment in FIG. 7, routing processing is performed in the order of the CAN bus having a long time to occupy the transfer destination CAN bus within, for example, the transmission cycle of the message transferred by the message having a higher priority than the message to be transferred. The routing table 14 is set so that the ID number is “150” in the CAN bus 2 immediately after “(3) transmission processing to the first transfer destination bus” is performed in the gateway device 5. The message transfer has started. Then, transmission of the message is started on the other node 6 of the CAN bus 3 as the transfer destination (the start time is indicated as “other node transmission request time”). In this case, messages with ID numbers of “160” or less are also transmitted, but these messages have a larger ID number than messages with an ID number of “150” and have lower transmission priority. For this reason, when the transmission of the message whose ID number is “160” that has already started transmission at the time when “(4) transmission processing to the second transfer destination bus” is performed in the gateway device 5, priority is given. For example, the message having the ID number “150” is transferred, and after completion of the transfer, the transmission of each message having the ID number “170” or less is started. Therefore, the “time required for transfer” of the message whose ID number is “150” is shortened.

  On the other hand, in the message with the ID number “300”, the time occupied by the high priority message within 100 msec of the transmission cycle is as follows. In the CAN bus 2, a message having a period of 10 msec is transmitted 10 times within 100 msec, and messages having a higher priority than the message having the ID number “300” are five ID numbers “100” to “150”. “250 × 5 × 10 = 12,500 μsec” is the time for a message having a higher priority than the message with ID number “300” to occupy the transfer destination CAN bus within 100 msec. On the CAN bus 3, a message with a period of 10 msec is transmitted 10 times within 100 msec, and a message having a higher priority than a message with an ID number of “300” has an ID number of “100”, “150” to “190”. Therefore, “250 × 6 × 10 = 15000 μsec” is obtained. Therefore, in this case, it is advantageous to transfer a message from the CAN bus 3.

  In the message with the ID number “100”, the time that the message having the higher priority than the message with the ID number “100” occupies the transfer destination CAN bus within 100 msec is equal in the CAN buses 2 and 3. Become. In this case, the CAN bus having a higher CAN bus load ratio has a higher probability of being hit during the transmission of another message. Therefore, in this example, the CAN bus 3 having a higher bus load ratio is given priority. The message is transferred (see FIG. 2).

DESCRIPTION OF SYMBOLS 1 CAN bus 2 CAN bus 3 CAN bus 5 Gateway apparatus 14 Routing table

Claims (3)

In the gateway device that performs transfer processing for each bus when transferring the same message to multiple buses on the network,
Receiving means for receiving a message transmitted from any node connected to the bus;
Recording means for recording the order of transfer when transferring the same message to the bus and a plurality of the buses to which the message is transferred for each identification display of the message;
Determining means for determining the transfer destination bus corresponding to the identification display with reference to the recording means for the identification display of the message received by the receiving means;
Transmitting means for transmitting a transfer message to the transfer destination bus determined by the determining means;
With
The recording means records, as the transfer order, a message having a transmission priority higher than that of the message to be transferred in a bus order in which the time for occupying the transfer destination bus is long.
A gateway device characterized by that.   When the time for which a message having a higher transmission priority than the message to be transferred occupies the transfer destination bus is the same for a plurality of buses, the recording unit transfers the messages in the order of the buses having the highest bus load ratio. The gateway device according to claim 1, wherein the gateway device is recorded as follows. In a network system in which a gateway device and a plurality of buses are connected on a network,
The gateway device is the gateway device according to claim 1 or 2,
A network system characterized by this.

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