JP2015210667A - Communication unit and can(control area network) communication control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow communication modules connected to CAN(Control Area Network) buses having different communication speeds to communicate with each other without increasing a communication load.SOLUTION: A communication unit is characterized to control CAN communication between modules connected to a plurality of CAN buses having different communication speeds by a CPU disposed in a microcomputer by connecting a plurality of different CAN controllers connected to the CAN buses having different communication speeds to a plurality of serial ports disposed in the microcontroller, and processing CAN messages input from the CAN buses via the CAN controllers and the serial ports on the basis of input serial port IDs and CAN message IDs.

Description

  The present invention relates to a communication unit and a CAN communication control program.

  CAN (Control Area Network) is a network that can be constructed at low cost because of its simple network configuration. Furthermore, CAN communication is known as a highly reliable communication method that has an excellent failure detection function.

  In the CAN, one CAN controller is installed for each CAN bus. The CAN controller controls so that a signal flowing through the CAN is normally transmitted to each module in accordance with a CAN communication protocol.

JP 2005-196568 A

  However, when CAN includes CAN buses having different communication speeds, modules on different CAN buses cannot directly communicate with each other. Therefore, conventionally, modules on different CAN buses communicate with each other via a gateway. However, there is a problem that a network construction cost is increased due to installation of a gateway and the communication load is increased.

  An object of the present invention is to enable communication between communication modules connected to CAN buses having different communication speeds without increasing a communication load.

  The communication unit according to an aspect includes a plurality of CAN controllers respectively connected to a plurality of CAN buses having different communication speeds, and a plurality of serial ports connected to the CAN controllers to the CAN buses having different communication speeds. And a microcomputer having a CPU (Central Processing Unit) for controlling CAN communication between the devices connected to each other.

  Communication modules connected to CAN buses having different communication speeds can communicate without increasing the communication load.

FIG. 1 is a block diagram illustrating an example of a configuration of a CAN according to the first embodiment. FIG. 2 is a block diagram illustrating an example of the internal configuration of the CAN controller. FIG. 3 is a block diagram showing an example of the internal configuration of the microcomputer. FIG. 4 is a diagram illustrating an example of a table indicating processing contents. FIG. 5 is a flowchart showing a procedure for processing a received frame input by the CAN controller. FIG. 6 is a flowchart illustrating a procedure of processing a frame received by the microcomputer that has received the frame from the CAN controller. FIG. 7 is a flowchart showing a procedure for instructing frame transmission from the microcomputer to the CAN controller. FIG. 8 is a flowchart showing a procedure in which a CAN controller to which a frame transmission command is issued generates a transmission frame and sends it to the CAN bus based on an instruction from the microcomputer. FIG. 9 is a block diagram illustrating an example of a configuration in which the microcomputer 150 stores and reads a table in an external memory according to the second embodiment. FIG. 10 is a diagram illustrating an example of an output queue according to the third embodiment. FIG. 11 is a diagram illustrating control when transmission data that exceeds a predetermined waiting time occurs in the queue according to the third embodiment.

  Hereinafter, a communication unit and a CAN communication control program according to the present application will be described with reference to the accompanying drawings. Note that this embodiment does not limit the disclosed technology. Each embodiment can be appropriately combined within a range in which processing contents are not contradictory.

[Configuration of CAN according to Embodiment 1]
FIG. 1 is a block diagram illustrating a CAN 1 that is an example of a configuration of a CAN according to the first embodiment. As illustrated in FIG. 1, the CAN 1 includes a communication unit 100, buses 10 and 20, and modules 11, 12, 21, and 22. The communication unit 100 includes a CAN controller 110 connected to the CAN bus 10, a CAN controller 120 connected to the CAN bus 20, and a microcontroller (hereinafter referred to as a microcomputer 150) that controls communication between the CAN bus 10 and the CAN bus 20. .

  The CAN bus 10 and the CAN bus 20 are buses having different communication speeds. For example, in the example of FIG. 1, the communication speed of the CAN bus 10 is 500 kbps, and the communication speed of the CAN bus 20 is 125 kbps. The modules 11 and 12 connected to the CAN bus 10 are modules that perform higher-speed communication than the modules 21 and 22, such as ABS (Antilock Brake System) and ECM (Engine Control Module). On the other hand, the modules 21 and 22 connected to the CAN bus 20 are modules that perform lower-speed communication than the modules 11 and 12, such as a DIM (Driver Information Module) and a CCM (Climate Control Module).

  The CAN controller 110 and the CAN controller 120 perform frame communication with the modules 11, 12, 21, and 22 in accordance with the communication speeds of the CAN bus 10 and the CAN bus 20, respectively. The CAN controller 110 and the CAN controller 120 identify the type of frame, select information from the frame, and convert it into serial data of a predetermined standard. Then, CAN controller 110 and CAN controller 120 transmit serial data to microcomputer 150 via serial port 151 and serial port 152 of microcomputer 150.

  Here, there are four types of frames distributed in CAN: (1) data frame, (2) remote frame, (3) overload frame, and (4) error frame. The frame has a different data format for each type. Of these frames, an overload frame and an error frame are frames exchanged between the modules 11, 12, 21, and 22 and the microcomputer 150 when an overload or error abnormality occurs, respectively. A data frame for sending data to another module and a remote frame for requesting a data frame from another module are frames exchanged between the modules 11, 12, 21, 22 and the microcomputer 150 at normal times. Note that the data frame and the remote frame include a message ID corresponding to the processing content to be commanded.

[Configuration of CAN Controller according to Embodiment 1]
FIG. 2 is a block diagram illustrating an example of the internal configuration of the CAN controller according to the first embodiment. The CAN controller 110 according to the first embodiment includes a CAN I / F (InterFace, hereinafter the same) 112, a message filter 114, a serial I / F 116, and a transmission engine 118. The CAN I / F 112 determines the type of frame received from the modules 11 and 12 via the CAN bus 10, extracts predetermined information from the frame in a format corresponding to the type of frame, and outputs it to the message filter 114. The CAN I / F 112 converts the message received from the transmission engine 118 into a frame and transmits the frame to the modules 11 and 12 via the CAN bus 10.

  The message filter 114 filters the predetermined information received from the CAN I / F 112 based on the type, and outputs it to the serial I / F 116. The serial I / F 116 serially converts the message received from the message filter 114 and outputs it to the microcomputer 150 via the serial port 151.

  Further, the serial I / F 116 converts serial data including a message from the serial port 151 into data in an internal format of the CAN controller 110 and outputs the data to the transmission engine 118. The transmission engine 118 extracts predetermined information from data including a message received from the serial I / F 116, generates data including a message in a format of a type based on the predetermined information, and outputs the data to the CAN I / F 112. When receiving data including a message from the transmission engine 118, the CAN I / F 112 converts the data into a frame and transmits the frame to the modules 11 and 12 via the CAN bus 10.

  FIG. 3 is a block diagram showing an example of the internal configuration of the microcomputer 150. In FIG. 3, among the serial signals input from the serial ports 151 and 152, SDA is a data line for transmitting a data signal, and is connected to a CPU 155 that controls the microcomputer 150. SCK is a clock line, and a common internal clock signal is input to the serial ports 151 and 152. The CPU 155 refers to the table 160 and specifies the content of information included in the frame received by the serial ports 151 and 152. Further, the CPU 150 sends information instructing frame creation and transmission to the CAN controllers 110 and 120 via the serial ports 151 and 152.

  The serial communication shown in FIG. 3 is a two-wire system, and for example, an I2C (Inter-Integrated Circuit, registered trademark) bus can be used as a protocol. Although not shown, a three-wire serial communication protocol may be adopted, and in that case, SPI (Serial Peripheral Interface, registered trademark) or the like can be used.

  FIG. 4 is an example of the table 160 and shows processing corresponding to a signal input to the CPU. Here, the serial port number 161 indicates from which of the serial ports 151 and 152 the signal is. The message ID 162 is an ID included in the frame from which the signal is derived, and represents the process intended by the frame. As shown in the table 160, the processing content 163 corresponding to the combination of the serial port number 161 and the message ID 162 is registered in the table 160.

  For example, as a process corresponding to (serial port 1, message ID: # 1), the temperature module instructs to transmit data when this frame (remote frame) is received. Further, as processing corresponding to (serial port 1, message ID: # 2), the display module instructs to read and display data when receiving this frame (data frame). Since the microcomputer 150 is neither a temperature module nor a display module, it is discarded even if these messages are received.

  On the other hand, the process corresponding to (serial port 2, message ID: # 1) is an instruction to read data included in the frame when the engine module receives the data frame. Also, the processing corresponding to (serial port 2, message ID: # 2) is a process in which when the microcomputer receives this frame (data frame), it reads the data, performs a predetermined calculation to obtain a parameter, and obtains the result from the engine. Instructed to send to the module. When the latter message is received, the CPU 155 performs a predetermined calculation, and further transmits a data frame including the result to the engine module.

  FIG. 5 is a flowchart illustrating an example of processing a received frame input by the CAN controller 110. The CAN I / F 112 extracts predetermined information from the input received frame (S101), and transmits the analyzed information to the message filter 114 (S102). Next, the message filter 114 determines whether it is necessary to transmit the contents of the received frame to the microcomputer 150. If it is determined that transmission is necessary (S103, Yes), the information analyzed by the serial I / F 116 is determined. Is transmitted (S104), and is transmitted to the destination serial port 151 (S105). On the other hand, when it is determined that the content of the received frame does not need to be transmitted to the microcomputer 150 (S103, No), the received frame is discarded (S106).

  For example, when the CAN controller 110 receives the overload frame (3), the CAN controller 110 returns an overload flag in accordance with the CAN protocol, but the overload frame itself is sent to the microcomputer 150. It is determined that there is no need to transmit.

  In addition, when receiving the error frame (4), the CAN controller 110 increases the value of an error counter (not shown) according to the error state, but the error frame itself does not need to be transmitted to the microcomputer 150. Is determined.

  On the other hand, when the data frame (1) and the remote frame (2) are received, an RTR (Remote Transmission Request), a message ID, and the like are extracted from the frame. Here, the RTR is information indicating whether the frame is a data frame or a remote frame, and the message ID is information indicating data contents or a transmission node.

  The operation of the CAN controller described above shows only some basic functions, but the CAN controller 110 also executes processing related to basic functions such as communication arbitration and error detection defined in the CAN protocol.

  In addition, the CAN controller may have a high function such that the message filter 114 has a wide variety of sorting functions and reduces the load on the microcomputer.

  FIG. 6 is a flowchart illustrating an example of processing a frame received by the microcomputer 150 that has received a frame from the CAN controller 110.

  It is assumed that the microcomputer 150 has N serial ports and is connected to a port with a smaller number in order of increasing CAN bus communication speed. First, i = 1 is set (S201), and the presence or absence of reception to the i-th serial port (hereinafter referred to as "serial port i" or the like) is checked. If there is no reception (No in S202), i = i + 1 If i> N (S207 No), the process returns to S202. If i> N (S207 Yes), the process returns to S201.

  If there is a reception in S202 (S202 Yes), the microcomputer 150 determines whether the received frame is a remote frame (S203). If it is determined that the frame is a remote frame (S203 Yes), the microcomputer 150 refers to the message ID and determines whether the microcomputer 150 itself transmits a data frame to the remote frame (S204). If it is determined not to transmit (No in S204), the microcomputer 150 instructs to transmit a remote frame similar to a remote frame received from a serial port other than the serial port i that received the frame (S205). Exit. Here, whether or not the received frame is a remote frame can be determined by the above-described RTR included in the frame.

  On the other hand, if the microcomputer 150 determines that the data frame is to be transmitted (S204 Yes), the microcomputer 150 outputs an instruction from the serial port i so as to transmit the data frame from the CAN controller 110 (S209), and performs the process. finish.

  If the received frame is not a remote frame (No in S203), the overload frame and the error frame are blocked by the CAN controller 110 as described above, so the received frame is a data frame. Then, the message ID and the data are read and dealt with if necessary (S208), and the process is terminated.

  Heretofore, an example of the procedure in which the microcomputer 150 receives a frame from the CAN bus via the CAN controller and serial I / F has been shown.

  When the microcomputer 150 receives a remote frame requesting transmission of a data frame or notifies other CAN modules that the received data satisfies a predetermined condition, the microcomputer 150 transmits the frame to the CAN controller. Instruct. The process corresponding to (serial port 2, message ID: # 2) in FIG. 4 is an example of notifying that the data satisfies a predetermined condition. FIG. 7 shows an example of a flowchart showing a frame transmission command process from the microcomputer 150 to the CAN controller.

  First, the CPU determines the transmission contents and the serial port corresponding to the CAN bus to be transmitted (S301). Here, a plurality of transmissions may be transmitted to the same CAN bus, or a plurality of types of CAN buses may be transmitted. Next, it is determined whether the transmission frame includes a data frame (S302). If the data frame is not included (S302 No), the process proceeds to S304. If the data frame includes a data frame (S302 Yes), the transmission data is determined (S303). ) To S304. Here, the microcomputer 150 is the same as that shown in FIG. In S304, after i = 1 is set, it is checked whether transmission to the serial port i is included in the transmission target. If transmission is not included (S305 No), i = i + 1 is incremented. (S307) If i> N is not satisfied (No in S308), the process returns to S305. When the transmission target includes transmission to the serial port i (Yes in S305), the transmission command and the determined transmission content are output to the serial port i (S306), and the process proceeds to S307. If i> N in S308 (S308 Yes), the process is terminated.

  In FIG. 8, based on the instruction from the microcomputer 150 shown in FIG. 7, the CAN controller 110 connected to the serial I / F to which a frame transmission command is issued generates a transmission frame and sends it to the CAN bus 10. It is a flowchart which shows the example of the process to send out.

  The transmission command input from the microcomputer 150 is transferred to the transmission engine 118 via the serial I / F 116 (S401), and the transmission engine 118 extracts predetermined information from the transmitted transmission command and generates a frame (S402). . If transmission of the generated frame is permitted (S403, Yes), the generated frame is transmitted to the CAN I / F 112 (S404), converted into a CAN signal corresponding to the CAN bus 10, and transmitted (S405). On the other hand, when frame transmission is not permitted (S403, No), after waiting for a predetermined time (S406), the frame transmission permission is inquired again (S403).

  Here, when frame transmission is not permitted, for example, the error counter of the CAN controller 110 itself may exceed a predetermined value. In addition, communication on the CAN bus 10 is prohibited by the CAN protocol, such as receiving an error frame notifying that the error counter exceeds a predetermined value from another CAN controller connected to the CAN bus 10. Even in this case, frame transmission is not permitted. Furthermore, if the CAN controller 110 has a transmission frame buffer, and there is an untransmitted frame to be transmitted before the frame generated on the buffer, the CAN controller 110 itself has a configuration problem. In some cases, transmission is not permitted.

[Effect of Example 1]
As described above, by using the communication unit according to the present embodiment, communication between modules on the CAN bus having different communication speeds can be realized via a microcomputer without providing a gateway or the like.

  In addition, remote frames can be selectively transmitted to CAN buses with different communication speeds via a microcomputer, so that control for selecting and transmitting CAN buses with appropriate communication speeds according to the priority of transmission frames is realized. To do.

  Furthermore, since the process is determined based on the table for assigning the process to the pair of the serial port number 161 and the message ID 162, different processes can be assigned to the same message ID for each serial port. Get higher.

  Although the embodiments related to the disclosed apparatus have been described above, the present invention may be implemented in various different forms other than the above-described embodiments. Therefore, another embodiment included in the present invention will be described below.

  In the first embodiment, as shown in FIG. 3, the microcomputer 150 is provided with a table 160. However, a configuration in which the table 160 is read from the outside without being held in the microcomputer in advance is also conceivable.

  The microcomputer 150 shown in FIG. 9 shows a configuration in which the table 160 is stored in an external memory such as a USB (Universal Serial Bus) memory or an IC (Integrated Circuit) card, and the microcomputer reads the table 160 from the external memory. . Thus, if the setting of the microcomputer is stored in the removable external memory, the microcomputer can be operated based on the setting, so that the process of applying the setting of the microcomputer to another microcomputer becomes easy.

[Effect of Example 2]
As described above, in this embodiment, since the table indicating the processing contents for the CAN message is stored in the external memory, it is easy to change the processing contents for the message. The contents of the external memory can be easily backed up, and a plurality of settings can be easily managed by storing the contents in another large-capacity storage.

  In the first embodiment, as illustrated in the flowchart of FIG. 7, when the microcomputer 150 instructs the CAN controller to transmit a frame, the microcomputer 150 determines the serial port and transmission contents, and then transmits to the CAN controller via the determined serial port. The command and transmission contents are output (S306).

  However, as described above, it is conceivable that the serial port for transmitting a frame is not fixed to one, but is changed to another serial port or transmitted from a plurality of serial ports.

  Specifically, when a transmission command is issued from the microcomputer to the CAN controller, the CAN controller is inquired of whether or not transmission to the CAN bus is possible. If transmission is impossible, the queue may be controlled in step S306 so as to stop transmission from the inquired CAN controller and wait for transmission from another CAN controller instead.

  An example of the output queue and transmission data addition to the queue for realizing the above control is shown in FIG. The output queue 170 includes a serial port number 171 to be transmitted, a message ID 172, data 173 to be transmitted, and a waiting time 174. In the serial port number 171, the serial port 1 is connected to the fastest CAN bus, and the priority of transmission is higher in the upper frame. Now, in FIG. 10A, the transmission data determined in S306 is inserted at the last part of the waiting serial port to be output indicated by the arrows in FIG. The queue after insertion is as shown in FIG. Then, transmission data that can be output in order from the top of the queue shown in FIG. 10B is output. Among the above, the waiting time 174 is initially 0 like transmission data 177 and 178, but is incremented by 1 every time transmission data is output from the queue, and the transmission data is registered in the queue. It represents the time that has elapsed since then.

  Now, as shown in FIG. 10, data communicated via a high-speed CAN bus is highly urgent, and it makes sense that priority is given to transmission data of a serial port connected thereto. However, when there is a lot of transmission data with a high communication speed, only the transmission data with a high communication speed is processed, and transmission of the transmission data to the serial port corresponding to the CAN bus with a low communication speed may be delayed significantly. In order to avoid such a large delay, transmission data whose waiting time exceeds a predetermined threshold may be controlled so as to be transmitted from a serial port having a high priority.

  Control when transmission data exceeding a predetermined threshold occurs will be described with reference to FIG. First, before selecting transmission data from the queue, it is checked whether there is any registered transmission data whose waiting time exceeds a predetermined threshold. In FIG. 11A, the threshold value is set to 4, and the transmission data 179 in the bottom row indicated by the arrow corresponds to the condition with waiting time = 5. In FIG. 11 (b), the transmission data 179 is extracted, and in FIG. 11 (c), the serial port number of the extracted transmission data 179 is changed to serial port number 1 so as to be processed preferentially, and waiting at the same time. Change the time to zero. Then, the changed transmission data 180 is inserted into the last part of the serial port 1 in FIG. By processing in this way, the order of transmission of transmission data whose waiting time exceeds a predetermined threshold is increased, so transmission of transmission data transmitted from a serial port with low priority on the queue is greatly delayed. Can be avoided.

  In FIG. 11C, the transmission data 179 corresponding to the extracted transmission data 179 of the serial port 3 is deleted. However, if the data is deleted, the transmission data is not transmitted to the CAN bus that was initially set as the transmission destination. Therefore, the transmission data may be left without being deleted.

[Effect of Example 3]
As described above, in this embodiment, when the waiting time of a transmission frame exceeds a predetermined time, control is performed so that transmission is performed from a CAN bus having a higher communication speed, so transmission of transmission data is greatly delayed. Can be avoided.

10, 20 CAN bus 11, 12, 21, 22 Module 100 Communication unit 110, 120 CAN controller 112 CAN I / F
114 With message filter 116 Serial I / F
118 Transmission engine 150 Microcomputer 151,152 Serial port 155 CPU
160, 170 Table 161, 171 Serial port number 162, 172 Message ID
163, 173 Processing content 174 Wait time 177, 178, 179, 180 Transmission data

Claims (6)

A plurality of CAN controllers respectively connected to CAN buses having different communication speeds;
A communication unit, comprising: a microcomputer for controlling CAN communication between devices connected to the CAN buses having different communication speeds via a plurality of serial ports respectively connected to the CAN controller.   2. The communication unit according to claim 1, wherein the microcomputer receives the CAN signal by accessing the serial port in descending order of communication speed of the connected CAN bus. The microcomputer controls the CAN communication with reference to a storage unit that stores definition information defining processing contents corresponding to a combination of the identification information of the serial port and the identification information of the CAN message. The communication unit according to claim 1 or 2. The communication unit according to claim 1, wherein the microcomputer accesses the serial port in descending order of communication speed of a connected CAN bus and transmits a CAN signal. In response to a CAN message whose transmission standby time exceeds a predetermined value, the microcomputer changes the transmission source to a serial port corresponding to a CAN bus whose communication speed is higher than the serial port currently set as the transmission source. The communication unit according to any one of claims 1 to 4, characterized in that: On the computer,
Select CAN messages on CAN bus with different communication speeds,
Convert the selected CAN message into a serial signal,
Controlling the CAN message based on the ID of the serial port to which the CAN message is input and the ID of the CAN message;
A CAN communication control program for executing a process.

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