JP5836785B2 - Communication system and communication method - Google Patents

Description

The present invention is a communication in which a plurality of communication devices including a plurality of communication devices that transmit / receive information to / from each other are connected to one communication line, and the plurality of communication device groups can communicate by sharing one communication line. on the system及 beauty communication method.

  Conventionally, a communication protocol of CAN (Controller Area Network) has been widely adopted for communication between a plurality of electronic devices (communication devices) mounted on a vehicle (see Non-Patent Documents 1 and 2). In the CAN communication protocol, since a plurality of communication devices are connected to a common CAN bus, when a plurality of communication devices transmit information simultaneously, arbitration is performed in each communication device so that no collision occurs. Processing (arbitration) is performed, and high-priority information transmission is executed. In order to perform arbitration, each communication device outputs a transmission signal to the CAN bus and simultaneously detects the signal level of the CAN bus, and the signal level of the detected signal relative to the transmission signal output by itself is detected. When it changes from recessive to dominant, it determines that simultaneous transmission of communication has occurred and stops the transmission process. Since signals on the CAN bus are dominant over recessive signals, an electronic device that outputs dominant signals can continue transmission processing even if simultaneous transmission occurs.

  A plurality of communication devices mounted on a vehicle do not necessarily communicate at the same communication speed. For example, a communication device that performs communication at a communication speed of 500 kbps and a communication device that performs communication at a communication speed of 250 kbps are mixedly mounted on the vehicle. Since communication devices having different communication speeds cannot communicate directly, a communication system for a vehicle can be obtained by connecting communication devices having the same communication speed to one CAN bus and connecting a plurality of these communication device groups to a gateway. Is configured. When it is necessary to transmit / receive information between different communication device groups, the gateway receives information from one communication device group, converts the communication speed, and transmits this information to another communication device group.

ISO 11898-1: 2003 Road vehicles--Controller area network (CAN)-Part1: Data link layer and physical signaling ISO 11519-1: 1994 Road vehicles--Low-speed serial data communication--Part1: General and definitions

  When a plurality of communication devices having different communication speeds are mixed, a CAN bus is required for each communication speed (for each communication device group). Therefore, as the number of types of communication speeds increases, There is a problem that the number increases. This makes it difficult to mount the communication system in a limited space in the vehicle and increases the cost of the communication system.

The present invention has been made in view of such circumstances, and an object of the present invention is to allow a plurality of communication device groups to communicate with each other via a common communication line even when communication speeds are different. it is performed to provide a communication system及 beauty communication method capable.

The communication system according to the present invention is a communication system including a plurality of communication devices that transmit and receive continuous multiple bits of information each bit represented by a binary value of dominant or recessive via a common communication line. A plurality of communication device groups including a plurality of communication devices to be transmitted and received, and each communication device uses a different code sequence for each communication device group, and spreads and modulates a signal output to the communication line by a direct spreading code method After the modulation means and a dominant signal of information to be transmitted, a signal modulated by the spread modulation means for a predetermined time shorter than the information transmission time of 1 bit is output to the communication line, and then the communication line without signal output to, and for recessive of information to be transmitted, have a transmitting means does not perform the signal output to the communication line, respectively, wherein the communication device is the The communication information transmission / reception cycle is determined for each of the communication device groups so as to be a natural number multiple of the shortest cycle. Information on each bit is periodically transmitted with a difference in signal output timing so that signal output by the communication device group is not performed simultaneously .

Further, in the communication system according to the present invention, the communication device detects a code sequence of a signal on the communication line, a code sequence detected by the detection device, and a code sequence related to a communication device group to which the communication device belongs . A calculation unit that calculates a correlation value; and a determination unit that determines whether the signal detected by the detection unit is a signal related to a communication apparatus group to which the detection unit belongs according to the correlation value calculated by the calculation unit. It is characterized by having.

Further, the communication method according to the present invention includes a plurality of communication device groups each including a plurality of communication devices each transmitting and receiving information of a plurality of consecutive bits each represented by a binary value of dominant or recessive. A communication method in which the communication devices of each communication device group communicate via the common communication line, and the communication device transmits and receives the information of each bit by a natural number times the shortest cycle. Each communication device defines a code sequence that is different for each communication device group over a predetermined time shorter than the information transmission time for 1 bit with respect to the dominant information to be transmitted. After the signal spread-modulated by the direct spreading code method using the signal is output to the communication line, the signal to the communication line is not output, and the signal to the communication line with respect to the recessive information to be transmitted output Without, the communication device of each communication apparatus groups, such that the signal output is not performed simultaneously by the signal output and the other communication device group according to its own communication device group, each provided with a difference in the timing of the signal output Bit information is transmitted periodically .

In the present invention, when the information to be transmitted by each communication device in the communication system is dominant, a predetermined signal is transmitted to the communication line over a predetermined time shorter than this time for the information transmission time of 1 bit. After that, the signal output to the communication line is stopped. When the information to be transmitted is recessive, each communication device does not output a signal to the communication line. As a result, when the dominant transmission and the recessive transmission collide, a signal corresponding to the dominant is transmitted over a predetermined time on the communication line, so the communication device that has transmitted the recession detects the signal on the communication line. Thus, a dominant signal transmitted by another communication apparatus can be detected.
As described above, the communication devices belonging to one communication device group output a predetermined signal that is short with respect to the information transmission time for one bit, so that a signal is output on the signal line during the information transmission time for one bit. There can be no period. Therefore, during this period, communication devices belonging to other communication device groups can output signals. The predetermined signal output from each communication device to the dominant is a spread-modulated signal, and a common signal is output for each communication device group. Thereby, each communication apparatus can determine whether or not the signal on the communication line is a signal corresponding to the communication apparatus group to which the communication apparatus belongs. With these configurations, a plurality of communication device groups can share a communication line and communicate simultaneously.

  Further, in the present invention, a signal output as a dominant by each communication apparatus over a predetermined time is a signal that is spread-modulated by the direct spreading code method. The direct spreading code method is a method of performing modulation by multiplying an original signal wave by a pseudo-random binary code sequence called a spreading code. By appropriately selecting a code sequence to be multiplied and performing spread modulation using a different code sequence for each communication device group, the communication device on the receiving side is a signal of the communication device group to which it belongs or another communication device group Can be distinguished with high accuracy. As the code sequence, for example, a PN (Pseudorandom Noise) sequence M sequence or a quadratic residue sequence can be used.

  In the present invention, each communication device in the communication device group calculates a correlation value between a signal detected on the communication line and a signal output to the dominant by itself. Accordingly, each communication device can obtain a high correlation value if the detection signal on the communication line is the same as the signal transmitted by itself, and if the detection signal is a signal different from itself, the communication device can obtain a low correlation value. obtain. Therefore, for example, by determining whether or not the correlation value exceeds a threshold value, it is possible to determine whether or not the signal detected on the communication line is a signal related to the communication device group to which the device belongs.

In the present invention, the communication devices of each communication device group periodically transmit information of each bit, and this transmission cycle is determined for each communication device group. The transmission cycle of each communication device group is determined to be a natural number multiple (1 times, 2 times, 3 times,...) Of this cycle with respect to the shortest cycle of the communication device group in the communication system. In addition, the communication device of each communication device group transmits each bit so that the communication device of the other communication device group outputs its own spread-modulated signal while it is not outputting the spread-modulated signal. Information on each bit is periodically transmitted with a difference in timing (transmission timing is shifted).
As a result, when transmitting a plurality of continuous bits of information, if the first one bit of information is successfully shifted from the transmission timing of the other communication device group, the subsequent periodic information transmission is performed. Can be reliably performed without colliding with information transmission of other communication device groups.

  In the case of the present invention, when the information to be transmitted by each communication device in the communication system is dominant, a signal subjected to spread modulation over a predetermined time shorter than this time with respect to the information transmission time of 1 bit. Output to the communication line and thereafter stop outputting the signal to the communication line, and if the information to be transmitted is recessive, no signal is output to the communication line. As a result, each communication device can determine whether or not the signal on the communication line is a signal corresponding to the communication device group to which the communication device belongs. Communication can be performed. Therefore, since a plurality of communication device groups can be connected to a common communication line, the communication lines in the communication system can be reduced, and the communication system can be reduced in size (space saving) and reduced in cost. it can.

It is a schematic diagram which shows one structural example of a communication system. It is a block diagram which shows the structure of a communication apparatus. It is a schematic diagram for demonstrating the signal which each ECU transmits / receives in the communication system which concerns on this invention. It is a schematic diagram for demonstrating the signal which each ECU outputs in the case of information transmission of a dominant. It is a schematic diagram which shows an example of the signal transmitted / received in the communication system which concerns on this Embodiment. It is a flowchart which shows the process sequence at the time of ECU transmitting the 1st bit of transmission data. It is a flowchart which shows the process sequence at the time of ECU transmitting the arbitration field after the 2nd bit of information. It is a flowchart which shows the process sequence at the time of ECU transmitting the arbitration field after the 2nd bit of information.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a schematic diagram illustrating a configuration example of a communication system. The communication system according to the present embodiment includes, for example, a plurality of ECUs (Electronic Control Units) 1 mounted on a vehicle (not shown) as a communication device, and the plurality of ECUs 1 are connected via a common communication line 5. is there. In this communication system, it is possible to connect ECUs 1 having different communication speeds to the common communication line 5. In FIG. 1, the ECU 1 having a communication speed of 500 kbps is indicated by a solid line as the first group ECU 1a, and the communication speed is The 250 kbps ECU 1 is indicated by a broken line as the second group of ECUs 1b.

  Each ECU 1a in the first group can transmit and receive information to and from other ECUs 1a belonging to the first group at a communication speed of 500 kbps. Similarly, each ECU 1b in the second group can mutually transmit / receive information to / from another ECU 1b belonging to the second group at a communication speed of 250 kbps. Note that the first group of ECUs 1a and the second group of ECUs 1b cannot communicate information directly because they have different communication speeds. However, for example, a configuration in which the ECU 1 can switch the communication speed may be configured to transmit and receive information with both the first group ECU 1 a and the second group ECU 1 b.

  FIG. 2 is a block diagram showing a configuration of the communication apparatus (ECU 1). The ECU 1 includes a control unit 11, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, an input unit 14, an output unit 15, a CAN communication control unit 16, and the like. The control unit 11 is configured using an arithmetic processing device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and performs various controls by reading and executing a control program stored in the ROM 12. Processing can be performed.

  The ROM 12 is configured by a nonvolatile memory element such as an EEPROM (Electrically Erasable Programmable ROM) or flash memory, for example, and a control program executed by the control unit 11 and information necessary for processing performed by the control unit 11 Etc. are stored in advance. The RAM 13 is composed of a memory element such as SRAM (Static RAM) or DRAM (Dynamic RAM), for example, and information generated by the processing of the control unit 11 and information transmitted / received to / from another ECU 1. Etc. are stored.

  The input unit 14 receives a signal from an input device such as a sensor such as a vehicle speed sensor or a temperature sensor of a vehicle, or various switches for operation arranged inside and outside the vehicle, and performs sampling of the input signal or A / Information obtained by performing processing such as D conversion is given to the control unit 11. The output unit 15 is connected to a load such as a motor or a lamp, and outputs a drive signal for driving these loads in response to an instruction from the control unit 11. Note that the ECU 1 does not necessarily need to include both the input unit 14 and the output unit 15, and may be configured to include only one of them.

  The CAN communication control unit 16 has a terminal connected to the communication line 5, and transmits / receives information to / from another ECU 1 according to the CAN protocol via the communication line 5 connected to the terminal. Is. The CAN communication control unit 16 converts the transmission information given from the control unit 11 into transmission data (frame) according to the CAN protocol and gives the data to the transmission unit 17. The transmission unit 17 of the CAN communication control unit 16 outputs a signal to the communication line 5 according to the value of each bit of the given transmission data (0 (dominant) or 1 (recessive)). In the CAN protocol, a twisted pair line is used as the communication line 5, and the transmission unit 17 outputs a differential signal to the communication line 5. The transmission unit 17 sequentially processes each bit of transmission data composed of a plurality of bits. When the value of the processing target bit is dominant, the transmission unit 17 performs a predetermined signal (spread modulation signal) for a predetermined time Tp. Is output, then signal output to the communication line is stopped. In addition, when the value of the processing target bit is recessive, the transmission unit 17 does not output a signal to the communication line.

  Further, the CAN communication control unit 16 detects the signal level of the communication line 5 (potential difference between the two signal lines constituting the twisted pair line), so that the signal transmitted on the communication line 5 is either dominant / recessive. It has a receiving unit 18 that determines whether the signal is a corresponding signal and receives data in which each bit is represented by dominant / recessive. The CAN communication control unit 16 gives the data received by the receiving unit 18 to the control unit 11. Further, the CAN communication control unit 16 receives the data transmitted by the transmission unit 17 at the reception unit 18, and when the transmission data and the reception data do not match (the recessiveness of the transmission data changes to dominant in the reception data). When the transmission is performed by another ECU 1 connected to the communication line 5, an arbitration process is performed. The arbitration process performed by the ECU 1 is the same as that performed by the conventional CAN protocol, and thus detailed description thereof is omitted.

  FIG. 3 is a schematic diagram for explaining a signal transmitted and received by each ECU 1 in the communication system according to the present invention, in which the vertical axis represents the potential difference V between the twisted pair wires of the signal line 5 and the horizontal axis represents time t. It is. The illustrated example is a signal when transmission data changes from dominant to recessive. When transmitting the dominant data, the transmission unit 17 of the ECU 1 performs a spread modulation signal (shown as a hatched pulse in FIG. 3) in the period from the start time to the time Tp in the 1-bit transmission time Tb. Is output) until a 1-bit transmission time Tb is reached. Further, in the case of recessive, the transmission unit 17 does not output a signal for the entire transmission time Tb of 1 bit.

  FIG. 4 is a schematic diagram for explaining a signal that is output from each ECU 1 when transmitting dominant information. In the communication system according to the present embodiment, the CAN communication control unit 16 of each ECU 1 uses a signal obtained by spreading and modulating a pulse signal by the direct spreading code method as a signal to be output to the communication line 5 when transmitting dominant information. . The direct spreading code method is a method of performing modulation by multiplying an original signal (in this embodiment, a pulse signal) by a binary sequence called a spreading code. As the spreading code, for example, a code sequence called a PN sequence can be used.

  A PN sequence spreading code is a pseudo-random code that can be generated using a shift register, has a periodicity, and has a property such that the difference in number between 0 and 1 in the period is 1 or less. doing. Further, the PN sequence spreading code has the property that the absolute value of the autocorrelation of a signal having a time lag of 1/2 chip or more is 1 or less, and is characterized by good autocorrelation characteristics. Such a PN sequence spreading code includes, for example, codes such as an M sequence, a quadratic residue sequence, and a biprime number sequence. In the present embodiment, an M sequence is employed (however, the M sequence is not limited to this). Other codes may be employed). Note that a chip is a minimum unit of a spread code sequence. If the time is Tc and the code sequence length is Np, Tp = Np × Tc.

The M-sequence spreading code can be generated using a shift register based on a primitive polynomial such as the following equation (1).
h (x) = X ^k + h _k−1 x ^k−1 +... + h ₂ x ² + h ₁ x + 1 (1)
In this embodiment, the M-sequence spreading code is 7 chips, “1110010” is assigned to the first group, and “1101000” is assigned to the second group. As a result, the signal shown in FIG. 4 is obtained, and the transmission unit 17 of each ECU 1 outputs this signal onto the signal line 5 over time Tp when transmitting the dominant information.

  The receiving unit 18 of each ECU 1 samples the signal level of the communication line 5 at a predetermined period (for example, a time corresponding to 1/25 of the transmission time Tb of each bit), and samples over the transmission time Tb of each bit. From the result, a code sequence of a spread modulated signal transmitted as a dominant is detected. The receiving unit 18 calculates a correlation value (autocorrelation value) between the detected code sequence and the code sequence assigned to itself, and when the calculated correlation value exceeds a threshold, this signal is assigned to the group to which the signal belongs. Information reception processing is performed assuming that the information is transmitted by the ECU 1. On the other hand, when the calculated correlation value does not exceed the threshold value, the receiving unit 18 regards this signal as information of another group and does not perform information reception processing.

  For example, when the code sequence of the signal detected on the communication line 5 is “1110010”, the receiving unit 18 of the ECU 1 of the first group obtains a correlation value 7 between this code sequence and the code sequence “1110010” assigned to itself. When the code sequence calculated and detected on the communication line 5 is “1101000” of the second group, the correlation value−1 is calculated. The calculation of the correlation value by the receiving unit 18 compares the values of the chips of the two code sequences. If the values are the same, +1 is the comparison result, and if the values are different, -1 is the comparison result. This can be done by adding the comparison results. In addition, the receiving unit 18 can determine whether or not this signal belongs to a group to which the receiver belongs by determining whether or not the calculated correlation value exceeds 3, for example, as a threshold value.

  FIG. 5 is a schematic diagram illustrating an example of signals transmitted and received in the communication system according to the present embodiment. In FIG. 5, a signal output from the ECU 1a belonging to the first group to the communication line 5 is shown in the upper stage, and a signal output from the ECU 1b belonging to the second group to the communication line 5 is shown in the middle stage. The lower part of FIG. 5 shows a signal output to the communication line 5 in the communication system in which the first group and the second group are mixed. In addition, all signals are signals when information is transmitted continuously by dominant.

  For example, the ECU 1a belonging to the first group transmits information on each bit in the cycle Tb1. At this time, the ECU 1a outputs a signal subjected to spread modulation during the period from the start time to the time Tp1 in the information transmission time Tb1 of each bit, and does not output the signal after the time Tp1 has elapsed.

  On the other hand, for example, the ECU 1b belonging to the second group transmits information of each bit in the cycle Tb2. However, the period Tb2 of the second group is a natural number (1, 2, 3,...) Times the period Tb1 of the first group (Tb2 = 2 × Tb1 in the example shown in FIG. 4). Moreover, ECU1b outputs the signal which carried out the spread modulation in the period from the start time to time Tp2 among information transmission time Tb2 of each bit, and does not output a signal after progress of time Tp2. However, the time Tp1 of the first group and the time Tp2 of the second group are set so as to satisfy the condition of Tp1 + Tp2 <Tb1.

  In this communication system, the first group ECU 1a and the second group ECU 1a and the second group output signal so that the spread modulation signal output by the first group ECU 1a and the second group ECU 1b are not simultaneously performed. The group ECUs 1 b output dominant signals to the common communication line 5 at different timings. That is, during the period from when the first group ECU 1a outputs a signal for the time Tp1 until the 1-bit transmission time Tb1 elapses (the period during which the ECU 1a does not output a signal), the second group ECU 1b at the time Tp2 The output of the signal is performed.

  The CAN communication control unit 16 of the ECU 1 of each group outputs a signal subjected to spread modulation corresponding to the dominant in the transmission unit 17, and the correlation value with the signal detected by the reception unit 18 at this time does not exceed the threshold value. In this case, since the signal output of the first group and the second group is considered to have been performed at the same time, the transmission unit 17 performs retransmission at different timings. After the transmission unit 17 successfully transmits the information of the first bit by performing retransmission, the transmission cycle Tb1 of the first group and the transmission cycle Tb2 of the second group are natural number multiples. Are not simultaneously performed again, and the ECU 1a of the first group and the ECU 1b of the second group can transmit information after the second bit in their transmission cycle.

  Next, a procedure of communication processing performed by each ECU 1 of the communication system will be described using a flowchart. FIG. 6 is a flowchart showing a processing procedure when the ECU 1 transmits the first bit of the transmission data. The ECU 1 outputs a dominant signal to the communication line 5 as the first bit information. When performing information transmission, the CAN communication control unit 16 of each ECU 1 of the communication system first determines whether or not the communication line 5 is free (other ECUs 1 are not transmitting information) (step S1). If the communication line 5 is not free (S1: NO), the communication line 5 is on standby (receives information transmitted by another ECU 1).

  When the communication line 5 is vacant (S1: YES), the CAN communication control unit 16 outputs to the communication line 5 a signal subjected to spread modulation using the code sequence assigned to it by the transmission unit 17. (Step S2), the signal level of the communication line 5 is sampled by the receiving unit 18 (Step S3). Thereafter, the CAN communication control unit 16 determines whether or not a predetermined time Tp has elapsed from the start of signal output (step S4). If the time Tp has not elapsed (S4: NO), the process proceeds to step S2. The signal output and sampling are repeated.

  When the time Tp has elapsed (S4: YES), the CAN communication control unit 16 stops signal output by the transmission unit 17 (step S5), and continues sampling of the signal level of the communication line 5 by the reception unit 18. It performs (step S6). Thereafter, the CAN communication control unit 16 determines whether or not the 1-bit information transmission time Tb has elapsed since the start of signal output (step S7). When the information transmission time Tb has not elapsed (S7: NO) The process is returned to step S5, the signal output stop state is maintained, and the signal level sampling is repeated.

  When the information transmission time Tb has elapsed (S7: YES), the CAN communication control unit 16 acquires the code sequence of the signal on the communication line 5 from the sampling result of the reception unit 18, and assigns the acquired code sequence to itself. A correlation value with the obtained code sequence is calculated (step S8), and it is determined whether or not the calculated correlation value exceeds a threshold value (step S9). If the calculated correlation value does not exceed the threshold value (S9: NO), the CAN communication control unit 16 waits for a predetermined time (step S10), returns the process to step S2, and retransmits the information. When the calculated correlation value exceeds the threshold (S9: YES), the CAN communication control unit 16 starts information transmission processing for the second and subsequent bits of information to be transmitted (step S11), and information transmission processing for the first bit Exit.

  Information such as a threshold value for comparison with a code sequence necessary for transmission / reception of information and a calculated correlation value is stored in advance in the ROM 12 of each ECU 1, and the control unit 11 receives information such as a code sequence and a threshold value from the ROM 12. And the above processing is performed.

  7 and 8 are flowcharts showing a processing procedure when the ECU 1 transmits an arbitration field for the second and subsequent bits of information. The CAN communication control unit 16 of each ECU 1 of the communication system acquires 1-bit information of transmission data that has not been transmitted (step S21), and determines whether or not the acquired information is dominant (step S22). If the information to be transmitted is dominant (S22: YES), the CAN communication control unit 16 outputs the signal subjected to spread modulation using the code sequence assigned to it by the transmission unit 17 to the communication line 5 (Step S22). S23) When the information to be transmitted is not dominant but recessive (S22: NO), the transmission unit 17 stops signal output to the communication line 5 (step S24). The CAN communication control unit 16 samples the signal level of the communication line 5 at the receiving unit 18 (step S25), and determines whether or not a predetermined time Tp has elapsed from the start of the bit transmission processing ( Step S26). If the time Tp has not elapsed (S26: NO), the process returns to step S25, and signal level sampling is repeated.

  When the time Tp has elapsed (S26: YES), the CAN communication control unit 16 stops signal output by the transmission unit 17 (step S27), and the signal output onto the communication line 5 from the sampling result by the reception unit 18 Is determined to be dominant (step S28). If the signal is dominant (S28: YES), the CAN communication control unit 16 further determines whether or not the transmission unit 17 has performed recessive information transmission (step S29). If the transmission unit 17 has transmitted recessive information (S29: YES), the CAN communication control unit 16 determines that information transmission from another ECU 1 has been performed, and starts arbitration processing (step S30). The transmission process is terminated. The arbitration processing procedure is the same as that according to the conventional CAN protocol, and a detailed description thereof will be omitted.

  If the signal on the communication line 5 is not dominant and is recessive (S28: NO), or if the transmitter 17 is not performing recessive information transmission (S29: NO), the CAN communication controller 16 uses this bit. It is determined whether or not the 1-bit information transmission time Tb has elapsed since the start of the transmission process (step S31). When the information transmission time Tb has not elapsed (S31: NO), the CAN communication control unit 16 stands by until the information transmission time Tb has elapsed. When the information transmission time Tb has elapsed (S31: YES), the CAN communication control unit 16 determines whether or not transmission has been completed for all bits of the information to be transmitted (step S32). If the transmission of all bits has not been completed (S32: NO), the CAN communication control unit 16 returns the process to step 21 and transmits information of the next bit. When transmission of all bits is completed (S32: YES), the CAN communication control unit 16 ends the transmission process.

  In the communication system configured as described above, each ECU 1 in the communication system stops signal output after outputting a spread-modulated signal having a time Tp shorter than 1-bit information transmission time Tb with respect to dominant information transmission. This is a configuration in which the first group and the second group perform spread modulation using different code sequences. With this configuration, when the ECU 1a of the first group and the ECU 1b of the second group are connected to the common communication line 5 and information is transmitted and received, the CAN communication control unit 16 of each ECU 1a, 1b is on the communication line 5. Since it can be determined whether or not the signal is related to its own group, a plurality of groups can share the communication line 5 and communicate simultaneously.

  In addition, a configuration in which each ECU 1 outputs a signal that is output over a predetermined time with respect to dominant information transmission is a signal obtained by spreading and modulating a pulse signal by a direct spreading code method, and performing spread modulation using a different code sequence for each group; Thus, each ECU 1 calculates the correlation value between the signal detected on the communication line 5 and the signal output by itself, thereby determining whether or not the signal on the communication line 5 relates to its own group. Can be easily and accurately determined.

  While the ECU 1 of one group does not output a signal, the ECU 1 of the other group outputs a signal, and the transmission cycle Tb2 of the second group is set to a natural number multiple of the transmission cycle Tb1 of the first group. Thus, after successfully transmitting the first 1 bit, each ECU 1 can reliably perform subsequent information transmission without colliding with information transmission of other groups.

  In the present embodiment, the communication system is mounted on the vehicle. However, the present invention is not limited to this. The communication device is not limited to the ECU 1. The configuration of the communication system shown in FIG. 1 (the number of ECUs 1, the connection form of the ECU 1, etc.) is merely an example, and the present invention is not limited to this. Further, although the twisted pair line is used as the communication line 5, the present invention is not limited to this, and other structures such as using one line as the communication line 5 may be used. In addition, although the communication speed of the first group is 500 Kbps and the communication speed of the second group is 250 Kbps, these communication speeds are merely examples and are not limited thereto. The communication speeds of the first group and the second group may be the same.

  In the above-described embodiment, the communication system includes two groups. However, the configuration is not limited to this, and the communication system may include three or more groups. In this case, the signal output time Tp of each group is set so that three or more spread-modulated signals can be accommodated in the shortest 1-bit information transmission time Tb, and each group is based on a different code sequence. It is necessary to output a signal.

  In the above-described embodiment, the transmission timing is shifted so that the spread modulated signal output from the first group ECU 1a and the spread modulated signal output from the second group ECU 1b do not overlap. The information of each bit is transmitted periodically, but the present invention is not limited to this. Even if the spread-modulated signal output from the first group ECU 1a and the spread-modulated signal output from the second group ECU 1b are partially or entirely overlapped and output onto the communication line 5. Any configuration may be used as long as the calculated correlation value exceeds the threshold and each ECU 1 can determine the presence or absence of a signal related to the group to which the ECU 1 belongs.

1, 1a, 1b ECU (communication device)
5 Communication line 11 Control unit 12 ROM
13 RAM
14 input unit 15 output unit 16 CAN communication control unit (spreading modulation means, transmission means, detection means, calculation means, determination means)
17 Transmitter (transmission means)
18 Receiver (detection means)

Claims (3)

In a communication system including a plurality of communication devices that transmit and receive information of a plurality of consecutive bits each represented by a binary value of dominant or recessive via a common communication line.
A plurality of communication device groups including a plurality of communication devices that transmit and receive information to and from each other,
Each communication device
Spreading modulation means for spreading and modulating a signal to be output to the communication line by a direct spreading code method using a different code sequence for each communication device group ;
The signal output to the communication line is output after the signal subjected to the spread modulation by the spread modulation means is output to the communication line over a predetermined time shorter than the information transmission time of 1 bit with respect to the dominant information to be transmitted. the not performed, and for recessive of information to be transmitted, and transmission means does not perform the signal output to the communication line possess respectively,
The period in which the communication device transmits and receives information of each bit is determined for each communication device group so as to be a natural number multiple of the shortest cycle,
The communication devices of each communication device group provide information on each bit by providing a difference in signal output timing so that signal output by its own communication device group and signal output by another communication device group are not performed simultaneously. Is transmitted periodically . A communication system characterized by the above . The communication device
Detecting means for detecting a code sequence of a signal on the communication line;
Calculating means for calculating a correlation value of a code sequence detected by the detecting means and a code sequence related to a communication device group to which the detection apparatus belongs ;
And determining means for determining whether the signal detected by the detecting means is a signal related to a group of communication devices to which the apparatus belongs, according to the correlation value calculated by the calculating means. The communication system according to 1 . A plurality of communication device groups each including a plurality of communication devices that transmit and receive continuous plural bits of information each bit represented by a binary value of dominant or recessive are connected to a common communication line, and communication of each communication device group A communication method in which an apparatus performs communication via the common communication line,
A period for transmitting and receiving the information of each bit by the communication apparatus is determined for each communication apparatus group so as to be a natural number multiple of the shortest period,
Each communication device is spread-modulated by a direct spreading code method using a different code sequence for each communication device group over a predetermined time shorter than an information transmission time of 1 bit with respect to a dominant information to be transmitted. After outputting the signal to the communication line, the signal output to the communication line is not performed, and the signal output to the communication line is not performed for the recessive information to be transmitted ,
The communication devices of each communication device group provide information on each bit by providing a difference in signal output timing so that signal output by its own communication device group and signal output by another communication device group are not performed simultaneously. Is periodically transmitted .

Images