Communication device, communication system, and time synchronization method

Abstract

This technology provides a way to improve the time synchronization accuracy in in-vehicle communication lines using a simple circuit configuration. [Solution] The communication device is included in a plurality of nodes 40A, 20B, 40B, 15, 25, 35, 45, 55, 65 connected to the in-vehicle communication line 110, and comprises a control unit 11 and a transceiver 12. The control unit outputs a first time synchronization frame. The transceiver transmits the first time synchronization frame output from the control unit to the in-vehicle communication line using the Physical Layer Collision Avoidance method and notifies the control unit that the first time synchronization frame has been transmitted.

Description

[[Technical Field]]

[0001] The present disclosure relates to communication technology via an in-vehicle communication line. [[Background Art]]

[0002] The network controller described in Patent Document 1 is one of a plurality of nodes in a 10BASE-T1S network, and includes a microcontroller unit (MCU) and a Physical Layer (PHY) circuit. In a 10BASE-T1S network, access is controlled by the Physical Layer Level Collision Avoidance (PLCA) scheme, and transmission opportunities are determined by the round-robin scheme. Therefore, when performing time synchronization in a 10BASE-T1S network, the time at which the PHY circuit transmits the time synchronization frame to the network may be later than the time at which the MCU transmits the time synchronization frame to the PHY circuit, that is, the time stamp added to the time synchronization frame.

[0003] Therefore, in the above network controller, the PHY circuit includes a circuit that detects a synchronization time frame and a circuit that provides a time stamp, and adds a time stamp to the synchronization time frame. [[Prior Art Documents]] [[Patent Documents]]

[0004] [[Patent Document 1]] Japanese National Publication of International Patent Application No. 2021-527355 [[Summary of Invention]] [[Problem to be Solved by the Invention]]

[0005] Since the PHY circuit of the above network controller includes a circuit that detects a synchronization time frame and a circuit that provides a time stamp, the circuit configuration is complicated. Consequently, the cost of the network controller increases.

[0006] One aspect of this disclosure is the provision of a technology that improves the time synchronization accuracy in in-vehicle communication lines with a simple circuit configuration. [Means for solving the problem]

[0007] A communication device in one aspect of this disclosure is included in a plurality of nodes (40A, 20B, 40B, 15, 25, 35, 45, 55, 65) connected to an in-vehicle communication line (110), and comprises a control unit (11) and a transceiver (12). The control unit is configured to output a first time synchronization frame. The transceiver is configured to transmit the first time synchronization frame output from the control unit to the in-vehicle communication line using the Physical Layer Collision Avoidance method, and to notify the control unit that the first time synchronization frame has been transmitted.

[0008] According to the communication device of this disclosure, the transceiver notifies the control unit that it has transmitted a first time synchronization frame. Therefore, the control unit can detect the time when the first time synchronization frame was actually transmitted to the in-vehicle communication line. Notifying the control unit that the transceiver has transmitted a first time synchronization frame can be achieved with a simple circuit. Therefore, by adding a simple circuit to the transceiver, the time synchronization accuracy between nodes of the in-vehicle communication line can be improved.

[0009] Another aspect of this disclosure is a time synchronization method performed by a transceiver (12) of a communication device included in a plurality of nodes (40A, 20B, 40B, 15, 25, 35, 45, 55, 65) connected to an in-vehicle communication line (110), wherein the transceiver receives a time synchronization frame from a control unit (11) of the communication device, transmits the time synchronization frame to the in-vehicle communication line using the Physical Layer Collision Avoidance method, and notifies the control unit that the time synchronization frame has been transmitted.

[0010] The above method produces the same effect as the above-mentioned communication device.

[0011] A communication system (100A, 100B) in another aspect of the present disclosure comprises a master node and a slave node connected to an in-vehicle communication line (110). The master node comprises a control unit (11) and a transceiver (12). The control unit (i) outputs a first time synchronization frame to the transceiver, (ii) obtains a timestamp in response to notification from the transceiver that the first time synchronization frame has been transmitted, and (iii) outputs a second time synchronization frame containing the timestamp to the transceiver. The transceiver (i) transmits the first time synchronization frame output from the control unit to the slave node via the in-vehicle communication line using the Physical Layer Collision Avoidance method, (ii) notifies the control unit that the first time synchronization frame has been transmitted, and (iii) transmits the second time synchronization frame output from the control unit to the slave node via the in-vehicle communication line. The slave node is configured to synchronize its time with the master node's time based on the time it received the first time synchronization frame and the timestamp of the second time synchronization frame.

[0012] According to the above communication system, the slave node can obtain the reception time when it receives the first time synchronization frame and the transmission time when the first time synchronization frame is sent to the in-vehicle communication line. Based on the reception time and transmission time, the slave node can calculate a time offset relative to the master node and synchronize its time with the master node. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example of the configuration of an in-vehicle communication system according to the first embodiment. [Figure 2] This figure shows another example of the configuration of the in-vehicle communication system according to the first embodiment. [Figure 3] This figure shows the data flow of PLCA in the in-vehicle communication system according to the first embodiment. [Figure 4]This is a block diagram showing the functions of the controller and transceiver of a node in an in-vehicle communication system according to the first embodiment. [Figure 5] This figure shows the Sync / Follow-up sequence in the in-vehicle communication system according to the first embodiment. [Figure 6] This figure shows the Pdelay Request / Pdelay Response sequence in the in-vehicle communication system according to the first embodiment. [Figure 7] This is a block diagram showing the functions of the controller and transceiver of the node in the in-vehicle communication system according to the second embodiment. [Figure 8] This figure shows the Sync / Follow-up sequence in the in-vehicle communication system according to the second embodiment. [Modes for carrying out the invention]

[0014] (1. First Embodiment) <1-1. Structure> <1-1-1. Overall Structure> Referring to Figures 1 and 2, the configurations of the in-vehicle communication systems 100A and 100B according to this embodiment will be described. In-vehicle communication system 100A is an example of a communication system mounted on a vehicle, and in-vehicle communication system 100B is another example of a communication system mounted on a vehicle.

[0015] The in-vehicle communication system 100A comprises multiple nodes, a first communication line 110, a second communication line 120, and a third communication line 130. The multiple nodes include a first domain electronic control unit (ECU) 10A, a second domain ECU 20A, a third domain ECU 30A, a fourth domain ECU 40A, ECUs 15, 25, 45, sensors 35, 55, and actuators 65.

[0016] In an in-vehicle communication system 100A, ECUs, sensors, actuators and the like mounted on a vehicle are grouped by functional area. First, second, third and fourth domain ECUs 10A, 20A, 30A and 40A integrally control ECUs, sensors, actuators and the like belonging to a specific functional area. For example, the first domain ECU 10A supervises processing of cameras, radars and the like belonging to an advanced driving assistance system (ADAS) domain. The second domain ECU 20A supervises processing of digital meters, infotainment systems, driver monitoring systems and the like belonging to a cockpit domain. The third domain ECU 30A supervises processing of engines, transmissions, motors and the like belonging to a powertrain domain. The fourth domain ECU 40A supervises processing of lights, doors, air conditioners and the like belonging to a body domain.

[0017] The first communication line 110 is an Ethernet (registered trademark) communication line that supports multi-drop connections in addition to point-to-point connections. Specifically, the first communication line 110 complies with the 10BASE-T1S protocol. 10BASE-T1S is standardized in IEEE 802.3cg.

[0018] The second communication line 120 is a communication line that only enables point-to-point connections. Specifically, the second communication line 120 complies with the 10BASE-T1 protocol. 10BASE-T1 is standardized in IEEE 802.3cg. The third communication line 130 complies with a protocol other than Ethernet. For example, the third communication line 130 complies with a protocol such as Controller Area Network (CAN) or Local Interconnect Network (LIN), or is a straight line.

[0019] The first domain ECU 10A is connected to the second domain ECU 20A via the second communication line 120 and the third communication line 130. The second domain ECU 20A is connected to the third domain ECU 30A via the second communication line 120. Further, the second domain ECU 20A is connected to the ECU 15 via the third communication line 130. The third domain ECU 30A is connected to the fourth domain ECU 40A via the first communication line 110. Further, the third domain ECU 30A is connected to the ECU 25 and the sensor 35 respectively via the third communication line 130. The fourth domain ECU 40A is bus-connected to the ECU 45, the sensor 55, and the actuator 65 via the first communication line 110. The fourth domain ECU 40A, the ECU 45, the sensor 55, the actuator 65, and the first communication line 110 constitute a bus-type network 110A.

[0020] An in-vehicle communication system 100B includes a plurality of nodes, a first communication line 110, and a second communication line 120. The plurality of nodes include a central ECU 10B, a first zone ECU 20B, a second zone ECU 30B, ECUs 15, 25, 45, sensors 35, 55, and an actuator 65.

[0021] In the in-vehicle communication system 100B, a vehicle is divided into a plurality of zones, and the vehicle is managed in units of zones. The first zone ECU 20B controls ECUs, sensors, actuators and the like arranged in the first zone. The second zone ECU 30B controls ECUs, sensors, actuators and the like arranged in the second zone. The central ECU 10B cooperates with the first zone ECU 20B and the second zone ECU 30B to overall and centrally manage the entire vehicle.

[0022] The first zone ECU20B is connected to the central ECU10B via the second communication line 120 and to the second zone ECU30B via the first communication line 110. The first zone ECU20B is bus-connected to ECU15, ECU25 and sensor35 via the first communication line 110. The second zone ECU30B is connected to the central ECU10B via the first communication line 110 and the second communication line 120. The second zone ECU30B is bus-connected to ECU45, sensor55 and actuator65 via the first communication line 110. The first zone ECU20B, ECU15, ECU25, sensor35 and the first communication line 110 constitute a bus-type network 110B. The second zone ECU30B, ECU45, sensor55, actuator65 and the first communication line 110 constitute a bus-type network 110C. In this embodiment, the first communication line 110 corresponds to the in-vehicle communication line of this disclosure.

[0023] Each node of the in-vehicle communication systems 100A and 100B includes a controller 11 and a transceiver 12. The controller 11 includes a processor 11a and memory 11b. The processor 11a implements various functions by executing various programs stored in memory 11b. Memory 11b includes, for example, Random Access Memory (RMA) and flash memory. RAM is used as a work area when processing is executed by the processor 11a. Flash memory stores programs.

[0024] Transceiver 12 is an interface, or PHY, implemented in the physical layer of the OSI reference model. Transceiver 12 is directly connected to one of the first, second, or third communication lines 110, 120, or 130. Controller 11 is connected to transceiver 12 by signal lines and is connected to one of the first, second, or third communication lines 110, 120, or 130 via transceiver 12.

[0025] Transceiver 12 communicates with other transceivers 12 via one of the first, second, or third communication lines 110, 120, or 130. Transceivers 12 in the bus-type networks 110A, 110B, and 110C have Physical Layer Collision Avoidance (PLCA) implemented. PLCA uses scheduled control to avoid collisions. In the bus-type networks 110A, 110B, and 110C, transceiver 12 transmits Ethernet frames to the first communication line 110 according to PLCA. In PLCA, the transmission opportunity for each node is determined using a round-robin method. The round-robin method is a technique that uses resources in sequence.

[0026] Figure 3 shows the data flow of PLCA in a bus-type network with N+1 nodes. One of the N+1 nodes acts as the coordinator, and the remaining nodes act as followers. The coordinator is assigned ID=0 and manages the communication opportunities for each node. Followers are assigned IDs=1 to N and send frames on the transmission opportunities assigned to the coordinator. The coordinator sends a BEACON to reset the TO_TIMER (timer) and start the PLCA cycle. The BEACON is a synchronization signal to all nodes.

[0027] In the first cycle, N+1 nodes skip their respective transmission opportunities by not sending a frame. Therefore, the first cycle is the minimum PLCA cycle. In the second cycle, after the timer is reset, node "1" sends a frame, and node "2" skips. Node "3" sends a COMMIT signal and then sends a frame. A node sends a COMMIT signal when it has a transmission opportunity but cannot immediately start sending a frame. This stops the timers of other nodes and makes them wait. Nodes "4" through "N" skip. In the third cycle, after the timer is reset, N+1 nodes each send a COMMIT signal and then send the largest size frame. Therefore, the third cycle is the maximum PLCA cycle.

[0028] In another embodiment, the in-vehicle communication system 100A is not limited to four domain ECUs, but may have one, two, three, or five or more domain ECUs. Any number of ECUs and / or sensors and / or actuators may be connected to each domain ECU. Furthermore, the in-vehicle communication system 100A does not have a second communication line 120 and / or a third communication line 130. The in-vehicle communication system 100B is not limited to two zone ECUs, but may have one zone ECU or three or more zone ECUs. Furthermore, the in-vehicle communication system 100B may have one zone ECU and a central ECU integrated into one unit. Any number of ECUs and / or sensors and / or actuators may be connected to each zone ECU. Furthermore, the in-vehicle communication system 100B does not have a second communication line 120, and may have an additional third communication line such as CAN or LIN.

[0029] <1-1-2.Functional configuration> When multiple nodes in a network operate in coordination, it is necessary for all nodes to share the same accurate time. In the in-vehicle communication systems 100A and 100B, time synchronization is achieved between nodes connected via the first communication line 110, the second communication line 120, or the third communication line 130.

[0030] Referring to Figure 4, the functions related to time synchronization of the controller 11 and transceiver 12 will be described. The controller 11 includes a timestamp acquisition unit 111 and a time synchronization unit 112. The transceiver 12 includes a transmit / receive unit 121, a time synchronization frame detection unit 122, a notification unit 123, and a PLCA unit 124.

[0031] The time synchronization unit 112 generates a first time synchronization frame and outputs it to the transceiver 12. The PLCA unit 124 outputs the first time synchronization frame received from the time synchronization unit 112 to the time synchronization frame detection unit 122 when it has a transmission opportunity assigned to its node. When the time synchronization frame detection unit 122 detects the first time synchronization frame, it notifies the notification unit 123 that the first time synchronization frame has been detected and outputs the first time synchronization frame to the transmit / receive unit 121. The transmit / receive unit 121 transmits the first time synchronization frame to the first communication line 110, the second communication line 120, or the third communication line 130. The notification unit 123 notifies the controller 11 that the first time synchronization frame has been transmitted.

[0032] The timestamp acquisition unit 111 acquires a timestamp in response to notification from the notification unit 123 that the first time synchronization frame has been transmitted. This timestamp matches the actual transmission time of the first time synchronization frame and is used for time synchronization of the slave node. The timestamp acquisition unit 111 sends the acquired timestamp to the time synchronization unit 112. The time synchronization unit 112 outputs a second time synchronization frame containing the timestamp to the transceiver 12. The PLCA unit 124 receives the second time synchronization frame from the time synchronization unit 112 and outputs the second time synchronization frame to the transmit / receive unit 121 via the time synchronization frame detection unit 122. The transmit / receive unit 121 transmits the second time synchronization frame to the first communication line 110, the second communication line 120, or the third communication line 130.

[0033] Here, when transceiver 12 transmits the first time synchronization frame using the PLCA method, a difference may occur between time t1 and time t1' due to the waiting time for the transmission opportunity. Time t1 is the time when controller 11 transmits the first time synchronization frame to transceiver 12. Time t1' is the time when transceiver 12 transmits the first time synchronization frame to the first communication line 110.

[0034] Therefore, if the time synchronization unit 112 transmits a second time synchronization frame containing a timestamp for time t1 to the first communication line 110 via the transceiver 12, the time synchronization accuracy between nodes may decrease. To address this, the transceiver 12 is equipped with a notification unit 123. The notification unit 123 can be composed of a simple circuit and notifies the controller 11 that the first time synchronization frame has been transmitted. As a result, the timestamp acquisition unit 111 can acquire a timestamp indicating time t1'.

[0035] Note that transceivers 12 of nodes not connected to the bus-type networks 110A, 110B, and 110C do not need to be equipped with a time synchronization frame detection unit 122, a notification unit 123, and a PLCA unit 124.

[0036] <1-2. Time synchronization process> Referring to Figures 5 and 6, the time synchronization process performed by the nodes of the bus network 110A will be described. This time synchronization process can also be applied to the nodes of the bus networks 110B and 110C. One of the multiple nodes included in the bus network 110A acts as the master node, and the other nodes act as slave nodes. The slave nodes adjust their own time to match the time of the master node. The PLCA coordinator may be the master node, or the follower may be the master node. Hereinafter, the controller 11 and transceiver 12 of the master node will be referred to as the first controller 11A and the first transceiver 12A, and the controller 11 and transceiver 12 of the slave nodes will be referred to as the second controller 11B and the second transceiver 12B.

[0037] First, let's explain the Sync / Follow-up sequence shown in Figure 5. In S1, the time synchronization unit 112 of the first controller 11A transmits a Sync frame to the first transceiver 12A at time t1. The Sync frame is a time synchronization frame defined by the Precision Time Protocol.

[0038] In S2, the PLCA unit 124 of the first transceiver 12A transmits the Sync frame received from the first controller 11A to the first communication line 110 via the time synchronization frame detection unit 122 and the transmit / receive unit 121 at the PLCA transmission opportunity (specifically, at time t1'). Time t1' is later than time t1.

[0039] In S3, the transmitting / receiving unit 121 of the second transceiver 12B receives a Sync frame via the first communication line 110. The transmitting / receiving unit 121 of the second transceiver 12B then transmits the received Sync frame to the second controller 11B via the time synchronization frame detection unit 122 and the PLCA unit 124.

[0040] In S4, the time synchronization unit 112 of the second controller 11B receives a Sync frame at time t2 and records the timestamp for time t2. In S5, the notification unit 123 of the first transceiver 12A receives notification from the time synchronization frame detection unit 122 that it has detected a Sync frame, and notifies the first controller 11A that it has sent the Sync frame to the first communication line 110.

[0041] In S6, the timestamp acquisition unit 111 of the first controller 11A receives notification from the notification unit 123 that a Sync frame has been sent, acquires the timestamp for time t1', and records the timestamp.

[0042] In S7, the time synchronization unit 112 of the first controller 11A generates a Follow-up frame containing the recorded timestamp and transmits the Follow-up frame to the first transceiver 12A. The Follow-up frame is a time synchronization frame as defined by the Precision Time Protocol.

[0043] In S8, the PLCA unit 124 of the first transceiver 12A transmits the Follow up frame received from the first controller 11A to the first communication line 110 via the time synchronization frame detection unit 122 and the transmit / receive unit 121 when the PLCA transmission opportunity arises.

[0044] In S9, the transmit / receive unit 121 of the second transceiver 12B receives a Follow Up frame via the first communication line 110. The transmit / receive unit 121 of the second transceiver 12B then transmits the received Follow Up frame to the second controller 11B via the time synchronization frame detection unit 122 and the PLCA unit 124. As a result, the second controller 11B obtains the time t1' and time t2.

[0045] Next, we will explain the Path delay (Pdelay) Request / Pdelay Response sequence shown in Figure 6. In S10, the time synchronization unit 112 of the second controller 11B sends a Pdelay Request frame to the second transceiver 12B at time t3. The Pdelay Request frame is a time synchronization frame defined in the Precision Time Protocol.

[0046] In S20, the PLCA unit 124 of the second transceiver 12B transmits the Pdlay Request frame received from the second controller 11B to the first communication line 110 via the time synchronization frame detection unit 122 and the transmit / receive unit 121 at the PLCA transmission opportunity (specifically, at time t3'). Time t3' is later than time t3.

[0047] In S30, the transmit / receive unit 121 of the first transceiver 12A receives a Pdlay Request frame via the first communication line 110. The transmit / receive unit 121 of the first transceiver 12A then transmits the received Pdlay Request frame to the first controller 11A via the time synchronization frame detection unit 122 and the PLCA unit 124.

[0048] In S40, the time synchronization unit 112 of the first controller 11A receives a Pdlay Request frame at time t4 and records the timestamp for time t4. In S50, the notification unit 123 of the second transceiver 12B receives notification from the time synchronization frame detection unit 122 that it has detected a Pdlay Request frame, and notifies the second controller 11B that it has sent the Pdlay Request frame to the first communication line 110.

[0049] In S60, the timestamp acquisition unit 111 of the second controller 11B receives notification from the notification unit 123 that a Pdlay Request frame has been sent, acquires the timestamp for time t3', and records the timestamp.

[0050] In S70, the time synchronization unit 112 of the first controller 11A generates a Pdlay Response frame containing the timestamp of the recorded time t4, and transmits the Pdlay Response frame to the first transceiver 12A. The Pdlay Response frame is a time synchronization frame defined in the Precision Time Protocol.

[0051] In S80, the PLCA unit 124 of the first transceiver 12A transmits the Pdlay Response frame received from the first controller 11A to the first communication line 110 via the time synchronization frame detection unit 122 and the transmit / receive unit 121 when there is an opportunity to transmit the PLCA.

[0052] In S90, the transmit / receive unit 121 of the second transceiver 12B receives a Pdlay Response frame via the first communication line 110. The transmit / receive unit 121 of the second transceiver 12B then transmits the received Pdlay Response frame to the second controller 11B via the time synchronization frame detection unit 122 and the PLCA unit 124. As a result, the second controller 11B acquires time t3' and time t4 in addition to time t1' and time t2.

[0053] The time synchronization unit 112 of the second controller 11B calculates a time offset Δt (i.e., a time correction value) to match the time of the master node using the times t1', t2, t3', and t4. (i) t2 = t1' + Δt + ΔT and (ii) t4 = t3' - Δt + ΔT hold true. ΔT is the transmission path delay. From this, Δt = ((t2 - t1') - (t4 - t3')) / 2 and ΔT = ((t2 - t1') + (t4 - t3')) / 2 are calculated. The time synchronization unit 112 of the second controller 11B corrects the time of its own node with the time offset Δt.

[0054] Here, the transmission path delay ΔT may be a predetermined fixed value. If the transmission path delay ΔT is a predetermined fixed value, the time offset Δt is calculated as Δt = t2 - t1' - ΔT, or Δt = t3' - t4 + ΔT. Therefore, in this case, the master node and slave node may execute only the processes S1 to S9 and not the processes S10 to S90. Alternatively, the master node and slave node may execute only the processes S10 to S90 and not the processes S1 to S9. In this embodiment, the Sync frame and Pdlay Response frame correspond to the first synchronization time frame of this disclosure, and the Follow up frame and Pdlay Response frame correspond to the second synchronization time frame of this disclosure.

[0055] <1-4. Effects> The first embodiment described in detail above provides the following effects. (1) The notification unit 123 of the transceiver 12 notifies the controller 11 that it has transmitted a Sync frame or Pdlay Response frame to the first communication line 110. Therefore, the controller 11 can detect the time t1' or time t3' when the Sync frame or Pdlay Response frame was actually transmitted to the first communication line 110. The notification unit 123 can be implemented with a simple circuit. Therefore, by adding a simple circuit to the transceiver 12, the time synchronization accuracy in the bus-type networks 110A, 110B, and 110C can be improved.

[0056] (2) The controller 11 can obtain a timestamp in response to a notification from the notification unit 123 and detect the time t1' or time t3' when the Sync frame or Pdlay Response frame was sent.

[0057] (3) The controller 11 of the master node sends a Follow-up frame containing the timestamp of time t1' to the first communication line 110 via the transceiver 12. The controller 11 of the slave node obtains the timestamp from the received Follow-up frame and can synchronize its time with the master node based on the timestamp.

[0058] (4) The slave node can obtain the time t2 when the slave node receives the Sync frame and the time t1' when the Sync frame is transmitted to the first communication line 110. The slave node can then calculate a time offset Δt relative to the master node based on times t1' and t2, and synchronize its time with the master node.

[0059] (2. Second Embodiment) <2-1. Differences from the First Embodiment> The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. Note that the same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0060] In the first embodiment described above, the notification unit 123 of the transceiver 12 always notifies the controller 11 that it has transmitted a Sync frame or a Pdlay Response frame. In contrast, the second embodiment differs from the first embodiment in that, when a predetermined condition is met, the notification unit 123 of the transceiver 12 disables (i.e., stops) notifying the controller 11 that it has transmitted a Sync frame or a Pdlay Response frame. The predetermined condition is that the maximum PLCA delay is below a threshold.

[0061] As shown in Figure 7, the controller 11 has a delay evaluation unit 113 in addition to the functional configuration of the controller 11 according to the first embodiment. The delay evaluation unit 113 calculates the maximum PLCA delay. The maximum PLCA delay is the largest possible delay that can occur in PLCA. Specifically, when the number of nodes in the network is N+1 and the master node is node "N", the maximum PLCA delay is the time from when node "0" transmits a frame until node "N" transmits a frame. When the maximum PLCA delay occurs, nodes "1" to "N-1" transmit the COMMIT signal and then transmit the largest size frame.

[0062] When the number of nodes is small, the maximum PLCA delay may be less than the threshold. If the maximum PLCA delay is less than the set threshold, the difference between time t1 and time t1', and the difference between time t3 and time t3' will be sufficiently small. Therefore, even if the time offset Δt is calculated using time t1 and t3 instead of time t1' and t3', the decrease in time synchronization accuracy will be suppressed. Thus, if the maximum PLCA delay is less than the threshold, the notification unit 123 does not notify the controller 11.

[0063] <2-2. Processing> Referring to Figure 8, the Sync / Follow-up sequence performed by the nodes of the bus-type network 110A will be described.

[0064] In S200, the delay evaluation unit 113 of the first controller 11A calculates the maximum PLCA delay. If the maximum PLCA delay is greater than the threshold, the master node and slave node execute processes S1 to S9 and S10 to S90. If the maximum PLCA delay is less than or equal to the threshold, the first controller 11A proceeds to process S210.

[0065] In S210, the delay evaluation unit 113 of the first controller 11A notifies the first transceiver 12A that the maximum PLCA delay is below a threshold. In S220, the notification unit 123 of the first transceiver 12A receives notification from the delay evaluation unit 113 that the maximum PLCA delay is below a threshold, and disables the notification from the first controller 11A.

[0066] In S230, the time synchronization unit 112 of the first controller 11A transmits a Sync frame to the first transceiver 12A at time t1. In S240, the time synchronization unit 112 of the first controller 11A records a timestamp for time t1.

[0067] In S250-S270, the first transceiver 12A, the second transceiver 12B, and the second controller 11B perform the same processing as in S2-S4. In S280-S300, the first controller 11A, the first transceiver 12A, and the second transceiver 12B perform the same processing as in S70-S90.

[0068] Furthermore, in the Pdelay Request / Pdelay Response sequence, the first controller 11A, the first transceiver 12A, the second transceiver 12B, and the second controller 11B perform the same processing as in S10-S40 and S60-S90. However, in S60, the second controller 11B records the timestamp for time t3.

[0069] As a result, the time synchronization unit 112 of the second controller 11B acquires the times t1, t2, t3, and t4. Based on Δt=((t2-t1)-(t4-t3)) / 2 and ΔT=((t2-t1)+(t4-t3)) / 2, the time synchronization unit 112 of the second controller 11B calculates the time offset Δt and the transmission line delay ΔT.

[0070] <2-3. Effects> The second embodiment described in detail above achieves the effects (1) to (4) of the first embodiment mentioned above, and further achieves the following effects.

[0071] (5) When the maximum PLCA delay is below the threshold, the slave node can determine that the difference between time t1' and time t1, and the difference between time t3' and time t3 are sufficiently small. Therefore, in such cases, the slave node can maintain sufficient time synchronization accuracy even if it calculates the time offset Δt using times t1 and t3 instead of times t1' and t3'. Thus, without reducing time synchronization accuracy, the transceiver 12 can stop unnecessary notification processing and reduce the processing load.

[0072] (3. Other Embodiments) Although embodiments of this disclosure have been described above, this disclosure is not limited to the embodiments described above and can be implemented in various modified forms.

[0073] (a) Multiple functions of one component in the above embodiment may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Furthermore, some of the configuration of the above embodiment may be omitted. Furthermore, at least some of the configuration of the above embodiment may be added to or replaced with the configuration of other above embodiments.

[0074] [Technical Concept Disclosed in This Specified Specification] [Item 1] A communication device included in a plurality of nodes (40A, 20B, 40B, 15, 25, 35, 45, 55, 65) connected to an in-vehicle communication line (110), A control unit (11) configured to output a first time synchronization frame, The system includes a transceiver (12) configured to transmit the first time synchronization frame output from the control unit to the in-vehicle communication line using the Physical Layer Collision Avoidance method, and to notify the control unit that the first time synchronization frame has been transmitted. Communication device. [Item 2] The control unit (11) is configured to acquire a timestamp used for time synchronization between nodes of the in-vehicle communication line in response to being notified that the transceiver (12) has transmitted the first time synchronization frame. The communication device described in item 1. [Item 3] The control unit (11) is configured to output a second time synchronization frame containing the acquired timestamp to the transceiver (12). The transceiver is configured to transmit the second time synchronization frame output from the control unit to the in-vehicle communication line. The communication device described in item 2. [Item 4] The aforementioned first time synchronization frame is a Sync frame as defined by the Precision Time Protocol. A communication device described in any one of items 1 to 3. [Item 5] The aforementioned first time synchronization frame is a Path delay Request frame as defined by the Precision Time Protocol. A communication device described in any one of items 1 to 4. [Item 6] The transceiver (12) is configured to stop notifying the control unit (11) that it has transmitted the first time synchronization frame when a predetermined condition is met. A communication device described in any one of items 1 through 5. [Item 7] A time synchronization method performed by a transceiver (12) of a communication device included in a plurality of nodes (40A, 20B, 40B, 15, 25, 35, 45, 55, 65) connected to an in-vehicle communication line (110), The control unit (11) of the communication device receives a time synchronization frame, The aforementioned time synchronization frame is transmitted to the in-vehicle communication line using the Physical Layer Collision Avoidance method. The control unit is notified that the aforementioned time synchronization frame has been transmitted. Time synchronization method. [Item 8] A communication system (100A, 100B) comprising a master node and a slave node connected to an in-vehicle communication line (110), The master node comprises a control unit (11) and a transceiver (12), The control unit is configured to (i) output a first time synchronization frame to the transceiver, (ii) obtain a timestamp in response to notification from the transceiver that it has transmitted the first time synchronization frame, and (iii) output a second time synchronization frame containing the timestamp to the transceiver. The transceiver is configured to (i) transmit the first time synchronization frame output from the control unit to the slave node via the in-vehicle communication line using the Physical Layer Collision Avoidance method, (ii) notify the control unit that the first time synchronization frame has been transmitted, and (iii) transmit the second time synchronization frame output from the control unit to the slave node via the in-vehicle communication line. The slave node is configured to synchronize its time with the master node's time based on the time it received the first time synchronization frame and the timestamp of the second time synchronization frame. Communication system. [Explanation of Symbols]

[0075] 11...Controller, 12...Transceiver, 110...First communication line, 111...Timestamp acquisition unit, 100A, 100B...In-vehicle communication system, 112...Time synchronization unit, 113...Delay evaluation unit, 121...Transmit / receive unit, 122...Time synchronization frame detection unit, 123...Notification unit, 124...PLCA unit.

Claims

1. A communication device included in a plurality of nodes (40A, 20B, 40B, 15, 25, 35, 45, 55, 65) connected to an in-vehicle communication line (110), A control unit (11) configured to output a first time synchronization frame, The system includes a transceiver (12) configured to transmit the first time synchronization frame output from the control unit to the in-vehicle communication line using the Physical Layer Collision Avoidance method, and to notify the control unit that the first time synchronization frame has been transmitted. Communication device.

2. The control unit (11) is configured to acquire a timestamp used for time synchronization between nodes of the in-vehicle communication line in response to being notified that the transceiver (12) has transmitted the first time synchronization frame. The communication device according to claim 1.

3. The control unit (11) is configured to output a second time synchronization frame containing the acquired timestamp to the transceiver (12). The transceiver is configured to transmit the second time synchronization frame output from the control unit to the in-vehicle communication line. The communication device according to claim 2.

4. The aforementioned first time synchronization frame is a Sync frame as defined by the Precision Time Protocol. The communication device according to claim 1 or 2.

5. The aforementioned first time synchronization frame is a Path delay Request frame as defined by the Precision Time Protocol. The communication device according to claim 1 or 2.

6. The transceiver (12) is configured to stop notifying the control unit (11) that it has transmitted the first time synchronization frame when a predetermined condition is met. The communication device according to claim 1 or 2.

7. A time synchronization method performed by a transceiver (12) of a communication device included in a plurality of nodes (40A, 20B, 40B, 15, 25, 35, 45, 55, 65) connected to an in-vehicle communication line (110), The control unit (11) of the communication device receives a time synchronization frame. The aforementioned time synchronization frame is transmitted to the in-vehicle communication line using the Physical Layer Collision Avoidance method. The control unit is notified that the aforementioned time synchronization frame has been transmitted. Time synchronization method.

8. A communication system (100A, 100B) comprising a master node and a slave node connected to an in-vehicle communication line (110), The master node comprises a control unit (11) and a transceiver (12), The control unit is configured to (i) output a first time synchronization frame to the transceiver, (ii) acquire a timestamp in response to notification that the transceiver has transmitted the first time synchronization frame, and (iii) output a second time synchronization frame containing the timestamp to the transceiver. The transceiver is configured to (i) transmit the first time synchronization frame output from the control unit to the slave node via the in-vehicle communication line using the Physical Layer Collision Avoidance method, (ii) notify the control unit that the first time synchronization frame has been transmitted, and (iii) transmit the second time synchronization frame output from the control unit to the slave node via the in-vehicle communication line. The slave node is configured to synchronize its time with the master node's time based on the time it received the first time synchronization frame and the timestamp of the second time synchronization frame. Communication system.

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