Commander subscriber station for serial bus system, responder subscriber station and method of communicating in serial bus system

Abstract

A commander subscriber station, a responder subscriber station and a method of communicating in a serial bus system for a serial bus system. A commander subscriber station for a serial bus system, a responder subscriber station for a serial bus system, and a method for communicating in a serial bus system are provided. The commander subscriber station has a communication control device for controlling communication of a subscriber station of the bus system with at least one other subscriber station and for evaluating at least one signal received from a bus of the bus system depending on a predetermined first frame or a predetermined second frame, the bit time in the first communication phase can be different from the bit time in the second communication phase in the case of a frame, and a state information module for evaluating at least one signal received from the bus with respect to a predetermined control bit.

Description

Technical Field

[0001] The present invention relates to a commander user station for a serial bus system, a responder user station for a serial bus system and a method for communicating in a serial bus system. Background Art

[0002] Bus systems are used in many areas of technology for communication between technical devices, such as sensors and control devices.

[0003] It is known to use Classical CAN and / or CAN FD, both of which are standardized in the international standard ISO 11898-1:2015, for communication between devices in a vehicle and / or in the case of other technical devices.

[0004] A subscriber station of such a bus system is also referred to as a node. Such a subscriber station has a microcontroller which supports all functions of the above-mentioned standards for Classical CAN and / or CAN FD.

[0005] In such a bus system, there may be at least one user station that only has to perform (one or more) very simple functions, such as a signal light, in particular a light emitting diode (LED), which can be switched on or off and / or whose color should change as required under the control of a microcontroller of another user station. In addition, there may be and can be operated sensors that should provide their detection data to the microcontroller of another user station from time to time. Such a user station for performing simple functions may also be referred to as a responder. A user station with a microcontroller that controls a responder is also referred to as a commander.

[0006] In order to connect responders to the CAN bus system more cost-effectively, the specification of the CAN protocol variant "CAN FD Light" is currently being coordinated. "CAN FD Light" is also referred to as FDL for short and specifies communication between a commander and at least one responder. In FDL communication, frames should be used without bit rate switching. FDL is currently specified in CiA 604-1 and should also be adopted in the next revision of ISO 11898-1.

[0007] FDL is specific to CAN bus systems, where a commander CAN user station controls the functionality (or functionality) of multiple responder CAN user stations. FDL does not support arbitration. Therefore, to communicate with the responders, the commander uses the principle "polling", which is also called "polling". The commander is a control device with a microcontroller running application software on it. The microcontroller contains a CAN controller which can send and receive CAN FD frames according to ISO 11898-1:2015. Polling is also done by sending CAN FD frames.

[0008] The responder is an application specific integrated circuit, also known as an ASIC, and has an FDL controller. The responder has little or no local computing power and can manipulate simple functions such as LED on / off, LED color as described above. The responder sends CAN FD frames only if it is invited to do so by the commander through polling.

[0009] In order to enable cost-effective integration of the responder on a single ASIC in a mixed semiconductor process, such as bipolar transistor(s) and CMOS transistor(s) and DMOS transistor(s) (BCD technology), the FDL controller is integrated in the responder. The FDL controller is significantly simplified compared to the CAN FD controller.

[0010] After polling by the commander, the responder CAN user station (responder) sends its functional information, such as sensor values, to the commander CAN user station (commander) via a normal CAN FD message. However, it is problematic that the commander must also be informed of the operating status of the responder. For this purpose, either the FDL controller of the responder uses frames with a longer data field, in which the functional information and the status information are combined. Or, after a new poll by the commander, the information is sent via the bus in a separate additional CAN FD message.

[0011] A significant disadvantage is that the aforementioned options for sending information to the commander take additional time for transmission on the bus, so that communication between the FDL commander and other CAN FD user stations in the bus system is slowed down, thereby reducing the net data rate that can be transmitted by the bus system. Summary of the invention

[0012] Therefore, the object of the present invention is to provide a commander user station for a serial bus system, a responder user station for a serial bus system, and a method for communicating in a serial bus system that solve the above-mentioned problems. In particular, a commander user station for a serial bus system, a responder user station for a serial bus system, and a method for communicating in a serial bus system should be provided, wherein responder status information can be transmitted in the bus system between a responder CAN user station and a commander CAN user station superior to the responder CAN user station not only with high error robustness but also with a high net data transmission rate.

[0013] This object is achieved by a commander user station for a serial bus system having the features of claim 1. The commander user station has a communication control device for controlling the communication of a user station of the bus system with at least one other user station and for evaluating at least one signal received from a bus of the bus system according to a predetermined first frame, in which the bit time in a first communication phase can differ from the bit time in a second communication phase, and a status information module for evaluating at least one signal received from the bus with respect to a predetermined control bit, wherein the communication control device is designed to request a responder user station located downstream of the commander user station to send at least one first signal via the bus according to a predetermined second frame different from the predetermined first frame when using a predetermined second frame, and wherein the status information module is designed to instruct the communication control device based on the evaluation of the value of the predetermined control bit: to request the responder user station to send at least one second signal via the bus according to a second predetermined frame when using a second predetermined frame in order to receive status information from the responder user station.

[0014] The described commander user station is designed via a status information module to not send information about the fault containment function of the CAN protocol or not expect said information from the responder when communicating with the responder user station, in particular in the control field. As a result, when communicating from a responder user station to its commander user station, already existing control bits, in particular the ESI bit, can be used in the CAN FD frame to transmit information from the responder user station to the superior commander user station. However, the commander user station can use the original fault containment function unchanged, according to which the commander user station uses its error counter (Error-Counter) and can enter the error passive state (Error-Passive) or the bus off state (Bus-Off), as described in ISO11898-1:2015. However, when communicating with other non-responder user stations, the described commander user station can send and receive information about the fault containment function of the CAN protocol in the control field of the frame as usual.

[0015] As a result, the commander subscriber station is further made CAN FD-compatible and very advantageously receives additional information without sending additional frames / messages, in particular CAN FD frames, via the bus or without using longer data fields in the frames / messages.

[0016] If the ESI bit is not used in any other way, the responder subscriber station always sends the ESI bit as "0" in the FD (or more precisely FDL) frames sent by it. The commander subscriber station is designed to recognize the state of the connected responder subscriber station based on the ESI bit via the status information module about the responder subscriber station.

[0017] Furthermore, the responder subscriber station described does not have an error counter (Error-Counter) because the fault containment function of the CAN protocol is omitted. Therefore, the responder can neither change to the error passive state (Error-PassiveState) nor shut down from the bus (Bus-Off).

[0018] Overall, the described subscriber stations together contribute to making the bus system more cost-effective, while still enabling robust or reliable CAN communication.

[0019] Advantageous further embodiments of the subscriber station are described in the dependent claims.

[0020] A predetermined control bit according to a predetermined second frame can be set for information about the presence or absence of an error-passive state of a user station that has sent a received signal to the bus, wherein the status information module is designed to evaluate the predetermined control bit according to the predetermined second frame as a change in status information of a responder user station, which is controlled via the bus using the commander user station and cannot enter the error-passive state.

[0021] It is conceivable that the status information module is designed to instruct the communication control device to request the responder user station when using the predetermined second frame: if the evaluation of the signal received from the bus shows that the value of the predetermined control bit according to the predetermined second frame corresponds to information about the existence of an error-passive state of the user station that has sent the received signal to the bus, then send a second signal according to the predetermined second frame via the bus.

[0022] The commander user station may be a CAN FD user station, wherein the predetermined first frame is a CAN FD frame in a FEFF format, and wherein the predetermined second frame is a CAN FD frame in a FBFF format.

[0023] The status information module may have an evaluation block for evaluating the predetermined control bit.

[0024] The communication control device can be designed to negotiate with other subscriber stations in a first communication phase of a predetermined first frame which of the subscriber stations of the bus system receives at least temporarily exclusive, conflict-free access to the bus in a subsequent second communication phase.

[0025] The aforementioned object is also achieved by a responder subscriber station for a serial bus system having the features of claim 7 . The responder user station has a communication control device for controlling the communication between the user stations of the bus system and the superior commander user station, and for evaluating at least one signal received from the bus of the bus system according to the frame, wherein the bit time in the first communication phase can be different from the bit time in the second communication phase, and a status information module, which is designed to detect a change in the status information of the responder user station, wherein the status information module is designed to indicate in a predetermined control bit of a first frame that can be sent by the responder user station to the commander user station for a first message after the change after detecting the change in the status information of the responder user station: a change in the status of the responder user station has been obtained, wherein the communication control device is designed to send a signal according to the first frame for the first message on the bus after the change to the commander user station at the request of the commander user station, wherein the status information module is designed to insert the changed status information into the data field of the second frame of the second message to the commander user station after the change, and wherein the communication control device is designed to send a signal according to the second frame for the second message on the bus after the change to the commander user station at the request of the commander user station.

[0026] The responder subscriber station may be designed to evaluate the status information detected by the status information module with respect to at least one parameter, but not to enter an error-passive state even if an error is evaluated to be present at the responder subscriber station.

[0027] The status information may include at least one information regarding communication between the responder user station and a superior commander user station.

[0028] Additionally or alternatively, the status information comprises at least one information about a status of a technical application of the responder user station.

[0029] Additionally or alternatively, the status information is specified individually for the responder subscriber station depending on the technical application of the responder subscriber station.

[0030] It is possible that the status information comprises at least one information about a health status of the responder user station and wherein the health status is no reception of frames by the commander user station since a predetermined waiting time or an erroneous behavior of a technical application of the responder user station.

[0031] It is conceivable that the status information module has a detection block for detecting the status information; an evaluation block for evaluating the detection result of the detection block based on at least one parameter; and an insertion block for inserting the status information into the frame to be created by the responder user station based on the evaluation performed by the evaluation block.

[0032] At least two user stations may be part of a bus system, which further comprises a bus, wherein the at least two user stations are connected to one another via the bus such that the user stations can communicate serially with one another, and wherein at least one user station is the aforementioned commander user station and at least one user station is the aforementioned responder user station, wherein each of the at least two user stations further comprises a sending / receiving device for sending transmission signals to a bus of the bus system and / or for receiving signals from the bus of the bus system.

[0033] Optionally, the bus system also has at least one third user station, which is designed to negotiate with other user stations (10; 20; 30) in a first communication phase (451) of a predetermined first frame (450): which of the user stations (10, 20, 30) of the bus system (1) is granted at least temporarily exclusive, conflict-free access to the bus (40) in a subsequent second communication phase (452).

[0034] The aforementioned object is also achieved by a method for communication in a serial bus system according to claim 16. The method is carried out with the aforementioned commander subscriber station and the aforementioned responder subscriber station.

[0035] This method provides the same advantages as mentioned previously with respect to the user stations.

[0036] Other possible implementations of the present invention also include combinations not explicitly mentioned of features or embodiments described above or below with respect to the embodiments. Here, those skilled in the art will also add individual aspects as improvements or supplements to the corresponding basic forms of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be described in more detail below with reference to the accompanying drawings and according to embodiments.

[0038] Figure 1 shows a simplified block diagram of a bus system according to a first embodiment;

[0039] Figure 2 The format of a CAN FD frame according to the aforementioned standard ISO 11898-1:2015 is shown for messages which can be sent by a transmitting / receiving device of a user station of a bus system according to the first exemplary embodiment;

[0040] Figure 3 The format of a CAN FD frame without bit rate switching is shown for the message Figure 2 The CAN FD frame may be sent by a transmitting / receiving device of a user station, in particular a responder user station, of the bus system according to the first embodiment;

[0041] Figure 4 shows a simplified schematic block diagram of a first user station (commander) of a bus system according to a first embodiment;

[0042] Figure 5 shows the time course of a digital transmission signal during operation of the bus system in the case of a first subscriber station, which is connected to the same bus of the bus system as at least one second subscriber station;

[0043] Figure 6 The time course of the bus signals CAN_H and CAN_L in the case of a first subscriber station according to the first exemplary embodiment is shown;

[0044] Figure 7 The time course of the difference voltage VDIFF of the bus signals CAN_H and CAN_L in the case of a first subscriber station according to the first exemplary embodiment is shown;

[0045] Figure 8 showing a time course of a digital receive signal generated by a first or second user station from a signal received from a bus, the signal received from the bus being based on a transmit signal from the first user station; and

[0046] Fig. 9 A simplified schematic block diagram shows a second user station (responder) of a bus system according to a first exemplary embodiment.

[0047] In the figures, identical or functionally identical elements are provided with the same reference symbols unless otherwise indicated. DETAILED DESCRIPTION

[0048] Figure 1 As an example, a bus system 1 is shown which is designed in particular essentially for a CAN bus system, a CAN FD bus system and / or modifications thereof as described below. The bus system 1 can be used in a vehicle, in particular a motor vehicle, an aircraft or the like, or in a hospital or the like.

[0049] exist Figure 1In the figure, the bus system 1 has a plurality of user stations 10, 20, 30, which are connected to the bus 40 by means of a first bus core 41 and a second bus core 42, respectively. For example, the user station 10 is a commander user station and the user station 20 is a responder user station, as will be described in more detail below. The bus cores 41, 42 may also be referred to as CAN_H and CAN_L and are used for electrical signal transmission in the sending state after coupling in a dominant level or generating a recessive level or other level for the signal. Messages 45, 46 can be transmitted serially in the form of signals between the individual user stations 10, 20, 30 via the bus 40. If an error occurs when communicating on the bus 40, such as Figure 1 As shown by the jagged black block arrow in FIG. 4 , an error frame (ErrorFrame) 47 having an error flag (Error Flag) and an error delimiter (Error Delimiter) may be optionally sent. Figure 1 The user stations 10 , 20 , 30 are, for example, control devices, sensors, display devices, etc. of a motor vehicle or other technical installations, as described in more detail below.

[0050] like Figure 1 As shown in FIG. 1 , the user station 10 has a communication control device 11, a transmitting / receiving device 12, and a status information module 15. The user station 20 has a communication control device 21, a transmitting / receiving device 22, and a status information module 25. The user station 30 has a communication control device 31 and a transmitting / receiving device 32. The transmitting / receiving devices 12, 22, and 32 of the user stations 10, 20, and 30 are respectively directly connected to the bus 40, even if this Figure 1 Not clarified.

[0051] The communication control device 11, 21, 31 is used to control the communication of the corresponding user station 10, 20, 30 via the bus 40 with at least one other user station of the user stations 10, 20, 30 connected to the bus 40. For this purpose, the communication control device 11, 31 creates and / or reads a first message 45, which is, for example, a CAN FD message 45. The CAN FD message 45 is constructed based on the CAN FD format, which is related to Figure 2 When necessary, the communication control device 11, 21, 31 creates a transmission signal TxD, which is described below with respect to Figure 5 In addition, the communication control device 11, 21, 31 reads or decodes the received signal RxD, which will be described below with respect to Figure 8 Describe in more detail.

[0052] The communication control device 11, 31 can be implemented at least partially as a conventional CAN controller according to ISO 11898-1:2015, that is, as a CAN FD-compatible classic CAN controller or a CAN FD controller. In the case of a CAN FD message 45, a number of 0 to 64 data bytes can be included, which are still transmitted at a significantly faster data rate than in the case of a classic CAN message. In particular, the communication control device 31 is implemented as a conventional CAN FD controller.

[0053] The communication control device 11 is also designed to provide a CAN FD message 45 to at least one of the user stations 20, 30 or to receive an FDL message 46 from the user station 20 as required. When sending and receiving the FDL message 46, the corresponding status information module 15, 25 is used. The FDL message 46 is constructed based on the FBFF format from ISO 11898-1:2015, which is about Figure 3 Described in more detail.

[0054] The communication control device 11 creates and thus reads a first message 45 or creates and reads a second message 46, wherein the first and second messages 45, 46 differ by their data transmission standards, namely in this case CAN FD and FDL. As already mentioned above with regard to the prior art, only frames without bit rate switching are used in FDL communication and FDL does not support arbitration.

[0055] The communication control device 21 is designed as an FDL controller. Furthermore, there is a status information module 25 which has a functionality compatible with that of the status information module 15. The communication control device 21 creates and reads a second message 46, for example an FDL message.

[0056] To communicate with the user station 20, the user station 10 sends a poll to the user station 20 via the bus 40. Figure 3 Only when the commanding user station 10 has invited the responding user station 20 by polling, the user station 20 will give the corresponding Figure 3 The message 46 of the FDL frame is sent to the user station 10.

[0057] Therefore, the user station 10 has the function of the instruction giver / inquirer and the user station 20 has the function of the FDL responder. Therefore, the user station 10 is also referred to as the FDL commander below, and the user station 20 is also referred to as the FDL responder.

[0058] Figure 2Frame 450 is shown for a message 45 in the CAN FD format FEFF with up to 64 data bytes, which is created by one of the subscriber stations 10, 30. CAN FD frame 450 is provided by one of the communication control devices 11, 31, namely encoded in a digital transmission signal TxD, to the associated transmitting / receiving device 12, 32 for transmission on bus 40.

[0059] Frame 450 is divided into two communication phases, which are called arbitration phase 451 (first communication phase) and data phase 452 (second communication phase). Frame 450 starts and ends in arbitration phase 451. Frame 450 starts with an SOF bit and has an arbitration field 453 (Arbitration field), a control field 454 (Control field), a data field 455 (Data field), a checksum field 456 (CRC field), an acknowledgment field 457 (ACK=Acknowledge) and a frame end field EOF (EOF=End of Frame).

[0060] The bits in the arbitration phase 451 of the frame 450 may have a longer bit time than the bits in the data phase 452, such as Figure 2 The switch from a bit with the bit time of the arbitration phase 451 to a bit with the bit time of the data phase 452 is performed in the BRS bit, as in Figure 2 Indicated by SP.

[0061] exist Figure 2 The bits shown with a bold line at their bottom line in FIG. 4 are sent as dominant or "0" in frame 450. Figure 2 The bits shown in bold at their top line in FIG. 4 are sent as recessive or "1" in frame 450. Figure 2 Such bits, shown in bold in FIG. 4 , have predetermined fixed or specified values ​​in frame 450 .

[0062] The arbitration field 453 includes an identifier of the frame 450 in the basic ID field and the ID-ext field. The identifier has 29 bits. The SRR bit and the IDE bit are set between the basic ID field and the ID-ext field. The RRS bit is arranged at the end of the arbitration field 453. Figure 2 The FEFF format is shown with a 29-bit "Extension Identifier".

[0063] The control field 454 begins with the FDF bit, followed by the res bit. This is followed by the BRS bit and the ESI bit. The ESI bit is the first bit in the frame 450 with the bit time of the data phase 452.

[0064] The control field 454 ends with a DLC field, in which the length of the subsequent data field 455 is encoded. For the frame 450, the res bit must be sent with a logical value of 0, in other words as a (logical) 0, i.e. explicitly. However, if the user station 20 receives the res bit with a logical value of 1, in other words as a (logical) 1, i.e. implicitly, the receiving user station 20 sees a protocol abnormal event PAE and enters this state or enters a reintegration mode of operation.

[0065] If the DLC field of the control field 453 has a value of 0, the data field 455 does not exist. The data field 455 has a length corresponding to the value encoded in the DLC field. As previously mentioned, this value can be up to 64 bytes.

[0066] The checksum field 456 contains in the field SBC the number of filling bits modulo 8 inserted into the frame 450 according to the bit-stuffing rule, i.e., after five identical bits, a bit that is inverted can be inserted. In addition, the checksum field 456 contains in the CRC field a CRC checksum, which can also be referred to as CRC-Checksumme, and ends with the subsequent CRC delimiter CRC-Del.

[0067] The switch from the bit with the bit time of the data phase 452 to the bit with the bit time of the arbitration phase 451 takes place in the bit CRC-Del, as in Figure 2 Indicated by SP.

[0068] Acknowledge field 457 contains a bit ACK slot where a subscriber station that is currently only a receiver of frame 450 and not a transmitter of the frame may or may not acknowledge correct reception of frame 450 from bus 40. Acknowledge field 457 ends with a bit ACK-Del, also called an ACK delimiter.

[0069] The bit sequence marking the end of the frame 450 is set in the end-of-frame field EOF. Therefore, the bit sequence of the end field (EOF) is used to characterize the end of the frame 450. The end field (EOF) is caused together with the ACK delimiter, and a number of 8 recessive bits are sent at the end of the frame 450. This is a bit sequence that cannot appear in the frame 450. As a result, the end of the frame 450 can be reliably recognized by the user station 10, 30.

[0070] After the 7-bit end field (EOF), the frame 450 is followed by an inter-frame space (IFS—Inter Frame Space), which is Figure 2 In the case of CAN FD, the interframe space (IFS) is designed according to ISO 11898-1: 2015. The interframe space (IFS-Inter Frame Space) has at least 3 bits.

[0071] Furthermore, the mentioned fields and bits are known from ISO 11898-1:2015 and are therefore not described in more detail here.

[0072] exist Figure 2 In the present example, in the arbitration phase 451 of CAN FD, by means of an identifier (ID) with, for example, bits ID28 to ID18 in the arbitration field 453, it is negotiated bit by bit between the user stations 10, 30: which user station 10, 30 wants to send a message 45, 46 with the highest priority and thus obtain exclusive access to the bus 40 of the bus system 1 for the next transmission in the subsequent data phase 452. In the arbitration phase 451, the physical layer is used as in the case of CAN and CAN FD. The physical layer corresponds to the bit transmission layer or layer 1 of the known OSI model (Open Systems Interconnection model). The user station 20 as an FDL responder user station does not support arbitration, as mentioned previously and as will be described in more detail below. In order to be able to work without CAN arbitration, in which the known CSMA / CR method resolves conflicts when two CAN nodes start messages simultaneously, the commander must predetermine: which responder can send a message and when. That is, if the commander has invited a specific responder for transmission by polling, the commander waits until the responder has replied before the commander sends any other messages. If a responder that has been polled but has not yet started its reply sees another message start on the CAN bus 40, it considers its polling to be complete and does not start its message 46. Document CiA604-1 specifies the earliest possible point in time at which a responder can reply to a poll with a message. If a responder needs more time to prepare to send data, the start of the transmission can be delayed. The reply times of the individual responders in a CAN system are known to the commander.

[0073] Conflicts between an FDL responder (e.g., user station 20) and a commander or possibly other CAN FD nodes that contain arbitration functionality (e.g., user station 30) can also be avoided by assigning an identifier with a higher arbitration priority to the responder for transmission. This means that if other nodes simultaneously initiate a message as responder, they lose the arbitration and become receivers.

[0074] Only when the subscriber station 10 as sender wins the arbitration and thus has exclusive access to the bus 40 of the bus system 1 for sending, the subscriber station 10 as sender of the message 45, 46 starts to send the bits of the data phase 452 onto the bus 40. The same applies to the subscriber station 30 if it wants to send a message 45 onto the bus 40.

[0075] Figure 3 For message 46, it is shown that a user station (responder) or its communication control device 21 provides the associated transmitting / receiving device 22 with an FDL frame 460 for transmission to bus 40, that is, in a manner encoded in the digital transmission signal TxD. In this case, the communication control device 21 creates the frame 460 in the present exemplary embodiment in a manner compatible with CAN FD, as also shown in Figure 3 As explained in .

[0076] according to Figure 3 , the FDL frame 460 is also divided into different communication phases 451, 452 for CAN communication on the bus 40, namely the arbitration phase 451 and the data phase 452. The frame 460 has an arbitration field 463, a control field 464, a data field 465, a checksum field 466 and an acknowledgement field 467 after the start bit (SOF). This is followed by the frame end field EOF, as shown in accordance with Figure 2 As in the case of frame 450.

[0077] The FDL format corresponds to the FBFF format from ISO11898-1:2015. In this format, the sender can decide whether the sender sets the BRS bit to 1 or 0, where BRS=Bit Rate Switch or bit rate switching. If the BRS bit is set to 1, the bit rate is increased or the bit time is shortened in the data phase 452. If the BRS bit is set to 0, the bit rate or bit time is the same in the two communication phases 451, 452. It is currently stipulated in FDL that the bit rate is not switched within the 460 frame. Therefore, BRS=0 is sent. In this case, the commander must set the BRS bit to 0 in the message 46 to the responder so that the responder understands the commander.

[0078] However, in the arbitration phase 451, in communicating with the FDL of frame 460, the responder does not perform arbitration, which was previously performed on Figure 2 Instead, the communication control device 21 is designed as an FDL responder, and the identifier (ID) to be written into the frame 460 is assigned to the responder. If the user station 20 (responder) receives the poll from the user station 10 (commander), the user station 20 sends a poll to the user station 10 via the bus 40 according to Figure 3 FDL frame 460 or message 46. In order not to interfere with the arbitration between the user stations 10 and 30 on the bus 40, the message 46 of the user station 20 therefore has an identifier (ID) with a higher priority than the identifiers (ID) of the user stations 10 and 30.

[0079] When changing to the data phase 452, no bit rate switch occurs in the frame 460. That is, the bit times of the bits of the arbitration phase 451 and the data phase 452 are identical. However, it is possible that the bit times in the first communication phase (arbitration phase) 451 can differ from the bit times in the second communication phase (data phase) 452.

[0080] In the data phase 452, in addition to a portion of the control field 464 of the frame 460, the message 46 or the valid data of the FDL frame 460 from the data field 465 and the checksum field 466 are sent. At the end of the checksum field 466 or before the confirmation field 467, according to Figure 3 From the data phase 452, the arbitration phase 451 is entered again.

[0081] As in Figure 3 As shown in FIG. , the user station 20 partially uses the format known from CAN / CAN FD according to ISO 11898-1:2015, in particular up to and including the FDF bit, in the arbitration phase 451 as the first communication phase, such as Figure 2 As shown in . However, the user station 20 uses the FDL format described below in the first communication phase and in the data phase 452 as the second communication phase starting from the FDF bit. As in the case of CAN FD, recessive and dominant levels are used in the FDL data phase 452 for transmission on the bus 40.

[0082] Generally speaking, two different stuffing rules are applied when generating the frame 460. Until the FDF bit in the arbitration field 453, the CAN FD or Figure 2 The dynamic bit stuffing rule of the frame 450 applies, so that one inverse stuffing bit can be subsequently inserted after 5 identical bits. In the data phase 452 until before the SBC field, the fixed stuffing rule applies, so that a fixed stuffing bit can be inserted after a fixed number of bits. Alternatively, instead of only one stuffing bit, a number of 2 or more bits can be inserted as fixed stuffing bits.

[0083] In the present exemplary embodiment, the ESI bit known from CAN FD is used to communicate at least one status information to the FDL commander. Figure 1 In the example case, the FDL commander is user station 10.

[0084] The DLC field and data field 465 are as previously described for Figure 2 In particular, when the DLC field of the control field 463 has a value of 0, the data field 465 has a length of 0 bytes.

[0085] After the data field 465, a checksum field 466 follows in the frame 460, which is structured as in the case of CAN FD, such as Figure 2 as shown in .

[0086] This is followed by an acknowledgement field 467 which is structured as in the case of CAN FD, as also in Figure 2 The acknowledgement field 467 contains a bit ACK time slot in which a user station that is currently only a receiver of the frame 460 and not a transmitter of the frame may or may not acknowledge the correct reception of the frame 460 from the bus 40. The acknowledgement field 467 ends with a bit ACK-Del, which is also called an ACK delimiter.

[0087] After the confirmation field 467, the frame 460 is followed by the end field (EOF = End of

[0088] Frame (frame end)), such as in accordance with Figure 2 This is not the case with CAN FD.

[0089] The end field (EOF) is 7 recessive bits long.

[0090] After the end field (EOF), in frame 460 follows the inter-frame space (IFS-Inter Frame Space), as previously described with respect to Figure 2 450 as explained in the frame.

[0091] Figure 4 The basic structure of a subscriber station 10 is shown with a communication control device 11, a transmitting / receiving device 12 and a status information module 15 which is part of the communication control device 11. In the case of a subscriber station 20, the status information module 25 is partially designed identically to the status information module 15. The subscriber station 30 is designed in the same manner as the status information module 15. Figure 4 , but the user station 30 does not have a status information module 15, as also shown in Figure 1 Therefore, the user station 30 is not described separately.

[0092] according to Figure 4In addition to the communication control device 11 and the transmitting / receiving device 12, the user station 10 has a microcontroller 13 to which the communication control device 11 is assigned, and a system ASIC 16 (ASIC=application-specific integrated circuit), which can alternatively be a system basis chip (SBC), on which the functions required for the electronic components of the user station 10 can be combined. The system ASIC 16 has in particular an application 161, which can be designed as a computer program (App) or software. Such an application is a technical application 161. The application 161 is, for example, any application in a vehicle. In particular, the application is a windshield washing system and / or a driver assistance system or the like. For example, the windshield washing system controls the movement of at least one windshield wiper (actuator) using data from a rain sensor and / or a wind sensor and / or a speed sensor and / or a light sensor and / or can switch a warning light (actuator) on or off. However, the application is not limited to a windshield washing system or parts thereof.

[0093] In addition to the transmitting / receiving device 12, an energy supply device 17 is installed in the system ASIC 16, which supplies electrical energy to the transmitting / receiving device 12. The energy supply device 17 usually provides a voltage CAN_Supply of 5V. However, according to requirements, the energy supply device 17 can provide other voltages with other values. Additionally or alternatively, the energy supply device 17 can be designed as a power supply.

[0094] If the communication control device 11 creates a frame 460 and / or evaluates a frame 460 in which no bit rate switching / bit rate conversion is performed, the communication control device 21 acts as an FDL commander.

[0095] The status information module 15 has an evaluation block 151 and an output block 152. The evaluation block 151 has an evaluation unit 1511 and a storage unit 1512, in which the responder status information RSI can be stored. The status information module 15 can be implemented at least partially as software.

[0096] Evaluation block 151, in particular its evaluation unit 1511, is designed to evaluate the ESI bit in the received signal RxD of the message 46 according to the frame 460. For the frame 460, the responder, for example the subscriber station 20, has created a transmit signal TxD according to the request of the subscriber station 10, which the subscriber station has sent to the bus 40. Evaluation block 151 stores the value of the ESI bit or the responder status information RSI read out from the frame 460 in a storage unit 1512. The responder status information RSI can be arranged in the data field 465 of the frame 460 of the message 46.

[0097] Output block 152 is designed to access responder status information RSI in storage unit 1512 and output information RSI to, in particular, application 161 and / or microcontroller 13. The function of status information module 15 and the ESI bit and the connection to responder status information RSI are also described in detail. Fig. 9 Described in more detail.

[0098] The transmitting / receiving device 12 further comprises a transmitting module 121 and a receiving module 122. Even though the transmitting / receiving device 12 is always discussed below, it is alternatively possible to arrange the receiving module 122 in a separate device outside the transmitting module 121. The transmitting module 121 and the receiving module 122 can be constructed as in the case of a conventional transmitting / receiving device 22. The transmitting module 121 can in particular comprise at least one operational amplifier and / or a transistor. The receiving module 122 can in particular comprise at least one operational amplifier and / or a transistor.

[0099] The transmitting / receiving device 12 is connected to the bus 40, more precisely to its first bus core 41 for CAN_H and its second bus core 42 for CAN_L. The voltage supply of the energy supply device 17 is carried out via at least one terminal 43 for supplying electrical energy, in particular the supply voltage CAN-Supply, to the first and second bus cores 41, 42. The connection to the ground or CAN_GND is achieved via the terminal 44. The first and second bus cores 41, 42 are terminated with a terminal resistor 49.

[0100] Even if connected Figure 4 For the sake of simplicity, the first and second bus cores 41 , 42 are not shown in the figure, and in the transmitting / receiving device 12 they are connected both to a transmitting module 121 (also called a transmitter) and to a receiving module 122 (also called a receiver).

[0101] During operation of the bus system 1, Figure 4 The transmitting module 121 of the communication control device 11 can convert the transmission signal TxD of the communication control device 11 into the corresponding signals CAN_H and CAN_L for the CAN or CAN FD of the bus cores 41 and 42 in series, and transmit these signals at the terminals for CAN_H and CAN_L to the bus 40. The communication control device 11 (serially) transmits Figure 5 The transmission signal TxD is sent to the transmission module 121 via the terminal TXD. Figure 4 As shown in Figure 5 As shown in , the transmit signal TxD has the voltage states H (High=high) and L (Low=low) with the corresponding voltage U.

[0102] according to Figure 6In the example of CAN_H and CAN_L, at least in the arbitration phase 451, the signals CAN_H and CAN_L have dominant and recessive bus levels 401, 402, as is known from CAN. A difference signal VDIFF=CAN_H-CAN_L is formed on the bus 40, which Figure 7 4 is shown for the arbitration phase 451. In the arbitration phase 451, individual bits of the signal VDIFF with a bit time t_bt1 can be detected with a reception threshold T_a of, for example, 0.7 V. In the data phase 452 of the frame 450, the bits of the signals CAN_H and CAN_L can be sent faster than in the arbitration phase 451, i.e. with a shorter bit time t_bt2, as mentioned above. Thus, in the case of CAN FD for the frame 450, in the data phase 452, the signals CAN_H and CAN_L differ from the conventional signals CAN_H and CAN_L at least in terms of their faster bit rate.

[0103] Figure 5 The sequence of states H and L of the transmission signal TxD and Figure 6 The states 401, 402 of the signals CAN_H, CAN_L obtained therefrom and Figure 7 The resulting profile of voltage VDIFF in φ 401 is used only to clarify the function of subscriber station 10. The sequence of data states for bus states 401, 402 can be selected as required.

[0104] The receiving module 122 receives Figure 6 The signals CAN_H and CAN_L received from the bus 40 shown in FIG. Figure 7 The difference voltage VDIFF of the received signal RxD is formed. Figure 8 The receiving module 122 receives the digital receiving signal RxD according to Figure 6 or Figure 7 At sampling point AP, at least one of the signal VDIFF or the signal CAN_H, CAN_L received from the bus 40 is sampled. Figure 8 The received signal RxD is shown in FIG. Figure 4 As shown in FIG. , the receiving module 122 forwards the receiving signal RxD to the associated communication control device 11 .

[0105] For message 46 based on frame 460, Figures 5 to 8 The signals apply accordingly.

[0106] according to Fig. 9In addition to the communication control device 21 and the transmitting / receiving device 22, the user station 20 has a simple control unit (FSM) or optionally a microcontroller 23 to which the communication control device 21 is assigned, as well as a system ASIC 26 (ASIC=application-specific integrated circuit), which can alternatively be a system basis chip (SBC) on which a plurality of functions necessary for the electronic components of the user station 20 are combined. The system ASIC 26 has in particular an application 261, which can be designed as a computer program (App). Such an application is a technical application 261. Application 261 is, for example, an application 161 ( Figure 4 ) A control device for a sensor, transmitter, actuator, etc. that controls or should provide data to application 161.

[0107] In addition to the transmitting / receiving device 22, an energy supply device 27 is also installed in the system ASIC 26, which supplies electrical energy to the transmitting / receiving device 22. The energy supply device 27 usually provides a voltage CAN_Supply of 5V. However, according to requirements, the energy supply device 27 can provide other voltages with other values. Additionally or alternatively, the energy supply device 27 can be designed as a power supply.

[0108] The communication control device 21 creates a frame 460 in which no bit rate switching or bit rate conversion is performed and / or evaluates such a frame 460 based on a frame 460 received from the commander user station 10. The communication control device 21 can also be called an FDL responder. The communication control device 21 can create a frame 460, for example, after changing the previous state of the user station 20 or only after the request of the commander user station 10. However, the device 21, 22 can only send such a frame 460 to the bus 40 based on the request (polling) of the commander user station 10.

[0109] also, Fig. 9 The sending module 222 is used in conjunction with the previously Figure 4 The sending module 122 is constructed in the same manner as described.

[0110] Fig. 9 The status information module 25 has a detection block 251, an evaluation block 252 and an insertion block 253. The evaluation block 252 has an evaluation unit 2521 and a storage unit 2522, in which the responder status information RSI and / or at least one parameter or setpoint value SW can be stored.

[0111] The detection block 251 detects the current state or current state information RSI of the user station 20 (responder). The detection block 251 stores its detection result in the storage unit 2522 of the evaluation block 252.

[0112] The evaluation block 251, in particular its evaluation unit 2521, is designed to evaluate whether, for example, the current state or current state information RSI of the subscriber station 20 (responder) stored in the storage unit 2522 has changed or remains different. Depending on the result, the evaluation block 252 controls the insertion block 253 to insert the ESI bit of the frame 460 according to the current state information RSI of the subscriber station 20 (responder). To this end, the insertion block 253 sets the value of the ESI bit according to the current state information RSI of the subscriber station 20 (responder).

[0113] If the current state or the current state information RSI of the subscriber station 20 (responder) has therefore changed, the responder sends the ESI bit, for example as logic 1, in its next message 46 created on the basis of the frame 460 .

[0114] After evaluating frame 460 with its module 15, subscriber station 10 (commander) then sees a value for the ESI bit that is not equal to the predefined value, i.e., a logical 0. Subscriber station 10 (commander) therefore sends a status request message created based on frame 460 to subscriber station 20 (responder). In response thereto, subscriber station 20 (responder) replies with frame 460, into which the status data of the responder are inserted into data field 465 of said frame 460. Additionally or alternatively, subscriber station 20 (responder) can insert diagnostic data into data field 465.

[0115] Therefore, the user station 10 (commander) only asks the responder for status data and / or diagnostic data when the current state of the user station 20 (responder) has changed and the responder has notified this using the ESI bit. The user station 10 (commander) therefore does not regularly request this from the responder. This is particularly advantageous because the state is more likely to change rarely, but the commander does not know when the state changes and must frequently ask for this reason.

[0116] Thus, when the user station 10 (commander) queries, changes in the status information RSI of the user station 20 (responder) can be sent based on the evaluation result of the evaluation block 252 and with the help of the ESI bit of the frame 460. The frame 460 is created by the user station 20 (responder) as a message 46 and is sent serially to the user station 10 (commander).

[0117] Fig. 9 The status information module 25 is designed, for example, for at least one of the following options for selecting the status information RSI for the ESI bit: Depending on the type of the status information RSI for the ESI bit, the detection block 151 performs its detection.

[0118] For example, the status information RSI for the ESI bit may be at least one piece of information used for FDL communication, namely:

[0119] Option a): The user station 20 (responder) has received an invalid frame 460 since its last transmitted frame 460.

[0120] Option b): User station 20 (responder) must recalibrate from its last sent frame 460.

[0121] Option c): The user station 20 (responder) cannot start its last transmission task because it cannot recognize the idle state on the CAN bus 40 in time. The idle state can occur in the interframe space (IFS), which can appear between two frames 450, 460 or two frames 450, 450 or two frames 460, 460 or two frames 460, 450.

[0122] Option d): One of the options a) or b) or c) mentioned above.

[0123] To this end, the detection block 251 may have at least one counter and / or at least one logic circuit for counting the transmitted or received frames 460 for detecting which state of the user station 20 (responder) is present. If a frame 460 or a predetermined bit of a frame 460 is correctly received, the detection block 251, for example, increments or decrements at least one counter by a predetermined value for the purpose of detection. In addition, there may be an additional counter that counts the communication cycle, for example by incrementing the count value of the counter after each switch between the phases 451, 452.

[0124] In particular, invalid received frames 460 can be counted. Furthermore, in particular the duration can be detected with respect to the last transmitted frame 460 and / or received invalid frames 460 and / or the last transmitted frame 460 and / or the calibration of the subscriber station 20 (FDL responder).

[0125] The status information module 15, 25 thus causes the user station 10 (commander) to request status data from the user station 20 (responder) only when this is also necessary, i.e. when the current status of the responder has changed. As a result, no unnecessary messages 46 are sent between the user stations 10, 20 via the bus 40. As a result, more bandwidth is left on the bus 40 for other messages 45, 56, which in particular contain application data, such as detection results of the application 161, 261, etc.

[0126] The status information modules 15 , 25 thus ensure that the bus 40 is not occupied for too long or too frequently, so that the bus 40 has more capacity for useful data.

[0127] This has the added advantage that the number of responders that can be connected to the same bus 40 can be increased if required.

[0128] According to a second exemplary embodiment, the user station 20 is designed to display the application state of at least one application 261 of the ASICS 26 as status information RSI for the ESI bit. Such a state is, in particular, the exceeding of a temperature threshold value (limit value).

[0129] Accordingly, the detection block 251 has at least one temperature sensor in order to determine the information of the ESI bit for the FDL communication. In addition, at least one counter can be included, with which the duration for the temperature increase is detected.

[0130] According to a third embodiment, the user station 20 is designed to display the health status of the user station 20 (responder) as status information RSI for the ESI bit. This health status is in particular that the user station 20 (responder) has not received a frame 460 from the user station 10 (commander) since the duration T_timeout, and / or the user station 20 (responder) detects an erroneous behavior of its application 261, which is, for example, a sensor or actuator or has at least one such sensor or actuator.

[0131] Accordingly, the detection block 251 has at least one counter, with which a duration T_timeout is detected in order to specify information about the ESI bit for the FDL communication. The duration T_timeout can also be stored as a parameter or setpoint value SW in the memory unit 2522. In addition, at least one sensor can be included, with which an erroneous behavior of the application 261 of the user station 20 (transponder) can be detected.

[0132] According to the fourth embodiment, the following applies to the communication between the user station 20 (responder) and its superior user station 10 (commander).

[0133] The function of the ESI bit is defined individually for each user station 20 (responder) according to the application. Therefore, the detection block 251 can define the information of the ESI bit by accessing the storage block.

[0134] In at least one first responder ASIC 26, the ESI bit has a predetermined first function. In at least one second responder ASIC 26, the ESI bit has a different, ie, predetermined second function. The commander knows his responders and can therefore interpret the ESI bit correctly.

[0135] It is also possible for the commander to assign various functions to the ESI bits via configuration depending on the operating mode.

[0136] With each of the above-described embodiments of subscriber stations 10 , 20 , communication in bus system 1 can be improved, so that the net data rate in bus system 1 can be increased.

[0137] All previously described embodiments of the user stations 10, 20, 30, the bus system 1 and the methods executed therein can be used individually or in all possible combinations. In particular, all features of the previously described embodiments and / or modifications thereof can be combined as desired. Additionally or alternatively, in particular the following modifications are conceivable.

[0138] Although the invention has been described above using a CAN bus system as an example, it can be used in any communication network and / or communication method in which two different communication phases are used, in which different bus states are generated for the different communication phases.

[0139] In particular, the bus system 1 according to the embodiment can be a communication network in which data can be transmitted serially at two different bit rates. It is advantageous, but not a mandatory prerequisite, that in the case of the bus system 1, exclusive, conflict-free access to the common channel for the user stations 10, 20, 30 is guaranteed at least within certain time intervals.

[0140] The number and arrangement of the user stations 10, 20, 30 in the bus system 1 of the embodiment is arbitrary. It is possible that one or more of the user stations 10 or 30 are present in the bus system 1. It is possible that more than one user station 10 is present in the bus system 1, to which at least one user station 20 is assigned, as described previously. It is conceivable that no user station 30 is present in the bus system 1. In particular, there is only one user station 10 (commander) and at least one user station 20 (responder).

[0141] It is conceivable that in the case of a subscriber station 10 the module 15 is arranged separately from the communication control device 11 .

Claims

1. A commander user station (10) for a serial bus system (1), having a communication control device (11) for controlling the communication of a user station (10) of the bus system (1) with at least one other user station (10; 20; 30), and for evaluating at least one signal (VDIFF) received from a bus (40) of the bus system (1) according to a predetermined first frame (450) or a predetermined second frame (460), in which case the bit time (tbtl) in a first communication phase (451) can differ from the bit time (tbt2) in a second communication phase (452), and a status information module (15) for evaluating at least one signal (VDIFF) received from said bus (40) with respect to a predetermined control bit (ESI), The communication control device (11) is designed to request a responder user station (20) located below the commander user station (10) to send at least one first signal (VDIFF) via a bus (40) according to a predetermined second frame (460) different from the predetermined first frame (450), when using a predetermined second frame (460), and The status information module (15) is designed to instruct the communication control device (11) based on the evaluation of the value of the predetermined control bit (ESI): to request the responder user station (20) to send at least one second signal (VDIFF) via the bus (40) according to the second predetermined frame (460) in order to receive status information (RSI) from the responder user station (20) when using a second predetermined frame (460).

2. The commander user station (10) according to claim 1, wherein a predetermined control bit (ESI) according to a predetermined second frame (460) is set for information on the presence or absence of an error passive state of a user station (10; 30) that has sent a received signal (VDIFF) to the bus (40), and The status information module (15) is designed to evaluate a predetermined control bit (ESI) according to a predetermined second frame (460) as a change in status information (RSI) of a responder user station (20), wherein the responder user station (20) is controlled via a bus (40) using the commander user station (10) and cannot enter an error-passive state.

3. A commander user station (10) according to claim 1 or 2, wherein the status information module (15) is designed to instruct the communication control device (11) to request the responder user station (20) when using the predetermined second frame (460): if the evaluation of the signal (VDIFF) received from the bus (40) shows that the value of the predetermined control bit (ESI) according to the predetermined second frame (460) corresponds to information about the existence of an error passive state of the user station (10; 30) that has sent the received signal (VDIFF) to the bus (40), then send the second signal (VDIFF) according to the predetermined second frame (460) via the bus (40).

4. The commander user station (10) according to claim 1, wherein the commander user station (10; 30) is a CAN FD user station, wherein the predetermined first frame (450) is a CAN FD frame in FEFF format, and The predetermined second frame (460) is a CAN FD frame in FBFF format.

5. The commander user station (10) according to claim 1 or 2, wherein the status information module (15) has an evaluation block (152) for evaluating the predetermined control bit (ESI).

6. A commander user station (10) according to any of the preceding claims, wherein the communication control device (11) is designed to negotiate with other user stations (10; 20; 30) in a first communication phase (451) of a predetermined first frame (450): which of the user stations (10, 20, 30) of the bus system (1) obtains at least temporarily exclusive, conflict-free access to the bus (40) in a subsequent second communication phase (452).

7. A responder user station (20) of a serial bus system (1), having A communication control device (21) for controlling the communication of a user station (20) of a bus system (1) with a higher-level commander user station (10), and for evaluating at least one signal (VDIFF) received from a bus (1) of the bus system (1) according to a frame (460), wherein a bit time (t_bt1) in a first communication phase (451) can differ from a bit time (t_bt2) in a second communication phase (452), and a status information module (25) designed to detect changes in status information (RSI) of a responder user station (20), The state information module (25) is designed to indicate, after detecting a change in the state information (RSI) of the responder user station (20), in a predetermined control bit (ESI) of a frame (460) that can be sent by the responder user station (20) to the commander user station (10) for a first message (46) after the change, that a change in the state of the responder user station (20) has been detected, wherein the communication control device (21) is designed to send a signal (TxD) for a first message (46) after the change to the bus (40) to the commander subscriber station (10) upon request of the commander subscriber station (10), wherein the status information module (25) is designed to insert the changed status information into a data field (465) of a frame (460) of a second message (46) to the commander user station (10) after the change, and The communication control device (21) is designed to send a signal (TxD) for a second message (46) after the change to the bus (40) to the commander subscriber station (10) upon request of the commander subscriber station (10).

8. A responder user station (20) according to claim 7, wherein the responder user station (20) is designed to evaluate the status information (RSI) detected by the status information module (25) with respect to at least one parameter (SW), but does not enter an error passive state even if the evaluation shows that an error exists at the responder user station (20).

9. The responder user station (20) according to claim 7 or 8, wherein the status information (RSI) includes at least one information about the communication between the responder user station (20) and a superior commander user station (10).

10. A responder user station (20) according to any one of claims 7 to 9, wherein the status information (RSI) comprises at least one information about the status of a technical application (261) of the responder user station (20).

11. The responder user station (20) according to any one of claims 7 to 10, wherein the status information is individually specified for the responder user station (20) depending on the technical application (261) of the responder user station (20).

12. A responder user station (20) according to any one of claims 7 to 11, wherein the status information (RSI) comprises at least one information about the health status of the responder user station (20), and The health status is either the commander user station (10) not receiving a frame (460) since a predetermined waiting time (SW) or an erroneous behavior of a technical application (261) of a responder user station (20).

13. The responder user station (20) according to any one of claims 7 to 12, wherein the status information module (25) has The detection block (251) is used to detect the status information (RSI), an evaluation block (252) for evaluating the detection result of the detection block (151) based on at least one parameter (SW), and An insertion block (153) for inserting status information (RSI) into a frame (460) to be created by the responder user station (20) based on the evaluation performed by the evaluation block (252).

14. A bus system (1) having a bus (40), and at least two user stations (10; 20; 30) which are connected to each other via a bus (40) so that they can communicate with each other serially, and at least one of which is a commander user station (10) according to any one of claims 1 to 6 and at least one of which is a responder user station (20) according to any one of claims 7 to 13, Each of the at least two user stations (10; 20; 30) further comprises a transmitting / receiving device (12; 22) for transmitting a transmit signal (TxD) to a bus (40) of the bus system (1) and / or for receiving a signal (VDIFF) from the bus (40) of the bus system (1).

15. The bus system (1) according to claim 13 further comprises at least one third user station (30), which is designed to negotiate with other user stations (10; 20; 30) in a first communication phase (451) of a predetermined first frame (450): which of the user stations (10, 20, 30) of the bus system (1) obtains at least temporarily exclusive, conflict-free access to the bus (40) in a subsequent second communication phase (452).

16. A method for communicating in a serial bus system (1), wherein the method is implemented using a commander user station (10) according to any one of claims 1 to 6 and a responder user station (20) according to any one of claims 7 to 13.

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