Configuration of a bus system

Abstract

Method (200) for automatically configuring a bus system (1) with several bus participants (100) connected to a bus line (10), comprising the following steps: - Measuring (210) of line lengths to line ends (12) of the bus line (10) by the bus participants (100); - Using the measured line lengths to determine (230) two bus participants (100) as termination participants (102), which are arranged at line ends (12) of the bus line (10) and are connected by the bus line (10) via a connecting section with a maximum line length; - automatic switching (240) of bus termination devices (120) to the bus line (10) in the termination participants (102) by means of control units (130) of the termination participants (102).

Description

[0001] The present invention relates to a method for automatically configuring a bus system, a bus system and a bus participant for a bus system.

[0002] Bus systems are used in automation technology for data transmission between individual, distributed bus participants to control and monitor technical systems. These bus participants can be, for example, sensors for detecting the state of the technical system or actuators for influencing its state. Typically, the individual bus participants are distributed throughout the system and interconnected via the bus system. In building automation, bus systems are used, for example, to control automatic wall closures such as doors, windows, and the like. These closures use actuators such as drives, electronic locks, and similar devices, and sensors such as motion detectors, switches, buttons, card readers, and the like.

[0003] Specifications for the structure and data transmission in bus systems for automation technology are defined in various standards. Examples of such bus systems are CAN bus, LON bus, KNX bus, and PROFIBUS.

[0004] Bus systems typically use bus lines, such as twisted-pair copper cables, for data transmission. The individual bus participants are connected to these lines. For smooth communication, it is necessary to terminate the bus line with impedance matching to prevent distortion of the communication signals transmitted over the bus line. This is usually achieved by installing terminations at predetermined points along the bus line, such as its ends, which terminate the bus line with a specified impedance.

[0005] Documents DE 10 2010 000 249 A1 and DE 100 48 744 A1 each describe bus systems in which terminating resistors are arranged at both ends of a linear bus line. Furthermore, each bus system includes a single measuring device that can perform a test of the bus line.

[0006] Precise positioning and dimensioning of the terminations are usually determined by the user or installer of the bus system and generally require a thorough understanding of the bus topology and thus in-depth system knowledge. Therefore, users without any in-depth knowledge of the bus system's operation will find it extremely difficult and costly to correctly terminate and commission the bus system.

[0007] The object of the invention is to provide a method for the automatic configuration of a bus system, a bus system and a bus participant for a bus system in such a way that the bus system in question can be put into operation particularly easily.

[0008] This problem is solved by a method for automatically configuring a bus system, a bus system, and a bus participant for a bus system according to the independent claims. Further developments are specified in the dependent claims.

[0009] A procedure for the automatic configuration of a bus system with multiple bus participants connected to a bus line comprises the following steps: - Measuring cable lengths to the cable ends of the bus line by the bus participants; - Using the measured line lengths to determine two bus participants as termination participants, which are arranged at the line ends of the bus line and connected by the bus line via a connecting section with a maximum line length; - Automatic connection of bus termination devices to the bus line in the termination participants by means of control units of the termination participants.

[0010] The present invention is based on the finding that a particularly simple commissioning of a bus system can be achieved by having the bus participants of the bus system automatically and independently determine the termination devices at which termination devices for terminating the bus line must be installed, and then automatically connecting the bus termination devices to the bus line by the termination devices themselves. Thus, no knowledge of the exact bus topology is required by the user for the commissioning of such a bus system, and bus participants added or removed before the bus system configuration are automatically taken into account. Furthermore, it is not necessary for the termination devices to be physically accessible for setting the bus termination devices, which further reduces the installation effort.Finally, malfunctions of the bus system due to missing or incorrectly placed bus termination devices can be easily eliminated through automatic configuration.

[0011] The claimed method can be used to configure bus systems with different topologies. For example, the bus system may have a line topology where the bus line has only two ends and all bus participants are connected to the bus line between any two end devices located at the line ends. In this case, the bus termination devices are connected to the bus line at each end device. However, the bus system may also have a topology with spur lines, so that the bus line has more than two ends. In this case, only two of the line ends, namely the two ends furthest apart, are terminated with a bus termination device.

[0012] Within the framework of the specified procedure, each bus participant can, for example, measure the line lengths to all ends of the bus line. After the individual bus participants have measured the line lengths, the termination participants can be determined by comparing the line lengths measured by each bus participant. It can then be verified which two bus participants have measured the greatest line length to each end of the line. These two bus participants then constitute the termination participants. If more than two bus participants have measured the same maximum line length, the two termination participants can be selected from among these bus participants, provided that, according to the bus system specification, only exactly two bus participants can function as termination participants.After the end participants have been determined and the bus termination devices have been automatically connected to the bus line, the claimed procedure may also include an initialization of the bus system for normal operation and / or a commencement of normal operation of the bus system.

[0013] To enable the comparison of line lengths, the bus participants can transmit their respective measured line lengths via the bus line. For this purpose, the bus participants can communicate via the bus line in a special operating mode, whereby this special operating mode is implemented without bus termination devices connected to the bus line. Such a special operating mode can, for example, be implemented with a reduced data rate compared to a normal operating mode.

[0014] The termination participants are determined by a termination determination device of the bus system. The termination determination device can be implemented in a single bus participant, in which case it comprises a single termination determination module located in that bus participant. However, the termination determination device can also be implemented in several or all bus participants, each comprising a termination determination module implemented in the respective bus participants.

[0015] Therefore, the termination participants can be determined by a single bus participant, which acts as a coordinating participant for configuring the bus system. The individual bus participants can, for example, transmit the line lengths they measure, at least or exclusively, to the coordinating participant. The individual bus participants can also transmit the line lengths they measure to all other bus participants. The termination participants can then be independently determined by means of termination determination modules located in each individual bus participant, whereby each bus participant independently decides whether or not it acts as a termination participant.

[0016] Individual bus participants can measure the line lengths to the ends of the bus line by communicating with each other, for example, by exchanging so-called ranging messages. The transmission and reception times of the ranging messages exchanged between the bus participants can be measured, and the propagation time, and thus the line length between the bus participants, can then be calculated from these transmission and reception times. Alternatively, individual bus participants can also measure the line length to the ends of the bus line independently and without communicating with other bus participants. For example, bus participants can determine the line lengths to the ends by measuring the propagation time of measurement signals transmitted by the individual bus participants on the bus line and reflected at the line ends.

[0017] The bus line can consist of a multi-core cable, for example, a two-core cable. The data signals transmitted via the bus line can be encoded as differential levels, for example, as differential voltage levels, between the individual cores of the bus line. Two or more cores of the bus line can be connected together with impedance matching via the bus termination device. The bus termination devices for terminating the bus line can, for example, be terminating resistors with a predefined impedance, i.e., a predefined DC and / or AC resistance. Correct dimensioning and positioning of the bus termination devices ensures, among other things, that no reflections of the transmitted data signals occur at the ends of the bus line, which could interfere with the individual bus participants and thus prevent the data signals transmitted via the bus line from being read.

[0018] For normal operation of the required bus system, the bus line must be terminated at each of its two furthest ends with a bus termination device. For example, normal operation may require exactly two bus termination devices to be connected to the bus line at the two furthest points. The bus system could, for example, be a CAN bus. The bus termination devices could, for example, each be a terminating resistor with a resistance value of 120 Ω.

[0019] The bus system could, for example, be a building automation system that connects bus devices distributed throughout a building. For instance, the bus system could be designed to control wall locking systems, such as door systems, window systems, or the like. The individual bus devices could then be actuators, which initiate the movement of a wall locking device, such as a door, window, or similar, or of parts thereof, or sensors, which detect control commands for the movement of the wall locking device. The actuators could be, for example, drives or motorized locks, while the sensors could be push buttons, motion detectors, light barriers, or similar devices.

[0020] The bus system can, for example, be configured as a so-called door bus and include all sensor and actuator units located in the vicinity of an automatically moving door as bus participants. Furthermore, such a door bus can include a communication participant as an additional bus participant, enabling communication with door bus systems located at other doors. Different bus protocols can be used for communication between the individual door buses on the one hand, and for communication between the door bus systems on the other.

[0021] Each bus participant can measure the line lengths to the ends of the bus line using a measuring device connected to the bus line. For communication over the bus line, each bus participant can be connected to the bus line via a bus interface, which acts as a transceiver. The bus interfaces generate and measure the signal levels (physical layer) required for communication over the bus line.

[0022] The measuring devices can be implemented separately from the bus connections. To define the termination participants, the relevant bus participant can include a termination determination module, which can be implemented, for example, as a software module in a control unit of the relevant bus participant. The control unit can be, for example, a programmable logic unit such as a microcontroller, FPGA, ASIC, or microprocessor.

[0023] The sophisticated procedure for automatically configuring the bus system can be performed, for example, every time the bus system is switched on. For instance, the procedure can be performed upon a subsequent switch-on after the bus system has been previously switched off and its topology has been modified, such as by adding or removing bus participants.

[0024] In a further development of the method, the individual bus participants measure the line lengths to the line ends by measuring the transit time of a measurement signal transmitted by the respective bus participant on the bus line. With such a transit time measurement, no communication between the individual bus participants via the bus line is necessary, making the measurement of the line lengths particularly easy.

[0025] The measurement signal can, for example, comprise one or more pulses, such as square waves, and the individual bus participants can determine the reception times of individual edges of the pulses reflected at the line ends in order to calculate the propagation time of the measurement signal to each line end. The measurement signal can also have a signal parameter that varies over time according to a predefined pattern, and the propagation time of the measurement signal from the respective bus participant to the line end and back can then be calculated from the parameter values ​​of the signal parameter present at the time of transmission and reception.

[0026] For example, the measurement signal can be a frequency-modulated continuous wave (FMCW) signal, and the signal parameter can be the frequency of the measurement signal. The frequency of the measurement signal can then be varied cyclically with a predefined frequency response, such as a linear frequency response. The received measurement signal can then be compared with a reference signal generated in the bus participant, and the propagation time of the measurement signal to the end of the line and back can be calculated from the difference between the reference signal and the measurement signal, using the known temporal modulation profile. The comparison between the reflected measurement signal and the reference signal can be performed, for example, by mixing the two signals to determine the line length from the difference frequency between the two signals.

[0027] To separate the measurement signals of the individual bus participants during reception, each measurement signal can have a unique separation parameter. Such a separation parameter could be, for example, a frequency or a unique identifier encoded in the measurement signal. This identifier could be encoded in the measurement signal using common modulation techniques, such as amplitude or phase modulation. Alternatively, to avoid interference, the measurement signals of the individual bus participants can be transmitted with a time delay.

[0028] In a further development of the method, the cable lengths to the cable ends are determined from the propagation times of signal components of the measurement signal reflected at each cable end. This means that only a single measurement signal is required to determine the cable lengths to all cable ends, and the cable lengths to all cable ends of the bus line can be determined particularly quickly.

[0029] In a further development of the procedure, all bus participants communicate their measured line lengths via the bus line to determine the final participants. This ensures that at least one of the bus participants has all measured line lengths available and that at least the bus participant in question can determine, by comparing all measured line lengths, those bus participants that the bus line connects via a link with the maximum line length.

[0030] Individual bus participants can communicate their measured line lengths to a predetermined bus participant, such as a coordinating participant who determines the final participants, via the bus line. However, bus participants can also communicate their measured line lengths to all other bus participants via the bus line, for example, using broadcast messages. In this case, all measured line lengths are available to all bus participants, allowing each participant to independently decide whether or not to act as a final participant.

[0031] For example, bus participants can communicate with each other in a special operating mode while the termination devices are being defined. This special operating mode can be used without the bus termination devices connected to the bus line. For instance, communication in this special operating mode can be performed at a lower data rate than in normal operating mode. Therefore, bus participants can communicate with each other during the termination device definition process regardless of whether the bus termination devices are connected to the bus line or not.

[0032] In a further development of the procedure, the bus participants communicate with each other in special operating mode during the determination of the termination participants, whereby the special operating mode is carried out without the bus termination devices connected to the bus line. This makes it possible to communicate the measured line lengths via the bus line even before the bus termination devices are switched on.

[0033] Alternatively, the special operating mode can also be carried out with bus termination devices connected to the bus line, whereby it is also possible that only a part of the bus termination devices of all participants connected to the bus line are connected to the bus line.

[0034] In a further development of the procedure, communication over the bus line in special operating mode is carried out at a lower data rate than in normal operating mode with connected bus termination devices. This prevents reflections of the data signals used for communication at the ends of the bus line, which can occur without correctly positioned bus termination devices, from interfering with communication. Alternatively or additionally, communication over the bus line in special operating mode can also be carried out at higher signal levels than in normal operating mode. If the bus system is a CAN bus, for example, communication in special operating mode can be carried out with a differential signal level of 7 V in low-speed CAN mode and with a differential signal level of 2 V in normal operating mode in high-speed CAN mode.

[0035] In a further development of the procedure, the termination participants are defined by a coordinating participant, who initiates the activation of the bus termination devices in the termination participants by sending at least one termination message via the bus line. By defining the termination participants centrally in the coordinating participant, it is possible, for example, to easily select two termination participants even in cases where more than two line ends of the bus line are connected via a link with maximum line length.

[0036] In a master-slave bus system, the coordinating participant can be a predefined bus master, which controls communication within the bus system during normal operation. In this case, for example, only the coordinating participant can have a termination determination module of the termination determination device for defining the termination participants.

[0037] The coordinating participant can also be automatically determined among the bus participants at the beginning of the process, for example, through initial communication between the bus participants. This initial communication can also be carried out in the special operating mode. The coordinating participant can be identified, for example, using unique identifiers that the individual bus participants transmit via the bus line. In the case of a CAN bus, such an identifier could be, for example, a device ID of the participant or an identifier of a bus message that the bus participant sends to determine the coordinating participant. The coordinating participant could, for example, be the bus participant that transmits the identifier with the highest or lowest value.If the coordinating participant is automatically determined among the bus participants at the beginning of the claimed procedure, then all bus participants have a final determination module of the final determination device and the final determination module of the coordinating participant is used to determine the final participants.

[0038] In a further development of the procedure, the individual bus participants independently define their role as final participants, for example, by comparing their own measured cable lengths with those measured by the other bus participants. This allows for the determination of final participants in a particularly simple and flexible way, without having to designate a coordinator beforehand. The bus participants thus decide independently whether or not they themselves will act as final participants.

[0039] To define their role as closing participants, all bus participants contain a closing determination module of the closing determination facility. The closing determination facility then defines the two closing participants by having the individual closing determination modules of the closing determination facility, located within the bus participants, determine whether the bus participant in question functions as a closing participant or not, ensuring that only two closing determination modules designate their respective bus participant as a closing participant.

[0040] To enable each bus participant to define their role as a termination participant, the procedure allows all bus participants to communicate their measured cable lengths to all other bus participants via the bus line, for example, in special operating mode and / or by means of broadcast messages. The individual bus participants can then use their termination determination module to check whether a cable length they measured at a particular end of the bus line corresponds to the maximum cable length of all measured cable lengths and / or whether another bus participant has measured the maximum cable length. The bus participants that have themselves measured the maximum cable length can then define themselves as the termination participants.

[0041] In a further development of the procedure, the individual bus participants define their role as final participants based on a prioritization parameter if more than one connection path with maximum line length has been measured. Each bus participant can be assigned a unique parameter value of the prioritization parameter, and those bus participants that have measured the maximum line length and whose prioritization parameter values ​​meet a predefined criterion can be designated as final participants. For example, their prioritization parameter must exhibit an extremal value, such as the highest or lowest value.

[0042] This allows only two bus participants to be selected and designated as termination participants, even in bus systems where more than one connection has the maximum line length. The prioritization parameter can be, for example, the identifier described in connection with the selection of the configuration participant. Alternatively, the prioritization parameter can be a time interval used to initialize the timers of each bus participant, and those bus participants whose timers expire first can be designated as termination participants. Each bus participant can notify the other bus participants of the expiration of its timer by means of a message transmitted on the bus line in special operating mode.

[0043] In a further development of the method, the bus system is a serial data bus, for example, a CAN bus. Serial data buses have particularly simple wiring and can therefore be installed very easily and cost-effectively. If it is a CAN bus, the bus termination units can be implemented as resistors with a resistance value of 120 Ω.

[0044] Further development of the procedure includes: - Measuring the impedance of the bus line in each bus participant before measuring the line lengths, - Comparing the measured impedance with a specified impedance in each bus participant, where the measurement of the line lengths in the individual bus participants is only carried out if the respective measured impedance exceeds a predetermined impedance, for example by a predetermined threshold value.

[0045] Measuring the impedance of the bus line ensures, before measuring the line lengths, that no termination devices are connected to the bus line. This allows the line lengths to the ends of the bus line to be reliably and unambiguously determined by each bus participant using a reflection measurement. The specified impedance can, for example, correspond to the impedance of a bus line terminated at only one end; for a CAN bus, this might be 120 Ω. The threshold value can be, for example, at least 5%, at least 10%, or at least 20% of the specified impedance.

[0046] In a further development of the method, the individual bus participants perform the measurement of the line lengths, while the bus connections of the bus participants are switched to high impedance. This ensures that a measurement signal used to determine the line lengths is reliably reflected at the individual line ends and that the line lengths can be correctly determined from the reflections.

[0047] Switching the bus connections to high impedance can also involve completely disconnecting them from the bus line. After measuring the line lengths, the procedure can include switching the bus connections back to low impedance or reconnecting the bus connections of the individual bus participants to the bus line. Additionally, the bus termination devices of the individual bus participants are also disconnected from the bus line while the individual bus participants perform the line length measurements.

[0048] A sophisticated bus system comprises several bus participants connected to a bus line, as well as a termination device. Each bus participant has its own bus termination device for impedance-matched termination of the bus line. Furthermore, each bus participant has measuring devices designed to measure the cable lengths to the ends of the bus line. The termination device is also designed to use the measured cable lengths to identify two bus participants as terminations. These terminations are located at the ends of the bus line and are connected by the bus line via a connecting section with a maximum cable length.Furthermore, each individual bus participant has control units designed to automatically connect the bus termination devices of the respective bus participant to the bus line if the bus participant in question has been designated as a termination participant.

[0049] The bus system is designed to be configured using the claimed method. Therefore, all advantages and enhancements disclosed in connection with the claimed method also apply to the claimed bus system, and vice versa. In the claimed bus system, all bus participants can have a termination determination module of the termination determination device, or only a single bus participant can have one, acting as a coordinating participant.

[0050] A suitable bus participant for a bus system comprises a measuring device designed to measure line lengths to all ends of the bus line, a bus termination device for impedance-matched termination of the bus line, and a control unit designed to automatically connect the bus termination device to the bus line if the bus participant has been designated as a termination participant.

[0051] The qualified bus operator is trained to be used in the qualified bus system. Therefore, all benefits and further training disclosed in connection with the qualified bus system also apply to the qualified bus operator, and vice versa.

[0052] The invention is explained below with reference to figures. These figures are shown schematically: Fig. 1 a first embodiment of a bus system with multiple bus participants; Fig. 2 a bus participant of the bus system; Fig. 3 a method for automatically configuring the bus system; Fig. 4 the bus system according to the first embodiment with a measurement signal; Fig. 5 the bus system according to the first embodiment with two connected bus termination units; Fig. 6 a second embodiment of the bus system; Fig. 7 the bus system according to the second embodiment with two connected bus termination units; Fig. 8 a third embodiment of the bus system; and Fig. 9 the third embodiment of the bus system with two connected bus termination units.

[0053] Fig. Figure 1 shows a bus system 1 according to a first claimed embodiment with several bus participants 100 connected to a bus line 10. The bus system 1 is designed as a CAN bus, and the bus line 10 comprises two conductors (not shown) on which communication signals are transmitted, which are designed as differential voltage levels between the two conductors.

[0054] Bus system 1 is implemented in a line topology, with a first bus participant 161 connected at one end 12 of the bus line, followed sequentially along bus line 10 by a second bus participant 162, a third bus participant 163, and a fourth bus participant 164. A fifth bus participant 165 is connected at another end 12 of bus line 10. A first line segment 21 of bus line 10 is located between the first and second bus participants 161 and 162, a second line segment 22 between the second and third bus participants 162 and 163, a third line segment 23 between the third and fourth bus participants 163 and 164, and a fourth line segment 24 between the fourth and fifth bus participants 164 and 165.

[0055] The bus participants 100 are trained to perform a procedure for the automatic configuration of bus system 1. For this purpose, the bus participants 100 assign the following to the Fig. Figure 2 shows a schematic and partial representation of the structure. The bus participants 100 comprise a control unit 130, which is designed as a programmable logic unit and is connected to the two lines 11 of the bus line 10 via a bus interface 140. The bus interface 140 is implemented as an integrated circuit and implements OSI layer 1 of the CAN bus protocol used for communication via the bus line 10, i.e., the physical layer. In particular, the bus interface 140 forms a transceiver that generates and measures the voltage levels used for communication between the bus participants 100. All further layers of the CAN bus protocol are implemented as software modules in the control unit 130.

[0056] Each bus participant 100 has a bus termination device 120 with a terminating resistor 124 that can be switched between the two conductors 11 of the bus line 10 by means of a switching device 122. The connection of the bus termination device 120 to the bus line 10 is controlled by the control unit 130 by controlling the switching state of the switching device 122. Furthermore, each bus participant 100 has a measuring device 110, which is connected to the bus line 10 upstream of the bus connection 140 and is designed to measure the line lengths between the respective bus participant 100 and the line ends 12 of the bus line 10. The measuring devices 110 are each controlled by the control unit 130 of the respective bus participant 100.

[0057] Each bus participant 100 also has an impedance measuring device 115, which is likewise connected to the two conductors 11 of the bus line 10. The impedance measuring device 115 is designed to measure the impedance of the bus line 10 and to provide the control unit 130 with a corresponding impedance measurement value.

[0058] Each control unit 130 of the bus participants 100 contains a termination determination module 150 as a software module. This module is configured to determine, based on the line lengths measured by the measuring device 110, the line lengths measured by the other bus participants 100 and communicated via the bus line 10, and a prioritization parameter 132 stored in the control unit 130, whether the respective bus participant 100 is connected to the bus line 10 as a termination participant at one of the line ends 12 and therefore whether the bus termination device 120 in the respective bus participant 100 must be connected to the bus line 10. The termination determination modules 150 of the individual bus participants 100 connected via the bus line 10 together form a termination determination device of the bus system 1.

[0059] In Fig. Figure 3 shows the procedure 200 for the automatic configuration of the bus system 1, which is executed by the termination determination device to determine those bus participants 100 in which the bus termination devices 120 are connected to the bus line 10. At the beginning of the procedure 200, each bus participant 100 switches (202) the bus connections 140 to a high-impedance state. Subsequently, (205) each bus participant 100 measures the impedance of the bus line 10 using the impedance determination devices 115 and compares (207) the measured impedance with a predetermined impedance, which, in the case of the bus system 1 configured as a CAN bus, corresponds to an impedance of 120 Ω.The measured impedance exceeds the specified impedance when no bus termination device 120 is yet connected to the bus line 10 and consequently the line lengths to all line ends 12 of the bus line 10 can be determined by means of a reflection measurement.

[0060] If the measured impedance exceeds the specified impedance, (210) each individual bus participant 100 measures the line lengths up to the line ends 12 of the bus line 10. For this purpose, (212) each individual bus participant 100 sends a measurement signal on the bus line 10 using their measuring device 110, while their bus interface 140 is held in a high-impedance state. If one of the impedances measured by the bus participants 100 does not exceed the specified impedance, the procedure 200 is aborted, for example, by the relevant bus participant 100 sending an error message via the bus line 10.

[0061] As in Fig. As shown in Figure 4 for the second bus participant 162, a signal component 31, 32 of the measurement signal 30 is transmitted to a bus participant 100, which is connected to the bus line 10 between the two line ends 12, in the direction of each of the two line ends 12 of the bus line 10. A first signal component 31 of the measurement signal 30 propagates via the first line segment 21 to the line end 12 located at the first bus participant 161, and a second signal component 32 of the measurement signal 30 propagates via the second, third, and fourth line segments 22, 23, 24 to the line end 12 located at the fifth bus participant 165. Due to the different line lengths to the line ends 12, the first signal component 31 is reflected at the respective line end 12 before the second signal component 32 and is subsequently received at the second bus participant 162 before the second signal component 32.

[0062] Analogous to the second bus participant 162, the third and fourth bus participants 163 and 164 each receive two signal components of their measurement signal reflected at the two line ends 12. In contrast, the two bus participants 161 and 165 located at the line ends 12 each receive only a single reflection of the measurement signal they transmitted at the opposite line end 12. As in Fig. As shown in Figure 3, (215) the bus participants 100 determine, after receiving 214 the reflected measurement signals 30, the propagation times of the individual received signal components and from the propagation times the line lengths to the two line ends 12.

[0063] After measuring the line lengths (210), each individual bus participant (220) activates a special operating mode in which communication on bus line 10 takes place using low-speed CAN signals. Subsequently, each bus participant (225) communicates the line lengths they have measured to all other bus participants (100) via broadcast messages over bus line 10, so that all line lengths measured by the other bus participants (100) are available in every bus participant (100).

[0064] Subsequently, two termination participants located at the line ends 12 are designated. For this purpose, (232) each individual bus participant 100 compares the line lengths they have measured with the line lengths measured by the other bus participants 100 using their termination determination module 150. If the comparison reveals that one of the self-measured line lengths corresponds to a maximum line length, the relevant bus participant 100 designates its role as a termination participant and (240) connects its bus termination device 120 to the bus line 10.

[0065] As in Fig. As shown in Figure 5, in the first embodiment of bus system 1, the first bus participant 161 and the fifth bus participant 165 each determine that a line length they have measured corresponds to the maximum line length. Subsequently, the first and fifth bus participants 161 and 165 each define their role as termination participants 102 and connect (240) their bus termination device 120 to the bus line 10. Thus, the bus line 10 of bus system 1 is correctly terminated.

[0066] As in Fig. As shown in Figure 3, after switching on the bus termination devices 120 (240), the bus connections 140 are each connected to the bus line 10 in the individual bus participants 100 (255), and the individual bus participants 100 enter a normal operating mode in which they communicate via high-speed CAN signals over the bus line 10. Subsequently, an initialization 260 takes place, and the bus system 1 operates in normal operating mode.

[0067] Fig. Figure 6 shows a second embodiment of a bus system 1 with several bus participants 100, which is connected by means of the in Fig. The second embodiment of the bus system 1 is configured as shown in the procedure 200. Unless otherwise described or illustrated, the second embodiment of the bus system 1 is configured as described in the Fig. Figure 1, the first embodiment of the bus system 1, is disclosed.

[0068] The bus system 1 according to the second embodiment has a star topology in which a first bus participant 161 is connected via a first line segment 21 of a bus line 10 to a second bus participant 162, via a second line segment 22 of the bus line 10 to a third bus participant 163, via a third line segment 23 of the bus line 10 to a fourth bus participant 164, and via a fourth line segment 24 of the bus line 10 to a fifth bus participant 165. The second, third, fourth, and fifth bus participants 162, 163, 164, and 165 are each arranged at line ends 12 of the bus line 10.

[0069] In the second embodiment of the bus system 1, the bus participants 162, 163, 164, 165 arranged at the line ends 12 each measure three different line lengths to the other three line ends 12, and the first bus participant 161 connected away from the line ends 12 measures a total of four line lengths to the total of four line ends 12.

[0070] In the bus system 1 according to the second embodiment, the connecting path running via the third and fourth line segments 23, 24 between the fourth bus participant 164 and the fifth bus participant 165 has the maximum line length. Consequently, the result within the framework of the Fig. In the second embodiment of the bus system 1, a comparison 232 of the measured line lengths, as described in the second embodiment, of the method 200 shows that the fourth bus participant 164 and the fifth bus participant 165 each measured the maximum line length using the signal components of their measurement signal propagating via the third and fourth line segments 23, 24. Based on this comparison 232, the fourth and fifth bus participants 164, 165 then each connect their bus termination devices 120 to the bus line 10 as termination participants 102, as described in Fig. 7 is shown.

[0071] Fig. Figure 8 shows a third embodiment of a bus system 1, which is connected to the one described in Figure 8. Fig. The third embodiment of the bus system 1 can be automatically configured according to the methods described in section 3. Unless otherwise described or illustrated, the third embodiment is configured as disclosed in connection with the second embodiment of the bus system 1.

[0072] At the in Fig. In the third embodiment of the bus system 1 shown in Figure 8, a first bus participant 161 is connected via a bus line 10 to a second, third, and fourth bus participant 162, 163, 164. A first line segment 21 of the bus line 10, which connects the first and second bus participants 161, 162, and a second line segment 22 of the bus line 10, which connects the first and third bus participants 161, 163, each have the same segment length. The first bus participant 161 is connected to the fourth bus participant 164 via a third line segment 23 of the data line 10. The fourth bus participant 164 is in turn connected to a fifth bus participant 165 via a fourth line segment 24 of the bus line 10 and to a sixth bus participant 166 via a fifth line segment 25 of the bus line 10.The fourth and fifth line segments 24, 25 each have the same segment length as the first and second line segments 21, 22.

[0073] In the third embodiment of the bus system 1, prioritization parameters 132 are stored in the first, second, third, fourth, fifth and sixth bus participants 161, 162, 163, 164, 165, 166, which have a higher value from the first bus participant 161 through the second, third, fourth and fifth bus participants 162, 163, 164, 165 to the sixth bus participant 166.

[0074] In the third embodiment of bus system 1, the second and third bus participants 162, 163, as well as the fifth and sixth bus participants 165, 166, each measure the maximum line length using the signal components propagating via the first and second line segments 21, 22, the third line segment 23, and the fourth and fifth line segments 24, 25, respectively. In bus system 1, according to the CAN bus protocol specification, only two bus termination devices 120 may be connected to the bus line 10, and the bus line 10 must also connect the bus participants 100 with connected bus termination devices 120 via a connection path with the maximum line length.Therefore, in the third embodiment of the bus system 1, the bus termination device 120 of either the second or the third bus participant 162, 163, as well as the bus termination device 120 of either the fifth or the sixth bus participant 165, 166, must be connected to the bus line 10.

[0075] The specification of 230 of the participants in the final process includes, in the procedure for the automatic configuration of the in Fig. In the bus system 1 shown in Figure 8, the terminating devices are automatically selected from all bus participants 100 that have measured the maximum line length. For this purpose, all bus participants 100 of bus system 1 send the value of their prioritization parameter to all other bus participants 100, for example, along with the line lengths they have measured. Bus participants 162, 163, 165, and 166 that have measured the maximum line length compare their prioritization parameter value 132 with the values ​​of the other bus participants 162, 163, 165, and 166 that have also measured the maximum line length. The bus participant 162, 163, 165, or 166 whose prioritization parameter value 132 meets a predefined condition, for example, has a minimum value, then connects its bus termination device 120 to the bus line 10.In the third embodiment of bus system 1, this is the second bus participant 162, since the values ​​of the prioritization parameter in the third embodiment of bus system 1 have an increasing value from the first to the sixth bus participant 161, 166.

[0076] Subsequently, all remaining bus participants 100, i.e., at least the third, fourth, and fifth bus participants 163, 164, and 165, measure the line lengths again using a propagation delay measurement. The bus participants 100 then determine the number of signal components with which they measured the maximum line length, for example, by measuring the amplitudes of the received reflection signals and comparing them with the signal level of a single signal component.

[0077] After the bus termination device 120 in the second bus participant 162 is switched on, the measurement signals 30 emitted by the bus participants 163, 165, 166 are only reflected at the unterminated line ends 12. The third bus participant 163 therefore continues to measure the maximum line length with two signal components, whereas the fifth and sixth bus participants 165, 166 now only measure the maximum line length with one signal component each.

[0078] Those bus participants 100 for whom the number of signal components used to measure the maximum line length has not decreased after the bus termination device 120 in the second bus participant 162 has been switched on, i.e., the second and third bus participants 162 and 163, keep their bus termination device 120 disconnected from the bus line 10. In contrast, one of the bus participants 100 for whom the number of signal components measuring the maximum line length has decreased after the bus termination device 120 of the second bus participant 162 has been switched on, i.e., either the fifth or sixth bus participant 165 or 166, is selected as an additional termination participant for connecting its bus termination device 120 to the bus line 10. The bus participant 100 selected is the one whose prioritization parameter has the lowest value.

[0079] At the in Fig. In the bus system 1 shown in Figure 8, the number of signal components measuring the maximum line length does not decrease for the third bus participant 163 after the bus termination device 120 of the second bus participant 162 is switched on, so that the third bus participant 163 continues to keep its bus termination device 120 disconnected from the bus line 10. In contrast, the number of signal components measuring the maximum line length decreases for the fifth and sixth bus participants 165 and 166, respectively. Since the prioritization parameter of the fifth bus participant 165 is lower in importance than the prioritization parameter of the sixth bus participant 166, the termination determination module 150 of the fifth bus participant 165 designates the fifth bus participant 165 as an additional termination participant 102 and switches it on, as shown in Figure 8. Fig. 9 is shown, whose bus termination device 120 is also connected to the bus line 10.

[0080] In alternative embodiments of the bus systems 1 shown in the preceding figures, the termination participants 102 are determined by the termination determination module 150 of a coordination participant, wherein the coordination participant is selected from the bus participants 100 based on the value of the prioritization parameter, namely as the bus participant 100 with the lowest-value prioritization parameter. To select the coordination participant, the individual bus participants 100 transmit their prioritization parameters in special operating mode via the bus line 10 to all other bus participants 100, and the bus participant 100 with the lowest-value prioritization parameter assumes the role of the coordination participant.

[0081] The bus participants 100 then transmit the line lengths they have measured to at least the coordinating participant, and the termination determination module 150 of the coordinating participant determines the two termination participants according to the procedure 200 described above. To activate the bus termination devices 120, the termination determination module 150 of the coordinating participant transmits termination information in special operating mode via the bus line 10 to each of the two termination participants 102, which then connect their bus termination devices 120 to the bus line 10.

[0082] The coordinating participant is also trained to coordinate the measurement of line lengths by the individual bus participants 100 by transmitting measurement commands to each bus participant 100 via bus line 10. This ensures, in particular, that only one bus participant 100 performs a line length measurement on bus line 10 at any given time. The coordinating participant is also trained in how, in connection with the Fig. 8 and Fig. 9 described, to coordinate the switching on of a single bus termination device 120 by one of the bus participants 100 and the remeasuring of the line lengths by the other bus participants 100, if individual bus participants 100 initially measure the maximum line length with more than one signal component. Reference symbol list 1 bus system 10 Bus line 11 leaders 12 Line end 21 first line segment 22 second line segment 23 third line segment 24 fourth line segment 25 fifth line segment 30 Measurement signal 31 first signal component 32 second signal component 100 bus passengers 102 graduates 110 Measuring device 115 Impedance determination device 120 bus terminal equipment 122 Switching device 124 Termination resistor 130 control unit 132 Prioritization parameters 140 bus connection 150 Final Determination Module 161 first bus participant 162 second bus participant 163 third bus participant 164 fourth bus participant 165 fifth bus participant 166 sixth bus participant 200 procedures 202 Switching in high-impedance state 205 Measuring Impedance 207 Comparing the measured impedance with the specified impedance 210 Measuring cable lengths 212 Emitting a measurement signal 214 Receiving reflected measurement signals 215 Determining a running time 220 Activating a special operating mode 225 Communication of line lengths 230 Determining two finalists 232 Comparison of cable lengths 240 Switching on bus termination devices 250 Connect to data bus 255 Switching to normal operating mode 260 Initialization and Operation

Claims

[1] Method (200) for automatically configuring a bus system (1) with several bus participants (100) connected to a bus line (10), comprising the following steps: - Measuring (210) of line lengths to line ends (12) of the bus line (10) by the bus participants (100); - Using the measured line lengths to determine (230) two bus participants (100) as termination participants (102), which are arranged at line ends (12) of the bus line (10) and are connected by the bus line (10) via a connecting section with a maximum line length; - automatic switching (240) of bus termination devices (120) to the bus line (10) in the termination participants (102) by means of control units (130) of the termination participants (102). [2] Method (200) according to claim 1, characterized by, that the individual bus participants (100) each measure the line lengths to the line ends (12) by means of a time-of-flight measurement of a measurement signal (30) sent out by the respective bus participant (100) on the bus line (10). [3] Method (200) according to claim 2, characterized by , that the line lengths to the line ends (12) are determined from the transit times of signal components (31, 32) of the measurement signal (30) reflected at the individual line ends (12). [4] Method (200) according to any one of the preceding claims, characterized by , that all bus participants (100) communicate the line lengths they have measured via the bus line (10) to determine (230) the final participants (102) (225). [5] Method (200) according to any one of the preceding claims, characterized by , that the bus participants (100) communicate with each other in a special operating mode during the determination (230) of the final participants (102), and that the special operating mode is carried out without the bus termination devices (120) connected to the bus line (10). [6] Method (200) according to claim 5, characterized by , that communication via the bus line (10) in special operating mode is carried out at a lower data rate than in normal operating mode with connected bus termination devices (120). [7] Method (200) according to any one of the preceding claims, characterized by , that the final participants (102) are determined by a coordinating participant, and that the coordinating participant initiates the activation of the bus termination devices (120) in the termination participants (102) by sending at least one termination message via the bus line (10). [8] Method (200) according to any one of claims 1 to 6, characterized by, that the individual bus participants (100) independently determine their role as final participants (102), for example by comparing self-measured line lengths with line lengths measured by the other bus participants (100). [9] Method (200) according to claim 8, characterized by , that the individual bus participants (100) determine their role as termination participants (102) based on a prioritization parameter (132) if more than one connection route with maximum line length has been measured. [10] Method (200) according to any one of the preceding claims, characterized by , that the bus system (1) is a serial data bus, for example a CAN bus. [11] Method (200) according to any of the preceding claims, characterized by , that the procedure (200) includes: - Measuring (205) the impedance of the bus line (10) in each bus participant (100) before measuring (210) the line lengths, - Comparing (207) the measured impedance with a predetermined impedance in each bus participant (100); and that the measurement (210) of the line lengths in the individual bus participants (100) is only carried out if the respective measured impedance exceeds a predetermined impedance, for example by a predetermined threshold. [12] Method (200) according to any of the preceding claims, characterized by , that the individual bus participants (100) perform the measurement (210) of the line lengths, while bus connections (140) of the bus participants (100) are switched with high impedance. [13] Method (200) according to any of the preceding claims, characterized by , that the procedure (200) includes: - Connecting (250) the bus connections (140) of the individual bus participants (100) to the bus line (10) after switching on (240) the bus termination devices (120), - Initialization and operation (260) of the data bus. [14] Bus system (1) with several bus participants (100) connected to a bus line (10) and a termination device, wherein each bus participant (100) has bus termination devices (120) for impedance-matched termination of the bus line (10), wherein each bus participant (100) has measuring devices (110) designed to measure line lengths to line ends (12) of the bus line (10), wherein the termination determination device is configured to designate two bus participants (100) as termination participants (102) using the measured line lengths, which are arranged at line ends (12) of the bus line (10) and are connected by the bus line (10) via a connecting section with a maximum line length, wherein the individual bus participants (100) each have control units (130) which are configured to automatically connect the bus termination device (120) of the respective bus participant (102) to the bus line (10) if the relevant bus participant (100) has been designated as a termination participant (102) by the termination determination device. [15] Bus passengers (100) for a bus system (1) with a measuring device (110) which is designed to measure line lengths to all line ends (12) of the bus line (10), a bus termination device (120) for impedance-matched termination of the bus line (10), and a control unit (130) which is designed to automatically connect the bus termination device (120) to the bus line (10) if the bus participant (100) has been designated as a termination participant (102).

Images