BUS NODE AND PLUG-IN CONNECTOR FOR A COMMUNICATION BUS SYSTEM WITH BUS TERMINATION MEANS - Patent application

Abstract

The present invention relates to a communication bus system using at least one twisted pair cable as physical medium. Such a communication bus system requires a bus termination at least at an end bus node 100, CU3. Often a communication bus system comprises several identical bus nodes connected to a communication bus B1. The present invention proposes bus nodes CU1-CU3 with an interface circuit IF to the communication bus B1, which interface circuit IF has a bus termination circuit arrangement BT with at least one connection arrangement CC1-CC6 to at least one component J1-J3. In this way it is easy to activate or deactivate the bus termination for a single bus node by manually plugging in a component during the manufacturing process.

Description

[Technical field]

[0001] The present invention relates to the technical field of networking electronic components in vehicles, in particular commercial vehicles. Vehicles are increasingly being equipped with electronic components that can exchange messages with each other. For that purpose, various communication networks have been developed. The communication protocol most frequently used in vehicles is the CAN bus communication protocol. The CAN bus corresponds to the "Controller Area Network" and was already seen in vehicles in 1991. The CAN bus communication protocol was standardized in 1994 and has the ISO standard number ISO 11898. Since then, different variations of the bus system have been standardized. A very prominent example is the so-called vehicle bus, based on the SAE standard J1939 published by the Society of Automotive engineers (now known as "SAE International"). [Background technology]

[0002] CAN bus wiring typically uses unshielded twisted pair cable as the physical transmission medium, although some manufacturers prefer to use shielded twisted pair cable.

[0003] The topology of the CAN bus corresponds to a linear bus wire on which several bus nodes can be attached. The maximum data rate is 500 kbit / s for the classic CAN bus and 5 Mbit / s for the extended version CAN-FD with an extended payload field. ISO 11898 specifies the maximum number of CAN nodes that can be connected to the bus wire as 32. ISO standard 11898 specifies that the CAN bus cable is a single twisted pair cable with a characteristic impedance of 120 Ω. Furthermore, the standard specifies that both ends of the bus must be terminated with a resistance equal to the characteristic impedance of the cable. Communication over the CAN bus wire requires, according to ISO standard ISO 11898-5:2007, that the bus wire be terminated to avoid signal reflections at the ends of the cable. The most common bus termination techniques are standard termination and split termination, where standard termination is in the form of a single resistor and split termination corresponds to a configuration of two resistors in series and a capacitor connecting the point between them to ground.

[0004] FIG. 1 illustrates an example of a standard termination technique. Three bus nodes ECU1-ECU3 are connected to a CAN bus B1. Two twisted-pair bus wires are labeled CH and CL, corresponding to CAN-High and CAN-Low. At both ends of the linear bus wire B1, the twisted-pair cable is terminated by soldering resistors R1 to the bus wires CH and CL. The resistors R1 should have a resistance of 120 Ω, corresponding to the impedance of the bus cable of 120 Ω. The resistors R1 are located inside the bus nodes ECU1 and ECU3. For illustration purposes, the resistors R1 are shown as being built into the bus cable. The basic architecture of the bus nodes is also shown in FIG. 1. The symbols H1-H3 represent the host controllers of each bus node. The symbols CCT1-CCT3 represent the CAN controllers of each bus node ECU1-ECU3. The symbols CT1-CT3 represent the CAN transceivers of each bus node ECU1-ECU3.

[0005] Any Electronic Control Unit (ECU) that wants to participate in CAN communication needs a CAN interface, which contains a CAN controller and a CAN transceiver. The CAN controller performs the communication functions defined by the CAN protocol and greatly assists the host. The CAN transceiver connects the CAN controller to the physical transmission medium.

[0006] Figure 2 illustrates the basic split termination technique. The CAN bus is located on the left side of the drawing. Two connection points with the two bus wires CH and CL are visible on the left. On the right side of the drawing, the CAN transceiver is illustrated and labeled CT1. Split termination uses two resistors R2 and R3 that are equal to half the characteristic impedance of the cable, i.e., 60 Ω. A capacitor C1 is also placed between the series combination of the two resistors R2 and R3 and ground. The capacitance of capacitor C1 is typically 4.7 nF. Although the split termination technique uses more components, it offers the added benefit of forming a low pass filter to prevent high frequency interference on the bus wire B1 from passing through the CAN transceiver CT1.

[0007] More sophisticated bus termination techniques are known, for example from US Pat. No. 5,399,623 and US Pat. No. 5,499,633, which improve the robustness of CAN communication against disturbances.

[0008] In modern vehicles, there are a variety of electronic components that have the ability to communicate via internal communication buses, including but not limited to the CAN bus. Among them are ECUs, sensor units, actuator units, communication units, etc. Examples of ECUs are engine control units, brake control units, transmission control units, ADAS control units (advanced driver assistance systems), safety system control units such as airbag control units and seat belt reinforcement control units, air conditioning control units, etc. Examples of actuator units are electric motors, solenoid valves, electric pumps, electric compressors, electric heaters, etc. Examples of sensor units are camera units, radar units, lidar units, ultrasonic units, thermal transducers, rotation sensors, voltage measurement units, current measurement units, inertial measurement units, magnetic field measurement units, light sensors, etc.

[0009] The components are not connected to a single communication bus, but to several communication buses interconnected using gateway units. Sometimes the electronic control unit ECU has a private CAN bus to which all actuators and / or sensors are connected.

[0010] An example of such an ECU is an Electronically Controlled Air Suspension System ECU, the so-called ECAS-ECU. Such systems are deployed in commercial vehicles and also in other vehicles such as automobiles.

[0011] FIG. 3 shows a commercial vehicle 10 with three axles: a front axle, a rear axle and a lift axle. It is a towing vehicle or other type of utility vehicle. Other examples are utility vehicles used in agriculture, construction vehicles or campers. Finally, it should be noted that this list is not exhaustive. The term "commercial vehicle" is also used here only for illustrative purposes. The invention can also be used for other vehicles. Thus, passenger cars can be equipped with the subject matter of the invention as well. Other vehicles include buses, construction machines, harvesting machines, but also motorcycles, robots, aircraft and drones. But it can also be a trailer vehicle, for example a trailer vehicle used in agriculture or a trailer vehicle attached to a construction vehicle. Large caravans, leisure trailers and sports trailers are also suitable.

[0012] The vehicle 10 is typically equipped with a drive unit corresponding to an internal combustion engine. Of course, other types of drive units can also be incorporated in the towing vehicle. A further example is an electric motor in combination with a storage battery or a fuel cell. Of course, a braking system is also included. In the case of a commercial vehicle, a braking system with service brakes and retarder brakes can be provided. Those components are not shown in FIG. 3.

[0013] FIG. 3 illustrates an ECAS system of a commercial vehicle 10. The ECAS-ECU is given the reference number 100. The remaining components CU1 to CU3 are ECAS actuators controlled by the ECAS-ECU 100. These ECAS actuators are so-called ECAS-SPA (Electronically Controlled Air Suspension Smart Pneumatic Actuator) devices. These ECAS actuators CU1 to CU3 also have control capabilities and are themselves connected to one or more sensor units that provide feedback on the control process. The main task of the ECAS actuators CU1 to CU3 is to increase or decrease the pressure in the air spring bellows FB1 to FB6, which are respectively mounted on the side of each axle of the vehicle 10. FIG. 3 illustrates a vehicle with three axles: a front axle VA, a rear axle HA and a lift axle LA. A pressure accumulator PR is mounted on the vehicle 10 to supply compressed air to the pneumatic system of the vehicle. The ECAS system is also a pneumatic system and must be connected to the pressure accumulator PR. The pressure lines directing compressed air to the ECAS actuators CU1-CU3 are designated by the reference CAL. Each ECAS actuator CU1-CU3 includes one or more solenoid valves, a host controller, and a bus interface to a private CAN bus B1 of the ECAS-ECU 100. The ECAS-ECU 100 is connected to a vehicle CAN bus conforming to SAE-J1939 and communicates with other ECUs via the vehicle CAN bus or another vehicle communication bus. The ECAS system uses the ECAS actuators to control the suspension characteristics of the vehicle.

[0014] ECAS systems have been used in automobiles since the early 1980s. Sometimes, relatively large steady axle load differences occur on the rear axles of automobiles between unladen and fully loaded conditions. They cause problems for the design of steel springs in unladen and partially loaded conditions. The suspension characteristics deteriorate. ECAS systems are used to solve those problems. The main advantages are: a) The full spring deflection can be utilized to compensate for dynamic axle load changes; a) Steady axle load changes are compensated for by pressure changes; C) Driving comfort is improved. d) The wheels are always in close contact with the road, which leads to improved braking and steering behavior and significantly increases tire life; It is.

[0015] Suspension control must be performed for each axle or air spring bellow, and the ECAS system has multiple, i.e. two or more, equal ECAS actuators (as modulators, slaves) and one ECAS-ECU (as control device, master).

[0016] 3, there is one ECAS-ECU 100 and three identical ECAS actuators CU1-CU3 (one per axle). All four ECAS devices are connected to the same CAN bus B1, but only the first ECAS device 100 and the last ECAS device CU3 must use bus termination according to ISO standard ISO11898-5:2007.

[0017] A switchable split termination can be realized with the aid of software: from US Pat. No. 5,399,433 a software-controllable CAN bus termination component is known, which makes it possible to correctly connect bus nodes to a CAN bus in terminated and non-terminated positions.

[0018] In the case of software configuration, a digital output of one microcontroller is used to activate the CAN termination. The drawback is that a software fault can interrupt the entire CAN communication for all devices. Furthermore, during the CAN identifier learning procedure, software-controlled termination is not practical, since the procedure requires CAN termination, which can only be performed after each bus node knows the CAN identifier ID assigned to it (a chicken-and-egg causality dilemma). If a shielded CAN bus cable is required, additional pins are required.

[0019] In the case of switchable termination by hardware means, the resistors R2, R3 for split termination must be integrated either into the sockets of the bus node, into the plug connector or into the wiring harness of the bus cable. For split termination, a third pin is required to connect the resistors R2, R3 to the ground capacitor C1 in order to realize an RC low pass that only affects the noise by means of a virtual zero. The disadvantages of this design are the complexity of the mechanical manufacture in terms of water tightness, double-occupied crimp terminals, corrosion protection of the solder joints, mechanical stresses and especially the costs due to the third pin. Again, if a shielded CAN bus cable is required, an additional pin is required.

[0020] The midpoint of the split termination is a so-called virtual zero, which means that the voltage at that point is zero due to the need for signal cancellation on the CAN-High and CAN-Low bus wires. The resistors R2, R3 and the capacitor C1 of the split termination form an RC low-pass filter that only attenuates noise signals, but does not attenuate the differential CAN bus signal due to the virtual zero.

[0021] There are also several economic constraints for mass production of such equivalent bus nodes. To produce them cheaply and reduce the degree of complexity, the equivalent bus nodes should preferably be identical in the manufacturing process. However, the question arises as to how this can be realized, since the CAN termination is applied only to the last device in the series of equivalent devices in the bus node. The last device is defined as the device that is physically farthest from the domain ECU with respect to the wiring harness. For functional safety reasons during the CAN-ID learning procedure, it makes sense to use a hardware solution to configure the bus nodes that should use the bus termination.

[0022] The usual implementation places resistors R2 and R3 between the CAN-High and CAN-Low input pins at the socket of the bus node. But in case of split termination, a third connection with a virtual zero is also necessary. Therefore, due to the importance of the virtual zero, a simple two-pin solution is not possible. Otherwise an RC low pass would affect not only the noise but also the differential CAN bus signals. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] U.S. Patent Registration No. 10785066 [Patent Document 2] German Patent Publication No. 102018220073 [Patent Document 3] European Patent Publication No. 2166717 Summary of the Invention [Problem to be solved by the invention]

[0024] In view of the above, the object of the present invention is to design a CAN bus termination with a hardware construction approach which overcomes the abovementioned weaknesses. In particular, the solution should meet the requirements for mass production of identical bus nodes in a uniform manner. Furthermore, for this purpose only a minimum number of additional pins should be provided in the connector. The manufacturing costs are minimized. Double occupancy crimp terminals are not permitted. [Means for solving the problem]

[0025] This object is achieved by a bus node for a communication bus system according to claim 1 and by a plug-in connector for connecting a communication bus to a socket of the bus node according to claims 14 and 15. The dependent claims contain advantageous developments and improvements of the invention which result from the following description of these measures.

[0026] In a general embodiment of the invention, a bus node comprises an interface circuit to a communication bus that requires a bus termination at least at an end of the communication bus, the interface circuit comprising bus termination circuitry, and the bus termination circuitry further comprising at least a connection arrangement for at least one component.

[0027] As an extreme, the invention allows a solution for bus termination in the form of standard or split termination, with only two pins without external resistors. If these pins are shorted via a jumper in the wire harness, the bus termination is enabled, otherwise it is disabled. If these pins are not shorted, the bus termination is disabled, otherwise it is enabled. Furthermore, if a shielded bus cable is used to shield the bus wire harness, one pin can be internally connected to the so-called bus shield.

[0028] The present invention may be used with different types of communication buses, including but not limited to a CAN bus.

[0029] In one preferred embodiment, said component comprises at least one jumper. The advantage of this proposal is that it is cheap, easy to handle during production and very reliable, since it allows to design the jumper with a gasket so that the contact clamp into which the jumper is plugged is sealed against dirt and moisture, so that corrosion is not an issue. When a jumper is not plugged into a connection arrangement, the contact clamp is easily protected against dirt and moisture by having a blind plug inserted in the corresponding opening.

[0030] For communication buses in the automotive field, it is common for them to have at least one single twisted pair cable as physical medium, because they are light and rather inexpensive cables. It is very advantageous that i) both wires are in close contact with each other by uniform twisting, so that the impedance deviation through the wire is minimized, and more importantly, ii) the wires can be more easily installed and twisted so that both wires are of the same length in order to reduce distortion of the cable. Especially for these twisted pair cables, the solution according to the invention is advantageous.

[0031] In an extended embodiment, the connection arrangement comprises a contact clamp for a single jumper and a bus termination switching means which activates or deactivates the termination of at least one twisted pair cable when the single jumper is plugged in or removed therefrom. This embodiment allows a solution that adds only two pins to the connection arrangement. The jumper contacts these two pins when plugged in and placed in the contact clamp. This solution of adding only two pins is reasonable when a bus connector of minimum size and low cost needs to be used. Another advantage concerns the long-term reliability of the connector. If the connector comprises a minimum number of pins, the risk of corrosion and poor contact is reduced. For the same size connector, these pins have a greater thickness which increases the contact quality and mechanical stability.

[0032] It is advantageous to provide at least one electronic switch for said bus termination switching means, which is controlled by the voltage drop occurring when a single jumper is inserted into or removed from the corresponding contact clamp. Such an electronic switch can be provided either separately in the electronic circuit or integrated in an integrated circuit. Also, different types of electronic switches are available, which results in a great flexibility in the design of the electronic circuit of said bus termination switching means.

[0033] In particular, transistors are used as electronic switches. Many different types of transistors can be used, if necessary. With regard to the "active low" configuration of said bus termination switching means using N-channel enhancement mode MOSFET transistors, it is advantageous if said bus termination switching means further comprises an inverter, the input of which is connected to a pull-up resistor, at which a high potential is present. This inverter inverts the potential of its input, so that a low potential is present at the gate electrode, and the N-MOSFET transistor is held in a non-conductive state. When the pin connected to the gate of the N-MOSFET transistor goes to a low potential, i.e. when a high potential is present at the gate due to the inverter, the MOSFET transistor is switched into a conductive state, thereby enabling the bus termination. This inverter converts the low potential at its output into a high potential, so that the transistor is in a conductive state. The pull-up resistor has the effect that the bus termination remains disabled (normally off configuration) unless a jumper is inserted in the contact clamp.

[0034] For the active low configuration, it is advantageous for the first contact clamp to be connected to the input of said inverter and for the second contact clamp to be connected directly or via a resistor to ground, a pull-up resistor also being connected to the conductor path connecting the first contact clamp to the input of the inverter.

[0035] This solution has the additional advantage that the second contact clamp is electrically connected to the shield of said twisted pair cable. If a shielded bus cable is used, only a single pin needs to be added to the connector configuration. A high resistance resistor (preferably 11 kΩ) is placed between the first contact clamp and ground. Preferably, this type of resistor should be sized to withstand long periods of erroneous current flow due to a reverse polarity fault.

[0036] Another embodiment of the invention relates to an "active high" configuration of said bus termination switching means, in which said at least one electronic switch is also a transistor, in particular an N-channel enhancement mode MOSFET transistor, whose gate electrode is connected to a pull-down resistor and to a first contact clamp for a single jumper, and whose second contact clamp for a single jumper is connected to a voltage source. The advantage of this configuration is that no inverters need to be introduced into the circuit design.

[0037] A variant of the invention is also proposed that does not require an electronic switch, which in the above connection configuration comprises contact clamps for two jumpers, the first of which, when plugged into or unplugged from its corresponding contact clamp, connects a first bus wire of the twisted pair cable to a first end of the termination circuit, and the second of which, when plugged into or unplugged from its corresponding contact clamp, connects a second bus wire of the twisted pair cable to a second end of the termination circuit.

[0038] All of these different variations and embodiments are suitable for the two most common bus termination techniques: standard termination and split termination.

[0039] To achieve the termination, the termination circuit advantageously comprises either a single termination resistor for standard termination, or a split termination configuration consisting of two termination resistors connected in series and a coupling capacitor connected to ground and to the series connection of the two termination resistors.

[0040] The proposed invention can advantageously be utilized in a bus node further comprising an electronic unit configured to perform a control of the actuators of the vehicle and / or an electronic unit configured to perform data collection of sensor units of the vehicle.

[0041] One example of an advantageous use of the invention is an electronic unit arranged to perform the control of at least one solenoid valve of an electronically controlled air suspension system ECAS of a vehicle.

[0042] Likewise, the electronic unit is configured to carry out data acquisition of sensors, in particular distance sensors or pressure sensors, of the electronically controlled air suspension system ECAS of the vehicle.

[0043] Another embodiment of the invention relates to a plug-in connector for connecting a communication bus to a socket of a bus node according to the invention. The plug-in connector comprises contact clamps for two jumpers and contact clamps for the twisted pair wires of the communication bus, and it is proposed that, when a first jumper is plugged in, the first jumper connects a first twisted pair wire of the communication bus with a first end of a termination circuit in said bus node, and, when a second jumper is plugged in, the second jumper connects a second twisted pair wire of the communication bus with a second end of a termination circuit in said bus node. Such a plug-in connector is suitable for a network that is configured to provide a connection arrangement for two jumpers.

[0044] Similarly, another embodiment of the invention is a plug-in connector for connecting a communication bus to a socket of a bus node according to the invention, which plug-in connector comprises a contact clamp for a single jumper and a contact clamp for the twisted pair wires of the communication bus, characterized in that when the plug-in connector is plugged into said socket of said bus node, a first contact clamp for the single jumper is connected to a control line of the bus termination circuitry and a second contact clamp is connected to a supply voltage line or to a ground line. This embodiment is adapted to use the single jumper solution according to the invention.

[0045] An extended solution for a single jumper plug connector comprises that the second contact clamp is further connected to the shield of the twisted pair cable. This solution is suitable for terminating shielded twisted pair cables and requires only one additional pin in the cable connector.

[0046] In the following, an embodiment of the invention is illustrated in the drawings and will be explained in more detail with reference to the drawings. [Brief description of the drawings]

[0047] [Figure 1] Block diagram of a method for interconnecting electronic components using the CAN bus [Diagram 2] Circuit diagram for implementing split termination in a CAN node [Diagram 3] Schematic diagram of a commercial vehicle with three axles [Figure 4] Schematic diagram of the use of the split termination implementation for a CAN bus end node in the commercial vehicle shown in FIG. [Diagram 5] Schematic diagram of a switchable CAN bus termination solution based on a simple component in the form of a single jumper to achieve active low. [Figure 6] Schematic diagram of a switchable CAN bus termination solution based on a simple component in the form of a single jumper to achieve active high [Figure 7]Schematic diagram of a second proposed switchable CAN bus termination solution based on two components in the form of jumpers [Figure 8] Schematic diagram of the interconnection of three identical bus nodes using a CAN bus cable, where two jumpers are inserted only at the end bus node, so that bus termination is only active at the end bus node DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] This description clarifies the fundamentals of the present disclosure, and it should be understood that those skilled in the art may devise various configurations which, although not expressly described herein, embody the fundamentals of the present disclosure and are intended to be protected within their scope.

[0049] 4 shows the connection between the ECAS-ECU 100 and the three ECAS devices CU1 to CU3, as well as the CAN bus B1. The ECAS-ECU 100 and the end ECAS device CU3 are provided with a bus termination circuit in the form of a split termination with termination resistors R2 and R3 and a coupling capacitor C1 therebetween.

[0050] Efficient mass production of identical ECAS units CU1-CU3 requires identical circuit designs. To address this, it is the idea of ​​the present invention to provide each ECAS unit CU1-CU3 with a termination circuit, either in the form of standard termination or split termination. This termination circuit is part of a wider bus termination circuitry that is extended by circuits that help to place simple components that can enable or disable bus termination in each ECAS unit CU1-CU3. Such simple components represent hardware means. Examples of them are simple jumpers and switches, e.g. DIP switches. However, DIP switches do not have the same reliability as jumpers, especially with regard to protection against moisture, dirt and mechanical vibrations. The jumpers are plugged into their corresponding contact clamps and remain there for the duration of the product's life. Another more sophisticated example of a component is photoelectric material. Such devices are known in the form of electrically programmed EPROM memories. And after the individual ECAS units are installed during mass production of the vehicle, for those ECAS units that require bus termination, workers manually erase the EPROM memory using an ultraviolet lamp. The bus termination circuitry can be designed so that the termination is normally off and is switched on only after erasing the EPROM memory, or vice versa.

[0051] FIG. 5 illustrates a first detailed embodiment of the invention, which relates to a solution using a single jumper as a component. The reference IF denotes a CAN bus interface circuit. A CAN bus interface usually consists of a CAN transceiver and a CAN controller. Here, only the CAN transceiver CT1 is illustrated. However, this CAN transceiver CT1 is illustrated as being connected to an internal bus IB, which connects the CAN transceiver CT1 to a CAN controller chip (not illustrated), which may be a stand-alone chip or may be integrated in the host controller of the ECAS device. The twisted pair of the CAN bus B1 is illustrated on the left. The bus shield is given the reference BS. This is a conventional one- or two-layer metallic material shield, as is commonly known, in the form of a braid or metal foil. The bus cable terminates in a plug connector PL, which is equipped with a certain number of contact pins. The CAN-High bus wire CH is crimped to a first pin of the plug connector PL at contact point CC1. The CAN-Low bus wire CL is crimped at the contact point CC2 to a second pin of the plug connector PL. Furthermore, this plug connector PL is provided with two additional pins. One is associated with a contact clamp CC3 and the other with a contact clamp CC4. For the purpose of configuration, a jumper J1 is plugged into the contact clamps CC3 and CC4. A socket S1 into which the plug connector PL is plugged is attached to the ECAS device CU1-CU3. The socket S1 is provided with corresponding contact clamps CC1-CC4 into which the contact pins of the plug connector PL are inserted. The interface circuit IF further comprises a bus termination circuit arrangement BT. This arrangement comprises a termination circuit ST, a bus termination switching means BTS and further individual elements. The contact clamps CC1-CC3 in the socket S1 are of primary importance. CC1 and CC2 are connected with the internal bus wires leading to the CAN bus transceiver CT1. These bus wires are also connected to the termination circuit ST already presented above, which comprises the two resistors R2, R3 and the coupling capacitor C1 of the split termination, to which a bus termination switching means BTS has been added.These include two transistors T1, T2 and an inverter IL. The transistors T1, T2 are illustrated as N-channel enhancement mode MOSFET transistors. The output of the inverter IL is connected to the gate electrodes of the transistors T1, T2. The drain electrode of the transistor T1 is connected to a resistor R2. The drain electrode of the transistor T2 is connected to a resistor R3. The source electrodes of the transistors T1, T2 are both connected to a capacitor C1. The input of the inverter IL is forward connected to a diode D1 which is connected to a contact clamp CC3. A high-value pull-up resistor R4 is connected to the supply voltage and is placed before the diode D1. A resistor R5 is connected to the contact clamp CC4 and to ground potential.

[0052] This bus termination circuit configuration BT is a so-called "BT normally-off" circuit design, whose function is as follows: When the plug-in connector PL is inserted into the socket S1, the following happens, unless the jumper J1 is inserted: The bus wires CH and CL are connected to the CAN transceiver CT1 and the termination circuit ST. Since the resistance value of the pull-up resistor R4 is low, 11 kΩ, compared to the high resistance value of the inverter IL, the potential at the input of the inverter IL remains high, so that the split termination is not activated. Since the potential at the input of the inverter IL is high, the potential at the output is low, so that the transistor is held in a non-conducting state via the gate electrode. Now, if the jumper J1 is inserted into the contact clamps CC3, CC4 of the plug-in connector PL, the resistance value of the resistor R5 to ground is low, e.g. 1 kΩ, so that the voltage drop via the pull-up resistor R4 is large. Thus, the potential at the input of the inverter IL is low, which generates a high potential at the output, which in turn switches the transistors T1 and T2 into a conducting state, thus enabling and operating the termination circuit ST. The diode D1 only serves as a protection diode against inadvertent reverse polarity contact. This diode D1 is therefore not necessary for the bus termination circuit configuration BT to function. The manufacturer can decide in which ECAS units CU1 to CU3 he wants to enable the bus termination. As explained before, the bus termination must be enabled at least at the end of the CAN bus B1. In this example of Fig. 3 and Fig. 4, the bus termination is enabled only in the ECAS unit CU3. Therefore, the jumper J1 is inserted only in the ECAS unit CU3. It should be added that for the ECAS-ECU 100, the bus termination is always enabled, so no jumper configuration method is necessary. This can be easily done by hard wiring.

[0053] In one embodiment, the voltage source 30 corresponds to a "clamp 30" corresponding to a battery voltage in the automotive field. In another embodiment, the voltage source corresponds to a "clamp 15" corresponding to a switched battery voltage in the automotive field, which supply voltage is provided, for example, after pressing the start button.

[0054] Due to the resistor R5 of high resistance (preferably 11 kΩ) between the contact clamp CC4 and ground, the pin of the contact clamp CC4 can also be used to contact the CAN bus shield BS. The CAN bus shield BS is not always necessary, but some customers prefer to have it, since it improves noise immunity. This is another advantage of this circuit design. This type of resistor must be sized so that it can withstand long-term erroneous currents due to the occurrence of an inadvertent reverse polarity fault. Furthermore, the pull-up resistor does not necessarily have to be provided in the form of a single physical component. It can also be realized by a separate circuit consisting of several passive and active electronic components. For example, this is advantageous to achieve lower steady-state currents.

[0055] FIG. 6 illustrates a proposal for a circuit design in a so-called “active high” configuration. The same references represent the same components as in FIG. 5. The difference is that the inverter IL is not necessary. However, if the inverter IL is omitted, the supply voltage must be adjusted. A resistor R6 replaces the pull-up resistor R4, but is connected to ground potential, and therefore serves as a pull-down resistor. The ground potential is often called “clamp 31” in the automotive field. A resistor R7 replaces the pull-down resistor R5 and is connected to the supply voltage 30. The resistor R7 has a resistance of 11 kΩ, and the resistor R6 has a resistance of, for example, 100 kΩ. If the jumper J1 is not plugged in, the potential of the gate electrodes of the transistors T1 and T2 remains “low”, thereby keeping the transistors T1 and T2 in a non-conducting state due to the pull-down resistors. When jumper J1 is inserted, pull-up resistor R7 provides a high potential to the gate electrodes, switching transistors T1 and T2 into a conducting state, thereby enabling the split termination. Thus, the "active high" configuration according to Figure 6 provides the same "BT normally off" functionality as the "active low" configuration of Figure 5.

[0056] Similarly, the circuit design can be configured to provide a "BT normally-on" function. This can be easily achieved by replacing the enhancement-mode MOSFET transistors with depletion-mode MOSFET transistors. Alternatively, different circuit designs can be implemented using bipolar transistors or other forms of electronic switches, including so-called "bilateral switches".

[0057] FIG. 7 shows another embodiment using two jumpers as components. Again, the same references refer to the same components as in FIG. 5. This two-jumper solution has the advantage that no bus termination switching means are required in the interface circuit IF. These termination circuits ST remain in the interface circuit IF, but they are contacted manually, thereby eliminating the need for electronic control. Bus termination switching means in the form of two transistors and an inverter can be omitted, thus making the electronic circuit design cheaper. As long as no jumpers are inserted in the plug socket PL, the ECAS device remains without bus termination. The first jumper J2 is inserted into the contact clamps CC5 and CC7. In this way, the bus wire CH is connected to the branch of the resistor R2 of the split termination circuit ST. The second jumper J2 is inserted into the contact clamps CC6 and CC8. In this way, the bus wire CL is connected to the branch of the resistor R3 of the split termination circuit ST. This solution has the advantage that the costs of the bus termination circuitry BT are significantly reduced, on the one hand, but on the other hand, the costs for the plug-in connector PL2 and the socket S2 increase, and therefore there is greater flexibility in choosing the circuit design according to the needs.

[0058] In another embodiment of the invention, the previously described hardware configuration solution can be combined with the software-controlled termination enable method by implementing a wired-OR characteristic (either jumper-based enable or software-controlled enable) or a wired-AND characteristic, where software-controlled enable is only performed if the enable is confirmed by the hardware-based configuration or vice versa (two-factor confirmation), and bus termination enable / disable is only valid.

[0059] FIG. 8 illustrates a typical practical implementation of connecting equivalent bus nodes to a CAN bus. As explained before, the topology of this CAN bus corresponds to that of a linear bus. This can be realized by using one single linear bus cable B1 to which the end bus nodes 100 and CU3 are connected as illustrated in FIG. 4, and by using separate cable branches for the intervening bus nodes CU1 and CU2. These cable branches are physically connected to the linear bus cable B1. Instead of using this type of wire harness, which is not easy to manufacture, it is more practical to use the connected type of CAN bus cable illustrated in FIG. 8. In fact, two cables are attached to the plug connectors for the ECAS devices CU1 and CU2. For the ECAS device CU1, a first cable comes from the ECAS-ECU 100, and a second cable extends the bus wires to the ECAS device CU2. For the plug connector of the ECAS device CU2, a first cable comes from the ECAS device CU1, and a second cable extends the bus wires to the ECAS device CU3. With regard to the ECAS equipment CU3, only one cable is attached to the plug-in connector coming from the ECAS equipment CU3. Thus, as the ECAS equipment CU3 is the end equipment, two pins of the plug-in connector PL provided for further extension of the bus wires remain free. As these two pins are not used, they can be used for a bus termination configuration by plugging in two jumpers, as illustrated in FIG. 7 and also in FIG. 8. The different pins of the plug-in connector PL of the ECAS equipment CU3 are given the same reference numbers as those used in FIG. 7. It should be noted that while FIG. 8 illustrates pins CC1 and CC2 on the left side, they are actually located on the left side where pins CC5 to CC7 are also located. In this respect, the drawing is simplified for illustrative purposes.

[0060] Figures 5-7 show jumpers J1-J3 in the form of rigid wires. It should be noted, however, that jumpers made from flexible wires can also be used. Here, a single jumper exits from a connector and returns to the same connector. In another embodiment, a two-connector solution is used to link the bus nodes. In that case, a jumper exits from a first connector and returns to a second connector.

[0061] All examples and conditional language described herein are intended to be understood as not being limited to such specifically mentioned examples. For example, those skilled in the art will appreciate that the block diagrams presented herein represent conceptual diagrams of example circuits. Similarly, those skilled in the art will appreciate that the illustrated flow charts, state transition diagrams, pseudocode, and the like are various variations for representing processes substantially stored on a computer-readable medium and therefore executable by a computer or processor.

[0062] The present disclosure is not limited to the embodiments described herein. There is room for various adaptations and modifications that will occur to those skilled in the art based on their skills and that belong to the present disclosure. In particular, the application of the present invention is not limited to equivalent ECAS equipment. Other equivalent equipment exists in multiple forms in a vehicle. A vehicle typically has multiple brake actuators for different wheels, for example for realizing an electric parking brake that is also electronically controlled via a CAN bus. The present invention is also not limited to application via a CAN bus. Multiple communication bus systems that utilize a physical medium in the form of a twisted pair cable are readily available on the market, where bus termination is also an issue. The present invention is also used for these communication bus systems. Furthermore, the present invention is also used for communication bus systems outside the automotive field, such as field bus systems for machine control, process control, plant control, etc. [Explanation of symbols]

[0063] 10 Vehicles 100 ECAS-ECU B1 communication bus BS Bus Shield BT bus termination circuit configuration BTS Bus Termination Switching Means ECU1~ECU3 Electronic Control Unit D1 Diode CAL pressure line CC1~CC8 Connector clamp CH CAN-High bus wire CL CAN-Low bus wire CT1~CT3 CAN transceivers CTR1~CTR3 CAN controllers CU1~CU3 Solenoid valve control units C1 Capacitor FB1~FB6 Air Spring Bellows HA rear axle H1~H3 Host IB Internal communication bus IF interface circuit IL Inverter J1~J3 Jumper LA Lift Axle PR pressure accumulator PL1, PL2 plug connector R1 terminating resistor R2,R3 split terminating resistor R4 Pull-up resistor R5 Pull-down resistor R6 Pull-down resistor R7 Pull-up resistor S1 Insertion Socket ST split end T1, T2 transistors VA front axle

Claims

1. A bus node comprising an interface circuit (IF) for a communication bus (B1), the communication bus (B1) requiring a bus termination at least at an end point of the communication bus (B1); The interface circuit (IF) is provided with a bus termination circuit configuration (BT), At the bus node, A bus node, characterized in that the bus termination circuitry (BT) comprises at least one connection arrangement (CC1-CC6) to at least one component (J1-J3).

2. 2. The bus node according to claim 1, A bus node, said components (J1-J3) comprising at least one jumper (J1-J3).

3. 3. The bus node according to claim 1, A bus node, wherein said communication bus (B1) comprises at least one single twisted pair cable as a physical medium.

4. 4. The bus node according to claim 3, A bus node, said connection arrangement (CC1-CC6) comprising a single jumper (J1) and contact clamps (CC3, CC4) for a bus termination switching means (BTS), said bus termination switching means (BTS) enabling or disabling the termination of said at least one twisted pair cable when said single jumper (J1) is inserted or removed therefrom.

5. 5. The bus node according to claim 4, The bus node, said bus termination switching means (BTS) comprising at least one electronic switch (T1, T2) controlled by the voltage drop occurring when said single jumper (J1) is inserted into or removed from its corresponding contact clamp (CC3, CC4).

6. 6. The bus node according to claim 5, Regarding the active low configuration of the bus termination switching means (BTS), the at least one electronic switch (T1, T2) is a transistor, in particular an N-channel enhancement mode MOSFET transistor, and the bus termination switching means (BTS) further comprises an inverter (IL) controlling at least one transistor, the input of which is connected to a pull-up resistor (R4) at the bus node.

7. 7. The bus node according to claim 6, A bus node, the first contact clamp (CC3) being connected to the input of the inverter (IL) and the second contact clamp (CC4) being connected to ground either directly or via a resistor (R5).

8. 8. The bus node according to claim 7, A bus node, said second contact clamp (CC4) also being electrically connected to the shield (BS) of said twisted pair cable.

9. 6. The bus node according to claim 5, For an active high configuration of said bus termination switching means (BTS), said at least one electronic switch (T1, T2) is a transistor, in particular an N-channel enhancement mode MOSFET transistor, the control electrode of the transistor being connected to a pull-down resistor (R6) and to a first contact clamp (CC3) for a single jumper (J1), the second contact clamp (CC4) for the single jumper (J1) being connected to a voltage source (30) bus node.

10. 4. The bus node according to claim 3, A bus node, the connection configuration comprising contact clamps (CC5, CC6, CC7, CC8) for two jumpers (J2, J3), a first jumper (J2) connecting a first bus wire (CH) of a twisted pair cable to a first end of a termination circuit (ST) when the first jumper (J2) is plugged into or unplugged from its corresponding contact clamp (CC5, CC7), and a second jumper (J3) connecting a second bus wire (CL) of the twisted pair cable to a second end of the termination circuit (ST) when the second jumper (J3) is plugged into or unplugged from its corresponding contact clamp (CC7, CC8).

11. A bus node according to any one of claims 4 to 10, A bus node, wherein the termination circuit (ST) comprises a single termination resistor (R1) or a split termination circuit configuration consisting of two termination resistors (R2, R3) connected in series and a coupling capacitor (C1), the coupling capacitor (C1) being connected to ground and to the series connection of the two termination resistors (R2, R3).

12. A bus node according to any one of claims 1 to 11, The bus node comprises an electronic unit configured to perform control of actuators of the vehicle (10) and / or an electronic unit configured to perform data collection of sensor units of the vehicle (10).

13. 13. The bus node according to claim 12, A bus node, wherein said electronic unit is configured to perform the control of at least one solenoid valve of an electronically controlled air suspension system ECAS of a vehicle (10).

14. A plug-in connector (PL) for connecting a communication bus (B1) to a socket (S1) of a bus node (ECU, CU1 to CU3) according to any one of claims 1 to 3, The plug-in connector (P1) is provided with contact clamps (CC5, CC6, CC7, CC8) for two jumpers (J2, J3) and contact clamps (CC1, CC2) for the twisted pair wire of the communication bus (B1), and the first jumper (J2) connects the first twisted pair wire (CH) of the communication bus (B1) to one end of the termination circuit (ST) of the bus node when the first jumper (J2) is plugged in, and the second jumper (J3) connects the second twisted pair wire (CL) of the communication bus (B1) to the other end of the termination circuit (ST) in the bus node (ECU, CU1 to CU3) when the second jumper (J3) is plugged in.

15. A plug-in connector (PL) for connecting a communication bus (B1) to a socket (S1) of a bus node (ECU, CU1 to CU3) according to any one of claims 4 to 9, This plug-in connector (P1) is provided with contact clamps (CC3, CC4) for a single jumper (J1) and contact clamps (CC1, CC2) for the twisted pair wires of a communication bus (B1), characterized in that when this plug-in connector (PL) is plugged into the socket (S1) of the bus node (ECU, CU1 to CU3), the first contact clamp (CC3) is connected to a control line of the bus termination circuit configuration (BT) and the second contact clamp (CC4) is connected to a power supply voltage line or a ground line.

16. A plug-in connector (PL) according to claim 15, A plug-in connector, wherein said second contact clamp (CC4) is further connected to a shield (BS) of said twisted pair wire cable.

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