EP3556058A1

EP3556058A1 - Subscriber station for a bus system and method for data transmission in a bus system

Info

Publication number: EP3556058A1
Application number: EP17811285.0A
Authority: EP
Inventors: Simon Weissenmayer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2016-12-14
Filing date: 2017-12-06
Publication date: 2019-10-23
Also published as: KR20190103202A; CN110301115A; CN110301115B; WO2018108666A1; DE102016224961A1

Abstract

The invention relates to a subscriber station (10) for a bus system (1; 2) and to a method for data transmission in a bus system (1; 2). The subscriber station (10) comprises a transmit/receive device (12) for transmitting a message (45; 46; 47) to and/or receiving a message (45; 46; 47) from a further subscriber station (20; 30) on the bus system (1; 2) by means of a bus (40), wherein the transmit/receive device (12) is designed to reduce a differential voltage from a first predetermined voltage level for a data transmission in a first time segment to a second predetermined voltage level for a data transmission in a second time segment or to raise same again from the second predetermined voltage level to the first predetermined voltage level and to reduce the decision threshold (125, 126) for the reception of bits of the message (45; 46; 47) in the second time segment from a first predetermined threshold value for a data transmission in the first time segment to a second predetermined threshold value for a data transmission in the second time segment or to raise same again from the second predetermined threshold value to the first predetermined threshold value, and wherein the subscriber station (10) is designed to send or to receive the messages (45; 47) in the second time segment with a higher data transmission rate than in the first time segment.

Description

Description title

Subscriber station for a bus system and method for data transmission in a bus system

Technical area

The present invention relates to a subscriber station for a bus system and a method for data transmission in a bus system, in which a protocol for CAN or CAN FD is performed with lower voltage than usual.

PRIOR ART In vehicles, for example, CAN networks are provided in which

Messages can be transmitted using the CAN and / or CAN FD protocol, as described in the current ISO-CD-11898-1 CAN protocol specification with CAN FD. With CAN, the data rate can not be further increased in many cases, because otherwise the voltage edges would have to be chosen so steeply that more electromagnetic emissions would be generated than permitted. In earlier times, there was only one long CAN bus, all

ECUs in the vehicle has interconnected. Nowadays there are many shorter CAN buses due to the large number of participants. The short cable lengths ensure a better signal-to-noise ratio.

Increasing communication on the CAN bus requires an increase in data rate beyond CAN FD. The applicant was therefore considered, instead of the previous CAN bus system to use a bus system in which a lower

Voltage (low voltage) than the usual high voltage of 5V or 3.3V used in digital systems. Such lower voltage systems are known as LVDS (Low Voltage Digital System).

The problem, however, is that existing bus systems are not compatible with an LVDS subscriber station based on the LVDS system. The LV messages of the LVDS subscriber stations are transmitted by the

Destined subscriber stations of the conventional subscriber stations. Therefore, in an existing standard CAN system all existing

Subscriber stations to be converted to a LVDS system. This is very expensive and costly.

Disclosure of the invention

It is therefore an object of the present invention to provide a subscriber station for a bus system and a method for data transmission in a bus system, which solve the aforementioned problems. In particular, a control device for a bus system and a method for

Data transmission can be provided in a bus system, in which the data transfer rate on the bus compared to previous solutions can be increased even further, so as to accelerate error-free communication over the bus.

The object is achieved by a subscriber station for a bus system with the features of claim 1. The subscriber station includes a

Transceiver for sending a message to and / or

Receiving a message from another subscriber station of the

Bus system via a bus, wherein the transceiver is configured to lower a differential voltage from a first predetermined voltage value for a data transmission in a first time period to a second predetermined voltage value for a data transmission in a second time period or again from the second predetermined Raise voltage value to the first predetermined voltage value and decrease the decision threshold for receiving bits of the message in the second time period from a first predetermined threshold for a data transmission in the first period to a second predetermined threshold for a data transmission in the second period or again from the second predetermined threshold to raise the first predetermined threshold, and wherein the

Subscriber station is configured to send the messages in the second period of time with a higher data transmission rate than in the first

Period of time.

With the subscriber station, the data transmission rate can be increased many times compared to conventional CAN or CAN FD.

Another advantage is that of the subscriber station

conducted LV communication, which runs with a lower voltage (low voltage) than with the otherwise usual in digital systems high

Voltage (high voltage) of 5V or 3.3V does not bother a standard CAN or standard CAN FD communication on the bus. The LVCAN subscriber station generates smaller differential voltages during data transmission than

common. The differential voltages are so small that they can not be perceived by standard CAN subscriber stations because the

Differential voltages below the decision threshold of 1 V, e.g. at 0.5 V or even negative.

Advantageously, the subscriber station is designed so that standard CAN subscribers are tolerant of the LV differential voltage changes made by the described subscriber station and none

Send error messages. As a result, several LV-CAN subscriber stations can communicate undisturbed. However, that's before

described subscriber station designed so that they can switch to the standard protocol if necessary and then also can exchange information with standard CAN subscriber stations. The executed by the subscriber station described method is therefore fully compatible with previous CAN bus systems. Standard CAN or standard CAN FD subscriber stations can therefore be gradually replaced in the bus by LV-CAN users.

Advantageous further embodiments of the subscriber station are specified in the dependent claims.

According to one embodiment, the transceiver has a port and is configured depending on a signal on the port

Connection to lower the difference voltage and the decision threshold or to increase the difference voltage and the decision threshold.

Additionally or alternatively, the transceiver can be configured to evaluate a content of the message and, depending on the content of the message, to lower the differential voltage and the decision threshold or to increase the differential voltage and the decision threshold.

According to one embodiment, the transceiver has a first terminal and is configured, depending on a signal at the first terminal, the differential voltage with a first predetermined one

To generate voltage value for a data transmission, a second

A terminal for receiving the bits having the decision threshold having the first predetermined threshold and a third terminal and being configured to, depending on a signal at the third terminal, apply the difference voltage to a second predetermined voltage value for one

Generate data transmission, and a fourth port for receiving the bits with the decision threshold having the second predetermined threshold. According to one embodiment, the subscriber station also has a

A communication controller configured to send the messages in the second time period with stuff bits at the locations where the stuff bits are expected upon synchronization of the subscriber stations of the bus system, and / or the communication controller or the transceiver is configured, the stuff bits with the Differential voltage level and the data transfer rate to create, as in the first period. Additionally or alternatively, the

Communication control device or the transmitting / receiving device to be configured to create a recessive stuffing bit directly in sequence in addition to a dominant Stuff bit.

The first time period is preferably a time period in which it is determined which subscriber station at least temporarily receives exclusive, collision-free access to the bus or a common channel of the bus. The second period of time is preferably a period of time in which the subscriber station has exclusive, collision-free access to the bus or a common channel of the bus.

It is conceivable that the levels of the differential voltage have on average values that lie in a range of -1 V and 3 V. Additionally or alternatively, the differential voltage may have a value that is in a range of 0.2V <UD ^ 1V.

According to one embodiment, the transceiver can be configured to modulate an LV transmission in parallel to a transmission with the first predetermined current value. Additionally or alternatively, the subscriber station may include an error counter configured to count how many times a transmission attempt is aborted, and wherein the transceiver is configured to switch to a transmission mode in which the differential voltage is switched to the first predetermined voltage mode, to send the messages only at the original level and original data rate when a count of the error counter exceeds a predetermined value.

Perhaps the bus system is a CAN bus system or a CAN FD bus system. Additionally or alternatively, it is possible that at least one reflection reduction unit is arranged at the transmitting / receiving device, which is connected between two bus wires of the bus in order to reduce reflections in the bus system. The subscriber station described above may be part of a bus system, which also includes a bus, via which at least two subscriber stations are connected to each other so that they can communicate with each other. In this case, the bus system can also have a switch which is connected between at least two of the subscriber stations in order to divide the bus into approximately equal parts.

The above object is further achieved by a method for

Data transmission according to claim 10 solved in a bus system described above. In the method, in the bus system, a transmission

/ Receiving means for transmitting a message to and / or receiving a message from another / n subscriber station of the bus system used over a bus, wherein the transceiver means a

Differential voltage from a first predetermined voltage value for a data transmission in a first time period to a second predetermined

Lowers the voltage value for a data transmission in a second time period or raises it again from the second predetermined voltage value to the first predetermined voltage value and the decision threshold for receiving bits of the message in the second time period from a first predetermined threshold for a data transmission in the first

Period of time to a second predetermined threshold for a

Data transmission in the second period of time decreases or again from the second predetermined threshold to the first predetermined

Threshold raises, and wherein the subscriber station is configured, the messages in the second period with a higher

Data transmission rate to send than in the first period.

The method offers the same advantages as previously described in relation to the

Subscriber station are called.

Further possible implementations of the invention also include not explicitly mentioned combinations of before or below with respect to the

Embodiments described features or embodiments. The skilled person will also add individual aspects as improvements or additions to the respective basic form of the invention. drawings

The invention is described in more detail below with reference to the accompanying drawings and to exemplary embodiments. Show it:

1 is a simplified block diagram of a bus system according to a first embodiment;

FIG. 2 is a diagram illustrating a structure of a message transmitted from a subscriber station of the bus system according to the first embodiment

Embodiment is sent;

3 shows a simplified structure of a transmitting / receiving device of a first and third subscriber station according to the first embodiment;

4 shows a schematic profile of a differential voltage of CAN_H-CAN_L over time during a useful data transmission in a second subscriber station according to the first exemplary embodiment;

5 shows a schematic course of a differential voltage of CAN_H-CAN_L over time during a useful data transmission at the first or third subscriber station according to the first exemplary embodiment;

6 shows a schematic profile of a differential voltage of CAN_H-CAN_L over time during a useful data transmission at the first or third subscriber station according to a second exemplary embodiment;

7 shows a schematic curve of a differential voltage of CAN_H-CAN_L over time during a user data transmission at the first or third subscriber station according to a third exemplary embodiment;

8 shows a schematic profile of a differential voltage of CAN_H-CAN_L over time during a useful data transmission in the first and third subscriber stations according to a fourth exemplary embodiment; 9 shows a simplified structure of a transmitting / receiving device of a first and third subscriber station according to a fifth embodiment; and

10 is a simplified block diagram of a bus system according to a sixth embodiment.

In the figures, identical or functionally identical elements are provided with the same reference numerals, unless stated otherwise.

Description of the embodiments

1 shows a bus system 1, which may be, for example, a CAN bus system, a CAN FD bus system, etc. The bus system 1 can be used in a vehicle, in particular a motor vehicle, an aircraft, etc., or in the hospital, etc. However, the bus system 1 is not limited to a CAN bus system. In Fig. 1, the bus system 1 has a plurality of subscriber stations 10, 20, 30 which are each connected to a bus 40 having a first bus core 41 and a second bus wire 42. The bus wires 41, 42 can also be called CAN_H and CAN_L and serve to couple in the dominant state in the transmission state. Via the bus 40 messages 45, 46, 47 can be transmitted in the form of signals between the individual subscriber stations 10, 20, 30.

In addition, at least two of the subscriber stations 10, 20, 30, in this embodiment, the subscriber stations 10, 30, for sending or

Receive data in the form of messages or lower-level signals

Level configured as 5V or 3.3V, which is the usual voltage level in digital systems. Messages or lower level signals than 5V or 3.3V are also referred to below as LV messages whose bits are also referred to as LV bits. In the subscriber stations 10, 30, the voltage of the signal to ground has a value of about 1.2 V or has the differential voltage a value that is in a range of 0.2V <UD ^ 1V. Of the

Differential voltage signal level usually has a value which is in a range of 0.2 V <U _D <1V. The subscriber stations 10, 20, 30 may, for example, control devices or

Display devices or sensors of a motor vehicle.

As shown in FIG. 1, the subscriber stations 10, 30 each have one

Communication control device 11, a transmitting / receiving device 12, an error counter 15 and a reflection reduction unit 16. The error counter

15 may also be part of the communication control device 11 in at least one of the subscriber stations 10, 30. The operation of the error counter 15 is described in more detail with reference to FIG. By contrast, according to FIG. 1, the subscriber station 20 has a communication control device 11 and a transmitting / receiving device 13. The transmitting / receiving devices 12 of FIG

Subscriber stations 10, 30 and the transmitting / receiving device 13 of the subscriber station 20 are each connected directly to the bus 40, although this is not shown in Fig. 1. The communication control device 11 is for controlling a

Communication of the respective subscriber station 10, 20, 30 via the bus 40 with another subscriber station connected to the bus 40

Subscriber stations 10, 20, 30. The communication control device 11 may be designed like a conventional CAN controller or CAN FD controller. The transmitting / receiving device 12 is used to transmit the messages 45, 47 and will be described in more detail below. The transmitting / receiving device 13 may be designed like a conventional CAN transceiver or CAN FD transceiver. With the reflection reduction unit 16 reflections can be suppressed, resulting from open bus wire ends, connectors or branches in the bus 40. The reflection reduction unit 16 is preferably connected between the two bus wires 41, 42 of the bus 40. The

Reflection reduction unit 16 may be configured, for example, as a Zener diode which at as many points as possible the differential voltage UD on the bus 40th to at least 0 V and a maximum of 2V limit. In order to be able to suppress reflections likewise for LV bits, the voltage is limited to a maximum of 0.5 V or even 0.2 V during the transmission of LV bits, if appropriate in addition. In time for the transfer of bits at the original level, the 0.5 V limit is canceled, so that the limitation acts on 2 V. However, a hard limit of 0.5 or 0.2 V would mean that no standard 2 V bit can be transmitted. Therefore, the procedure is that only if one can be expected with an LV transmission, then as many as possible

Subscriber stations 10, 20, 30 limit the voltage to a maximum of 0.5 or 0.2 V, but only so long as the short-circuit current caused by the limitation, namely the current through the Zener diode, does not exceed a certain value. If the short circuit current is e.g. greater than 0.3mA, the limit is switched from 0.5 or 0.2V to 2V, allowing a standard 2V bit to be sent.

As shown in FIG. 2 based on the CAN frame message 46 at the top of FIG. 2 and a CAN FD frame at the bottom of FIG. 2, each as voltage U over time t, CAN communication on the bus 40 are basically divided into two different time periods, namely the Arbitrierungsphasen 451, 453 shown only schematically and a data area 452, which is also called data phase in CAN-FD. With CAN-FD the bitrate for the following data phase is reduced to z. B. 2, 4, 8Mbps increased. Thus, in CANFD, the bit rate in the arbitration phases 451, 453 is less than the bit rate in the data area 452. In the case of CANFD, the data area 452 is significantly shorter than the data area 452 of the CAN frame.

In the arbitration phase 451, 453 it is determined which of the currently transmitting subscriber station (s) 10, 20, 30 of the bus system 1 at least temporarily receives an exclusive, collision-free access to the bus 40 of the bus system 1. In the data area 452, the payload of the message 46 is transmitted by the subscriber station, which has won the arbitration.

Fig. 3 shows the terminals of a transmitting / receiving device 12 and the error counter 15 with a value of 7 for the counter 151 more accurate. Consequently the transmitting / receiving device 12 has, in addition to a first connection for the transmission signal Tx and a second connection for the reception signal Rx connections for the bus signals CAN_H and CAN_L, a connection LV which is in particular an input connection. In addition, the transmitting / receiving device 12 has a current source 121.

Depending on a signal at the terminal LV, the transceiver 12 switches to LV operation. In LV operation, the transceiver 12 lowers the current source 121 from the standard 33 mA to 8.3 mA to send an LV message 45, 47 with LV bits. In addition, in particular simultaneously, the transmitting / receiving device 12 lowers the

Decision threshold for the reception of LV-bits from 1 V to half of the voltage limit, so for example 0.25 V or 0.1 V, from. Likewise, in particular at the same time, the transmitting / receiving device 12 lowers the

Voltage limiting from 2 V to preferably 0.5 V or 0.2. The procedures for this are illustrated in FIGS. 4 to 6.

Fig. 4 shows the signal levels for a differential voltage UD during the

User data transmission of a standard CAN message 46. Here, at the transceiver 12, a decision threshold 125 for the reception of

Bits set to 1V. Thus, bits are detected when the signal level for a differential voltage UD rises above 1 V during the payload transmission of a standard CAN message 46. In Fig. 4 is a phase of the user data transmission of a standard CAN message

46 between two stuff bits 60 having a bit duration Tl. The stuff bits 60 are inserted into the standard CAN message 46 by the communication controller 11 at predetermined intervals to produce a

Synchronization of the subscriber stations 10, 20, 30 of the bus system 1 to allow.

With the standard CAN or standard CAN FD, the

Decision threshold 125 constantly to 1 V. In contrast, Fig. 5 shows the signal levels for a differential voltage UD during the payload transmission of an LV-CAN message 45, 47. Here, to ensure the best possible compatibility with existing ones

to achieve the described standards, even with the LV messages 45, 47 first transmit the bits with a normal level, as with a standard CAN message or standard CAN FD message 46. Only after successful

Arbitration, the levels are reduced and thus LV bits 65 transmitted with a bit duration T3. In Fig. 5, the bit duration T3 is only half as long as the bit duration T1 of a stuff bit 60. In particular, an LV bit may take 1/8 or 1/32 of the time required for a standard arbitration bit to transmit , The LV recessive bit 1 has a differential voltage below 0.25V while the subdominant LV bit 0 has a differential voltage greater than 0.25V. A subdominant LV bit 0 can always be overdriven by a dominant standard bit 0. An LV message 45, 47 can have the same content as a standard CAN or CN FD message, with LV messages with more than 64 bytes being permitted, the LV bit times in the data part being shorter than the one

Arbitrierungsbitzeiten may be in the header and the transmission of LV bits can be announced by one or more standard bits in the header.

Thus already in the market located subscriber stations, such as

Subscriber station 20, detect no errors, stuff bits 60 can be inserted into the messages 45, 47 at the standard level and standard length intervals usually expected.

Optionally, the communication controller 11 or the transceiver 12 may be configured to create a recessive stuff bit directly in sequence in addition to a dominant stuff bit.

According to FIG. 5, after the arbitration in the payload data, a stuff bit 60 whose duration or bit duration T 1 is equal to the standard length of the stuff bit 60 is initially expected or transmitted at the transceiver 12. Thereafter, after lapse of a predetermined time T2 equal to half the time Tl, a decision threshold 121 for receiving bits is set to 0.25V. Thus, signal levels are detected as bits when the signal level for the differential voltage UD during payload transmission standard CAN message or standard CAN FD message 46 rises above 0.25V. Upon receipt of the dominant stuff bit 60 with the time Tl and the receipt of a recessive stuff bit 60A with the further time Tl payload bits follow 65 with a bit duration T3. When a stuff bit 60 is received again, the transceiver 12 raises the decision threshold

121 for the reception of bits again from 0.25 V to 1 V, as shown in Fig. 5. Switching the decision threshold 121 to the

Decision threshold 125 occurs after expiration of the time period T2 after the beginning of recognition of the second dominant stuff bit 60 in FIG. 5.

The payload transmission of an LV message 45, 47 may be fully compatible with a transmission according to the CAN protocol or the CAN FD protocol.

In the fully compatible LV-CAN according to FIG. 5, the subscriber stations 10, 30 thus additionally send standard-level stuff bits 60 during the

User data transmission to the expected by the standard CAN subscriber station 20 bodies. The subscriber stations 10, 30 as LV receivers change the decision threshold between 0.25 V and 1 V according to whether an original level bit or an LV bit 65 is expected.

In the case of a communication in bus system 1, the two levels of CAN-H and CAN-L move around 2.5 V as long as no standard CAN (FD) messages are sent. The differential voltage is therefore 0 V. Ordinary CAN stations , like the subscriber station 20, recognize the start of a data transmission only when the difference voltage between CAN-H and

CAN-L has a certain threshold of e.g. Exceeds 1V.

During communication in the bus system 1, for example, the LVCAN subscriber station 10 first tries to transmit its (LV message) 45 with LV level. If this is not possible, because it is from another LV message 47,

electromagnetic radiation or a standard message 46

destroyed dominated, the subscriber station 10 tries to send the message 45 according to the standard protocol. The transmission attempt of the LV message 45 starts at the same time as a standard message 46, ie after the end of the three interframe space bits. If an LV message 45 at the same time how a standard message 46 is to be sent, then recognizes that the solver, in this example, the subscriber station 10, at the latest after the attempt to send the first recessive stuffing bit 60 after 6 LV bits, because the differential voltage is not less than 0.1 V. falls or because the voltage rises above 1V. The subscriber station 10 as LV transmitter recognizes that the

Subscriber station 20 wants to send a standard message 46. Since the subscriber station 20 as a (standard) transmitter is still busy sending the first (Start Of Frame) standard bit after 6 LV bits, the subscriber station 10 as the LV transmitter can, without delay, try to change its LV Send message 45 as standard message 46 or message with standard header but with LV content.

Under special conditions, such as extreme temperatures, extreme humidity, short circuits with a spark, etc., the LV data transmission may be briefly disturbed, so that the transmission is interrupted by an error frame. Every time an LV transmission is aborted by an error frame, the transmission is repeated again at the original level and original data rate according to the CAN protocol or the CAN FD protocol.

Therefore, the transceiver 12 has an error counter 15 as previously described with reference to FIG. The error counter 15 counts the number of error frames. If so many messages are erroneously transmitted in sequence that the count 151 of the error counter 15 exceeds a threshold, then the messages are sent only at the original level and original data rate instead of LV level and LV data rate. A certain number of messages sent / received error-free reduces the count 151 of the error counter 15. If the count 151 of the error counter 15 has dropped far enough, the transmission of LV messages is resumed. Due to the intermediate transmission with standard levels, the bus load can increase so much that low-priority messages can no longer be sent. However, as a result of the fact that the high-priority messages can still be sent, safe emergency operation of the vehicle is possible. As soon as all normal CAN stations have been replaced by LV stations, the arbitration data can also be sent with LV levels. If the toggling between the levels is eliminated, the transceivers 12 can be made cheaper, since the LV connection can be dispensed with. However, then a safe emergency operation is only possible by reducing the data rate without level increase.

Fig. 6 shows the signal levels for a differential voltage UD during the

User data transmission of an LV-CAN message 45, 47 at a second

Embodiment. Here, the transceiver 12 is constructed in the same manner as in the previous embodiment. However, in the present embodiment, no synchronization is the

Subscriber stations 10, 20, 30 of the bus system 1 required. Therefore, no stuff bits 60 are transmitted at the original level. As a result, the transceiver 12 may continuously assert the decision threshold 121 during the payload transmission of an LV-CAN message 45, 47, as shown in FIG. The signal level of Fig. 6 corresponds to a pure LV-CAN in which the transmission of the stuffed-bit 60 with original level is dispensed with and the decision threshold remains permanently at 0.25V.

Thus, in CAN subscriber stations over the duration of

User data transmission need no synchronization or can detect LV level, are waived to the Stuff bits 60 with original level within the payload in favor of a higher data transfer rate.

Fig. 7 shows the signal levels for a differential voltage UD during the

User data transmission of an LV-CAN message 45, 47 in a third

Embodiment. Here, a similar data transmission as described with reference to FIG. 5. However, in the present embodiment, an LV level difference of + -0.5V instead of +0.5V is used as illustrated in FIG. This results in a larger voltage swing than in the case of FIG. 5, namely 1 V instead of 0.5 V, as in the example of FIG. 5. Compared to level differences of +0.5 V, the influence of interference radiation is reduced by the larger voltage swing of 1 V instead of 0.5 V. However, at the same time, the data transmission rate should be reduced to 1.6 or 2.4 times.

In a modification, it is also conceivable to work with an LV level difference of +1 V. However, this change is then no more

Fully compatible with the previous CAN protocol or CAN FD protocol.

Fig. 8 shows the signal levels for a differential voltage UD during the

User data transmission of an LV-CAN message 45, 47 at a fourth

Embodiment. Here, a similar data transmission as described with reference to FIG. 6. However, in the present embodiment, an LV level difference of + -0.5V instead of +0.5V is used, as previously described with reference to FIG. This results in a larger voltage swing of 1 V instead of 0.5 V, as in the example of FIG. 6.

Again, it is also conceivable in a modification to work with an LV level difference of +1 V, if the resulting lack of compatibility with the CAN protocol or CAN FD protocol in the bus system 1 is unproblematic.

9 shows a transmitting / receiving device 120 for a bus system 1 according to a fifth exemplary embodiment. In contrast to the preceding exemplary embodiments, instead of one connection LV, the transceiver 120 has two connections, namely an input LVR and an output LVT. The LVT output indicates when a standard bit on the bus 40 has been detected instead of an expected LV bit. Only if the LV operation is activated by the input LVR, then the limitation of the

Differential voltage switched to a maximum of 0.5 V or 0.2 V active. Otherwise, the transmitting / receiving device 120 is constructed in the same way as the transmitting / receiving device 12 according to the preceding

Embodiments.

In yet another embodiment, the transceiver 120 may include a LVRx terminal for the LV receive signal and a LVTx terminal for comprise the LV transmit signal, which may also be referred to as the third and fourth terminals of the transceiver 120. In this way, the LV transmission signal or LV reception signal can also already be created by the communication control device 11 or passed on to it.

With the additional RX input for sending LV bits, the

Connection LVTx for the LV transmit signal, as well as the additional RX input for received LV bits, the LVRx connection for the LV receive signal can not only in the transmission pauses in later development steps but also during a standard CAN transmission. Transmission be modulated in parallel. The modulation may be similar to modulating data onto a power line.

This would allow transmission of LV messages 45, 47 in parallel with standard CAN or CAN FD messages.

10 shows a bus system 2 according to a fifth embodiment. The bus system 2 is largely implemented in the same way as described in the bus system 1 according to the first embodiment. in the

In contrast to the bus system 1 according to the first embodiment, however, the bus system 2 additionally has a CAN switch 50. The CAN switch 50 is preferably installed in the middle of the bus 40, whereby two separate buses 40 are generated.

On the one hand, the CAN switch 50 has the advantage that only the messages 45, 46, 47 which are of interest for the respective other part of the bus system 2 are forwarded. As a result, the bus load decreases in addition, which, because of fewer interrupted data transmission attempts, the speed of the

Data transmission in the bus system 2 compared to the bus system 1 of the first embodiment further increased.

On the other hand, the CAN switch 50 has the advantage that it can be taken into account that the LV signals are very weak and therefore prone to

electromagnetic radiation. Therefore, LV messages are in Bus systems 2 with distant subscriber stations 10, 20, 30 in unfavorable environment or operating conditions often destroyed. To limit the irradiation, the bus length can be reduced by using the CAN switch 50.

The bus systems 1, 2 of the embodiments described above can make a contribution to the fact that ever higher data rates are needed, which is driven by flashing ever-increasing program levels in the shortest possible time. Flashing can be done with standard CAN, e.g. for cameras take 2.5 hours and more. Ideally, many electrical consumers are switched off during flashing and thus turned off electromagnetic Einstrahlquellen. In part, the

Control units or subscriber stations of the bus system 1, 2 also outside the vehicle at special stations flashed. Shorter and shielded cables can be used here, which reduces the radiation to a minimum.

All of the previously described embodiments of the bus systems 1, 2 of the

Subscriber stations 10, 20, 30 and the method may be used individually or in all possible combinations. In particular, all the features of the previously described embodiments and / or their modifications can be arbitrarily combined or omitted. In addition, the following modifications are conceivable, in particular.

The bus system 1, 2 described above according to the exemplary embodiments is described with reference to a bus system based on the CAN protocol or CAN FD protocol. However, the bus system 1, 2 according to the various embodiments may also be another type of

Be communication network. It is beneficial, but not inevitable

Requirement that in the bus system 1, 2 at least for certain

Time periods an exclusive, collision-free access of a subscriber station 10, 20, 30 is guaranteed on the bus 40 or a common channel of the bus 40. As an alternative to the previous embodiments, the LV transmitter can detect overshoot of the subdominant LV bit by a dominant standard bit by exceeding a differential voltage threshold between 0.1 V or 0.25 V and 1 V earlier.

As an alternative to the preceding embodiments, arbitration can also be carried out in such a way that it is only switched to large differential voltages if the arbitration according to the new method was unsuccessful and was reset to standard arbitration.

As an alternative to the previous embodiments, the limit of 0.2 V or 0.5 V can be increased to 2 V when through

Preceded collisions / errors sending a message with standard level can be expected.

The bus system 1, 2 according to the exemplary embodiments is in particular a CAN network or a CAN FD network or a Flex Ray network or an SPI network.

However, it is also conceivable that one of the two bus wires 41, 42 connected to ground and thus is a Masseader and the other of the two bus wires 41, 42 is a signal wire on which the bus signal for the messages 45, 46, 47 is transmitted ,

The number and arrangement of subscriber stations 10, 20, 30 in the

Bus system 1, 2 according to the embodiments is arbitrary. In particular, only subscriber stations 10 or subscriber stations 30 can be present in the bus systems 1, 2 of the exemplary embodiments.

The functionality of the embodiments described above can be implemented not only in a transceiver 12. Additionally or alternatively, the functionality can be integrated into existing products. In particular, it is possible that the functionality under consideration either in a transmitting / receiving device 12 as a separate electronic component (Chip) is realized or embedded in an integrated overall solution in which only one electronic component (chip) is present.

Claims

claims

1) subscriber station (10) for a bus system (1, 2), with

a transmitting / receiving device (12; 120) for transmitting a message (45; 46; 47) to and / or receiving a message (45; 46; 47) from a further subscriber station (20; 30) of the bus system (1; 2) via a bus (40),

wherein the transmitting / receiving device (12; 120) is configured, a differential voltage of a first predetermined

Voltage value for a data transmission in a first time period to a second predetermined voltage value for a

Lowering data transmission in a second time period or to raise again from the second predetermined voltage value to the first predetermined voltage value and a

Decision threshold (125, 126) for receiving bits of the message (45; 46; 47) in the second time period from a first predetermined threshold for data transmission in the first time period to a second predetermined threshold for data transmission in the second time period; raise again from the second predetermined threshold to the first predetermined threshold, and

wherein the subscriber station (10) is configured to receive the messages (45; 47) in the second time segment with a higher one

Send or receive data transmission rate than in the first period.

2) subscriber station (10) according to claim 1,

wherein the transmitting / receiving device (12; 120) has a

Terminal (LV), and wherein the transceiver (12; 120) is configured to lower the differential voltage and the decision threshold depending on a signal at the terminal (LV) or to increase the difference voltage and the decision threshold, and / or

wherein the transmitting / receiving device (12; 120) is configured to evaluate a content of the message (45) and, depending on the content of the message (45), the differential voltage and the

Decrease decision threshold or increase the difference voltage and the decision threshold (125, 126).

Subscriber station (10) according to claim 1 or 2,

wherein the transmitting / receiving device (12; 120)

- Has a first terminal (Tx) and is configured, depending on a signal at the first terminal (Tx) the

To generate differential voltage with a first predetermined voltage value for a data transmission,

- a second terminal (Rx) for receiving the bits with the decision threshold (125, 126) comprising the first

has predetermined threshold, and

- Has a third terminal (LVTx) and is configured, depending on a signal at the third terminal the

To generate differential voltage with a second predetermined voltage value for a data transmission, and

a fourth port (LVRx) for receiving the decision threshold bits (125, 126) representing the second

has predetermined threshold.

A subscriber station (10) according to any one of the preceding claims, further comprising communication control means (11) arranged to transmit the messages (45; 47) in the second time period with stuff bits (60) at the locations to which the stuff Bits (60) are expected during a synchronization of the subscriber stations (10, 20, 30) of the bus system (1, 2), and / or

wherein the communication control means (11) is configured to supply the stuffing bits (60) with the differential voltage level and the

Data rate to create, as in the first period, and / or wherein the communication control means (11) or the transceiver means (12; 120) is arranged to create a recessive stuff bit in direct succession in addition to a dominant stuff bit.

Subscriber station (10) according to one of the preceding claims, wherein the first time period is a time period in which it is determined which subscriber station (10, 20, 30) at least temporarily an exclusive, collision-free access to the bus (40) or a common channel of Buses (40) gets, and

wherein the second time period is a time period in which the subscriber station (10) has exclusive, collision-free access to the bus (40) or a common channel of the bus (40).

Subscriber station (10) according to one of the preceding claims, wherein levels of the differential voltage on average have values which lie in a range of 1 V and 3 V, and / or

wherein the differential voltage has a value that is in one

Range of 0.2 V <U _D ^ 1 V is located.

Subscriber station (10) according to one of the preceding claims, wherein the transceiver device (12; 120) is configured to modulate an LV transmission in parallel to a transmission with the first predetermined current value, and / or

wherein the subscriber station (10) has an error counter (15) configured to count how many times a transmission attempt is aborted, and wherein the transceiver (12; 120) is configured to switch to a transmission mode in which the differential voltage is switched to the first predetermined voltage value to send the messages (46) only at the original level and original data rate when a count (151) of the error counter (15) exceeds a predetermined value.

Subscriber station (10) for a bus system (1), wherein the bus system (1) is a CAN bus system or a CAN FD bus system, and / or

wherein at least one reflection reduction unit (16), which is connected between two bus wires (41, 42) of the bus (40), is arranged at the transceiver device (12; 120)

Reflections in the bus system (1) to reduce.

Bus system (1), with

a bus (40), and

at least two subscriber stations (10, 20, 30) according to one of the preceding claims, which are connected to one another via the bus (40) such that they can communicate with one another.

Method for data transmission in a bus system (1) in which a transmitting / receiving device (12; 120) for transmitting a

Message (45; 46; 47) from and / or receiving a message (45; 46; 47) from another subscriber station (20; 30) of the bus system (1; 2) over a bus (40) wherein the transceiver means (12; 120) applies a differential voltage from a first predetermined voltage value for a data transmission in a first time period to a second predetermined one

Voltage value for a data transmission in a second

Time interval decreases or again from the second predetermined voltage value to the first predetermined voltage value and a decision threshold (125, 126) for receiving bits of the message (45; 46; 47) in the second time period from a first predetermined threshold for a data transmission in the first time period to a second predetermined threshold for data transmission in the second time period or again from the second predetermined threshold to the first time

raises predetermined threshold, and wherein the subscriber station (10) is configured, the messages (45; 47) in the second

Send or receive time portion with a higher data transmission rate than in the first period.