WO2012136783A1

WO2012136783A1 - Method and device for transmitting data between connected bus systems

Info

Publication number: WO2012136783A1
Application number: PCT/EP2012/056311
Authority: WO
Inventors: Volker Blaschke; Juergen Schirmer; Markus Ihle; Andreas-Juergen Rohatschek; Tobias Lorenz
Original assignee: Robert Bosch Gmbh
Priority date: 2011-04-06
Filing date: 2012-04-05
Publication date: 2012-10-11
Also published as: DE102011006827A1

Abstract

The invention relates to a method for transmitting data between at least two bus systems (B1, B2, B3, B4) which are connected to each other by a device (300). Each bus system comprises at least one participating data processing unit (101-108) that can send and receive messages via the bus system in which said unit participates, said messages containing identifiers. A decision is made for each message that is present on at least one of the bus systems (B1, B2, B3, B4) connected to the device as to whether said message is buffered in a forwarding store (303) using an identifier of the message and filter information that is stored in a filter information unit (302) provided for this purpose.

Description

Description title

Method and device for data transmission between connected bus systems

State of the art

The invention relates to a device for data transmission between at least two bus systems connected to the device, each having at least one participating data processing unit, which can send and receive messages via the bus system in which it participates.

The Controller Area Network (CAN) and an extension of the CAN called "Time Triggered CAN" (TTCAN), for example, are known from the standards of the family ISO 11898-1 to -5, the first version on 02.05.2011 on the Internet Page http://www.semiconductors.bosch.de/ published document "CAN with Flexible Data Rate, White Paper, Version 1.0" introduces a modified data transfer protocol known as CAN FD, which includes an enlargement of the data field, as well as for a part of the CAN message shortening the bit length allows.

The media access control method used in CAN and CAN FD is based on bitwise arbitration. In the bitwise arbitration several subscriber stations can simultaneously transmit data via the channel of the bus system, without this disrupting the data transfer. The

Subscriber stations can continue to determine the logical state (0 or 1) of the channel when sending a bit over the channel. If a value of the transmitted bit does not correspond to the determined logical state of the channel, then the subscriber station terminates the access to the channel. At CAN, the bitwise arbitration is usually carried out based on an identifier or an identifier within a message to be transmitted via the channel. After a subscriber station has completely sent the identifier to the channel, it knows that it has exclusive access to the channel. Thus, the end of transmission of the identifier corresponds to a beginning of a release interval within which the subscriber station can exclusively use the channel. According to the protocol specifications of CAN and CAN FD, other subscriber stations may not access the channel, that is, send data to the channel until the transmitting subscriber station

Checksum field (CRC field) of the message. Thus, an end time of transmission of the CRC field corresponds to one end of the

Enable interval.

The bitwise arbitration thus achieves non-destructive transmission of those messages over the channel which the arbitration method has obtained. The protocols CAN and CAN FD are particularly suitable for transmitting short messages under real-time conditions, whereby it can be ensured by suitable assignment of the identifiers or identifiers that particularly important messages almost always the

Win arbitration and be sent successfully.

With the increasing networking of modern vehicles and the introduction of additional systems for improving, for example, driving safety or driving comfort, the demands on the carriers to be transferred are growing

Amounts of data and the latencies allowed during transmission. Examples are vehicle dynamics control systems, e.g. the electronic stability program ESP, driver assistance systems such. the automatic distance control ACC, or driver information systems such. the traffic sign recognition (see, for example, descriptions in "Bosch Automotive Manual", 27th edition, 2011, Vieweg + Teubner).

A known from the prior art solution for coping with the increasing volume of data is the division of the vehicle network into several subnets, which are interconnected via gateways. The disadvantage is that these gateways usually have a complex software, which reads in the transfer between different bus systems, the news content, if necessary reduced, for example

Data content further processed, merges various different sizes contained in new messages or resorted, and finally outputs the data in a modified form again. On the other hand, often messages are simply passed on.

It turns out that the state of the art does not provide satisfactory results in every respect.

Disclosure of the invention

In the following the invention will be described with its advantages with reference to drawings and exemplary embodiments. The object of the invention is not limited to the illustrated and described embodiments.

Advantages of the invention

The present invention is suitable for significantly reducing the bus load in the individual bus systems by dividing the respective bus network, that is, for example, the vehicle network. It advantageously represents a solution, which is particularly cost-effective in comparison with existing gateway solutions, for this division into subnetworks. Such a device according to the invention is also referred to below as a CAN switch. However, the designation as a CAN switch is only to be understood as limiting the field of application insofar as properties of the CAN protocol are used for the method according to the invention or in the device according to the invention. It also includes CAN FD in particular.

An advantage of the device according to the invention is that it manages without extensive software for processing the received messages, which saves programming and development effort and also costs for the provision of the necessary computing power can. The inventive method can be implemented in a device according to the invention largely in hardware.

If one wishes to provide the full gateway functionality and, for example, to further process data contents in the transfer between different bus systems or to assemble different sizes contained in new messages, then the CAN switch according to the invention can be used in combination with a gateway in an advantageous application form, which then becomes clear can be designed smaller and cheaper, since the upstream CAN switch, the forwarding of the messages, which should not be changed, the gateway decreases and thereby relieves the gateway.

A further advantage of the device according to the invention is that it provides a possibility of carrying out a prioritization independent of the values of the assigned identifiers or identifiers for forwarding the messages. This makes it possible to influence the average latency for the forwarding, which is advantageous in comparison to a reassignment of the identifiers on the bus systems, for example because it requires less coordination effort.

Another advantage is that by using the CAN switch, the vehicle network can be built in a star shape, which is often regarded as advantageous with respect to the existing possibilities for laying the cables in the vehicle structures.

It is by combining with different protocol converters

advantageously possible, the CAN switch also for integration of other bus systems, such. Ethernet, LIN, etc. in a common network with one or more CAN bus systems.

Another significant advantage is that the network built up with the CAN switch is robust compared to the previous version. defective subnets. So you can do the CAN switch also be used to decouple particularly vulnerable bus systems, for example in the front or rear of particularly worthy bus systems.

Due to the reduced utilization of the individual subnetworks or bus systems which are interconnected with the CAN switch, the use of the CAN switch advantageously achieves a shorter mean latency for the data transmission, at least among the subscribers of a bus system. drawings

The invention will be explained in more detail with reference to the drawings.

FIG. 1 shows an example of bus systems connected by the device according to the invention.

Figure 2a shows a gateway according to the prior art. FIG. 2b shows a gateway which can be used in conjunction with the device according to the invention.

FIG. 3 shows a schematic block diagram of a first

Embodiment of a device according to the invention.

FIG. 4 shows a schematic block diagram of a second one

Embodiment of a device according to the invention.

FIG. 5 shows by way of example a flowchart of the invention

Receiving process. FIG. 6 shows by way of example a flow diagram of the invention

Sending process.

Figure 7 shows an embodiment of the structure of the forwarding memory according to the invention. Description of the embodiments

In the following, exemplary embodiments of the method and the device according to the invention will be described. These concrete examples become the

Explanation of execution used, but do not limit the scope of the inventive concept.

FIG. 1 shows an example in which four bus systems B1, B2, B3 and B4 are interconnected by a device 100 according to the invention. Participants are interconnected by the individual bus systems, for example, subscribers 101 and 102 through the bus systems D1 and so on. The subscribers connected by one of the bus systems Bl, B2, B3 B4 can exchange messages via the respective bus system, for example in accordance with the specifications of the CAN or TTCAN protocol. In addition, messages between the different bus systems B1 to B4 can be exchanged by the device 100 according to the invention. Messages which are present on the bus system Bl can be forwarded, for example, to the bus systems B3 and B4, so that the subscribers 105 and 106 or 107 and 108 can receive the messages. Whether the participants actually receive the message here, as described above, depending on the identifier or the identifier. Likewise, the others may be connected to the device 100

Bus systems B2, B3 and B4 messages are passed through the device 100 to one or more other connected bus systems.

Of course, more or less than four bus systems can be interconnected.

FIG. 2 a shows a block diagram of a prior art CAN gateway 200, which can take over the task of the device 100 from FIG. A central microprocessor 201 is connected via lines 203a to 203d to a plurality of, in the illustrated example, four independent CAN controllers 202a to 202d, which use the CAN communication by means of the

Connections 204a to 204d perform on the four connected bus systems. Regardless of whether the news is unchanged from a Bus system must be passed to another bus system, the microprocessor 201 must read the data received, edit, and output to the respective CAN controller 202a to 202d. This creates a load on the microprocessor that is not really necessary.

FIG. 2 b shows a block diagram of a device 210 which is improved relative to the CAN gateway 200 and which can take on the task of the device 100 from FIG. It is composed of a much simpler CAN gateway 211 and a CAN switch 300 according to the invention. According to the invention, the CAN switch 300 takes over the transmission of unaltered messages from one bus system to another, while the gateway is only used when message contents are to be changed, rearranged, or assembled to new content. In an embodiment not shown separately, it is of course also possible for the CAN gateway 200 to be completely replaced by the CAN switch 300. This is particularly feasible if none of the above actions, so change, resorting, or new composition of messages to be performed. The CAN Switch 300 does not require a microprocessor itself, as it does not require any elaborate arithmetic operations

must perform. The detailed structure of the CAN switch is exemplified in more detail in Figures 3 and 4.

FIG. 3 shows the essential elements of the CAN switch 300 according to the invention. The heart of the CAN switch 300 is the relaying unit 304, which is connected to a plurality of, in the example shown, four CAN controllers 305a to 305d. Furthermore, the relaying unit 304 communicates with the forwarding memory 303, as well as with a

Filter information unit 302. The CAN controllers 305a to 305d are in communication with CAN transceivers 306a to 306d, which in turn are each connected to a CAN bus system Bl to B4. Optionally, the CAN switch 300 additionally comprises a configuration memory 301, which contains configuration and / or initialization data, for example for the filter information unit 302, the relaying unit 304 and the CAN controllers 305a to 305d can. Alternatively, these data can also be supplied to the CAN Switch 300 via a suitable interface.

Messages arriving from one of the bus systems are read in via a CAN transceiver 306 and a CAN controller 305 and handled by the receiving process running on the relaying unit 304. Depending on the content of the filter information unit 302, the read-in message is stored by the receiving process in the forwarding memory 303 or not.

In addition, the messages are also attached depending on the content of the filter information unit 302 data that indicate to which of the bus systems the message is to be passed. In addition, time information and / or prioritization information with the message can also be stored in the forwarding memory 303. Depending on this information, the messages stored in the forwarding memory 303 are output by the transmission process running on the relaying unit 304 on the provided bus systems.

The filter information unit 302 may, for example, be specified

Memory area in which the information is stored, which specify which messages from a given bus system, e.g. Bl, to which other bus systems, e.g. B2 and B4, to be passed. For example, it can be subdivided into a configurable number of data structures, with each data structure in a first data field being the same

Name of the bus system contains, from which the message is to be received, in a second data field, the identifier

or contains the identifier of the message to be received, and in one or more other data fields, the name of the bus system or the bus systems to which or which the message in question is to be transmitted. Alternatively, for example, ranges of acceptors to be accepted which are collected by a bus system, e.g. Bl, to another bus system, e.g. B2 or B4, to be passed. This can be done, for example, by intervals or by masking. Other data fields within a data structure can

For example, include prioritization information, which on the Transfer unit 304 to be entered for example in the forwarding memory 303 and / or be used by the running on the relaying unit 304 transmission process for prioritization. The optional configuration memory 301 is described as writable, non-volatile

Memory area, pronounced as EEPROM, for example. He can

For example, the configuration data for the CAN controller 305a to 305d, such as baud rate, bit timing parameters, etc. included. It can also contain the filter data and assignment data (identifiers, identifier intervals, masks, designation of the bus systems), which according to the preceding

Section in the filter information unit 302 are needed. Also

Prioritization information can be stored here, which via the

Filter information unit 302 or directly to the relaying unit 304 and / or the forwarding memory 303 can be transferred for consideration in the transmission process.

The forwarding memory 303 may, for example, be formed as a dynamic or static allocated memory area in which the messages selected for forwarding together with the additional ones

Information is stored as a continuous sequence of data structures. On the one hand, the memory area is sufficiently large to be selected, so that as many messages as possible can be stored in the forwarding memory even in the event of high data volumes. At the same time, the receiving process provides for discarding messages at full forwarding memory (see FIG. 5).

The relaying unit 304 may, for example, be designed as a microcontroller or ASIC. Essentially, it carries out two processes, firstly the reception process and secondly the transmission process. Both processes will be described in more detail in connection with FIGS. 5 and 6.

The CAN controllers 305a-d as well as the CAN transceivers 306a-d are standard components from the state of the art. They can be integrated as a single circuit, semi-integrated or separated from one another. Likewise, other components 301 to 304 the CAN switch according to the invention with each other or with the CAN controllers and / or CAN transceivers integrated or executed separately.

FIG. 4 shows an alternative embodiment 400 of the CAN switch according to the invention. In this embodiment, a CAN controller 305d and a CAN transceiver 306d is replaced by a protocol converter 405, in the illustrated case from CAN to Ethernet, and by an Ethernet protocol controller with integrated transceiver 406. Of course, several of the CAN modules could be replaced by corresponding modules. Instead of Ethernet, another bus protocol, e.g. LIN, MOST, etc. are used when the necessary protocol converters, protocol controllers and transceivers 405 and 406 are used. This makes it possible to expand the CAN switch to a gateway for various interconnected bus systems. In the illustrated case, in addition to three CAN bus systems, an Ethernet bus system could additionally be connected by the CAN switch, so that messages can be exchanged between the CAN bus systems and the Ethernet bus.

FIG. 5 illustrates in the form of a flowchart an example of the

inventive receiving process, which runs on the relaying unit 304. In element 501, a poll is cyclically issued as to whether a new message has been received. As soon as this question is answered in the affirmative, a receive counter is incremented in element 502. This is followed by a query in item 503 as to whether the received message is in accordance with the information in the

Filter information unit 302 is to be accepted or not. Will the

If the message is accepted, then a query is made in element 504 as to whether the rendering unit 304 has room for another message.

There are now two cases to distinguish: If there is enough space, the message is entered in element 508 in the forwarding memory 303. Subsequently, in the forwarding memory 303, a transmission bit provided for this purpose is set for each bus system on which the received message is to be forwarded. Furthermore, additional information, For example, the reception time, the priority of the message or other relevant information in the forwarding memory 303 are entered. For this purpose, information from the filter information unit 302 can also be used.

Returns the query in item 504 that there is not enough room in the

Relay unit 304 is present, then in element 505, a prioritization of the messages depending on the present in the forwarding memory 303 information for prioritization, for example, depending on their identifier, from the time of arrival or from the period of time, they in

Forwarding memory 303 are present, or of other criteria, which were stored in the forwarding memory. It is also possible to use combinations of the criteria mentioned for the prioritization. In element 506, the lowest priority message selected in the context of prioritization is discarded, and in element 507, an associated loss counter is subsequently incremented. Finally, as described above, in element 508, the newly arrived message with the send bits and the additional ones

Information entered in the freed memory area.

FIG. 6 shows in the form of a flow chart an example of the

transmission process according to the invention, which runs on the relaying unit 304. In element 601, a poll occurs cyclically, whether in

Forwarding memory 303 present at least one message with set send bit. If this is the case, then in item 602 that message

selected, which has the highest priority with respect to the transmission. This priority can be derived, for example, from identifier, from the time of arrival or from the time span which they present in forwarding memory 303, or from further criteria which have been stored in the forwarding memory. Again, combinations of the mentioned criteria can be used for the prioritization. The same priority information can be used for the selection of the highest priority message to be sent as for the selection of the lowest priority message to be dropped in the

Receiving process are used. But it can also be two

different values, a send priority and a rejection priority and be used. In item 603 that becomes that way

selected message is forwarded to the associated CAN controller 305a to 305d, from which it can communicate with the means of the usual CAN protocol and depending on the CAN bus configuration parameters, which the CAN

Controller has received, for example, from the configuration memory 301. In element 604, an associated transmit counter is incremented and in element 605 the transmit bit is reset. The send process then switches back to the cyclic query of element 601.

There are various possibilities for the execution of the transmission process and the reception process in the relaying unit 304: In one possible embodiment, only one transmission process according to FIG. 6 and FIG

Receiving process according to Figure 5 in the relaying unit 304 from. In another embodiment, separate broadcast processes and or

Receive processes for each of the connected bus systems or groups of connected bus systems. The assignment of the messages to the

various interconnected bus systems are within the process or multiple processes stored in the routing memory 303

Information, for example through the different bus systems

assigned send bits. The assignment is explained in more detail in connection with FIG.

Figure 7 shows schematically the structure of a forwarding memory 303. it consists of a plurality of memory area 701, the size and

Addressing can be fixed or can be adapted dynamically. Each of the storage areas 701 contains a message entry composed of a plurality of pieces of information. In one possible embodiment, each message entry contains a reception time 702, a series of transmission bits 703, as well as the complete content of the received message 704. The complete content of the message may be a bit-accurate image of the original message, but only the data of the message are stored, which carry information and are not specified by the CAN protocol. In particular, entry 704 must include the identifier and content of the data field, while, for example, the CRC field or the acknowledge bit could be omitted. In the subarea 702, as an alternative to the time of reception, a prioritization information could also be stored. Of course, this could also be stored as an additional entry in a separate, not shown subregion of the memory area 701. In the sub-area 703 are the various transmission bits, wherein in a preferred embodiment, a transmission bit is maintained at least for each of the connected buses. It is also possible to keep a number of transmission bits, which corresponds to the maximum number of connectable buses. Determines the relaying unit 304 based on the

Filter information unit 302 or the configuration information 301 that a message received from the bus system Bl message is to be sent, for example, on the bus systems B2 and B4, the B2 and B4 associated send bits are set in the sub-area 703. The sending then takes place, as described in connection with FIG. 6, by one or more transmission processes taking place in the forwarding unit 304.

Claims

claims

1) Method for data transmission between at least two bus systems (Bl, B2, B3, B4) connected to one another by a device (300), each having at least one participating data processing unit (101-108), which send messages via the bus system in which it participates and receive, the messages containing identifiers,

characterized in that for each message that is present on at least one of the device connected to the bus systems (Bl, B2, B3, B4), based on an identifier of the message and a filter information unit (302) provided in this filter information is decided whether the message is cached in a forwarding store (303).

2) Method according to claim 1,

characterized in that messages which are present in the forwarding memory (303) are forwarded to at least one of the further bus systems (Bl, B2, B3, B4) connected to the device, wherein based on a memory area stored in a memory area

Assignment information is selected to which or which of the other bus systems (Bl, B2, B3, B4) connected to the device, the messages present in the forwarding memory (303) are forwarded.

3) Method according to claim 2,

characterized in that it is decided on the basis of a stored in a designated memory area first prioritization information which at least one of the in the forwarding memory (303) cached messages, which of the messages in the

Forwarding memory (303) were cached, each next to the at least one on the basis of the assignment information selected bus system (Bl, B2, B3, B4) is forwarded. 4) Method according to one of claims 1 to 3,

characterized in that based on a stored in a designated memory area second prioritization information, which is associated with at least one of the caching messages in the forwarding memory (303), it is decided which of the messages that have been cached in the forwarding memory (303), if discarded there is not enough space in the forwarding memory (303) to store a new message present on one of the bus systems (B1, B2, B3, B4) connected to the device.

5) Method according to one of claims 2 to 4,

characterized in that the assignment information in the

Filter information unit (302) is stored. 6) Method according to one of claims 3 to 5,

characterized in that the first prioritization information and the second prioritization information are determined using the time of receipt of the respective message and / or the duration of the message in the

Forwarding memory (303) and / or a size, which in the

Filter information unit (302) is stored, derived.

7) Method according to one of claims 1 to 6,

characterized in that the first prioritization information and the second prioritization information are the same value.

8) Method according to one of claims 1 to 7,

characterized in that at least one of the bus systems connected by the device is a CAN bus system according to the standard ISO 11898 or a CAN FD bus system.

9) Method according to one of claims 1 to 8,

characterized in that at least one of the connected

Bus systems is a bus system which is subject to a second, different from the CAN protocol and the CAN FD protocol protocol, or an Ethernet Network, wherein in the device, a converter (405) is provided, which carries out the implementation of the messages between the CAN protocol and the second protocol. 10) Method according to one of claims 1 to 9,

characterized in that in the forwarding memory (303) registered messages that have been discarded before the successful transmission, are counted by a designated loss counter. 11) Method according to one of claims 1 to 10,

characterized in that the messages entered in the forwarding memory (303) which have been successfully transmitted are counted by a transmission counter provided therefor.

12) Device (300) for data transmission between at least two bus systems (Bl, B2, B3, B4) connected to the device, each having at least one participating data processing unit (101-108), which send messages via the bus system in which it participates can receive, the messages contain identifiers,

13) Device according to claim 12,

characterized in that the data transmission according to one of the methods according to claim 2 to 11 is performed.

14) gateway (210) for connecting a plurality of bus systems,

characterized in that the gateway comprises a device according to one of claims 12 or 13.