Communication method and system for motor vehicles

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DESCRIPTION

Procedure and communication device for motor vehicles

Technical field of the invention

The present invention refers to a method and a communication device in a network installed on board, in particular, of a motor vehicle, compatible with the LIN standard, in order to optimize the load on this network.

Technological background of the invention

The installation of an increasing number of electromechanical devices in motor vehicles has led to the multiplication of electrical circuits. To reduce the increasing complexity of cabling, techniques of the "network" or "bus" type have been adapted; already known in the field of computing, to the requirements of the automotive world.

Essential vehicle functions are typically performed "under the hood" using a high-speed, real-time network that connects to an electronic control unit (ECU is the established term for Electronic Control Unit), the actuators and the actuators. sensors for the engine, transmission, braking system, suspension, frame, etc. Often used for these functions is a Local Network of Controllers, or CAN (English acronym for Controller Area Network) that offers a high degree of security and a speed of the order of 1 Mbit / s.

For other less essential safety functions and comfort functions, called “cabin functions,” automobile manufacturers and semiconductor manufacturers have developed a Local Interconnect Network, or LIN (Local Interconnect Network).

This low cost secondary network is based on a UART / SCI interface that is standard for most microcontrollers. It works on the CAN bus and is specifically used for applications such as power mirrors, power seats, central locking, power windows and lighting systems.

From the initial version 1.0 of 1999 to version 2.0 of 2003, the specifications of the LIN network have undergone several evolutions that tend to facilitate the integration of a network and to improve the characteristics in real time.

All the details of these specifications are well known to the person skilled in the art, and only those necessary to understand the invention will be recalled below.

The exchange of information in the LIN network is based on the presence of a master station and one or more slave stations. Communication is always carried out at the initiative of the master station which sends a message header comprising a silence followed by a synchronization byte, and an identification or identifier byte.

A slave station that has decoded a predetermined identifier transmits a data frame in response comprising two, four, or eight bytes of data and a checksum.

The header and the data frame form a message frame.

It should be noted that the message identifier is representative of the content of the message, but not of its destination.

An IDF identifier [7: 0] consists of an identifier ID [0: 5] encoded in six bits and with two parity bits PO = ID0 + ID1 + ID2 + ID4 (mod. 2) and P1 = ID1 + ID3 + ID4 + ID5 (mod. 2).

There are 64 different identifiers, but only the first 60 (between 00 and 3B, in hexadecimal representation) correspond to message frames.

The last four identifiers are special identifiers, particularly for control, configuration and diagnostic frames.

The following table lists valid identifiers and identifiers according to revision 2.0 of the LIN protocol specifications:

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Table I

<td>Identifier ID [0: 5]</td><td>Identifier ID [7: 0]</td><td>Frame type</td>

<td>00 to 3B</td><td>P1P0ID [5: 0]</td><td>Message frame</td>

<td>3C</td><td>3C</td><td>Command frame (request from master station)</td>

<td>3D</td><td>7D</td><td>Command frame (request of the slave station in the frame)</td>

<td>3E</td><td>FAITH</td><td>User defined extended raster</td>

<td>3F</td><td>BF</td><td>Future extended type plot</td>

During the evolutions of the standard, the main characteristics of the LIN network have remained basically unchanged, and its speed is always limited to 20 Kbits / s due to limitations of electromagnetic compatibility and clock synchronization without the use of quartz or ceramic resonators. .

However, the "cabin functions" show an increasing consumption in the passband, in particular those concerning the advanced lighting system type AFS (Advanced / Adaptive Front Light System).

Directional lighting devices of the DBL type (English acronym for Dynamic Bending Light), or automatic adjustment of the level of the headlight beams based on the attitude of the vehicle of the LVL category (English acronym for Leveling of Vehicule Light), Connected via the network to the dedicated LCS (Light Control System) on-board computer, they require very short response times.

The extension of the network to control future applications such as multixenon headlights, ballasts or LEDs will further increase the load on the bus.

A first solution to absorb the increase in network load would be to increase the speed of the network. But the initial benefits (low cost, low disturbance) of the LIN network would be lost.

A second solution would be to change the standard and implement more advanced networks such as CAN, but here too the cost would be an obstacle.

A method using an extension of the LIN protocol is known from patent application US 2003/0070019 A1. This procedure allows the spontaneous transmission of information by slave stations, beyond the normal transmissions within a standardized cycle of interrogations or commands by the master station. In a space of time that separates the end of a message frame from the beginning of the next, a slave station with the opportunity to transmit information without being previously directed to the total duration of a standard cycle of interrogations-responses or commands- Answers remains at best unchanged from the norm.

There is, therefore, a need to optimize the load of a LIN network in order to preserve this economic standard for all the “cabin functions”, and in particular the management of the advanced lighting systems, present and futures, of the AFS type.

General description of the invention

The present invention therefore concerns a communication method in a network installed on board, in particular a motor vehicle, between a master station and a multitude of slave stations, of the type of those compatible with the standardized Network protocol. Local Interconnection (LIN).

In these methods, in a known manner, the slave stations transmit data frames on a serial bus in response to the emission by the master station of identifiers representative of the required content of these frames.

The method according to the invention is characterized, for its part, in that all or a part of each of the specific data frames linked to the same predetermined identifier is sequentially formed by each of the slave stations.

According to a first preferred embodiment of the invention, the slave stations broadcast a series of specific data frames in response to the transmission by the master station of a succession of several instances of this predetermined identifier in a number equal to that of the slave stations.

Very advantageously, each of the slave stations also emits an end-of-frame block composed of a checksum calculated on the series of specific data frames.

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Also advantageously, the master station issues an additional identifier before each broadcast of the succession of several instances of the predetermined identifier.

It benefits from the fact that this predetermined identifier is representative of a frame with response in the frame, and also that the additional identifier is representative of a request for the status of the slave stations.

Preferably, these default and additional identifiers are respectively composed of 7D and 3C bytes in hexadecimal representation.

According to a second preferred embodiment of the invention, each of said specific data frames is made up of several subframes of equal length and in a number equal to the number of slave stations.

In this second form, the last of the slave stations that must sequentially transmit the last of the subframes advantageously consecutively transmits an end-of-frame block preferably composed of a checksum calculated on all these sub-frames.

The invention also refers to a communication device in a network installed on board, in particular of a motor vehicle, characterized in that it consists of means for implementing the communication method described above.

The present application also refers to an information storage medium, characterized in that it stores one or more programs whose execution allows an implementation of the communication method according to the invention.

The same happens with a computer program in an information storage medium that consists of one or more sequences of instructions executable by an information processing unit such as a microprocessor, microcontroller, computer and / or state machine, allowing the execution of said sequences of instructions an implementation of the procedure briefly described above.

Another object of the present invention is a vehicle, in particular an automobile, characterized in that it implements a communication device, an information storage medium, or a computer program that respectively presents the characteristics set forth above.

These few essential specifications will have made clear to the person skilled in the art the advantages provided by this communication method in an on-board network compatible with the LIN protocol over the standard.

Detailed specifications of the procedure, and of a device adapted for its implementation, are given in the description that follows in connection with the accompanying drawings. It should be noted that these drawings have no other purpose than to illustrate the text of the description and do not in any way constitute a limitation of the scope of the invention.

Brief description of the drawings

Figure 1 schematically shows a series of standard LIN protocol message frame schedules.

Figure 2 schematically shows a series of standard LIN protocol command frame schedules.

Figure 3 schematically shows a series of command frame schedules implemented in the procedure according to the invention compatible with the LIN standard.

Figure 4 schematically shows a series of message frame schedules implemented in the method according to the invention compatible with the LIN standard.

Figure 5 is a schematic view of a control device for a directional lighting and headlamp adjustment system that implements the method according to the invention.

Description of some preferred embodiments of the invention

In order to show the differences between the data exchange schedules according to the protocol implemented by the invention and the schedules of the message and command frames of the standard LIN protocol, some examples of the latter have been represented, as an indication. , in Figures 1 and 2, respectively.

In Figure 1, the trace of the master station M shows that it emits on the bus a succession of identifiers 1 of values ​​IDF1, IDF2, IDF3, IDF4 between 00 and 3B, which correspond to message frames.

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This broadcast is filtered by four slave stations S1, S2, S3 and S4 that permanently listen to the traffic on the bus.

When one of the four stations S1, S2, S3, S4 recognizes an identifier 1 to which it is programmed to respond, it puts on the bus a specific data frame 2 of value DF1, DF2, DF3 or DF4 followed by a checksum 3 of CKS1, CKS2, CKS3, or CKS4 values.

The master station M of FIG. 2 emits on the bus a succession of identifiers 1 of values ​​3C and 7D that correspond to some command frames (see table I).

The request identifier 3C of request 4 of the master station M is followed by a data frame 5 of value NAD1, NAD2, NAD3 or NAD4 that allows one of the three slave stations S1, S2 or S3 to which the command is intended to be identified. The receiving station immediately transmits a specific data frame 3 of value DF1, DF2 or DF3 when it decodes the corresponding trigger identifier 7D 6.

Either by means of message frames (Figure 1) or by means of command frames (Figure 2), the standard protocol of the LIN network requires that a complete frame of data 2 of a length of two, four or eight be used bytes for each read of a status from a slave station.

For example, in the case of eight-byte frames, the LIN network only allows one frame every 10 ms at least, from which it follows that with the more slave stations S1, S2, S3, S4 the network has, the greater the periodicity of reading its status regardless of the length of the status word 2 to be transmitted.

As the general description of the invention has already briefly indicated, the principle of the communication procedure illustrated in the schedules of Figures 3 and 4 consists in sharing a data frame transmitted in response to an identifier between several slave stations.

According to the first embodiment of the invention, which corresponds to FIG. 3, the master station M will issue an identifier 4 of value 3C, that is to say a master request, to all the slave stations S1, S2, S3, S4.

These respond in turn in the frame initiated by the identifier 4 of code 3C upon receiving a succession of trigger identifiers 6 of code 7D by putting their specific data frames 7 of values ​​DS1, DS2, DS3 and DS4 in series on the bus followed by end-of-frame blocks 8 composed of respective CKS1, CKS2, CKS3 and CKS4 checksums.

Comparison of the schedules of Figures 1 and 3 makes clear the reduction in bus load achieved by the method according to the invention. Indeed, the status words 7 of the slave stations S1, S2, S3 and S4 issued in a command frame are advantageously shorter than the minimum of two bytes of a message frame. The same observation is necessary when comparing Figures 2 and 3. Indeed, there is no transmission of identification data 5 of the stations in the network.

According to the second embodiment of the invention, which corresponds to figure 4, the verification of the status of the slave stations S1, S2, S3 or S4 by the master station M is carried out by the master station by sending an identifier 1 of understood code between 00 and 3B, that is, an identifier 1 that corresponds to a message frame.

In response to this identifier 1, each of the slave stations S1, S2, S3 and S4 in turn emits a subframe 9 of value D1, D2, D3 or D4 in order to fill the data frame of the message.

The last slave station S4 completes the series of transmitted subframes 9 by a checksum 10 calculated on the set of these subframes 9.

The advantage of this second embodiment of the invention in terms of bus load with respect to the standard LIN protocol also appears clearly when comparing the schedules of Figure 4 with those of Figures 1 and 2:

- transmission of the same message identifier 1 for several slave stations S1, S2, S3, S4;

- a single data frame for the four slave stations instead of a full frame 2 per station;

- a single checksum 10.

The implementation of the communication method according to the invention in a LIN network 11, 12 used to control a directional lighting system 13, 14 and for adjusting the headlights 15, 16, as represented schematically in figure 5, translates into a clear improvement in system response time.

The master station of the network is a dedicated on-board computer 17 that constitutes the lighting control system (LCS).

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This calculator 17 usually comprises a central processing unit 18, of the microprocessor, microcontroller or similar type, a pre-recorded program memory 19 of the ROM type, a working memory 20 of the RAM type, and preferably a non-storage memory 21. FLASH type volatile.

These elements 18, 19, 20, 21 are structured around an internal bus 23 connected to an interface module 22 for the exchange of I / O information with the outside.

The interface module 22 comprises a UART 24 adapted to manage the serial communication protocol of the two left and right branches of a LIN network 11, 12 in which four slave stations 13, 15, 14, 16 composed respectively, are connected, on the one hand, by the DBLI left directional lighting system and the left headlight adjustment system and, on the other hand, by DBLD Right Directional Lighting System and LVLD Right Headlight Adjustment System.

These slave stations 13, 14, 15, 16 consist in a manner known per se of standard LIN interface circuits and network controllers that allow it to dialogue on the bus with the master station 17. These network controllers are microprogrammed from such that they sequentially generate the frames 7 or parts 9 of frames in response to the identifiers 1, 4, 6 emitted.

The control data of these systems 13, 14, 15, 16 depend on some parameters resulting from the functions "under the hood", such as the speed of the vehicle, or its attitude; the interface module 22 is therefore also connected to the CAN bus 25 of the vehicle.

Under the standard LIN network protocol, the actuators of the DBLI, LVLI, DBLD, LVLD systems are controlled together by a command frame, and the status sensors are read individually by a message frame.

A read / write sequence is traditionally the following:

<td>to)</td><td>command of the four DBLI slave stations,</td><td>LVLI,</td><td>DBLD, LVLD</td>

<td>b)</td><td>read DBLD;</td><td></td><td></td>

<td>c)</td><td>command of the four DBLI slave stations,</td><td>LVLI,</td><td>DBLD, LVLD</td>

<td>d)</td><td>reading DBLI;</td><td></td><td></td>

<td>and)</td><td>command of the four DBLI slave stations,</td><td>LVLI,</td><td>DBLD, LVLD</td>

<td>F)</td><td>reading LVLD;</td><td></td><td></td>

<td>g)</td><td>command of the four DBLI slave stations,</td><td>LVLI,</td><td>DBLD, LVLD</td>

<td>h)</td><td>LVLI reading.</td><td></td><td></td>

As already recalled, the LIN network only allows one frame every 10 ms at least, resulting in a delay of 80 ms between two consecutive readings of the status of a given slave station. This delay is not negligible when the limitation relative to the response time of the system is of the order of 40 ms to 100 ms, and when a degraded mode must be detected and indicated in less than 3 s.

When implementing the first embodiment of the communication method according to the invention, an example of a control sequence of the AFS systems 13, 14, 15, 16 is traditionally the following:

a) command of the four slave stations DBLI, LVLI, DBLD, LVLD;

b) issuing the read status command (3C);

c) command of the four slave stations DBLI, LVLI, DBLD, LVLD;

d) reading of the four slave stations DBLI, LVLI, DBLD, LVLD.

The duration of a control cycle is therefore reduced to 70 ms.

The use of the second embodiment of the communication method according to the invention leads to a further reduction in the cycle time. In this case, an example of a control sequence for AFS systems 13, 14, 15, 16 is traditionally the following:

a) command of the four slave stations DBLI, LVLI, DBLD, LVLD;

b) reading of the four slave stations DBLI, LVLI, DBLD, LVLD.

The duration of a control cycle is therefore only 20 ms.

In a manner known per se, the sequences of instructions that make it possible to carry out the previous control sequences or cycles are preferably stored in the ROM 19 of the LCS calculator 17.

They are preferably machine instructions, but in an equivalent way, they can be sequences of a control language interpreted by the CPU 18 at the time of their execution.

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The implementation of the communication method described above by means of a microprogrammed device, or even a wired logic of the ASIC type, would not go beyond the scope of the invention.

The person skilled in the art will have understood, in view of the foregoing, that a vehicle, in particular a motor vehicle equipped with the communication device, with the information storage medium and with the computer program described above, benefits from a lower cost of an on-board network architecture that can accommodate the most advanced electronic security and comfort systems, and therefore presents an obvious competitive advantage.

Obviously, the invention is not limited to the only two preferred embodiments described above.

On the contrary, it covers all other possible variants of realization, compatible with the LIN standard and its future developments, insofar as these are derived from the following claims.