Communication method and system for motor vehicles

[0001] The invention relates to a method and apparatus for communication in an embedded network, in particular a motor vehicle, in accordance with the LIN standard, to optimize the load on this network.

Technological background of the invention [0002] The use of an increasing number of electromechanical devices in motor vehicles has led to the multiplication of the number of electrical circuits. To reduce the increasing complexity of the cabling, it has been adapted to the requirements of the mechanical industry, to the type of "network" or "bus" technology already known in the field of computer science.

[0003] The basic functions of the vehicles are generally performed "under the engine hood", using high-speed real-time networks connecting to the electronic control unit (the English acronym ECU is the equivalent to the Electronic Control Unit) actuators and engine sensors, transmission, braking system, suspension, chassis, etc. A serial communication network or CAN (English acronym for Controller Area Network), providing a high level of security and bandwidth of 1 Mbit / s, is often used for these functions.

[0004] For other, less important safety and comfort functions, called "passenger compartment functions", the local communication network or LIN (English acronym for Local Interconnect Network) was developed by car builders and semiconductor manufacturers.

[0005] This low cost secondary network is based on the UART / SCI interface, which is standard for most microcontrollers. It works with the CAN bus and is especially used in applications such as electrically adjustable mirrors, electrically adjustable seats, central locks, window lifting and lighting systems.

[0006] From version 1.0 of 1999 to version 2.0 of 2003, the technical features of the LIN network have undergone numerous changes resulting in easier network integration and improved real-time features.

[0007] All details of these features are well known to the person skilled in the art and only those necessary for understanding the invention will be listed below.

[0008] Information exchange in a LIN network is based on the presence of one parent node and one or more slave nodes. Communication is always initiated by the parent node, which sends a message header containing silence followed by a synchronization octet and an identification octet or identifier.

[0009] After decoding the predetermined identifier, the slave node in response transmits a data frame containing two, four or eight data octets and a checksum.

[0010] The header and the data frame form a message frame.

[0011] It should be noted that the message identifier is representative of the message content, but not its purpose.

[0012] The IDF [7: 0] is formed from the ID [0: 5] encoded in six bits and two parity bits PO = ID0 + ID1 + ID2 + ID4 (mod.2) and P1 = ID1 + ID3 + ID4 + ID5 (mod. 2).

[0013] There are 64 different identifiers, but only the first 60 (from 00 to 3B, in hexadecimal) correspond to message frames.

[0014] The last four identifiers are special identifiers, particularly control frames, configuration and diagnostics.

[0015] The following table lists identifiers and identifiers allowed according to version 2.0 of the LIN protocol specification:

Table I

<td>Identifier ID [0: 5]</td><td>Identifier IDF [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>Control frame (master node request)</td>

<td>3D</td><td>7D</td><td>Control frame (slave node response in frame)</td>

<td>3E</td><td>FE</td><td>User-defined extended gateway</td>

<td>3F</td><td>BF</td><td>Future extension type gateway</td>

[0016] During the standard changes, the main properties of the LIN network were not thoroughly changed and its bandwidth is still limited to 20 Kbit / s due to the requirements of electromagnetic compatibility and clock synchronization without the use of quartz or ceramic resonator.

[0017] Well, "passenger compartment functions" are increasingly demanding in terms of bandwidth size, especially those belonging to the AFS (Advanced / Adaptative Front Light System) type lighting.

[0018] Directional lighting devices type DBL (English acronym Dynamic Bending Light) or automatic adjustment of the headlight beam level depending on the location of the car relative to the ground of the LVL category (English acronym Levelling of Vehicule Light), connected by a network with an individual LCS on-board computer (English acronym Light Control System), require very short response times.

[0019] Expanding the network to control future applications such as multi-xenon headlights, ballasts, LED lights will further increase bus load.

[0020] The first solution to address the increase in network load would be to increase its capacity. But the initial advantages (low cost, low interference) of the LIN network would be lost.

[0021] A second solution would be to change the standard and use more developed networks such as CAN, but in this case the cost would be daunting.

[0022] From the patent application US 2003/0070019 A1 a method is known which refers to the extension of the LIN protocol. This method allows direct information transmission from slave nodes, except for normal transmissions within the standard query or command cycle through the parent node. In the time interval separating the end of the message frame from the next, the slave node has the ability to send information without first addressing it, for the total duration of the standard cycle of response queries or response commands, remaining at least unchanged from the norm.

[0023] There is, therefore, a need to optimize the load on the LIN network to maintain this economic standard for the "passenger compartment function" assembly, in particular for controlling current and future lighting systems of the AFS type.

General description of the invention [0024] The invention aims at a method of communication in an embedded network, in particular a motor vehicle, between a master node and a number of slave nodes of the type according to the standard local communication network (LIN) protocol.

[0025] In these methods, as is known, data frames are transmitted by slave nodes in a serial bus in response to the sending by the parent node of identifiers representative of the required content of these frames.

[0026] The method according to the invention is characterized in that all or part of each of the specific data frames connected to the same predetermined identifier is created sequentially by each of the child nodes.

[0027] According to a first preferred embodiment of the invention, a series of specific data frames are transmitted by slave nodes in response to sending by the master, a string of several instances of this predetermined identifier in a number equal to the number of slave nodes.

[0028] Very preferably, each of the slave nodes also sends a frame end block, formed from a checksum calculated on a number of specific data frames.

[0029] Preferably, an additional identifier is also sent through the parent node, before each transmission of a series of several instances of the predetermined identifier.

[0030] Preferably, the predetermined identifier is representative of the frame with a response in the frame and also the additional identifier is representative of the state request of the slave nodes.

[0031] Preferably, these predetermined and additional identifiers are respectively formed from hexadecimal 7D and 3C octets.

[0032] According to a second preferred embodiment of the invention, each of the specific data frames is formed of several subframes of the same length and in a number equal to the number of sub-nodes.

[0033] In this second example, the last subordinate knots for sequential transmission of the last of the subframes preferably send sequentially a frame end block, preferably formed from a checksum, calculated on the whole of these subframes.

[0034] The invention also relates to a communication device in an embedded network, in particular a motor vehicle, characterized in that it comprises means for implementing the communication method described above.

[0035] An information storage medium, characterized in that it remembers one or more programs, the execution of which allows the communication method according to the invention to be carried out, is also an object of the invention.

[0036] Similarly, this applies to a computer program on an information storage medium containing one or more instruction sequences executable by an information processing unit, such as a microprocessor, microcontroller, computer and / or state machine, and the execution of the instruction sequence allows the method described in abbreviate above.

[0037] A vehicle, especially a mechanical one, characterized in that it implements a communication device, an information storage medium or a computer program, representing the respective features listed above, is also an object of the invention.

[0038] These few essential descriptions make the skilled person aware of the advantages that this method of communication provides in a built-in network compatible with the LIN protocol compared to the standard one.

[0039] Detailed descriptions of the method and device adapted to its implementation are provided in the description below with the accompanying drawing. It should be noted that this drawing is intended only to illustrate the text of the description and in no way limits the scope of the invention.

Short description of the drawing [0040]

Fig. 1 schematically shows a series of chronograms of message frames of the LIN standard protocol.

Fig. 2 schematically shows a series of chronograms of LIN standard protocol command frames.

Fig. 3 schematically shows a series of chronograms of command frames implemented in the method according to the invention in accordance with the LIN standard.

Fig. 4 schematically shows a series of chronograms of message frames implemented in the method according to the invention in accordance with the LIN standard.

Fig. 5 is a diagram of an apparatus for controlling the directional lighting system and adjusting the headlights, implementing the method according to the invention.

Description of preferred embodiments of the invention [0041] To properly show the differences between the data exchange chronograms implemented in accordance with the invention and the chronograms of message frames and LIN protocol protocol commands, examples of the latter for memory are given in Figs. 1 and 2 respectively.

[0042] In Fig. 1, the path from the master M shows that it transmits to the bus a series of identifiers 1 with the values ​​IDF1, IDF2, IDF3, IDF4, contained between 00 and 3B, corresponding to message frames.

[0043] This forwarding is filtered by four slave nodes S1, S2, S3 and S4, which constantly monitor bus traffic.

[0044] When one of the four nodes S1, S2, S3, S4 recognizes the identifier 1 to which it is programmed to respond, then places on the bus a specific data frame 2 with the value DF1, DF2, DF3 or DF4 followed by a checksum 3 with the value of CKS1, CKS2, CKS3 or CKS4.

[0045] The master node M in Fig. 2 sends a series of identifiers 1 with values ​​3C and 7D to the bus, corresponding to the command frames (see Table 1).

[0046] Following the identifier 3C of the request 4 of the parent M followed by a data frame 5 with the value NAD1, NAD2, NAD3 or NAD4, enabling identification of one of the three subordinate nodes S1, S2 or S3 for which the command is intended. The destination node immediately forwards the specific data frame 3 with the value DF1, DF2 or DF3 when it decodes the corresponding 7D commissioning identifier 6.

[0047] By means of message frames (Fig. 1) or by means of command frames (Fig. 2), the standard LIN protocol requires the use of the entire data frame 2 with a length of two, four or eight octets each time reading the state of the with a subordinate link.

[0048] For example, in the case of frames of eight octets, with a LIN network allowing only a minimum of one frame every 10 ms, it follows that the more the network has subordinate nodes S1, S2, S3, S4, the greater the periodicity of reading them status, regardless of the length of the status word 2 to be sent.

[0049] As has been briefly pointed out in the general description of the invention, the principle of the communication method, illustrated by the chronograms in Figures 3 and 4, is to divide the data frame sent in response to the identifier between several sub-nodes.

[0050] According to the first embodiment of the invention, corresponding to Fig. 3, the master node M sends an identifier 4 with a value of 3C, i.e. a master request, to all subordinate nodes S1, S2, S3, S4.

[0051] Each of the subordinate nodes in turn corresponds in a frame initiated by the identifier 4 of the 3C code when receiving a sequence of enabling identifiers 6 of the 7D code, placing in series on the bus its specific data frames 7 with the values ​​DS1, DS2, DS3 and DS4 followed by blocks end of frame 8, formed from the corresponding checksums CKS1, CKS2, CKS3 and CKS4.

[0052] The comparison of the chronograms of Figures 1 and 3 shows a reduction in bus load caused by the method according to the invention. Indeed, the status words of the 7 subordinate nodes S1, S2, S3, and S4 transmitted in the command frame are preferably shorter than a minimum of two octets of the message frame; the same statement is made when comparing Figs. 2 and 3. Indeed, there is no transmission of identification data for 5 nodes in the network.

[0053] According to a second embodiment of the invention, corresponding to Fig. 4, the reading of the status of the S1, S2, S3 or S4 subordinate nodes by the superior node M is implemented by sending a code identifier 1 between 00 and 3B, i.e. identifier 1 corresponding to the message frame.

[0054] In response to this identifier 1, each of the sub nodes S1, S2, S3 and S4 sends one subframe 9 with the value D1, D2, D3 or D4 successively to fill the message data frame.

[0055] The last slave S4 finishes the series of subframes 9 sent with a checksum of 10 calculated on the whole of these subframes 9.

[0056] The advantage of this second embodiment of the invention in terms of bus load over the LIN standard protocol is also evident when comparing the chronograms of Fig. 4 with the chronograms of Figures 1 and 2.

- sending the same identifier 1 of the message to several S1 sub-nodes,

S2, S3, S4;

- one data frame for four child nodes instead of one complete frame for each node;

- one checksum 10.

[0057] The implementation of the communication method according to the invention in the LIN network 11, 12 used to control the directional lighting system 13, 14 and to adjust the headlights 15, 16, such as shown schematically in Fig. 5, significantly improves the system response time.

[0058] The network master node is a special on-board computer 17 constituting the lighting control system (LCS).

[0059] This computer 17 normally includes a central processing unit 18 of microprocessor, microcontroller or similar type, pre-recorded ROM program memory 19, RAM working memory 20 and preferably FLASH permanent memory 21.

[0060] These elements 18, 19, 20, 21 form the architecture around the internal bus 23 connected to the interface module 22 for exchanging I / O information with the environment.

[0061] The interface module 22 comprises a UART integrated circuit 24 capable of managing the serial communication protocol of two branches, left and right, LIN networks 11, 12, to which four subordinate nodes 13, 15, 14, 16 are connected, formed first, respectively , by directional lighting system, left DBLG and headlight adjustment system, left LVLG and secondly, by directional lighting system, right DBLD and headlight adjustment system, right LVLD.

[0062] These subnodes 13, 14, 15, 16 contain in a known manner the LIN interface interface circuits and network controllers, enabling them to dialogue on the bus with the master node 17. These network controllers are micro-programmed to generate frames sequentially 7 or parts of 9 frames in response to sent identifiers 1, 4, 6.

[0063] The data controlling these systems 13, 14, 15, 16 depend on certain parameters derived from the function "under the hood", such as the speed of the vehicle or its position relative to the ground; the interface module 22 is therefore also connected to the CAN bus of the vehicle.

[0064] As part of the LIN standard network protocol, executive members of DBLG, LVLG, DBLD, LVLD are controlled together by a control frame, and status sensors are read individually by a message frame.

[0065] The read / write sequence is typically as follows:

a) control of four DBLG, LVLG, DBLD, LVLD sub nodes;

b) DBLD reading;

c) control of four sub-nodes DBLG, LVLG, DBLD, LVLD;

d) DBLG reading;

e) controlling four subordinate nodes DBLG, LVLG, DBLD, LVLD;

f) LVLD reading;

g) controlling four subordinate nodes DBLG, LVLG, DBLD, LVLD;

h) LVLG reading.

[0066] As already mentioned, the LIN network allows only a minimum of one frame every 10 ms, which generates an 80 ms delay between two consecutive readings of the status of a given slave node. This delay is not negligible when the system response time requirement is in the order of 40 ms to 100 ms, and the weakened method should be detected and signaled in less than 3 s.

[0067] In realizing the first embodiment of the communication method according to the invention, an example of an AFS 13, 14, 15, 16 control sequence is typically as follows:

a) control of four DBLG, LVLG, DBLD, LVLD sub nodes;

b) sending a status read command (3C);

c) control of four sub-nodes DBLG, LVLG, DBLD, LVLD;

d) reading of four DBLG, LVLG, DBLD, LVLD sub nodes.

[0068] The duration of the control cycle is then restored to 70 ms.

[0069] The implementation of the second embodiment of the communication method according to the invention leads to an additional reduction of the cycle time. In this case, an example of an AFS 13, 14, 15, 16 control sequence is typically as follows:

a) control of four DBLG, LVLG, DBLD, LVLD sub nodes;

b) reading of four DBLG, LVLG, DBLD, LVLD sub nodes.

[0070] The duration of the control cycle is then only 20 ms.

[0071] As is known, instruction sequences allowing the execution of the above sequences or cycles are preferably stored in ROM 19 of the LCS 17 computer.

[0072] This preferably applies to computer instructions, but in an equivalent manner may relate to the control language sequence interpreted by the CPU 18 at the time of their execution.

[0073] The implementation of the communication method previously described by means of a microprocessor device or even an ASIC type cable logic device also does not fall outside the scope of the invention.

[0074] Accordingly, one of ordinary skill in the art understands that a vehicle, especially a motor vehicle, equipped with a communication device, information storage medium and computer program, as described previously, uses a low cost architecture of an embedded network architecture capable of adopting the latest electronic safety systems and comfort, so it has obvious competitive advantages.

[0075] It is obvious that the invention is not limited to only two preferred embodiments described above.

On the contrary, it includes all other possible embodiments according to the LIN standard and their future extensions to the extent that would result from the following claims.