Data transfer protocol

Abstract

Data transmission protocol with a dominant-recessive bit behavior, preferably with a dominant first signal edge, comprising a command stage, a diagnostic stage and a confirmation stage, wherein the confirmation stage operates depending on the number of participants.

Description

[0001] The invention relates to a system for data transmission by means of a data transmission protocol, wherein the data transmission protocol is a data transmission protocol with a dominant-recessive bit behavior and wherein the data transmission protocol has a command stage, a diagnostic stage and a confirmation stage, wherein the confirmation stage operates depending on the number of participants, wherein the system comprises a bus, a master, at least two participants which are connected to the master via the bus, and at least one data packet which can be exchanged between the master and the participants, wherein the participants are energy storage modules of a multilevel converter system.

[0002] US 2002 / 0 002 647 A1 relates to a method in which the data to be transmitted is transmitted in units together with information necessary or useful for the transmission and / or use of the data. At least some of the units have at least one area defining a time slot within which freely selectable devices can output data representing freely selectable information to the bus at freely selectable times.

[0003] US 2013 / 0 139 018 A1 discloses a communication system in which a plurality of communication devices, such as an electronic control unit (ECU) mounted in a vehicle, send and receive data via a common communication line (a bus) and the communication device.

[0004] US 5 293 571 A relates to a method for acknowledging the reception of data in a multiplex transmission and, in particular, to a reception acknowledgment method for returning an acknowledgment signal having an NRZ (Non-Return-To-Zero) code to thereby efficiently transmit data in a multiplex transmission of a type.

[0005] A conventional Controller Area Network (CAN) protocol uses the acknowledgment bit to confirm the received data. However, this occurs regardless of the number of participants, also referred to as modules and / or slaves, and / or regardless of correct decoding. The acknowledgment bit is overwritten by each participant that has received the message without errors. This often involves sending a large amount of data.

[0006] It is therefore an object of the invention to provide a data transmission protocol, a system for data transmission and a method for transmitting data in which the amount of data is reduced.

[0007] This problem is solved by the subject matter and the method of the independent claims.

[0008] According to the invention, there is provided a system for data transmission by means of a data transmission protocol, wherein the data transmission protocol is a data transmission protocol with a dominant-recessive bit behavior and wherein the data transmission protocol has a command stage, a diagnostic stage and a confirmation stage, wherein the confirmation stage operates depending on the number of participants, wherein the system comprises a bus, a master, at least two participants which are connected to the master via the bus, and at least one data packet which can be exchanged between the master and the participants, wherein the participants are energy storage modules of a multilevel converter system.

[0009] According to the invention, the data transmission protocol has a dominant-recessive bit pattern. Preferably, this has a dominant first signal edge.

[0010] For example, the data transmission protocol can be called FAAD (Fast-Acknowledge-And-Data) protocol.

[0011] The data can consist of dominant and recessive bits. While a dominant 0 cannot be overwritten, a recessive 1 can. This principle is also known as arbitration. Arbitration regulates allocation to a bus system.

[0012] For example, one cycle of the data transmission protocol can last 50 µs.

[0013] The cycle can be divided into three different phases, namely a command stage, a diagnostic stage and an acknowledgment stage.

[0014] In the first phase, a master, for example, can send its control data to the participants. The control data can contain all the information a participant needs, for example, to switch the correct cells on or off. The cells can be cells of a multilevel converter system, for example.

[0015] With regard to a possible design of a multilevel converter system - for example with regard to the feasibility, a possible application and / or possible embodiments of the invention - reference is made to DE 10 2022 110 424 A1, the content of which is incorporated into this application.

[0016] If a node fails to successfully receive the control data, it cannot participate in switching the correct cells. In this case, the node enters a fail-safe mode. Either the failed node would disrupt the entire system, which is undesirable, or the system must now operate with one less node. In this case, the affected node does not participate in the confirmation stage, and the master can detect the failure of a node. In detail:

[0017] The data transfer protocol has one command level.

[0018] In this case, data is transferred from the master to the nodes. For example, the data can be sent from the master via a bus. Preferably, however, the nodes themselves do not communicate with each other and / or are not connected to each other.

[0019] In the command phase, for example, the master can send switching commands to the nodes. The length of the command phase can depend on how many nodes are connected and which data reduction technology is used.

[0020] Since this level is safety-critical and can represent a point of failure, it must preferably be fault-tolerant.

[0021] Each command cycle can end with a known synchronization sequence. For example, a TDMA (Time Division Multiple Access) scheme can be used. Here, commands can be sent at full speed and / or without the need for arbitration. Each node can, for example, initiate a synchronization algorithm with the received command data.

[0022] The data transfer protocol has a diagnostic level.

[0023] Data is transferred from participants to the master.

[0024] The diagnostic stage preferably begins with the data transfer between the nodes and the master. This stage serves as a feedback line from the nodes to the master, since all nodes need time to process the commands received in the command stage. This time can be used to send their diagnostic data.

[0025] For example, an update rate of 100 Hz per node can be implemented. For example, with a control frequency of 20 kHz, 200 nodes can be processed. In an implementation with 72 nodes, each node would have two cycles to send its data, resulting in an update frequency of 139 Hz. The amount of data that can be sent depends on the command level and the acknowledgement level, as these have a greater influence than the diagnostic level.

[0026] The data transfer protocol has a confirmation level.

[0027] The confirmation level works depending on the number of participants. Here, the participants' data is transferred to the master.

[0028] An important feature of the FAAD protocol is the confirmation level. This can be used, for example, to confirm the bus system.

[0029] While previous CAN protocols use the acknowledgment level to confirm received data regardless of the number of receivers and correct decoding, the FAAD protocol aims for acknowledgment from, say, up to 72 participants within the 50 µs cycle. The bit rate can be 8 Mbps, for example. Each acknowledgment ensures correct reception and decoding of the data for each participant.

[0030] It was surprising that the data transmission protocol offers the possibility of receiving confirmation from up to 72 participants per cycle. This is advantageous for error detection and additional communication between participants. After each cycle (50 µs), the master knows which participant has failed for some reason and can then activate the fail-safe mechanism.

[0031] Because the confirmation level depends on the number of participants, the amount of data can be reduced.

[0032] Further developments of the invention can also be found in the dependent claims, the description and the accompanying drawings.

[0033] Since the data transmission protocol has little in common with a traditional CAN FD protocol and therefore does not need to be compatible with other CAN transceivers, the 1 Mbps arbitration bit rate can be neglected. Furthermore, a specific control loop of 50 µs has the advantage of allowing a TDMA scheme to be used for data exchange. With a given TDMA scheme, arbitration is not required, as each participant has a specific time frame in which to exchange data. This allows for better bandwidth utilization.

[0034] According to another embodiment, the participants work synchronously.

[0035] Preferably, the participants are time synchronized, e.g. in the ns range.

[0036] For example, a time signal can be included in the data packet.

[0037] The invention relates to a system for data transmission using a data transmission protocol.

[0038] The system has at least or exactly one, preferably time-based, bus, at least or exactly one master and at least two participants that are connected to the master via the bus.

[0039] Fermer the system has at least one data packet that can be exchanged between the master and the participants.

[0040] The participants are connected to the master via a bus. Preferably, the participants themselves do not communicate with each other and / or are not connected to each other.

[0041] According to one embodiment, the data packet is designed as a UART packet (Universal Asynchronous Receiver and Transmitter).

[0042] A UART is an electronic circuit for digital serial interfaces.

[0043] For example, two data lines can be provided for communication, namely one for sending (TX - Transmit) and one for receiving (RX - Receive).

[0044] A clock is preferably not used for timing. Instead, so-called start bits (LOW) and stop bits (HIGH) are used. As soon as a device receives the start bit, it reads the data until it receives the stop bit.

[0045] For example, a UART packet consists of a start bit, eight information bits, an optional parity bit to detect transmission errors and at least or exactly one stop bit.

[0046] Depending on the application, other configurations are also conceivable, e.g. a start bit, five to a maximum of nine information bits, an optional parity bit and one or two stop bits.

[0047] According to a further embodiment, the data packet comprises a time signal.

[0048] Preferably, each participant can store a timestamp of the control data. The timestamps can be used to ensure synchronization accuracy of all participants to less than 20 ns.

[0049] There are different options for synchronization.

[0050] For example, to initiate synchronization, the master can terminate the command packets with a sync packet. After receiving the corresponding sync packet, all nodes enter sync mode and wait for the master's sync pulse. After a certain time, the master sends the sync pulse, which preferably consists of one bit, to all nodes.

[0051] The confirmation stage follows immediately after the synchronization pulse to maintain a precise synchronization point. With this synchronization, all participants synchronize each cycle with an accuracy of + / -10 ns.

[0052] To avoid additional processing time, no additional code is preferably required.

[0053] Another way to synchronize is based on a method that uses DMA (Direct Memory Access) controllers.

[0054] DMA controllers are independent hardware controllers that operate separately from the main MCU (Microcontroller Unit). Unlike the MCU, DMA controllers are capable of processing data transfer requests in parallel without requiring direct intervention from the MCU, meaning the MCU doesn't have to wait for each data transfer to complete.

[0055] The DMA controller can handle data transfer to offload the MCU. Each received UART packet triggers the DMA to write it to memory.

[0056] This trigger can be extended by modifying the DMA multiplexer register to write the current timestamp to a previously defined buffer. This timestamp process ensures that each UART packet is uniquely identified and can be precisely synchronized with other data. This allows all participants to synchronize to within + / - 20 ns, for example. To ensure correct synchronization, the synchronization can be checked at a later time. If synchronization fails or is triggered by an incorrect UART packet, an attempt is made to resynchronize or to enter fail-safe mode.

[0057] According to a further embodiment, only one information bit is transmitted per participant in the confirmation stage.

[0058] In addition, for example, a start bit and at least one stop bit can be transmitted.

[0059] The minimum that can be sent is a UART packet, which consists of, for example, a start bit, a stop bit and eight information bits.

[0060] In this case, only one information bit is transmitted per participant, indicating their confirmation. It would be a waste of bandwidth to transmit one bit and seven unused bits.

[0061] According to a further embodiment, several data packets are superimposed on one another.

[0062] Multiple UART packets can be overlaid so that the receiver receives only one message instead of several.

[0063] Since each node transmits only one bit of information, the CAN overlay function can collect eight times more data from a single UART packet than conventional methods. This method requires, for example, a total synchronization of at least + / -10 ns between the master and nodes.

[0064] According to the invention, the participants are energy storage modules of a multilevel converter system.

[0065] The multilevel converter system can be used, for example, in an electric vehicle.

[0066] The system always lets the cells know when they are switched on or off. The system ensures this precisely and / or in real time.

[0067] The participants report back their respective status, e.g. the charge level, the voltage and / or the temperature.

[0068] Finally, the invention relates to a method for transmitting data using a system according to the invention.

[0069] All embodiments and components of the devices described here are preferably designed to be operated, e.g., by means of a control device, according to the method described here. Furthermore, all embodiments of the devices described here, as well as all embodiments of the method described here, can be combined with one another, preferably independently of the specific embodiment in whose context they are mentioned.

[0070] The invention is described below by way of example with reference to the drawings. Fig. 1 a schematic representation of an embodiment of a data transmission protocol, Fig. 2 a schematic representation of an embodiment of a section of a system according to the invention, Fig. 3 a schematic representation of an embodiment of a data overlay according to the invention, and Fig. 4 a schematic representation of an embodiment of a system according to the invention.

[0071] First, it should be noted that the embodiments presented are purely exemplary in nature. Individual features can be implemented not only in the combination shown, but also individually or in other technically feasible combinations. For example, the features of one embodiment can be combined arbitrarily with features of another embodiment. Preferably, any number of participants is possible.

[0072] If a figure contains a reference symbol that is not explained in the immediately corresponding description, reference is made to the corresponding preceding or following explanations in the figure description. Thus, the same reference symbols are used for identical or comparable components in the figures and these are not explained again.

[0073] Fig. 1 shows a cycle of a data transmission protocol 10, which can last, for example, 50 µs.

[0074] In a command stage 12, data is transmitted from a master 14 to participants 16.

[0075] In a subsequent diagnostic stage 18, data is transferred from participants 16 to a master 14.

[0076] Finally, in a subsequent confirmation stage 20, data is transmitted from all participants 16 to a master 14.

[0077] In Fig. 2 shows a system for data transmission using a data transmission protocol 10.

[0078] The master 14 is connected to the participant 16 via a bus 22.

[0079] Compensation of propagation delay is important for synchronization.

[0080] Therefore, it is advantageous if the delay from the transmitter to the bus 22 is known so that each participant can compensate for its delay in order to achieve precise synchronization.

[0081] For example, there are four units: Participant Receive AR, Participant Transmit BT, Master Transmit AT, and Master Receive BR. These units represent the time delay in each part of the receiver.

[0082] To successfully compensate for the delay, each participant 16 must know their BT and AR, or their compensation factor. Unfortunately, BT and AR cannot be measured individually, but it is possible to compensate for the delay without knowing them.

[0083] As shown, the external paths are measurable for node 16 or master 14. A round trip with an internal or ideal delay of 0 ns takes approximately 240 ns. However, this is not feasible. Therefore, a predefined delay T1 can be introduced between AR and BT.

[0084] The ping packet is sent and received using AT+AR+T1+BT+BR. If the master 14 queries each participant 16 using the same approach, it can determine which participants 16 need to be compensated and by what factor.

[0085] Since there is only one master 14 in the system, the propagation delay of AT and BR is irrelevant. Therefore, the master 14 calculates a compensation factor for each participant 16 and sends it to each participant 16.

[0086] The compensation factor is an individually set artificial delay that ensures compensation for the CAN transceiver used.

[0087] Preferably, runtime compensation is performed in each startup phase to verify and / or guarantee changing runtime due to an aging and / or changing environment.

[0088] Self-compensation can be implemented by measuring BT+AR during transmission and adjusting the compensation factor. Thus, each participant 16 can compensate and / or adjust its own factor. Fig. 3 shows eight data packets S1 to S8 of participants 16. Each data packet S1 to S8 contains only one information bit B1 to B8.

[0089] A start bit SA and a stop bit SO of the master 14 can overlap with the information bits B1 to B8.

[0090] The receiver (master) (shown on the far right) can then receive the following signal, for example: 0|0000|0000|1.

[0091] The confirmation level 20 therefore works depending on the number of participants 16.

[0092] The data transfer protocol reduces the amount of data when transferring data.

[0093] Fig. Figure 4 shows an example of a data transmission system. Several data packets S1 to S9 are exchanged between the participants 16 and the master 14.

[0094] This is illustrated by the three phases of an electric motor. However, this does not necessarily involve a multi-phase system.

[0095] It is noted that "vorzugsweise" can be translated into English as "preferably." A feature introduced by "vorzugsweise" is purely optional, can be omitted, and does not constitute a limitation, for example, of the claims. List of reference symbols 10 Data transfer protocol 12 Command Level 14 Master 16 participants 18 diagnostic level 20 confirmation levels 22 buses AR Participant Reception BT Participant Send AT Master Send BR Master Reception S1 to S9 data package B1 to B8 information bit SA start bit SO stop bit

Claims

[1] System for data transmission by means of a data transmission protocol (10), wherein the data transmission protocol (10) is a data transmission protocol with a dominant-recessive bit behavior and wherein the data transmission protocol (10) - one command level (12), - a diagnostic level (18) and - has a confirmation level (20), wherein the confirmation level (20) operates depending on the number of participants (16), where the system - a bus (22), - a Master's degree (14), - at least two participants (16) connected to the master (14) via the bus (22), and - at least one data packet (S1-S8) exchangeable between the master (14) and the subscribers (16) comprises:, wherein the participants (16) are energy storage modules of a multilevel converter system. [2] System according to claim 1, characterized bythat the data transmission protocol (10) has a dominant first signal edge. [3] System according to one of the preceding claims, characterized by that the participants (16) work synchronously. [4] System according to one of the preceding claims, characterized by that the data packet (S1-S8) is designed as a UART packet. [5] System according to one of the preceding claims, characterized by that the data packet (S1-S8) contains a time signal. [6] System according to one of the preceding claims, characterized by that in the confirmation stage (20) only one information bit (B1-B8) is transmitted per participant (16). [7] System according to one of the preceding claims, characterized by that several data packets (S1-S8) are superimposed on each other. [8] A method for transmitting data using a system according to any one of the preceding claims.

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