Method for transmitting data from a transmitting unit to a receiving unit

Abstract

The invention relates to a method for transmitting data from a transmitting unit (12) to a receiving unit (14) via a two-wire communication interface, the method having the following method steps: - transmitting (110) data from the transmitting unit to the receiving unit according to a first data transmission mode, in which the data is transmitted from the transmitting unit to the receiving unit via a first data line and a second data line, wherein the receiving unit forms a differential signal from the signals received via the first data line and the second data line, compares the differential signal with an evaluation reference value, and detects a logical "1" or a logical "0" on the basis of the result of the comparison; - monitoring (120) the two data lines for potential faults affecting the first data line or the second data line; and - switching (130) from the first data transmission mode to a second data transmission mode if a fault has been detected in one of the two data lines.

Description

[0001] Method for transmitting data from a sending unit to a receiving unit

[0002] The present invention relates to a method for transmitting data from a transmitting unit to a receiving unit, as well as a corresponding receiving unit and a data transmission system comprising a transmitting unit and a receiving unit.

[0003] The present invention relates in particular to a method for differential data transmission, and preferably a method for transmitting data via a low-voltage differential signaling (LVDS) interface. Differential data transmission methods are well known in the art. In these methods, a transmitting unit sends signals to a receiving unit via a first data line and a second data line. The signals transmitted on the two data lines have different values, preferably with a first signal being provided on the first data line and a second signal being provided on the second data line, which is inverted compared to the first signal. For example, it may be provided that a voltage signal of 350 mV is provided on the first data line to transmit a logical "1", while a voltage signal of -350 mV is provided on the second data line.The receiving unit receives the two signals and generates a differential signal from them. In the example given, this differential signal can be 700 mV if a logical "1" is received. The receiver then compares this differential signal with a reference signal. If the differential signal is greater than 350 mV, for example, the receiving unit can conclude that the transmitting unit has transmitted a logical "1". Similarly, if a logical "0" is transmitted, a voltage signal of -350 mV can be provided on the first data line, while a voltage signal of 350 mV is provided on the second data line. This allows the receiving unit to determine a differential signal of -700 mV from the two received signals. Consequently, the receiving unit concludes that the transmitting unit is signaling a logical "0".Differential data transmission methods offer several advantages compared to single-ended methods, where only a variable signal is transmitted over a data line. In particular, differential data transmission methods exhibit higher noise immunity, especially less susceptibility to electromagnetic interference, and also enable higher data rates.

[0004] However, differential data transmission methods can fail if, for example, there is a short circuit on one of the data lines or if an open data line is present. In these cases, a reliable evaluation of the signals received via the two data lines is not possible.

[0005] Some of the methods known from the prior art propose approaches for detecting possible disturbances, but do not provide a solution for maintaining communication between the transmitting unit and the receiving unit even in the event of a disturbance.

[0006] Based on the problem described above, the object of the present invention is to provide a method for transmitting data from a transmitting unit to a receiving unit, in which the received data can be reliably evaluated even in the event of a malfunction, in particular in the event of a short circuit of a data line or in the event of an open data line.

[0007] To solve the aforementioned problem, the present invention proposes a method for transmitting data from a transmitting unit to a receiving unit via a two-wire communication interface, in particular via a Low Voltage Differential Signaling (LVDS) interface, wherein the method comprises the following steps: transmission of data from the transmitting unit to the receiving unit according to a first data transmission mode, wherein in the first data transmission mode the data is transmitted from the transmitting unit to the receiving unit via a first data line and a second data line, and the receiving unit forms a differential signal from the signals received via the first data line and the second data line and compares the differential signal with an evaluation reference value and detects a logical "1" or a logical "0" depending on the result of the comparison;

[0008] Monitoring of both data lines for possible malfunctions affecting the first line or the second line;

[0009] Switching from the first data transmission mode to a second data transmission mode if a fault is detected on one of the two data lines, whereby the receiving unit in the second data transmission mode evaluates only the data provided by the line not affected by the fault.

[0010] In the method according to the invention, data transmission from the transmitting unit to the receiving unit takes place during normal operation (i.e., when no fault is present) via an evaluation of the differential signal, while in the event of a fault, a second data transmission mode is used in which single-ended data evaluation takes place. On the receiver side, therefore, a differential evaluation of the signal takes place in the first data transmission mode, while in the second data transmission mode a single-ended data evaluation is performed (i.e., the evaluation of the signal present on a data line).This ensures that the advantages of differential data transmission are utilized during normal operation (in particular, a high data transmission rate can be achieved during normal operation), while in the event of a fault, communication does not cease completely, but instead an emergency operation can be maintained (albeit without the advantages achieved through differential data transmission). In the second transmission mode, the transmission efficiency is lower than in the first transmission mode; nevertheless, the method according to the invention allows for a more robust data transmission method compared to the prior art, thereby reducing the failure risk of the transmission system.

[0011] As will be explained in detail below, various approaches for fault detection can be employed within the scope of the present invention. In particular, during monitoring of the data lines, the voltage values ​​applied to the two data lines can be compared with reference voltage values ​​to check whether the applied voltage values ​​are within a normal range or outside the normal range, which can be considered an indication of a fault. Furthermore, a machine learning-based classifier, previously trained with training data, can also be used. During the training process, such a classifier can "learn" which voltage values ​​are present on the data lines during normal operation and which voltage values ​​indicate a fault.Furthermore, various measures can be taken within the scope of the present invention to operate the second data transmission mode (single-ended communication).

[0012] In the method according to the invention, it can be provided, in particular, that the receiving unit in the first data transmission mode evaluates the voltage across a termination resistor (also referred to as "first resistor" within the scope of the present invention), which is arranged in series with a switching element between the first data line and the second data line, wherein the switching element is designed to switch between an open, high-resistance state and a closed, low-resistance state. This allows the first and second data lines to be decoupled from each other, thereby simplifying the evaluation of the received data on one of the data lines. In the method according to the invention, it can be provided, in particular, that the switching element is opened if a fault is detected on the first or on the second data line during monitoring of the two data lines.In particular, the switching element can be designed to switch to the open (high-impedance) state in the event of a detected fault (especially a detected short circuit on one of the data lines or an open data line). This makes it possible to decouple the first and second data lines from each other if a fault is detected on one of the data lines. For example, if the first data line shorts to the supply voltage line, the absolute voltage potential of the termination resistor changes. In normal operation, this absolute voltage potential (also known as "common mode") is maintained at a level within a normal range.The short circuit shifts the absolute voltage potential at the two terminals of the termination resistor in the direction of the short circuit, preventing the differential signal from being correctly evaluated by the evaluation unit. Decoupling the two data lines prevents this effect, thus simplifying the evaluation of the signal tapped from one data line.

[0013] Furthermore, the inventive method can be designed to close the switching element if monitoring has previously shown that both data lines are free of interference. Switching back from the second data transmission mode to the first data transmission mode is then possible as soon as the previously detected fault has been rectified. This allows the advantages of differential data evaluation, and in particular the high transmission speed, to be utilized again as soon as the fault has been resolved.

[0014] According to some embodiments of the method according to the invention, the monitoring of the data lines for a possible fault may include monitoring of the data lines for an open circuit or a short circuit, and in particular monitoring of the data lines for a short circuit of one of the data lines to a ground connection or to a supply connection. This allows switching to the second data transmission mode in the event of a detected short circuit or open circuit, so that emergency operation can be maintained even in one of the aforementioned fault conditions.

[0015] Furthermore, the method according to the invention can include monitoring the two data lines by comparing a voltage signal applied to the first or second data line with at least one predetermined reference value. For example, a fault condition can be detected if a first reference value is exceeded or if a second reference value is undershot. This is based on the assumption that, under normal operating conditions, the voltage supplied to the first data line and the voltage supplied to the second data line assume a voltage value within a specific range. For example, if a voltage value greater than a first reference value is measured on the first data line, this can be considered an indication that the first data line is short-circuited to a supply voltage line.If, for example, a voltage value is measured on the first data line that is lower than a second reference value, this can be interpreted as an indication that the first data line is short-circuited to a ground line. In this way, simple and efficient monitoring of the data lines can be implemented. Digital switching elements, located on the receiver side, can be used to monitor the two data lines. Preferably, two comparators can be provided for each data line. A first comparator can compare the voltage applied to the first data line with a first reference value and provide an output signal that depends on the comparison result.Similarly, a second comparator can compare the voltage applied to the first data line with a second reference value and provide an output signal that depends on the comparison result. A third and a fourth comparator can then be used to monitor the second data line.

[0016] Furthermore, to solve the problem described above, a receiving unit for receiving data from a transmitting unit via a two-wire communication interface is proposed, specifically via a Low Voltage Differential Signaling (LVDS) interface, comprising: a first data line and a second data line, each designed to receive a (time-varying) signal; an evaluation unit, designed in a first data transmission mode to receive and evaluate the signals received via the two data lines, wherein the evaluation unit in the first data transmission mode is designed to reconstruct the received signals by calculating the difference between the received signals and by comparing a difference signal determined during reference formation with an evaluation reference value;and a monitoring unit designed to monitor the first data line and the second data line for possible disturbances affecting the first data line or the second data line; wherein the evaluation unit is furthermore designed to switch to a second receive mode in the event of a disturbance detected on a data line, wherein the evaluation unit in the second data transmission mode is designed to evaluate exclusively the data provided on the data line not affected by the disturbance. The receive unit according to the invention allows robust reception of the data received by the transmitting unit, which also enables data reception in the event of disturbances.

[0017] In the receiving unit according to the invention, a series circuit consisting of a termination resistor and a switching element can preferably be provided between the first data line and the second data line, wherein the switching element is designed to switch between an open, high-impedance state and a closed, low-impedance state. In particular, the switching element can be configured to switch to an open (i.e., high-impedance) state in the event of a detected fault and to switch to a closed state in the event of proper operation (i.e., when no fault has been detected).

[0018] Furthermore, the receiving unit according to the invention may include a control unit designed to move the switching element to the open state in the event of a fault on the first or second data line, and / or to move the switching element to the closed state if there is no fault on the first or second data line.

[0019] The control unit can be implemented, for example, as a microcontroller or as an FPGA.

[0020] Furthermore, the receiving unit according to the invention can be provided with a monitoring unit comprising at least one comparator designed to compare a voltage supplied on the first data line or on the second data line with a predetermined reference value and to generate an error signal if the supplied voltage exceeds or falls below the reference value. Alternatively, the monitoring unit can be provided with a microcontroller that detects the voltage applied to the first data line and the voltage applied to the second data line and compares each of these with two reference values. If at least one of the detected voltages exceeds a first reference value or falls below a second reference value, this can be considered an indicator of a fault.Consequently, the microcontroller detects a disturbance and generates an output signal to control the switching element. Specifically, in this case, the microcontroller can generate an output signal to open and close the switching element.

[0021] Furthermore, the receiving unit according to the invention may be provided with a monitoring unit comprising a first comparator designed to compare the voltage supplied on the first data line with a first reference value; a second comparator designed to compare the voltage supplied on the second data line with a second reference value; a third comparator designed to compare the voltage supplied on the first data line with a third reference value; and a fourth comparator designed to compare the voltage supplied on the second data line with a fourth reference value. The monitoring unit is preferably designed to generate an error signal to indicate a fault when the first comparator detects an exceedance of the first reference value.and / or the second comparator detects that the second reference value has been exceeded; and / or the third comparator detects that the third reference value has been undershot; and / or the fourth comparator detects that the fourth reference value has been undershot.

[0022] In particular, the first comparator can be designed to monitor the first data line for potential overvoltage, while the second comparator can be designed to monitor the second data line for potential overvoltage. Furthermore, the third comparator can be designed to monitor the first data line for potential overvoltage, while the fourth comparator can be designed to monitor the second data line for potential undervoltage.

[0023] Furthermore, the receiving unit according to the invention may include a pull-up resistor (also referred to as "second resistor" within the scope of the present invention) which is arranged between the first data line and a supply voltage line.

[0024] The receiving unit according to the invention may also include a pull-down resistor (also referred to as a "third resistor" within the scope of the present invention), which is arranged between the second data line and a ground line.

[0025] The pull-up resistor and the pull-down resistor can be designed as high-impedance resistors and, in particular, have a resistance of several kQ, so that in normal operation the voltage on the first data line and on the second data line is only marginally affected.

[0026] Furthermore, to solve the aforementioned problem, a system for transmitting data is proposed, comprising a transmitting unit, a receiving unit according to one of the embodiments described above, and a first data line and a second data line arranged between the transmitting unit and the receiving unit and connecting them together, wherein the transmitting unit is designed to provide a first voltage signal on the first data line and to provide a second voltage signal on the second data line.

[0027] The second voltage signal is preferably designed to have the same magnitude as the first voltage signal, but the opposite sign.

[0028] The present invention is explained in more detail below with reference to the figures. These figures show...

[0029] Fig. 1 shows an embodiment of the method according to the invention,

[0030] Fig. 2 shows a first embodiment of the system according to the invention, and

[0031] Fig. 3 shows a second embodiment of the system according to the invention.

[0032] Figure 1 schematically illustrates an embodiment of the inventive method 100 for transmitting data from a transmitting unit to a receiving unit via a two-wire communication interface. In a first method step 110, data is transmitted from the transmitting unit to the receiving unit according to a first data transmission module. In the first data transmission mode, the receiving unit evaluates the signals received via the first data line and the second data line, generating a differential signal and comparing it with an evaluation reference value. If the differential signal is greater than the evaluation reference value, the receiving unit can detect a logical "1". If the differential signal is not greater than the evaluation reference value, the receiving unit can output a logical "0".In a second process step 120, the two data lines are monitored for possible faults affecting either the first or the second data line. This monitoring can be carried out, in particular, by comparing the voltage values ​​present on the two data lines with reference voltage values. In a third process step 130, the system switches from the first data transmission mode to a second data transmission mode if a fault is detected on one of the two lines. In the second data transmission mode, the receiving unit evaluates only the data provided by the line not affected by the fault.The system therefore switches from a differential evaluation mode to a so-called single-ended evaluation mode, which means that the data rates achieved in the differential transmission mode are no longer possible, but advantageously ensures continued emergency operation.

[0033] Although the above-described procedural steps were referred to as the "first," "second," and "third" procedural steps, this designation does not restrict the order of the procedural steps. Rather, for example, the second procedural step (monitoring the data line) can be carried out simultaneously with the first procedural step.

[0034] Figure 2 schematically illustrates a first embodiment of the system 10 according to the invention. The system 10 comprises a transmitter 12 and a receiver 14. The transmitter 12 and the receiver 14 are connected to each other via a first data line 16 and a second data line 18. The receiver 14 has an evaluation comparator 24, which is designed to evaluate the voltage signals received on the first data line 16 and the second data line 18. The evaluation is performed by calculating the difference between the voltage signals received on the two data lines 16 and 18 and by comparing this difference with an evaluation reference value. If the difference between the voltage signal values ​​is greater than the evaluation reference value, a logical "1" is output at the evaluation comparator 24. If the difference is not greater than the evaluation reference value, a logical "0" is output at the evaluation comparator 24.

[0035] Between the first data line 16 and the second data line 18, a termination resistor 20 and a switching element 22 are provided on the receiver side, wherein the termination resistor 20 and the switching element 22 are connected in series. The switching element 22 is designed to switch the termination resistor 20. The switching element 22 can be controlled by a control unit 23. In the illustrated embodiment, the control of the switching element 22 by the control unit 23 is dependent on the monitoring of the first data line 16 and the second data line 18. The monitoring of the data lines 16, 18 is carried out in the embodiment shown in the figure.The system 10 shown in Figure 1 is implemented by the use of a first comparator 26 (also referred to as the "first monitoring comparator"), a second comparator 28 (also referred to as the "second monitoring comparator"), a third comparator 30 (also referred to as the "third monitoring comparator"), and a fourth comparator 32 (also referred to as the "fourth monitoring comparator"). Any two of the four comparators 26, 28, 30, 32 are configured to monitor one of the two data lines 16, 18. In particular, the four comparators 26, 28, 30, 32 are configured to monitor the voltages applied to the data lines 16, 18 and to generate an output signal indicating a fault. The output signals of the comparators 26, 28, 30, 32 can be transmitted to the control unit 23, which can be implemented, for example, as a microcontroller.If the control unit 23 receives output signals from the comparators 26, 28, 30, 32 indicating a fault, the control unit 23 can switch the switching element 22 to an open state. This decouples the first data line 16 and the second data line 18 from each other. Decoupling the two data lines 16 and 18 simplifies the evaluation of the received data, as it prevents any distortions caused, for example, by a short circuit in the first data line 16 or the second data line 18. If, for example, the first data line 16 is short-circuited to a positive supply terminal, both lines 16 and 18 are pulled to a short-circuit potential, which makes it difficult to evaluate the signals received at the evaluation comparator 24 due to signal distortion.In this case, the signals received by the evaluation comparator 24 may lie outside the evaluation range of the evaluation comparator 24 due to distortion.

[0036] Figure 3 shows a second embodiment of the system 10 according to the invention. In this embodiment, a pull-up resistor 34 and a pull-down resistor 36 are additionally provided. The pull-up resistor 34 connects the first data line 16 to a supply line. The pull-down resistor 36 connects the second data line 18 to a ground line. By using the pull-up resistor 34 and the pull-down resistor 36, a defined potential is provided at the first data line 16 and the second data line 18 in the event of a fault. This simplifies the evaluation of the received signals in the event of a fault.

[0037] REFERENCE MARK LIST

[0038] System Transmitting unit Receiving unit First data line Second data line Termination resistor Switching element Control unit Evaluation comparator First comparator Second comparator Third comparator Fourth comparator Pull-up resistor Pull-down resistor Procedure First procedure step Second procedure step Third procedure step

Claims

REQUIREMENTS 1. Method for transmitting data from a transmitting unit (12) to a receiving unit (14) via a two-wire communication interface, in particular via a Low Voltage Differential Signaling (LVDS) interface, wherein the method comprises the following process steps: Transmission (110) of data from the transmitting unit (12) to the receiving unit (14) according to a first data transmission mode, wherein in the first data transmission mode the data from the transmitting unit (12) to the receiving unit (14) is transmitted via a first data line (16) and a second data line (18), the receiving unit (14) forms a difference signal from the signals received via the first data line (16) and the second data line (18), compares the difference signal with an evaluation reference value and detects a logical "1" or a logical "0" depending on the result of the comparison; Monitoring (120) of the two data lines (16, 18) with regard to a possible fault concerning the first data line (16) or the second data line (18); and Switching (130) from the first data transmission mode to a second data transmission mode if a fault is detected on one of the two data lines (16, 18), wherein the receiving unit (14) in the second data transmission mode evaluates only the data provided by the data line (16, 18) not affected by the fault.

2. Method according to claim 1, characterized in that the receiving unit (14) in the first data transmission mode evaluates the voltage across a termination resistor (20) which is arranged in a series circuit with a switching element (22) between the first data line (16) and the second data line (18), wherein the switching element (22) is designed to switch between an open, high-resistance state and a closed, low-resistance state.

3. Method according to claim 2, characterized in that the switching element (22) is opened if a fault is detected on the first or on the second data line (16, 18) during the monitoring of the two data lines (16, 18).

4. Method according to claim 2 or 3, characterized in that the switching element (22) is closed if the monitoring has shown that both data lines (16, 18) are free of interference.

5. Method according to one of claims 1 to 4, characterized in that the monitoring of the data lines (16, 18) with regard to a possible fault includes monitoring of the data lines (16, 18) with regard to an open circuit or a short circuit, and in particular includes monitoring of the data lines (16, 18) with regard to a short circuit of one of the data lines (16, 18) to a ground connection or to a supply connection.

6. Method according to one of claims 1 to 5, characterized in that the monitoring of the two data lines (16, 18) comprises the comparison of a voltage signal applied to the first data line (16) or the second data line (18) with a predetermined reference value, wherein an error condition is detected in the event of an exceedance or a fall below the reference value.

7. Receiving unit (14) for receiving data from a transmitting unit (12) via a two-wire communication interface, in particular via a Low Voltage Differential Signaling (LVDS) interface, comprising: a first data line (16) and a second data line (18), each designed to receive a signal; an evaluation unit designed in a first data transmission mode to receive and evaluate the signals received via the two data lines (16, 18), wherein the evaluation unit in the first data transmission mode is designed to reconstruct the received signals by calculating the difference between the received signals and by comparing a difference signal determined during reference formation with an evaluation reference value; and a monitoring unit designed to monitor the first data line (16) and the second data line (18) for possible disturbances affecting the first data line (16) or the second data line (18);wherein the evaluation unit is also designed to switch to a second receive mode in the event of a disturbance detected on a data line (16, 18), wherein the evaluation unit in the second data transmission mode is designed to evaluate exclusively the data that is provided on the data line (16, 18) not affected by the disturbance.

8. Receiving unit (14) according to claim 7, characterized by a series circuit arranged between the first data line (16) and the second data line (18) comprising a termination resistor (20) and a switching element (22), wherein the switching element (22) is designed to switch between an open, high-impedance state and a closed, low-impedance state.

9. Receiving unit (14) according to claim 7 or 8, characterized by a control unit (23) designed to to move the switching element (22) to the open state in the event of a fault on the first or second data line (16, 18); and / or to move the switching element (22) to the closed state if there is no fault on the first data line (16) and the second data line (18).

10. Receiving unit (14) according to one of claims 7 to 9, characterized in that the monitoring unit has at least one comparator (26, 28, 30, 32) designed to compare a voltage supplied on the first data line (16) or on the second data line (18) with a predetermined reference value and to generate an error signal if the supplied voltage exceeds or is greater than the reference value.

11. Receiving unit (14) according to any one of claims 7 to 10, characterized in that the monitoring unit comprises a first comparator (26) configured to compare the voltage supplied at the first data line (16) with a first reference value; a second comparator (28) configured to compare the voltage supplied at the second data line (18) with a second reference value; a third comparator (30) configured to compare the voltage supplied at the first data line (16) with a third reference value; and a fourth comparator (32) configured to compare the voltage supplied at the second data line (18) with a fourth reference value; wherein the monitoring unit is preferably configured to generate an error signal designed to detect a disturbance of the to indicate the first data line (16) or the second data line (18) when the first comparator (26) detects an exceedance of the first reference value; and / or the second comparator (28) detects an exceedance of the second reference value; and / or the third comparator (30) detects a fall below the third reference value determined; and / or the fourth comparator (32) detects a fall below the fourth Reference value determined.

12. Receiving unit (14) according to one of claims 7 to 11, characterized by a pull-up resistor (34) arranged between the first data line (16) and a supply voltage line, and / or by a pull-down resistor (36) arranged between the second data line (18) and a ground line.

13. System (10) for transmitting data comprising a transmitting unit (12); a receiving unit (14) according to any one of claims 7 to 12; and a first data line (16) and a second data line (18) arranged between the transmitting unit (12) and the receiving unit (14) and connecting them together; wherein the transmitting unit (12) is configured to provide a first voltage signal on the first data line (16) and to provide a second voltage signal on the second data line (18).

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