Bus user, bus system and method for transmitting data in a two wire bus system

Abstract

To provide a method for transmitting data in a two wire bus system.SOLUTION: A bus user, a two wire bus system and a method for data transmission in a two wire bus system are proposed. The method comprises the steps of supplying the first bus user and the second bus user with a varying battery voltage and transmitting data from the first bus user to the second bus user by means of a modulation signal superimposed on the varying battery voltage, wherein the modulation signal follows the level of the varying battery voltage in a predetermined manner.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bus participant, a bus system and a method for transmitting data in a two-wire bus system, in particular to bus systems powered by battery technology and supplied with a variable (fluctuating) DC voltage (in particular an island bus system). [Background technology]

[0002] The current state of the art is known for bus systems that allow control devices to exchange information with relatively little cabling effort, particularly in automotive and aviation applications. Wired connection of control devices, in particular, allows for the distribution of information and the operating energy of bus participants via the bus line. In the current state of the art, modulation methods are generally defined independently of the current supply voltage. For example, 0 and 5 volt levels are defined to communicate different codes (low / high) using fixed, predetermined voltages. In current bus systems, such as PSI5, the master control device can only transmit to the bus participants at a low data rate if it simultaneously supplies the bus participants with a synchronous pulse architecture. In DSI3, the modulation voltage is tied to a fixed supply voltage, which requires a voltage regulator in the master control device to supply the bus participants. Summary of the Invention

[0003] The present invention proposes a method for transmitting data within a two-wire bus system. This can be understood as a galvanically / electrically implemented bus system. In this context, two control devices are interconnected via only two wires, through which they exchange information and receive electrical energy. In a first step, a first bus participant and a second bus participant are energized by a varying battery voltage. The reason for the battery voltage change is not important for the present invention. However, the battery voltage is essentially a DC voltage that may have dips or fluctuate depending on the operating state. In any case, data is exchanged from the first bus participant to the second bus participant by means of a modulation signal superimposed on the varying battery voltage. However, the modulation signal does not have a predetermined level relative to ground, but rather follows the level of the varying battery voltage in a predetermined manner. In particular, the varying battery voltage can be used to encode the data to be transmitted using a predetermined voltage dip relative to this varying battery voltage. In this regard, a high level is defined by subtracting a small voltage from the varying battery voltage, while a low level is defined by subtracting a larger predetermined voltage from the varying battery voltage. In this way, the modulated signal "drifts" along with the varying battery voltage, depending on the current level of the varying battery voltage. In this way, all bus participants can be permanently supplied with a varying battery voltage, and all bus participants can also experience the effect of the varying battery voltage on the level of the modulated switching signal. The receiving bus participants can receive the received data by AC voltage isolation of the modulated signal and subsequent digital conversion via a comparator with a variable threshold tracking. The data can be generated by "Manchester encoding." The data can be transmitted, for example, at a maximum rate of 125 kBit / s. Due to the modulated signal drifting along with the varying battery voltage signal, the present invention makes it possible to eliminate the need for an additional voltage regulator in the transmitting (especially the master) control device to supply the bus participants.The master operates using a varying modulation voltage that is derived directly from the battery voltage, for example, via a regulator stage and a driver stage. Therefore, as long as a predetermined difference between the high and low levels of the modulating signal is met, the actual level of the varying battery voltage is irrelevant to the decoding of the data. In particular, the stroke between the low and high levels can be predefined and can drift / float with the varying battery voltage.

[0004] The dependent claims indicate preferred variants of the invention. Advantageously, the battery voltage can be additionally filtered to suppress noise in the frequency range of the voltage modulation according to the invention. This does not mean that the (slowly) varying battery voltage is kept constant or sustained in the classical sense. In this way, a simple construction and reliable communication can be provided.

[0005] The remaining bus participants (simple participants or slaves) may, if necessary, have their own voltage regulators to generate a constant operating voltage from a varying battery voltage or from a varying battery voltage modulated in the manner according to the invention.

[0006] The present invention can be understood, inter alia, with regard to the voltage level of the modulated signal, in which the reference level is not 0 volts but rather the time-varying (slowly) changing voltage level of the battery voltage. Thus, the difference between the changing battery voltage (unmodulated supply voltage) and the high level of the modulated bus signal (modulation signal) can be kept constant over time. That is, the high level of the modulated signal is coupled with a fixed offset (difference) to the unmodulated supply voltage (varying battery voltage). Alternatively or additionally, the difference between the high and low levels of the modulated signal can be kept constant. Provided that all communication pairs within the two-wire bus system have a similar changing battery voltage at their disposal, this changing battery voltage can also be used to demodulate or receive data from the modulated / bus signal.

[0007] Optionally, the average value or operating point of the modulation stroke can be "suspended" with a predetermined offset under varying battery voltages. In other words, the average level (U _mod_high +U _mod_low )×½ is tracked over time with a fixed offset to each momentary level of changing battery voltage.

[0008] Preferably, all bus participants (master and all slaves) in a two-wire bus system can be supplied with energy by one and the same battery, which may provide a varying battery voltage. In this case, if the length of the bus system is short enough (in particular <20 m), it is guaranteed that all control devices receive a bus voltage that is sufficient for transmitting and receiving data as it should.

[0009] The modulation signal may be derived, for example, from a varying battery voltage via a predetermined modulation resistor. In this case, to generate the modulation signal, a predetermined current for a high level is drawn through the modulation resistor, thereby tapping a high level between the modulation resistor and a current source connected to electrical ground. Correspondingly, a greater predetermined current is drawn through the modulation resistor using the current source and / or additional current sources, thereby tapping a low level between the modulation resistor and one or more current sources. In this way, data is transmitted over the bus by each transmitting control device selectively pulling the bus voltage to a high level or a low level. Otherwise, the respective current source of each control device is turned off.

[0010] Preferably, the modulation signal can be generated from the varying battery voltage by a regulation stage and a driver stage. For this purpose, the regulation stage compares the modulation target voltage with the modulated actual voltage after the driver output stage, keeping the regulation difference small. Technically, the voltage drop at the driver output stage A small adjustment difference remains as a result of this. In other words, this adjustment difference is the difference between the varying battery voltage and the High level of the modulation signal, which is due to the voltage drop in the driver output stage. Depending on the technical design of the driver output stage as a push-pull stage, which can be realized, for example, as a unipolar transistor with a low resistance between drain and source in the on-state of the transistor, or by a bipolar transistor with a low saturation residual voltage, the voltage drop, and therefore the remaining adjustment difference, can be kept small, so that the High level of the modulation signal is as high as possible.

[0011] The two-wire bus system according to the invention eliminates the need for a voltage regulator in the first bus participant (master). Unregulated voltage levels are not an issue during modulation and demodulation of data communicated over the two-wire bus system due to the modulation principle according to the invention. In this way, costs can be saved and the complexity of the first bus participant / bus system can be reduced.

[0012] According to a second aspect of the present invention, a bus participant is proposed for use as a first bus participant in the method as described above. The first bus participant has a two-wire bus terminal for communicating with the bus participants and for acquiring the varying battery voltage. The remaining bus participants are energized by the first bus participant and addressed by data modulated onto the varying battery voltage. In this case, the first bus participant is adapted to cause the modulated signal to follow the level of the varying battery voltage in a predetermined manner. In other words, the high and low levels of the modulated signal drift together "under the surface" of the varying battery voltage.

[0013] According to a third aspect of the present invention, a bus system is proposed, comprising a first bus participant according to the above-described inventive aspect and at least one second bus participant connected to the first bus participant by a two-wire line. The features, combinations of features and advantages resulting therefrom clearly correspond to the features, combinations of features and advantages resulting therefrom detailed above in connection with the first and second aspects of the present invention, and reference is made to these aspects to avoid repetition.

[0014] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a two-wire bus system according to one exemplary embodiment of the present invention; [Figure 2] FIG. 2 is a voltage timing diagram illustrating the varying battery voltage UBatt and modulation voltage Umod. [Figure 3] FIG. 3 is an enlarged partial view of the voltage timing diagram of FIG. 2. [Figure 4] 1 is a schematic diagram of an exemplary embodiment of a bus participant according to the present invention with a controllable current sink; [Figure 5]2 is a schematic diagram of a regulation stage connected with a driver stage of an exemplary embodiment of a bus participant according to the invention; [Figure 6] 1 is a circuit diagram of the principle of an assembly in the receive path of a bus participant of a bus system according to the invention; [Figure 7] 1 is a flow diagram illustrating the steps of one exemplary embodiment of a method for transmitting data in a two-wire bus system according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0016] Figure 1 shows in a schematic diagram a two-wire bus system 10 in which a battery 7 supplies a first control device 1 in the form of a master with a varying battery voltage. is adapted to supply a varying battery voltage from a battery 7 to the second control device 2, the third control device 3 and the fourth control device 4, and to transmit data to the control devices 2, 3, 4 as bus participants.

[0017] The two-wire bus system 10 can be installed, for example, in cars, vans, trucks, air vehicles, and / or water vehicles. The on-board network voltage can be 12 volts, 24 volts, 48 ​​volts, or even 400 volts or 800 volts. The components of receiving and decoding the voltage-modulated Manchester-coded signals in the control devices 2, 3, 4 are AC voltage isolation of the modulated signals and their subsequent digital conversion via a comparator with variable threshold tracking. The assembly required for this is presented in connection with FIG. 6.

[0018] Figure 2 shows the varying battery voltage U Batt The voltage timing diagram shows the battery voltage U Batt rises from about 7 volts to about 16.5 volts, and then falls back to about 7 volts after about 0.4 ms.

[0019] Within such a voltage range, the fixed modulation voltage or Δ from high level to low level may have very low resolution, so that in the method according to the invention, the modulation signal U mod However, the battery voltage U Batt In other words, the corresponding low level of about 1.5 volts and high level of 5 volts at 0 seconds change to just under 10 volts (low level) and about 13.5 volts (high level) within the range of 0.20 ms to 0.40 ms. In other words, within the first time range, the modulation signal U mod The low level of the modulated signal U mod In fact, the high levels in the first time range are defined to be significantly lower than the low levels at later times. In other words, the high levels in the first time range (e.g., at 0 seconds) of the modulated signal U mod are defined to be lower than the low and high levels in the second (later) time range (from about 0.2 ms). The opposite applies to the second time range and to the third time range following from 0.50 ms, in which the low and high levels correspond to those in the first time range. In contrast, the modulation signal U mod The voltage stroke of remains constant over the entire time range (first to third time range) at about 3 volts. Correspondingly, the varying battery voltage U Batt and the modulating signal U mod The battery voltage U remains constant over time (approximately 3 volts) between the high and low levels. Batt and the superimposed modulated signal U mod The difference between the low level of the input and the low level of the output remains constant over time at about 6 volts.

[0020] FIG. 3 shows a portion of the voltage timing diagram shown in FIG. 2, from which both voltage signals U Batt and U modThe relationship between the filtered battery voltage U Batt gives the impression of being constant within the considered time range, while the high level U mod_high is U Batt This is due to the voltage drop U across the driver output stage. Treib The value below is equivalent to U mod_low In the case of mod_high -Equivalent to [0.5V to 2V]. Low level U mod_low Further voltage levels are possible for the 2-wire bus, which allows for higher bit rates. In this regard, for example, a first low level (not shown) of 0.5 volts minus the high level corresponds to the first symbol, and a second low level of 1 volt minus the high level corresponds to the second symbol. This also advantageously allows the voltage difference, i.e. the modulation voltage stroke, to be adapted to the line parameters of the bus and environmental influences in order to adapt the robustness of the data transmission to the specific two-wire line system. Attention should be paid to , both illustrated voltage transitions are not transmitted across the bus, but rather the changing battery voltage U Batt is provided, for example, only to the first control device 1, which then generates the modulated signal U for data transmission. mod is transmitted to control devices 2, 3, and 4 (see Figure 1) via a two-wire line.

[0021] FIG. 4 shows a schematic diagram of components for generating a varying modulated voltage on a two-wire line (bus) by, for example, a first bus participant (master) 1. Three controllable varying current sinks I1, I2, and I n The logic 8 controls the modulation of each switch S1, S2, and S n and is adapted to be activated via control line 7, whereby a digital (Manchester encoded) data stream is converted into a modulation current and ultimately into a varying modulation target voltage U Soll In this regard, the modulation target voltage USoll is revealed by the following formula.

[0022] U Soll =U BattFilter -R mod ×I Ges In the formula, U BattFilter is the filtered varying battery voltage, and R mod is the ohmic resistance of the modulation resistor, and I Ges is controlled by a controllable current source, modulating resistor R mod is the total current drawn through the voltage signal U Soll is sent to the regulation stage (shown in Figure 5). When necessary, the current sinks / sources I1, I2, and I n By means of the time-staggered switching of the pulses, the time shape of the target voltage stroke (pulse shaping) can be adapted, so that any pulse shape (e.g. rectangular, sinusoidal, triangular, or even edge-modified "only" to further reduce interference emissions) can be realized.

[0023] 5 shows a circuit including a regulation stage 5 and a driver stage 6 for use in a bus participant (master) according to the invention. The regulation stage 5 generates a modulated target voltage U Soll and the modulated real voltage U after the driver output stage mod , the adjustment difference is kept small compared to the voltage drop across the driver stage 6. Technically, a small adjustment difference remains as a result of the voltage drop across the driver stage 6. By technically designing the driver stage 6 as a push-pull stage, for example, with unipolar transistors having a low source resistance or bipolar transistors having a low saturation residual voltage, the voltage drop and therefore the remaining adjustment difference can be kept small.

[0024] Figure 6 shows the principle circuit of AC voltage coupling and subsequent digital conversion in the receiving path of a control device (especially a slave) when transmitting only two different voltage levels (High and Low). For example, when transmitting only two voltage levels, on the receiving side, the control devices 2, 3, 4 receive the modulated voltage U modA simple circuit structure is required to separate the modulated signal U from the average varying DC voltage component (AC voltage isolation). This is followed by voltage adaptation of the AC voltage signal, e.g. Manchester coded, symmetrical about 0 volts to the input voltage range of the subsequent comparator 11. The AC voltage isolation is performed by the AC voltage separator 9 and the capacitor C2. The filter network between the AC voltage separator 9 and the comparator 11 includes a low pass filter incorporating an ohmic resistor R1 and a capacitor C1. The comparator 11 then converts the modulated signal U mod , in which the switching threshold is generated directly from the low-pass filtered modulated signal. mod_digi The voltage supply U of the AC voltage separator 9 and the comparator 11 Sensor is realized from the modulated voltage by means of a voltage regulator, for example in an AC voltage separator 9 and a comparator 11.

[0025] 7 shows the steps of one exemplary embodiment of a method for data transmission in a two-wire bus system according to the invention. The method comprises, in a first step 100, the supply of a varying battery voltage to a first bus participant (master) and to a second bus participant (slave). This battery voltage can be understood as a DC voltage signal whose magnitude can (slowly) change over time. In this regard, this varying battery voltage can be, for example, a DC voltage signal whose magnitude can (slowly) change over time. The voltage may be shifted upward by 20%, 40%, 60%, or more. In a second step 200, data is transmitted from the first bus participant (master) to the second bus participant (slave) by a modulated signal superimposed on or written onto the varying battery voltage. The modulated signal follows the varying battery voltage level in a predetermined manner. In other words, the modulated signal hangs equidistant below each level of the varying battery voltage. While the varying battery voltage is sent to the first bus participant (master), the first bus participant (master) transmits the modulated signal via the two-wire line to the second and further bus participants.

[0026] The invention simplifies the voltage generation in the master control device for the sensors on the bus and allows data transmission from the master control device to the bus participants to be at least up to six times higher than, for example, the generation of parking sensors currently known in the state of the art, and allows uninterrupted operation of the sensors without intermediate energy storage in the communicating bus participants, which simplifies the construction and eliminates the need for hardware that was always necessary in the state of the art.

Claims

1. A method for transmitting data in a two-wire bus system (10), comprising: - the first bus participant (1) and the second bus participant (2) are supplied with a varying battery voltage (U Ｂａｔｔ ) (100); - the varying battery voltage (U Ｂａｔｔ ) is superimposed on the modulated signal (U ｍｏｄ ) to transmit data (200) from the first bus participant (1) to the second bus participant (2), and at that time, the modulated signal (U ｍｏｄ ) is the changing battery voltage (U Ｂａｔｔ ) in a predetermined manner; A data transmission method including:

2. - the varying battery voltage (U Ｂａｔｔ ) and the modulated signal (U ｍｏｄ ) High level (U ｍｏｄ＿ｈｉｇｈ ) and / or - said modulated signal (U ｍｏｄ ) High level (U ｍｏｄ＿ｈｉｇｈ ) and Low level (U ｍｏｄ＿ｌｏｗ 2. The method of claim 1, wherein the difference between

3. The modulated signal (U ｍｏｄ ) is the average value of the varying battery voltage (U Ｂａｔｔ 3. The method according to claim 1, wherein the time is followed with a predetermined offset of .

4. All bus participants (1, 2, 3, 4) in the two-wire bus system (10) are Ｂａｔｔ 4. The method of claim 1, wherein the power supply is a battery providing

5. The modulated signal (U ｍｏｄ ) is the modulation resistance (R ｍｏｄ ) by the changing battery voltage (U Ｂａｔｔ ) and the modulation resistor is derived from the modulation signal (U ｍｏｄ ) to generate a predetermined current (I Ｇｅｓ 5. The method according to claim 1, wherein the sieve is passed through by a flow of water.

6. The modulated signal (U ｍｏｄ ) High level (U ｍｏｄ＿ｈｉｇｈ ) and Low level (U ｍｏｄ＿ｌｏｗ ) is determined by a number of current sources (I １ , I ２ , I ｎ ) by the modulation resistor (R ｍｏｄ 6. The method of claim 5, wherein the signal is generated between the first and second inputs.

7. The modulated signal (U ｍｏｄ ) is controlled by the regulation stage (5) and the driver stage (6) to the varying battery voltage (U Ｂａｔｔ 7. The method of claim 1, wherein the hydroxybenzoate is produced from a hydroxybenzoate.

8. 8. The method according to any one of claims 1 to 7, wherein no voltage regulator is present in the first bus participant (1).

9. A bus entry device for use as a first bus entry device (1) according to the method of any one of claims 1 to 8, comprising: - For communication and varying battery voltage (U Ｂａｔｔ ) a two-wire bus terminal for acquiring The first bus participant (1) transmits the varying battery voltage (U) to the second bus participant (2) via the two-wire bus terminal. Ｂａｔｔ ) to provide energy by, and - transmitting the varying battery voltage (U Ｂａｔｔ ) is superimposed on the modulated signal (U ｍｏｄ ), and the first bus participant (1) is further adapted to transmit the modulated signal (U ｍｏｄ ) to the varying battery voltage (U Ｂａｔｔ ) in a predetermined manner.

10. - a first bus participant (1) according to claim 9, a second bus participant (2) connected to said first bus participant (1) by a two-wire line; A bus system (10) including:

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