EP1221220A2

EP1221220A2 - Method and device for bi-directional communication between at least two communication participants

Info

Publication number: EP1221220A2
Application number: EP00954377A
Authority: EP
Inventors: Wolfgang Drobny; Rainer Moritz; Bernhard Straub
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-09-29
Filing date: 2000-07-28
Publication date: 2002-07-10
Also published as: WO2001024441A2; DE19946776A1; JP2003527781A; WO2001024441A3; AU6685400A

Abstract

The invention relates to a method and device for bi-directional data transfer between at least two communication participants whereby data transfer is attained in one communication direction by altering a current and in another communication direction by altering a voltage. Data transfer in both communication directions to a communication path can be simultaneously in such a way that energy supply for both communications directions is maintained by means of a constant lower voltage and/or current limit or a separate energy supply for each communication participant.

Description

Method and device for bidirectional communication of at least two communication participants

State of the art

The invention relates to methods and apparatus for bidirectional data transmission between at least two communication participants according to the preambles of the independent claims. In particular, the data transmission takes place between a peripheral device and a

Control unit in an airbag system.

DE 196 09 290 AI shows an airbag system for protecting vehicle occupants. A plurality of sensor modules are provided therein, which are connected to a remote control unit via line pairs. The control unit controls a restraint device for vehicle occupants, such as in particular an airbag. The output signals from the sensor modules are in the form of mutually juxtaposed changes in the current flow on both

Cables, ie in the form of analog push-pull signals or in the form of a pulse train to the control unit. In the opposite direction, from the control unit to the sensor modules, the data are realized by changes in the voltage that are juxtaposed. Communication is delayed, that is, on the basis of a request signal in the form of changes in the voltage which are adjacent to one another, the control unit signals the start of transmission to the sensor modules and then the data are transmitted in the opposite direction, that is to say from the sensor modules to the control unit, the data are transmitted in the form of mutually adjacent changes in the current flow on the line pair.

Regarding the current interface, ie generally the direction of transmission from the sensor modules to the control unit, the unpublished German application 198 13 965.9 shows a method for transmitting digital data with a clock transfer generator that is controllable in its clock frequency. The data transmission from a peripheral device to a control device by means of signal edges of the current flow is described in a special form. The coding of the binary states is thus defined by a rising or falling signal edge, which must be detected in a certain time window. The data transfer clock generator frequency can be synchronized by additionally using Manchester coding. The time shift that occurs between the data pulses and the synchronization times of the edge changes is determined by a time-shifted sampling of the logic level

Data pulses considered. If the transmission were used bidirectionally according to this method, a time-shifted data transmission would also have to be used here.

In addition to the Manchester or Manchester II coding just mentioned, further coding methods, in particular cyclical coding methods, are known in data transmission technology, such as the Hamming code or the Abramson code, etc. The invention is based on the object, based on the description of the unpublished German application 198 13 965.9, to carry out a further development such that, in addition to the current interface shown therein, a bidirectional, simultaneous one

Data transmission in both directions is made possible.

Advantages of the invention

The invention is based on a method and one

Device for bidirectional data transmission between at least two communication participants, the data transmission in one communication direction being implemented by changes in a current flow and in the other communication direction by changes in a voltage, the data transmission in both communication directions being able to be carried out simultaneously on one communication path. The invention further develops the content of the unpublished German application 198 13 965.9 in such a way that bidirectional and simultaneous data transmission is possible in both communication directions. The content of the German application 198 13 965.9 is thus also the content of the illustrated invention.

Because the communication from the first

Communication subscriber, in particular a peripheral device to the second communication subscriber, in particular a control device, is realized by signal edges of the current flow, while the change in the voltage level

Communication from the control device to the periphery, wherein the transmission from the communication participant 1 to the communication participant 2, that is, from the periphery to the control device according to the above not previously published German application, is a fast digital Data transmission from the periphery to a control device with its characteristic advantages achieved and additionally the ability to bidirectionality of the interface achieved by sensing the change in the potential on the connecting line.

The Manchester code, in particular the Manchester II code, can expediently be adopted in both communication directions for coding the digital information. As a result, the data rates can be increased by self-synchronizing coding of the digital data for communication in both directions.

It is advantageous that the data transmission from communication participant 2, ie the control device to communication participant 1, ie the periphery, can be implemented by any coding, for example in addition to the Manchester or Manchester II code, for example also by the Hamming code or the Abramson code. Code, etc.

Advantageously, the interface according to the invention can make it possible to operate the interface according to the ISO 9141 standard by simply varying the components used (fitting variant).

When using Manchester coding, the synchronization takes place in the middle of a pulse, in particular a data pulse, and is therefore advantageously and always possible due to the edge change occurring there. The time period between two synchronization times in the middle of the pulse is expediently used in Manchester coding as the time range representing the clock frequency. Characterized in that the clock frequency is detected by means of the known counting of the oscillator clocks and the Data transfer generator takes the current clock frequency in the middle of the pulse, however, the data transfer generator detects the pulse level at different times, which means that it adapts to them advantageously. In order to be able to use a further advantage of Manchester coding, the 1-bit error detection, both pulse halves are expediently scanned at least once before and after the time of synchronization in the middle of the pulse. The scanning is advantageously carried out by means of multiple scanning within a scanning window. The advantages with regard to the direction of communication from the periphery to the control device are thus retained in full and can simultaneously be used in the opposite direction.

Thus, a simultaneous bidirectional data transmission between the two communication participants is advantageously advantageously possible, advantageously asynchronously.

Further advantageous embodiments result from the description and the claims.

drawing

A possible basic structure of a device for data transmission according to the invention is described in FIG.

Figure 2 shows in principle the data transmission from the communication participant 2, that is, the control unit to

Communication subscriber 1, i.e. the peripheral device. The transmission is shown on the one hand with an intermediate level and on the other hand with a real low level by switching on and off. As already mentioned, the transmission of the data from communication subscriber 1 to communication subscriber 2 is described in the not previously published German application 198 13 965.9 and is based on the content.

Description of the embodiments

Figure 1 shows a basic structure of the interface. 101 is a switching logic or semiconductor intelligence, in particular in the form of a

Microcontrollers, etc. shown. At least one peripheral device 100 is connected to the switching logic 101. The switching logic 101 with the at least one peripheral device 100 represents, for example, the communication subscriber Kl. A control device can thus also be provided as the communication subscriber 1. Line 114 is the output line from the switching logic 101. Line 115 is the input line which leads to the switching logic 101. The switching logic 101 is connected via line 114 to a consumer 102, which in turn is connected to a switching means 105, in particular a transistor. The switching means 105 is connected on the one hand to ground and on the other hand to another consumer 104. Consumer 104 is connected to a further consumer 106, which in turn is connected to ground. With consumer 104 and

Consumer 106 is connected to another consumer 109. On the opposite side, this is connected to a potential on pin 108, in particular the supply voltage UBAT. An energy store, in particular a capacitor 110, which is also connected to ground, is connected to the common potential point of the three consumers 104, 106 and 109. The common potential point or the common line section of the consumers 104, 106 and 109 and of the energy store 110 leads into a comparator 103. A pin 107 is also guided into the comparator 103 which has a potential VC. The comparator 103 is connected on the output side to the switching logic 101 via line 115. The components and connecting lines just described are parts of the periphery P according to the invention. This periphery P is via the

Transmission line T connected to the control unit area S. The transmission line T begins in the peripheral port Pp which is connected to the comparator 103 via the common line section described above. The connection of the control unit area S thus the connection to the transmission line T, that is to say the control unit port, is denoted by Ps. The transmission line T is connected via port Ps via line 118 to the communication subscriber K2 and at the same time to a consumer 111. Consumer 111 is also connected to communication subscriber K2 via a line 117. Likewise connected to line 117 is an energy store, in particular a capacitance 112, which is simultaneously connected to ground. Communication subscriber K2 contains an evaluation circuit or evaluation logic 113 or corresponding semiconductor intelligence in the form of, for example, a microcontroller and, with 116, an actual microcontroller of a control device. However, it is also conceivable that the evaluation circuit 113 and the microcontroller 116 are accommodated in an integrated module. 116 can thus only be a microcontroller, but also a complete control unit, in which case logic 113 can then be swapped out.

The interface according to the invention requires at least one electrical connection T between the periphery P and the control unit area S, which transmits the data information in both directions. The reference potential, in particular ground, can be the reference potential of the control device through a further electrical connection (not shown here) be or refer to the reference potential at another peripheral location. The switching logic 101 takes over the edge control according to Manchester II coding for output line 114 as well as the evaluation and further processing of the serial voltage levels, for example in Manchester II coding, for input line 115. Output line 114 thus represents the signal path of all data transmission to the control device, while input line 115 connects the communication to the periphery P with the switching logic 101.

Switching means 105 is described below as a bipolar transistor. However, the switching means 105 can also have a different configuration, for example a unipolar transistor or a further switching logic. The base of transistor 105 is controlled via load 102 as a voltage divider. If transistor 105 switches, an increased current flow is made possible via transmission line T, the potential of transmission line T being maintained due to load 104. A residual current can also be ensured via transmission line T via consumers 106, even when transistor 105 is closed.

Energy storage 110 may be one or more

Protection capacities are realized and contributes to smoothing the edges of the data transmission signal and reducing the radiation of the transmission line T. 103 shows a comparator circuit which serves to compare the potential of the transmission line T with the potential VC on pin 107 and thus transfers the coded digital message from the control unit area S to the switching logic 101 via line 115. A supply voltage, in particular UBAT, or the associated potential of pin 108 is coupled in via consumer 109. On the control unit side S, the logic 113 can be implemented, for example, by an ASIC. The typical potential on transmission line T is regulated by logic element 113.

If transistor 105 is switched, a voltage drops across consumer 111, which voltage is evaluated between lines 117 and 118 or their inputs in logic element 113. Logic element 113 can thus encode, in particular according to

Receive the Manchester II coding processed digital message of the periphery P to the control unit S, process it and, if necessary, forward it to the microcontroller 116. The energy store 112 is a protective capacitance for protection against voltage or interference coupling into the logic element 113.

Logic element 113 has the ability to reduce the potential of the transmission line T to a residual potential (e.g.> 100 mv) VTl or an intermediate potential VTlz and to raise it again to the typical potential on transmission line T by means of a corresponding control by the microcontroller 116. This potential change on transmission line T can be applied to the switching logic 101 on the peripheral side by means of the comparator circuit 103 and the comparison of the potential of the transmission line T with the potential via pin 107, VC via line 115. The output of the comparator circuit 103 thus transmits the coded, in particular Manchester II-coded, digital message of the switching logic 101

Communication participant, in particular a control unit, K2, which the switching logic 101 can then process. The control device side S can on the one hand be accommodated completely in the control device, and the control device can also comprise only the logic module 113 and the microcontroller 116 in addition to other known components. Then the circuit of elements 111, 112, 117 and 118 would be on the control unit side, but upstream of the actual control unit. Likewise, logic element 113, in particular as ASIC, could be upstream of the control unit as communication partner K2. Due to this possible outsourcing, which is also possible on the peripheral side P, one of

Peripheral device 100 and control device or microcontroller 116 independent transmission path that can be connected to this can be implemented in one device.

The implementation of the interface shown in FIG. 1 corresponds to the configuration variant mentioned according to ISO standard 9141. An intermediate potential is achieved by the connection 108 and the load 109 coupling in its potential. This potential is therefore between the residual potential when the switching means 105 is switched off and the potential when the switching means 105 is switched on. With this configuration variant, an interface according to ISO standard 9141 is achieved, that is to say operation according to ISO 9141 of the interface shown.

The other variant is created by omitting the branch with connection 108 and consumer 109. Consumers 104 and 106 are dimensioned differently accordingly. However, a charge pump, ie an energy supply, must be available on both sides for simultaneous transmission.

The timing of the interface is shown in Figure 2. Since the direction of communication from the periphery P to the control device side S of the unpublished German Application 198 13 965.9 is described in sufficient detail and its content is also the content of this application, FIG. 2 shows implementation options for the communication direction of the control device side S to the periphery P. Two options are presented for realizing simultaneous transmission in both communication directions.

The first is an implementation with intermediate potential VTlz, shown in signal flow SP1 with one-sided

Power supply on the peripheral side P or control unit side S of the transmission link, in particular through the previously described branch with connection 108 and consumer 109.

The second possibility is to provide own power supplies for the peripheral side P and the control device side S if these do not draw their energy via the electrical connection T of the interface. Then it only has to be ensured that the interface can be switched on and off repeatedly.

In Figure 2, the potential VT on the transmission line T is shown over time. VTh shows a high potential and VT1 the already mentioned residual potential or

Low potential. Option 1 also shows an intermediate level VTlz, an intermediate low level, so to speak.

The switch-on process creates a potential VTh at tl. The actual transmission of the data is then represented at time t2 by at least one start bit from t2 to t3. In the illustration, the Manchester II coding is also selected here, after which synchronization takes place in the middle of the pulse, which allows the advantages of the Manchester II coding for both communication directions to use. At time t3, there is then optionally a further start bit or the first data bit. Subsequently, further data bits are transmitted at times t4 and t5. For example, a total of 8 data bits, i.e. 1 byte, are transmitted per transmission frame. Following the data at time t6, a parity bit is then transmitted for data checking and finally a stop bit for frame limitation at time t7.

As shown, the digital messages can be encoded in accordance with the Manchester II encoding or in accordance with further, in particular cyclic, codes such as Hamming or Abramson.

The low level for SP 1 corresponds here to an intermediate level which is below the high level VTh. This level VTlz guarantees at the same time a sufficient current flow for the opposite direction, not shown, from the communication subscriber 1 to the communication subscriber 2

Sufficient transmission distance.

In the second case, from power supplies on both sides of the transmission path, the signal is changed from the low level VTl to the high level VTh when switching on at tll. Here too, at time t21, in the case of signal SP2, as in SP1, transmission is started with at least one start bit. A further start bit or the first data bit can be transmitted at time t31. Another data bit is transmitted at time t4l. The further procedure corresponds to that of SP1 with the difference that the change between the low potential VT1 and the high potential VTh is carried out. Since the current flow associated with the low potential VT1 in the opposite direction from K1 to K2 is not sufficient for data transmission, the use of own energy or power supplies on the peripheral side P and control unit side S is necessary for a simultaneous transmission. Otherwise, i.e. with SP2 without power supply on both sides, the interface would be switched off at level low VTl and no communication from peripherals to control unit, i.e. from K1 to K2, would be possible via changes in current flow. The communication directions would then have to be loaded with a time delay, ie the communication would take place with a time delay, as in the prior art.

In both cases SP1 and SP2, after the end of the communication with the stop bit at t7 or analogously with a stop bit not shown at SP2, the level of the transmission line T is returned to high potential VTh.

The methods and devices shown allow the high demands, in particular in the automotive sector, to be taken into account in terms of data security, data rate and system solution costs. This also enables the possibility of detecting and compensating for data failures during data transmission, while at the same time achieving greater robustness against EMC influences.

As already mentioned, the methods and the devices can be used independently of a special application, specifically wherever data transmission between at least two communication participants is desired. In addition to the airbag system mentioned, they also offer drive control, chassis and brake control as well as transmission control processes, etc. Likewise is one Communication of other electronics, such as door locks or window regulators with a control unit is being considered.

Claims

Expectations

1. Method for bidirectional data transmission between at least two communication participants, the data transmission in one communication direction due to changes in a current flow and in the other

Communication direction is realized by changing a voltage, characterized in that the data transmission in both communication directions can be carried out simultaneously on a communication path in that an energy supply for both

Communication directions is maintained by a constant minimum level of voltage and / or current flow or a separate power supply of each communication participant.

2. The method according to claim 1, characterized in that the data transmission takes place by changes in the voltage such that, in addition to a high level and a low level of the voltage, an intermediate level of the voltage is set and is switched to display the data between the high level and the intermediate level.

3. The method according to claim 1 and 2, characterized in that the minimum level corresponds to the intermediate level.

4. The method according to claim 1, characterized in that the data transmission takes place by changes in the voltage such that in addition to a high level, a low level of the voltage is set, and to display the data is switched between the high level and the low level.

5. The method according to claim 1, characterized in that at least in the communication direction of the data transmission by changing the current flow, the data-realizing data pulses are generated with an inverted and non-inverted pulse half and these are coded with an edge change lying between the pulse halves.

6. The method according to claim 1, characterized in that the communication direction of the data transmission by changing the voltage, the data-realizing data pulses are generated with an inverted and non-inverted pulse half and this with a flank change between the pulse halves with a cyclic code, in particular the Manchester, Hamming, or Abramson code.

7. Device for bidirectional data transmission between at least two communication participants with the first

Means which carry out the data transmission in one communication direction by changes in a current flow and second means which carry out the data transmission in the other communication direction by changes in a voltage, characterized in that there is a communication path on which the data transmission in both

Communication directions is carried out simultaneously in such a way that an energy supply for both communication directions is provided by first and / or second means is maintained by a constant minimum level of voltage and / or current flow or a separate power supply for each communication participant.

8. The device according to claim 7, characterized in that third means are included, which carry out the data transmission by changing the voltage such that in addition to a high level, a low level of the voltage is set, and switched to display the data between the high level and the low level a separate energy supply is included for each communication direction.

9. The device according to claim 7, characterized in that third means are included which carry out the data transmission by changing the voltage such that in addition to a high level and a low level of the voltage, an intermediate level of the voltage is set and to represent the data between the high level and the intermediate level is changed.

10. The device according to claim 7, characterized in that fourth means are included which realizing the data at least in the communication direction of the data transmission by changing the current flow

Generate data pulses with an inverted and non-inverted pulse half and manchode these with an edge change between the pulse halves.

11. The device according to claim 7, characterized in that fifth means are included, the data-implementing data pulses with an inverted and non-inverted in the communication direction of data transmission by changing the voltage Generate the pulse half and encode it with an edge change between the pulse halves with a cyclic code, in particular the Manchester, Hamming or Abramson code.