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EP-4285490-B1 - COMMUNICATION BUS SYSTEM, METHOD, AND SUBSCRIBER FOR TRANSMITTING DATA IN A SERIAL COMMUNICATION BUS SYSTEM

EP4285490B1EP 4285490 B1EP4285490 B1EP 4285490B1EP-4285490-B1

Inventors

  • MAURER, PETER
  • Fronen, Rob

Dates

Publication Date
20260513
Application Date
20220125

Claims (15)

  1. A method for transmitting data in a serial communication bus system, in which a bus master (28) and a plurality of subscribers (10) are connected in series with a two-wire line portion (24) between bus terminals (50, 52) of the bus master (28) and one of the subscribers (10) and with two-wire line portions (24), each connecting adjacent subscribers (10), of a differential two-wire data bus (26) to be operated at a predetermined common mode target level for data transmission by means of differential electrical signals from the bus master (28) to at least one of the subscribers (10), each subscriber (10) comprising an input (12) having two input terminals (14) connected to a two-wire line portion (24) and an output (16) having two output terminals (18) also connected to a two-wire line portion (24), in the method - data is transmitted from a first subscriber (10) to the bus master (28) via the two-wire data bus (26) in a direction opposite to the data transmission by means of differential electrical signals, in that a) a first subscriber (10) repeatedly feeds in or draws a data transmission current of a predetermined magnitude in a pulse-like manner at its input terminals (14) for transmitting data by means of non-differential signals to an adjacent second subscriber (10) connected via a two-wire line portion (24), b) the second subscriber (10) repeatedly draws or feeds in a compensation current corresponding to the data transmission current in a pulse-like manner at its output terminals (18) for maintaining the predetermined common mode target level, characterized in that a compensation current pulse generated in the second subscriber (10) with the magnitude required to maintain the common mode target level represents a binary data transmission from the first subscriber (10) to the second subscriber (10), and c) said second subscriber (10) repeatedly feeds in or draws a data transmission current of a predetermined magnitude in a pulse-like manner at its input terminals (14) for transmitting data by means of non-differential signals to an adjacent third subscriber (10) connected via a two-wire line portion (24), d) the steps b) and c) are performed for each subscriber (10) arranged between the first subscriber (10) and the bus master (28), and e) the bus master (28) repeatedly draws or feeds in a compensation current in a pulse-like manner at its bus terminals (50, 52) connected to a two-wire line portion (24) for maintaining the predetermined common mode target level, wherein a compensation current pulse generated in the bus master (28) with the magnitude required for maintaining the common mode target level represents a binary data transmission from the subscriber (10) connected to the bus master (28) via a two-wire line portion (24) to the bus master (28), whereby the data transmission from the first subscriber (10) to the bus master (28) is completed.
  2. The method according to claim 1, characterized in that if the subscriber transmitting data to the bus master (28) is the subscriber (10) adjacent to the bus master (28) and connected thereto via a two-wire line portion (24), data transmission is performed by repeatedly feeding in or drawing data transmission current on the part of the subscriber (10) at its input terminals (14) in a pulse-like manner and by repeatedly drawing or feeding in compensation current on the part of the bus master (28) at its bus terminals (50, 52) in a pulse-like manner.
  3. The method according to claim 1 or 2, characterized in that the pulse-like feeding or drawing of the data transmission current is at a frequency which is smaller than a first or equal to a first cutoff frequency, and in that only such infeeds or such draws of compensation current at the output terminals (18) of a subscriber (10) or at the bus terminals (50, 52) of the bus master (28) are interpreted as data transmission via a two-wire line section (24), the current pulses of which follow one another at a frequency which is smaller than the first or equal to the first cutoff frequency.
  4. A method for transmitting data in a serial communication bus system, in which a bus master (28) and a plurality of subscribers (10) are connected in series with a two-wire line portion (24) between bus terminals (50, 52) of the bus master (28) and one of the subscribers (20) and with two-wire line portions (24), each connecting adjacent subscribers (10), of a differential two-wire data bus (26) to be operated at a predetermined common mode target level for data transmission by means of differential electrical signals from the bus master (28) to at least one of the subscribers (10), each subscriber (10) comprising an input (12) having two input terminals (14) connected to a two-wire line portion (24) and an output (16) having two output terminals (18) also connected to a two-wire line portion (24), according to any one of claims 1 to 3, in the method - data is transmitted from the bus master (28) to one of the subscribers (10) and thus in the same data transmission direction as for data transmission by means of differential electrical signals from the bus master (28) to at least one of the subscribers (10) optionally also in that - the bus master (28) repeatedly changes the common mode level at its bus terminals (50, 52) in a pulse-like manner, starting from the target level, by a value within a predetermined range, - the change in the common mode level by the predetermined value at the input terminals (14) of a first subscriber connected to the bus master (28) via a two-wire line portion (24) is detected in the subscriber (10), and - this represents a binary data transmission from the bus master (28) to the first subscriber (10) by means of a non-differential electrical signal, e.g. a non-differential voltage signal.
  5. The method according to claim 4, characterized in that the binary data transmission between the bus master (28) and the first subscriber (10) and further from the first subscriber (10) to the second subscriber (10) adjacent thereto and so on from subscriber (10) to subscriber (10) up to a subscriber (10) to which the data transmission applies.
  6. The method according to claim 4 or 5, characterized in that the pulse-like change in the common mode level by the predetermined value is at a frequency which is smaller than or equal to a second cutoff frequency, and in that only such changes in the common mode level by the predetermined value detected in a subscriber (10) are interpreted as binary data transmission from the bus master (28) to a subscriber (10), the frequency of which is equal to or smaller than the second cutoff frequency.
  7. The method according to claim 6 and according to claims 4 or 5 and according to claim 3, characterized in that the two cutoff frequencies differ from each other by at least a factor of 10 or 100 or 1000.
  8. The method according to claim 7, characterized in that the second cutoff frequency is smaller than the first cutoff frequency.
  9. A subscriber of a serial communication bus system, in which a bus master (28) and a plurality of subscribers (10) are connected in series with a two-wire line portion (24) between bus terminals (50, 52) of the bus master (28) and one of the subscribers (10) and with two-wire line portions (24), each connecting adjacent subscribers (10), of a differential two-wire data bus (26) to be operated at a predetermined common mode target level for data transmission by means of differential electrical signals from the bus master (28) to at least one of the subscribers (10), each subscriber (10) comprising an input (12) having two input terminals (14) connected to a two-wire line portion (24) and an output (16) having two output terminals (18) also connected to a two-wire line portion (24), the subscriber being provided with - an input (12) having two input terminals (14) and an output (16) having two output terminals (18), - a controllable data transmission current source (46) for repeatedly feeding in and drawing a data transmission current at the two input terminals (14) in a pulse-like manner for transmitting data to another subscriber, the output terminals (18) of which are connected to the input terminals (14) of the subscriber, - a control circuit for maintaining the predetermined common mode target level at the two output terminals (18), and - a controllable compensation current source (38) for repeatedly drawing or feeding in a compensation current at the output terminals (18) in a pulse-like manner, - wherein the control circuit comprises a control signal driving the compensation current source (38) in order to feed in or draw compensation current for the purpose of maintaining the predetermined common mode target level, on the basis of which signal the data transmission current source (46) can be repeatedly controlled in a pulse-like manner in order to feed in and draw data transmission current at the two output terminals (18) if a change in the control signal (43) occurs with a predetermined minimum magnitude per unit of time, and wherein the subscriber repeatedly feeds in or draws the data transmission current in a pulse-like manner at its input terminals (14) for transmitting data by means of non-differential signals to an adjacent subscriber connected via a two-wire line portion (24),
  10. The subscriber according to claim 9, characterized in that the pulse-like feeding or drawing of data transmission current is at a repetition rate having a frequency smaller than or equal to a first cutoff frequency, and in that the control signal (43) is adapted to be supplied to a first low-pass filter (48) at the first cutoff frequency when it varies with exceeding the predetermined minimum magnitude.
  11. A subscriber of a serial communication bus system, in which a bus master (28) and a plurality of subscribers (10) are connected in series with a two-wire line portion (24) between bus terminals (50, 52) of the bus master (28) and one of the subscribers (10) and with two-wire line portions (24), each connecting adjacent subscribers (10), of a differential two-wire data bus (26) to be operated at a predetermined common mode target level for data transmission by means of differential electrical signals from the bus master (28) to at least one of the subscribers (10), each subscriber (10) comprising an input (12) having two input terminals (14) connected to a two-wire line portion (24) and an output (16) having two output terminals (18) also connected to a two-wire line portion (24), according to claim 9 or 10, the subscriber (10) being provided with - a controllable reference voltage source (42) for repeatably changing the common-mode level at the output terminals (18) in a pulse-like manner by a value within a predetermined range with respect to the predetermined target level, and - a detection circuit for detecting a deviation of the common mode level at the input terminals (14) by the predetermined value with respect to the target level and for outputting a detection signal when a deviation of the common mode level by a predetermined minimum value is detected, - wherein the reference voltage source (42) is controllable to change the common mode level based on the detection signal of the detection circuit.
  12. The subscriber according to claim 11, characterized in that the pulse-like change in the common mode level is at a repetition rate smaller than a second or equal to a second cutoff frequency, and in that the detection signal is adapted to be supplied to a second low-pass filter (58) at the second cutoff frequency.
  13. The subscriber according to claim 10 and 12, characterized in that the two cutoff frequencies differ from each other by at least a factor of 10 or 100 or 1000.
  14. The subscriber according to claim 13, characterized in that the second cutoff frequency is smaller than the first cutoff frequency.
  15. A communication system having a bus master (28) and a series connection of subscribers (10) connected thereto according to any one of claims 9 to 14, and/or for performing the method according to any one of claims 1 to 8.

Description

The invention relates to a method for transmitting data in a serial communication bus system. In this communication bus system, a bus master is serially connected to a series connection of a plurality of participants. The communication bus system has a differential two-wire data bus, operated with a predetermined common-mode setpoint level, for data transmission by means of differential electrical signals from the bus master to at least one of the participants. A two-wire line section is located between the bus terminals of the bus master and the participant adjacent to it in the series connection. Such two-wire line sections also connect the participants within the series connection. Each participant has an input with two input terminals connected to a two-wire line section and an output with two output terminals also connected to a two-wire line section. Except for the last participant in the series connection, the outputs are connected to a two-wire line section. The invention further relates to a participant for use in a method for transmitting data in a serial communication bus system. Finally, the invention also relates to communication bus systems with several such participants and for the transmission of data. Such daisy-chain communication bus systems are generally known and are preferred due to their simple structure and associated cost-effectiveness when it comes to controlling the participants of a communication bus system via the transmission of serial electrical signals. In this system, a participant receives a data stream at its input from the output of its upstream neighbor (i.e., neighboring the bus master), recognizes this stream, and generates an identical data stream at its output to forward to its downstream neighbor (unless the data stream is intended for the aforementioned participant). (Participant is determined). Daisy-chain communication bus systems are particularly suitable for lighting applications inside and outside a vehicle, for example for ambient light applications. A certain disadvantage of daisy-chain communication bus systems is that communication on the bus always occurs from the bus master to at least one (or even all) of the participants. However, it is sometimes desirable for the participants to at least send status information back to the bus master, such as confirmation that an address has been assigned to a participant. Concepts for such an "upstream" communication channel are in US-A-5 485 488 , from which a method according to the preamble of claim 1 is known, and in US-B-6 813 483 described. However, these concepts are relatively complex to implement. In this respect, it is an object of the invention to create a simplified concept for communication in a serial communication bus system in the opposite direction to the communication direction with differential electrical signals from one or more of the participants to the bus master. DE-B-10 2018 104 865 are a device for controlling electrical and/or electronic components of a vehicle module and such a vehicle module with automatic module addressing with clock synchronization. To solve this problem, the invention provides a method for transmitting data in a serial communication bus system, in which a bus master and a plurality of participants are connected in series with a two-wire line section between the bus terminals of the bus master and one of the participants, as well as with two-wire line sections connecting adjacent participants, of a differential two-wire data bus to be operated at a predetermined common-mode setpoint level for data transmission. by means of differential electrical signals (e.g. differential voltage signals) from the bus master to at least one of the participants, wherein each participant has an input with two input terminals connected by a two-wire line section and an output with two output terminals also connected by a two-wire line section, wherein in the method Data from a first participant to the bus master is transmitted via the two-wire data bus in a direction opposite to data transmission using differential electrical signals, by a) a first participant at its input terminals for the transmission of data by means of non-differential signals to a neighboring second participant connected via a two-wire line section repeatedly feeds in or takes out a data transmission stream of a predetermined size in pulses, b) the second participant repeatedly pulses a compensation current corresponding to the data transmission current at its output terminals to maintain the specified common-mode setpoint level, wherein a compensation current pulse generated in the second participant with the magnitude required to maintain the common-mode setpoint level represents a binary data transmission from the first participant to the second participant, c) this second participant repeatedly feeds or extracts a data transmission stream of the specified size at its input terminals for the transmission of data