Serial Bus Subscriber Signaling via Common-Mode Current Compensation

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Solution Overview

Problem

Daisy-chain communication bus systems primarily transmit data from the bus master to participants, lacking a simplified mechanism for participants to send status information back to the bus master, and existing upstream communication concepts are complex.

Innovation Solution

Participants transmit data to the bus master using differential electrical signals by injecting a pulsed data transmission current and maintaining a common-mode setpoint level through a compensation current, ensuring no common-mode level changes occur, allowing binary data transmission from participant to bus master.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If start and stop bits are added to each byte for asynchronous serial communication, then communication compatibility is improved, but communication time increases due to additional overhead bits

Engineering Contradiction:

Improvecommunication compatibilityVSAvoidcommunication time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The communication protocol is segmented into different modes: a first communication mode using start/stop bits for compatibility, and a second communication mode using a simplified protocol without start/stop bits for high-speed transmission. This segmentation allows the system to optimize for either compatibility or speed depending on the communication partner.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The communication mode is dynamically switchable between the first mode (with start/stop bits) and the second mode (without start/stop bits). The controller can adaptively choose the appropriate mode based on whether the communication partner supports the simplified protocol, thereby resolving the contradiction between compatibility and transmission speed.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If a simplified communication protocol without start and stop bits is used, then communication time is reduced, but compatibility with other devices is lost

Engineering Contradiction:

Improvecommunication timeVSAvoidcommunication compatibility

Core Design Contradiction:

Loss of timeVSAdaptability or versatility

Solution Approach 1:

The controller acts as an intermediary that translates between the simplified second communication protocol and the standard first communication protocol. When communicating with devices that don't support the simplified protocol, the controller automatically adds or removes start/stop bits, enabling compatibility without sacrificing the speed benefits of the simplified protocol for supported devices.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If baud rate is increased to improve transmission speed, then communication efficiency is improved, but transmission accuracy deteriorates due to signal interference

Engineering Contradiction:

Improvetransmission speedVSAvoidtransmission accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system maintains continuous high-speed communication using the simplified second protocol without the interruptions and overhead of start/stop bits. This continuous transmission mode improves efficiency while the controller's intelligent error checking and correction mechanisms maintain reliability, resolving the contradiction between speed and accuracy.

Inventive Principle:

Principle #20Continuity of useful action

4Adaptability or versatility

If a fixed communication protocol is used for all devices, then device compatibility is improved, but transmission speed is limited by the slowest device

Engineering Contradiction:

Improvedevice compatibilityVSAvoidtransmission speed

Core Design Contradiction:

Adaptability or versatilityVSSpeed

Solution Approach 1:

The controller is designed with multi-functionality to support both the standard first communication protocol and the simplified second communication protocol. This universal capability allows the system to automatically adapt to different device types and communication requirements, enabling high-speed transmission when possible while maintaining compatibility with slower or more traditional devices.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP4285490B1Communication bus system, method, and subscriber for transmitting data in a serial communication bus system

Publication Date: 2026.05.13 ELMOS SEMICON AG

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AI summary

In the case of the method and the subscribers and the communication bus system for transmitting data, in addition to the possibility from the bus master to the subscribers using differential electrical signals, a binary data transmission from the subscribers to the bus master is implemented by analysing the effect of changes to the common-mode level. For this purpose, a data transmission current is fed in or drawn at the input (12) of a subscriber (10), this being identified at the output (16) of a neighbouring subscriber (10), specifically based on the draw or the infeed of a compensation current in order to keep the common-mode level at the target value. A data transmission from the bus master (28) to the subscribers (10) using non-differential signals may take place in addition to the data transmission using differential electrical signals through a deliberate change in the common-mode level made by the bus master (28), this being identified at the input (12) of the first subscriber (10). This change in the common-mode level at the input (12) of a subscriber (10) is conveyed to a reference voltage source (42) at the output (16) of the subscriber (10), such that the same common-mode level shift as was sensed at the input (12) of the subscriber (10) is then generated at the output (16) of the subscriber (10).