CAN FD Coexistence via Modified Node Frame Tolerance
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Solution Overview
Problem
Existing CAN networks face limitations in data rate due to minimum bit time requirements and the relationship between data bits and frame bits, preventing seamless communication between Norm CAN and CAN FD nodes without all nodes supporting the CAN FD protocol.
Innovation Solution
Modifying Norm CAN implementations to tolerate CAN FD frames by ignoring them and not disturbing them, allowing coexistence with CAN FD nodes using the same bus wires, while modified nodes communicate using Norm CAN frames that can be received by both types of nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CAN FD frames are introduced to increase data rate, then bandwidth and effective data-rate are improved, but compatibility with existing Norm CAN nodes deteriorates
Solution Approach 1:
The patent introduces an intermediary mechanism where Norm CAN nodes detect and ignore CAN FD frames by identifying the extended data length code format. This intermediary detection layer allows CAN FD nodes to communicate at higher data rates while Norm CAN nodes continue to operate without interference, effectively mediating between the two protocols on the same bus.
Solution Approach 2:
The patent applies local quality by enabling different nodes to operate with different protocol capabilities. CAN FD nodes can send and receive CAN FD frames with extended data fields, while Norm CAN nodes send and receive only standard CAN frames. Each node type maintains its local operational characteristics without requiring all nodes to be upgraded, thus improving overall system adaptability.
2Productivity
If all nodes are upgraded to CAN FD protocol, then bandwidth and data rate are improved, but device complexity and cost increase
Solution Approach 1:
The patent segments the network into CAN FD-capable nodes and standard Norm CAN nodes, allowing gradual migration. Not all nodes need to be upgraded to CAN FD simultaneously. The network can be divided into segments where some nodes operate at enhanced data rates while others maintain legacy compatibility, reducing overall device complexity and implementation cost.
Solution Approach 2:
The patent implements partial action by allowing only the necessary subset of nodes to adopt CAN FD protocol. Instead of requiring universal adoption across all nodes, the system permits partial implementation where only nodes that benefit from or require higher data rates are upgraded to CAN FD, while other nodes continue operating with the standard protocol.
3Productivity
If CAN FD frames with longer data fields are used, then effective data-rate is improved, but interference with Norm CAN arbitration process increases
Solution Approach 1:
The patent applies preliminary action by having CAN FD nodes detect the presence of Norm CAN nodes on the bus before initiating CAN FD communication. The system preliminarily checks the network composition and adjusts its frame transmission accordingly, ensuring that CAN FD frames are only sent when no Norm CAN nodes are present that would be interfered with, thus preventing bus conflicts and harmful interference.
Data Source
AI summary
In a method for serial communication of data frames between nodes connected by a bus system, the transmitter and receiver roles are assigned to the nodes for each data frame by the arbitration procedure defined in the CAN-Standard ISO 11898-1. The exchanged data frames, which include multiple bits, have a logical structure according to the CAN-Standard ISO 11898-1, including a Start-Of-Frame-Bit, an Arbitration Field, a Control Field, a Data Field, a CRC Field, an Acknowledge Field and an End-Of-Frame Field. Each bit has a bit time which is divided into Time Segments. In response to a predefined value of a specific bit within the Control Field a first node of a first node group restarts its protocol decoding state machine and waits until it has synchronized itself to the bus activity and a second node of a second node group communicates using CAN FD Specification protocol.