Adjustable Oscillator Trimming for CAN-Bus Bit-Time Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
CAN-bus nodes require synchronized oscillators to prevent bit-errors, but high-precision oscillators are expensive and increase assembly costs, making it challenging to maintain synchronization without additional external components.
Innovation Solution
An adjustable oscillator's cycle-time is trimmed to match the predetermined bit-time of a CAN-bus by measuring cycles between signals and adjusting the oscillator using a controller module, allowing for the use of cheaper, lower-accuracy oscillators while maintaining synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-precision oscillators are used to maintain synchronization, then communication reliability is improved, but cost and assembly complexity increase
Solution Approach 1:
The patent replaces expensive high-precision oscillators with cheaper adjustable oscillators that have lower individual accuracy but can be dynamically adjusted. The oscillator is trimmed during operation to achieve the required synchronization, making the system less dependent on expensive pre-calibrated components.
Solution Approach 2:
The patent changes the frequency parameter of the adjustable oscillator dynamically by measuring the actual bit-time and trimming the oscillator's cycle time accordingly. This allows the oscillator to adapt to the actual bus conditions and achieve synchronization without requiring high initial precision.
2Measurement precision
If external oscillators are added to improve timing accuracy, then synchronization precision is improved, but device size and cost increase
Solution Approach 1:
The patent extracts the oscillator function from external components and integrates it within the communication controller. The adjustable oscillator is implemented using on-chip circuitry, eliminating the need for separate external oscillator components and reducing overall device size.
Solution Approach 2:
The patent makes the oscillator multi-functional by using it both for generating the bit-rate and for providing the clock signal for sampling and transmission. The same oscillator serves multiple timing functions, reducing the need for additional dedicated components.
3Ease of manufacture
If adjustable oscillators with lower accuracy are used, then cost is reduced, but synchronization precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the actual bit-time is measured by counting oscillator cycles between signal edges, and this measurement is used to trim the oscillator's cycle time. The feedback loop continuously adjusts the oscillator to maintain synchronization despite initial inaccuracies.
Solution Approach 2:
The patent performs preliminary trimming of the oscillator during initialization or setup phase. The oscillator is adjusted before normal operation based on initial measurements, ensuring that synchronization is achieved before actual communication begins.
Data Source
AI summary
A method for trimming a cycle time of an adjustable oscillator to match a Controller Area Network-bus (CAN-bus) operating with a predetermined bit time includes determining a measured number of cycles of an adjustable oscillator between a first signal and a second signal within a CAN frame transmitted on a CAN-bus; determining an information about a present cycle time of the adjustable oscillator using the measured number of cycles and a nominal number of cycles per bit time; and trimming a cycle time of an adjustable oscillator to match the CAN-bus operating with a predetermined bit time based on the determined information.