USB Data Communication Device Oscillator Calibration
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Solution Overview
Problem
Existing data communication devices using free-running oscillators for generating local clock periods are imprecise, leading to unreliable synchronization and potentially impossible data communication due to production spread, temperature variations, and aging, which affects the precision of sampling signals in USB devices.
Innovation Solution
A calibration step is performed to store a measured clock cycle count as a calibration value, which is used as the initial value in subsequent synchronization phases, compensating for oscillator-frequency imprecision and accounting for production spread, thereby ensuring more precise sampling signals and robust data communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a free-running oscillator is used to generate the local clock period, then the device structure is simple, but the precision of the sampling signal deteriorates due to oscillator-frequency imprecision
Solution Approach 1:
The patent performs a preliminary calibration action during an initial synchronization phase to measure the actual number of oscillator cycles in a bit period and store this as a calibration value. This preliminary measurement allows the system to compensate for oscillator imprecision in subsequent operation, resolving the contradiction between simple structure and precise sampling.
Solution Approach 2:
The patent implements feedback by using the measured calibration value to adjust the sampling signal generation. The calibration value representing the actual oscillator cycle count is fed back into the synchronization circuit to generate more precise sampling signals, thereby improving measurement precision while maintaining simple device structure.
2Ease of operation
If a preprogrammed fixed value is used as the initial value during initial synchronization phase, then the device operation is simple, but the reliability of data communication deteriorates due to production spread
Solution Approach 1:
The patent applies self-service by having the device automatically perform calibration during the initial synchronization phase without external intervention. The device measures its own oscillator characteristics and stores the calibration value, enabling it to compensate for production spread independently and reliably, thus improving data communication reliability while keeping operation simple.
Solution Approach 2:
The patent performs preliminary calibration action during the initial synchronization phase to determine the actual oscillator cycle count and store it as a calibration value. This preliminary self-measurement ensures that subsequent data communication operations use accurate sampling parameters, improving reliability without complicating normal operation.
3Device complexity
If the sampling signal is generated without compensation for environmental factors, then the device complexity is low, but the reliability of data communication deteriorates due to temperature variations and aging
Solution Approach 1:
The patent performs preliminary calibration to measure and store the actual oscillator cycle count at the time of device deployment. This preliminary action captures the oscillator's state under specific environmental conditions, allowing the system to compensate for future temperature variations and aging effects using this baseline calibration data, thereby improving reliability without significantly increasing device complexity.
Data Source
AI summary
A data communication device comprises an input circuit (DRTC) that converts external data (XDT) into internal data (IDT) on the basis of a sampling signal (SP). A synchronization circuit (SYNC) provides the sampling signal (SP) on the basis of an oscillator signal (OS) and a synchronization value (SV). The synchronization value (SV) is representative of a number of cycles of the oscillator signal (OS) contained within a time interval for a unit of external data. The synchronization value (SV) is an initial value (IV) during an initial synchronization phase and a measured value (MV) during a measurement-based synchronization phase. A control circuit (IFC) carries out a calibration step in which the initial value (IV) is a preprogrammed reset value (RV) and in which the measured value (MV) is stored as a calibration value (CV). The control circuit (IFC) applies the calibration value (CV) as the initial value (IV) in subsequent initial synchronization phases.