USB Communication Controller With FIFO Buffer for Slow Links
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
USB 2.0 systems face challenges in maintaining high-speed data transmission when the communication rate between a host and a device is lower than the native rate, leading to incomplete transactions due to excessive turn-around times, particularly in mobile devices using optical communication with lower transfer rates.
Innovation Solution
A communication controller that acts as both host-side and function-side controller, managing packet storage and retransmissions to ensure data packets are correctly transmitted within the USB standard time limits, even at lower transfer rates, by acknowledging receipt and storing packets for retransmission when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical communication is used between host and device, then wireless connectivity and mobility are improved, but data transmission rate decreases below USB 2.0 native rate
Solution Approach 1:
The host controller stores received USB packets in advance in a storage unit before the device controller is ready to process them. This preliminary storage action allows the system to bridge the speed gap between fast USB host and slower optical communication without data loss or transaction timeout.
2Adaptability or versatility
If data is transmitted at lower communication rate, then compatibility with mobile devices is improved, but turn-around time exceeds USB standard limits
Solution Approach 1:
The host controller performs preliminary reception and storage of USB packets before the device controller processes them. This eliminates waiting time and ensures that when the device is ready, data is immediately available for transmission, keeping turn-around time within USB standards.
Solution Approach 2:
The storage unit acts as an intermediary buffer between the host controller and device controller. It decouples the timing between fast USB host operations and slower device processing, allowing independent operation without violating USB protocol timing requirements.
3Reliability
If packets are retransmitted at lower speed, then data reliability is improved, but transaction completion within time limit becomes difficult
Solution Approach 1:
The host controller stores packets in advance before transmission to the device. This preliminary action ensures that retransmissions can occur immediately without waiting for re-preparation of data, maintaining both reliability and timing compliance.
Solution Approach 2:
The system uses USB protocol feedback mechanisms (ACK/NAK packets) to confirm successful reception and trigger retransmissions only when necessary. The storage unit ensures feedback loops complete within timing requirements by having data ready for immediate retransmission.
Data Source
AI summary
A two-way transmission system of the present invention is arranged in such a manner that, when a host-side controller confirms the receipt of an IN packet from a USB host, the host-side controller transfers the IN packet to a function-side controller, and receives a DATA packet from the function side. The received DATA packet is temporarily stored in a FIFO. At the time of the receipt of the IN packet again, the host-side controller supplies, to the USB host, the DATA packet stored in the FIFO.