USB Peripheral Speed Detection via Signal Pull-Up Timing
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Solution Overview
Problem
Conventional USB systems face difficulties in efficiently and quickly distinguishing between high/full speed and full speed USB peripheral devices, leading to delays in data communication due to the same voltage-to-time curve before a reset signal is sent, and requiring complex Data+ and Data− handshakes for identification.
Innovation Solution
The implementation of a USB peripheral device with first and second pull-up devices, coupled with a USB device transceiver, allows for the determination of high/full speed mode by detecting which data signal exceeds a threshold first, enabling accurate speed mode identification before a reset signal is sent, using separate signal pin settings for high/full and full speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional USB speed detection method is used, then low speed device identification is accurate, but high/full speed device differentiation is delayed and complex
Solution Approach 1:
The patent applies preliminary action by enabling the pull-up device before the reset signal is sent to differentiate high/full speed devices. The host controller enables the pull-up device during the connection time period (before reset), causing the Data+ signal to be pulled high. This preliminary signal configuration allows the host to detect the device type based on the Data− signal state before reset occurs, thereby identifying high/full speed devices earlier without waiting for the reset handshake sequence.
2Reliability
If conventional handshake protocol is used, then device identification is performed, but the process requires complex Data+ and Data− coordination
Solution Approach 1:
The patent applies the taking out principle by extracting the speed detection function from the complex reset handshake sequence. Instead of relying on the full Data+/Data− handshake protocol to determine device type, the invention isolates the detection to a specific signal state (Data− level) during the connection time period before reset. This extraction simplifies the identification process by removing the need for complex bidirectional handshaking while maintaining reliable device type differentiation.
3Adaptability or versatility
If speed mode determination is delayed until after reset signal, then all devices can use same detection protocol, but data transmission starts later
Solution Approach 1:
The patent applies preliminary action by performing speed mode determination during the connection time period (DCNN) before the reset signal is sent. The host controller configures the pull-up device in advance during DCNN, allowing the Data+ signal to be pulled high and the Data− signal state to indicate device type. This preliminary detection enables the system to identify high/full speed devices and initiate appropriate data transmission protocols earlier, improving productivity without sacrificing protocol universality.
Data Source
AI summary
A USB peripheral device and a method of determining USB speed mode. The method of determining USB speed mode for an USB peripheral device, wherein the USB peripheral device is coupled to an USB host through an USB transmission cable, and the USB transmission cable comprises power and ground lines for power supply, and first and second data signals for transmitting data, the method comprising the USB peripheral device pulling up voltage level of the first data signal with a first pull-up device, the USB peripheral device pulling up voltage level of the second data signal with a second pull-up device, and the USB host determining a high/full speed mode for the USB peripheral device, when detecting only one of the first and second data signals exceeding a threshold, and then detecting the other data signal exceeding the threshold in a predetermined period.