Interface system, switching method, USB key and UART terminal

Abstract

The invention discloses an interface system for a USB key, a switching method, a USB key and a UART (Universal Asynchronous Receiver / Transmitter) terminal. The interface system for the USB key comprises a USB key circuit and a terminal interface circuit connected with the USB key circuit, wherein the terminal interface circuit comprises a USB interface circuit or a UART interface circuit; the USB key circuit comprises a USB key interface of which an ID pin is connected with a GND pin of the USB key interface through a resistor R1; and an ID pin of the UART interface circuit is connected with a VCC pin of the UART interface circuit. The benefit that the interface mode is quickly switched according to judgment to the ID pin of the USB key interface is achieved, and as for the USB key powered by a built-in battery, the interface mode can be automatically switched according to the difference of connected terminal equipment in the non-stop state.

Description

technical field [0001] The invention relates to the technical field of data communication, in particular to an interface system and switching method for a USB key, a USB key and a UART terminal. Background technique [0002] In the commonly used switching technology, the level of the D- pin or D+ pin is judged after the USB key (smart key device) is powered on; if it is high level, the USB key enters the UART interface connection; if it is low level , and the USB key enters the USB (Universal Serial Bus, Universal Serial Bus) connection state. [0003] If the terminal connected to the USB Key is not ready, the signals on the D-pin and D+ pin are uncertain; for example, connecting the USB Key to a UART (Universal Asynchronous Receiver / Transmitter, Universal Asynchronous Transmitter) terminal device When on the UART port of the UART terminal device, the UART port of the UART terminal device needs to be initialized for a certain period of time after power-on; after the UART te...

AI Technical Summary

Problems solved by technology

[0003] If the terminal connected to the USB Key is not ready, the signals on the D-pin and D+ pin are uncertain; for example, connecting the USB Key to a UART (Universal Asynchronous Receiver / Transmitter, Universal Asynchronous Transmitter) terminal device When on the UART port of the UART terminal device, the UART port of the UART terminal device needs to be initialized for a certain period of time after power-on; after the UART terminal is turned on, if the UART port initialization is not completed at this time, the signal of the D- pin or D+ pin is Uncertain; if it is low, the USB Key will mistakenly think that it is connected to a USB terminal, thereby performing USB initialization, resulting in connection failure

If it is a USB Key powered by a built-in battery, after using the built-in power supply to turn it on, if the connected USB terminal or UART terminal is not turned on at this time, the levels of pins D- and D+ are also uncertain. The mode of the interface will also cause the connection to fail

After the USB Key powered by the built-in battery establishes communication with the USB terminal, if the USB key is not turned off at this time, if the UART terminal is inserted again, it will not be able to switch to UART communication; otherwise, the USB key powered by the built-in battery is connected to the UART terminal After the communication is established, if the USB key is not turned off, if the USB terminal is inserted again, the communication interface of the USB key cannot be switched to USB communication.

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