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The Info List - USB Adapter


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A USB
USB
adapter is a type of protocol converter which is used for converting USB
USB
data signals to and from other communications standards. Commonly, USB
USB
adaptors are used to convert USB
USB
data to standard serial port data and vice versa. Most commonly the USB
USB
data signals are converted to either RS232, RS485, RS422, or TTL-level UART serial data. The older serial RS423 protocol is rarely used any more, so USB
USB
to RS423 adapters are less common.

Contents

1 Uses 2 History 3 Architecture 4 References

Uses[edit] USB
USB
to serial RS232
RS232
adapters are often used with consumer, commercial and industrial applications and USB
USB
to serial RS485/ RS422
RS422
adapters are usually mainly used only with industrial applications. Currently, USB to TTL-level UART
UART
converters are used extensively by students and hobbyist as they can be directly interfaced to microcontroller. Adapters for converting USB
USB
to other standard or proprietary protocols also exist; however, these are usually not referred to as a serial adapter. The primary application scenario is to enable USB
USB
based computers to access and communicate with serial devices featuring D-Sub
D-Sub
(usually DB9 or DB25) connectors or screw terminals, where security of the data transmission is not generally an issue. USB
USB
serial adapters can be isolated or non-isolated. The isolated version has opto-couplers and/or surge suppressors to prevent static electricity or other high-voltage surges to enter the data lines thereby preventing data loss and damage to the adapter and connected serial device. The non-isolated version has no protection against static electricity or voltage surges, which is why this version is usually recommended for only non-critical applications and at short communication ranges. History[edit] Historically most personal computers had a built-in D-sub serial RS232 port, also referred to as a COM port, which could be used for connecting the computer to most types of serial RS232
RS232
devices. By the late 90’s many computer manufacturers started to phase out the serial COM port in favor of the USB
USB
port. By the mid 2000s some computers had both a serial COM port and a USB
USB
port, however many did no longer have a serial COM port by that time; and today most modern computers have no serial COM port but instead only USB
USB
ports instead. Since many serial devices with a RS232, RS485
RS485
or RS422
RS422
port are still in use and even still produced today, the disappearing of the serial COM port from personal computers has created a need for the USB
USB
to serial adapter. Architecture[edit]

Die of a PL2303HX USB
USB
to Serial Bridge Controller manufactured by Prolific Technology.

As a simplified example a typical standard USB
USB
to serial adapter consists of a USB
USB
processor chip which processes the USB
USB
signals. The USB
USB
processor sends the processed USB
USB
signals to a serial driver chip which applies the correct voltages and sends the processed data signals to the serial output.[1] For the computer to be able to detect and process the data signals drivers must be installed on the computer. When the USB
USB
to serial adapter is connected to the computer via the USB
USB
port the drivers on the computer creates a virtual COM port which shows up in Device Manager. This virtual COM port can be accessed and used as if it was a built-in serial COM port. However, the characteristics of the virtual COM port are not exactly the same as a real internal COM port, mainly due to data latency; which means that if very sensitive and precise data transfer is required, the USB to serial adapter might be unreliable and not a desired solution.[2] Virtual COM drivers are usually available for Windows, Linux and MAC only.[3] References[edit]

^ "5 Steps for Selecting the Right USB
USB
to Serial adapter". Retrieved 14 October 2012.  ^ " RS232
RS232
to USB
USB
converters". Retrieved 14 October 2012.  ^ " FTDI
FTDI
Drivers". Retrieved 14 October 2012. 

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USB

USB-IF specifications

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USB
3.0 USB
USB
3.1 USB
USB
3.2 USB
USB
Type-C USB
USB
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USB
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