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FTDI US232R : USB to RS-232 cable. A USB-to-serial adapter or simply USB adapter is a type of protocol converter that is used for converting USB data signals to and from serial communications standards (serial ports). Most commonly the USB data signals are converted to either RS-232, RS-485, RS-422, or TTL-level UART serial data.
It develops, manufactures, and supports devices and their related cables and software drivers for converting USB signals to and from various protocols, including RS-232/TTL serial (to provide support for legacy devices on modern computers lacking an accessible UART) and inter-chip communication bus protocols (e.g. SPI, I²C, JTAG, or GPIO) to ...
The DE-9 serial port on the PC does not provide any dedicated power source. The mouse driver holds the DTR and RTS lines high at all times so that the device has a source of power. Another category of devices commonly powered by the DTR line includes converters between RS-232 and other serial standards such as RS-422 and RS-485.
Software flow control is a method of flow control used in computer data links, especially RS-232 serial. It uses special codes, transmitted in-band, over the primary communications channel. These codes are generally called XOFF and XON (from "transmit off" and "transmit on", respectively). Thus, "software flow control" is sometimes called "XON ...
Disadvantages of USB compared to RS-232 are that USB is far less immune to electromagnetic interference (EMI) and that maximum cable length defined by standards is much shorter (15 meters for RS-232 versus 3–5 meters for USB, depending on the USB version and use of active cables). RS-232 cable lengths of 2000 meters are possible with ...
Third-party applications can add this ability, such as the open-source com0com, freeware HW VSP3, or the commercial Virtual Serial Port Driver. Some virtual serial ports emulate all hardware serial port functionality, including all signal pin states, and permit a large number of virtual ports in any desired configuration.
It is faster than the other common legacy port (serial port), requires no serial-to-parallel converter, and requires far less interface logic and software than a USB target interface. However, Microsoft operating systems later than Windows 95/98 prevent user programs from directly writing to or reading from the LPT without additional software ...
USB-IF's Approved Class Specification Documents. Class definitions for Communication Devices 1.2 (.zip file format, size 3.43 MB) Class definitions for Communication Devices 1.1; App Note, Migrating from RS-232 to USB Bridge Specification. Explains the use of USB CDC (Communications Device Class) ACM (Abstract Control Model) to emulate serial ...