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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.
A USB controller using UHCI does little in hardware and requires a software UHCI driver to do much of the work of managing the USB bus. [2] It only supports 32-bit memory addressing, [ 4 ] so it requires an IOMMU or a computationally expensive bounce buffer to work with a 64-bit operating system.
One solution is the use of a predefined USB device class. Operating systems provide built-in drivers for some of them. The most widely used device class for embedded devices is the USB communications device class (CDC). A CDC device can appear as a virtual serial port to simplify the use of a new device for older applications. Another solution ...
Retrieval of the descriptors would especially allow for determining the USB Class, VID, and PID, which are often used for determining the correct USB driver for the device. An USB device can be located by the bus:device address, or by the hub:port address. [16] Also, after the descriptors is retrieved, the host performs another control transfer ...
The USB mass-storage device class (MSC) Working Group develops and maintains the UASP specification; the USB Implementers Forum, Inc. (USB-IF) promotes the UASP technology. UAS drivers generally provide faster transfers when compared to the older USB Mass Storage Bulk-Only Transport (BOT) protocol drivers.
The change prevents the chip from being recognised by drivers of any OS, effectively making them inoperable unless the product ID is changed back. [14] The behaviour was supported by a notice in the drivers' end user license agreement, which warned that use of the drivers with non-genuine FTDI products would "irretrievably damage" them. [14]
This class can be used for industrial equipment such as CNC machinery to allow upgrading from older RS-232 serial controllers and robotics, since they can keep software compatibility. The device attaches to an RS-232 communications line and the operating system on the USB side makes the USB device appear as a traditional RS-232 port.
The signaling rate of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host and the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state ...