USB or Universal Serial Bus is a device which is used to connect the computers with the devices using a cable of four wires. It is a communication architecture. There is such a device which is used via USB and it is called USB printer. There are some of the technologies in the USB printer like Unidirectional parallel port, Bi-directional parallel port, Serial port, SCSI port and Ethernet/LAN. There are also some of the sophisticated interfaces of printer but all the above listed are most popular. As compared to the serial port, the USB offers gives throughput capability. Its speed is also greater than the serial port.
There are some of the classes of USB printers like the printer class subclass and protocol; the descriptors of endpoint, configurations, device and interfaces; the standard request of USB which are being used by the USB printer devices and the requests and the responses of USB class specific by the USB printers. There are some of the functional characteristics of USB printers and these include the operational model and the interfaces. There are different types of commands in the printers. Some of them control the interface of USB and the interface of printer. Through delivering the data on Bulk OUT endpoint something is being printed on the printer by the host. The data in this type can be of the form of HP, PCL, Post script and PDL. The data in it can also be encapsulated in the vendor specific PCP. This data can be a proprietary PDL or the simple data or text.
The printed page can be in the sequence. This sequence is described as follows: on the BULK OUT pipe the PDL data is being sent to the device. PDL is encapsulated in the PCP; if there is PCP used. For the responses the Bulk IN pipes are used. Get Port Status is used for the uni-directional interface. Status of this statement comes to the default pipe. There is another type of comand which controls the USB interfaces. There are standard requests in the commands. These requests can be Get Descriptor and Set Configuration. There are also some printer specific commands and these are Soft Reset and Get Port Status.
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There are two different types of requests to which a printer can respond. The standard USB device requests and Specific class requests. Standard USB device requests performs the functions generally and they support the bus related and bus functions. The requests in this type of request are Clear Feature, Get Configuration, Get Descriptor, Get Interface, Get Status, Set Address, Set Configuration, Set Descriptor, Set Interface and Set Feature. Class specific requests are used to transfer the data of commands to and from the hosts. There are many requests of class specific which are supported by the computers. Labels of these requests can be Get Device ID, Get Port Status and Soft Reset. There are some of the USB descriptors like device, configuration, interface and the endpoints which have Bulk OUT endpoint and Bulk IN endpoint.