COM ports , short for communication ports, are traditional serial port interfaces on IBM PC-compatible computers. They refers not only to physical ports, but also to virtual ports such as ports created by Bluetooth or USB-to-Serial adapters. USB-to-Serial adapters do two things: 1. They physically connect a serial cable to a USB port. 2. They have software drivers that create a Virtual COM Port. A Virtual COM Port created by a USB-to-serial adapter can be a setting that allows software products to connect to USB devices using COM port connections. A serial port (串行接口) is a serial communication interface through which information transfer in or out one bit at a time. Throughout most of the history of personal computers, data was transferred through serial ports to devices such as modems (调制解调器), terminals (终端机) and various of peripherals (外部设备). Serial ports are still used in applications such as industrial automation system, scientific instruments as they are simple, cheap and their console (控制) functions are highly standardized and widespread. A serial port requires very little supporting software from the host system. Modern computers without serial ports may require USB-to-Serial adapters to allow compatibility with serial devices. A parallel port (并行接口) is a parallel communication physical interface, which is also known as a printer port or Centronics port. It was originally known as the Parallel Printer Adapter on IMB PC-compatible computers as it was primarily designed to operate printers. Today, the parallel port is virtually non-existent because of the rise of USB devices. Universal Serial Bus (USB,通用串行总线) is an industry standard that defines the cables, connectors and communication protocols used in a bus (a bus/buss is a communication system that transfer data between components inside a computer or between computers) or connection, communication and power supply between computers and electronic devices. It was designed to standardize the connection of computer peripherals including keyboard, pointing devices, digital cameras, printers, portable media players, disk drives and network adapters to PC, both to communicate and to supply electric power. A device file is an interface for a device driver that appears in a file system as if it were an ordinary file. They allow software to interact with a device driver using standard input/output (I/O) system calls, which simplifies many tasks and unifies user-space I/O mechanisms. Device files often provide simple interfaces to peripheral devices such as printers and serial ports. Also, they can be used to access specific resources on those devices. Finally, device files are useful for accessing system resources that have no connection with any actual device.
LINUX下USB驱动移植 仇洁婷，陈儒军 在 Linux2.6 内核中有支持 USB 读写的驱动程序，需要选上相应的配置即可。 1 、让内核支持热插拔 General setup --- Support for hot-pluggable devices 2 、 USB 驱动设置 Device Drivers --- Generic Driver Options --- * Hotplug firmware loading support Block devices --- * Low Performance USB Block driver SCSI device support --- * SCSI generic support Probe all LUNs on each SCSI device USB support --- * Support for Host-side USB USB device filesystem---- * OHCI HCD support * USB Mass Storage support 3 、 加入了 MSDOS fs 和 VFAT fs 的支持。 File systems --- DOS/FAT/NT Filesystems --- * MSDOS fs support * VFAT (Windows-95) fs support (437) Default codepage for FAT (iso8859-1) Default iocharset for FAT * NTFS file system support NTFS debugging support NTFS write support 4 、加入分区支持 File systems --- Partition Types --- Advance Partition Selection 由于本系统采用的是 PQFP 封装 AT91RM9200 ，该芯片只有一个 usb 主端口，而 usb 从端口是不能用。在 Linux2-.6.21 启动时会有以下错误提示： new low speed USB device using at91_ohci and address 2 修改方法： 在 /linux/arch/arm/mach-at91/board-dk.c 文件，将 usb ports 值改为 1 ，则显示有一个 usb 端口。 static struct at91_usbh_data __initdata dk_usbh_data = { .ports =1,// 2, }; 最后是重新生成 uImage ，烧写内核。 挂载 USB 命令，将 USB 目录挂载到 /mnt/usb ： mount -t vfat -o /dev/uba1 /mnt/usb 卸载 usb 命令： umount /mnt/usb
标签: USB
