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Questions about USB ports and interactions

swodniW 141 Reputation points
2021-07-21T09:27:30.68+00:00

Hello everybody, i've found a lot of question here in microsoft Q&A and external sites about "Sending data through usb port" or "USB Ports" etc etc.
I've read every forum but i am still confused: (some questions)

  1. a usb port is a com port?
  2. why do a lot of people call usb port if usb is too generic?
  3. once i've sent a message, how will the device interact with me?
  4. what do drivers do when i send the message?
  5. if i interact with a keyboard, do i need the driver?
  6. can someone explain what happens when you plug a usb device? (yes i have found many sites explaining but i am not sure: where is the driver? Without a driver what will happen?

Thanks to everyone who answer this questions

Bye

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  1. AgaveJoe 31,341 Reputation points
    2021-07-21T14:52:57.753+00:00
    1. "The attached USB device might emulate a COM port though" What does this exactly mean

    The device behaves like it is attached to a COM (serial) port. A better way to say this is, the USB driver emulates a UART which is/was a physical chip set on a serial board. There is no lack of information on serial ports and UARTs. This information is also found in engineering and computer science courses.

    1. When a usb device is plugged in, the os will "analyze" the device but without the specific driver, this means there is a standard usb driver that "communicates" with the os and reveal the kind of device, after this the right driver will be installed. is this right?

    USB is hardware. The communication between USB devices and the system hardware is an openly published specification. What the USB device looks like to software depends on the device driver. It could look like a COM port, disk drive, etc.

    1. if i send a message to the device will it be received by the driver or by the device itself?

    A device driver translates communication between software, that thinks the device is a COM port for example, and USB hardware.

    1. if i send a message to a usb flash drive the flash drive will not answer, right?

    A USB flash drive emulates the file system. What message are you sending to the drive and what do you expect to happen? If you issue a dir F: (Windows) where F is the USB flash drive then you'll should expect a directory listing.

    1. "The term "usb port" doesn't mean anything. The B in USB means "bus", it is a generic way for any kind of device to talk to the machine. A driver is required to make the device usable." taken from stackoverflow can someone explain this to me. This sentence is confusing me.

    Are you asking what a bus is??? A bus can be physicals wires within a cable, copper lines etched into a circuit board, or even virtual. A USB cable has 4 wires; Vcc (5V), ground, data+, and data-. The data lines are 180 degrees out of phase which is a common method to reduce noise, increase throughput and data rates over a wire. The 5V powers devices on the line.

    1. a device that requires com wont need a driver?

    The original COM port was a physical 9-pin serial port used for COMmunication between systems and/or external devices. Any device that emulates a COM port (UART) attached to a USB line requires a driver.

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  1. Castorix31 91,871 Reputation points
    2021-07-21T09:32:43.303+00:00

    About everything is in MSDN at Universal Serial Bus (USB)

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