Parallel Serial Port problem

Discussion in 'The Projects Forum' started by ssembo, Jul 4, 2011.

  1. ssembo

    Thread Starter Member

    Dec 13, 2010
    Hello guys, my laptop has only a serial port but am told that inorder to control circuits using PC, i need a parallel port. How do i use this serial port to work as a parallel port software wise.

  2. Wendy


    Mar 24, 2008
    You can use any port you choose for a control circuit, but you will need the appropriate circuit and circuitry. Do you have a USB port, for example? There are lots of USB interfaces out there. You can also find a lot of stuff for the RS232 port too. Google is your friend.

    The parallel port is easy to use because all the circuitry (and most of the software) is there on older computers. As you move away from DOS into Win2000, XP, and beyond the software looses the ability.

    Senior Member

    Jul 1, 2008
    Because the Parallel Port has 8 inputs and outputs it's easier to directly drive multiple low current devices but programming (in VB6) is not as direct as the serial port. Inputting and outputting data is much more complex with the parport. In VB, all calls to the parport are in Hex which I don't find as intuitive as serial port code that uses the MSComm32.ocx. The other downside to the parallel port is if you don't have one. USB/Parallel Port converters won't help you. They will drive only printers and some other peripherals specified by the manufacturer of the converter. You can't use them without a .dll that your code can call.

    USB/Serial converters are a very different animal, they use generic .dll's that merge nearly seamlessly with MSComm.
  4. SgtWookie


    Jul 17, 2007
    If you want to be able to use your program and hardware with any newer computer, you should start off with USB, as parallel printer ports and RS-232 ports are all but extinct.

    USB also has a much higher data transmission rate than either RS-232 or the old Centronics printer ports.
  5. davebee

    Well-Known Member

    Oct 22, 2008
    It used to be fairly easy to access a parallel port but with newer operating systems, it's getting harder and harder, and that's assuming your pc even has a parallel port.

    Another option is to use a microcontroller - a single chip computer that you program from a PC, then the microcontroller performs the actual device control.

    It is kind of a big step to learn microcontrollers, but it's getting so hard to access the parallel port, I think it probably would be easier to learn how to use a microcontroller than it would be figure out how to patch an accessory parallel port into a modern computer, then figure out how to have your program access it as a general purpose IO port.

    It would probably cost about the same price to buy an external USB parallel port as it would to buy a simple microcontroller and its programming interface.

    Another good point about microcontrollers is they do a far better job of device control than a parallel port ever could.

    Senior Member

    Jul 1, 2008
    USB (Universal Serial Bus) means just that, it's a Bus. It can't be treated as an autonomous port until a device that's recognized is plugged into it. The USB port will recognize an external device only after the driver for same has been installed on your PC. The only exception to this rule is a "Human Interface Device" (HID) as are classified by by industry standards. For these, Microsoft provides generic drivers, which include things like Flash Drives. Unlike RS232 or the Centronics standard, a USB device must provide embedded data to the PC that identifies it. There is no way, that I know of, to simply hang a home brew circuit on a USB port. For sure there are USB control board kits on web but they all come with drivers and sometimes software complete with GUI.

    As a furthermore... Even PICs programmed via USB have to follow these rules. EI, the programming board has a chip on it that identifies it after the drivers are installed on the PC.