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Question on wiring fire wire to usb wire?

  1. Jul 9, 2012 #1
    Can i wire fire wire to usb wire? What i mean is cut one end off on a fire wire and one end off a usb wire and wire the two together would that work?
  2. jcsd
  3. Jul 9, 2012 #2
    You mean using a Firewire cable for USB? Firewire is 110Ω differential impedance, USB is 90Ω. I would be careful if you run USB2. For USB 1, I don't think you'll have a problem. Secondly, you are going to have to change the two end connectors to fit for USB, that will cause reflection.

    Go buy a cable, why do you want to monkey with RF stuff?

    If you try to connect a USB port to Firewire port..............You're funny!!!
  4. Jul 10, 2012 #3


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  5. Jul 10, 2012 #4
    Why do people want to use adapter? Get a real USB or Firewire cable!!!!
  6. Jul 10, 2012 #5


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    I imagine he wants to use a firewire device and only has USB on a computer.

    Haven't heard of firewire for years, though. Some video cameras used to use the Firewire system for outputting video.
  7. Jul 10, 2012 #6
    To the best of my knowledge, you cannot interface USB to Firewire. Firewire has two pairs of signals and USB has one pair. Firewire is peer to peer where USB is master and slave. The physical layer, protocode are totally different. There is no way you can hook up a USB device onto Firewire or the other way around.

    Those adaptor are just switching connectors only. It takes a micro controller the interface FW to USB.
  8. Jul 10, 2012 #7
    I have had to install a firewire card in my desktop to support my old video camera.
  9. Jul 10, 2012 #8
    I designed both, I don't like FW at all. The 110Ω differential pair make it harder on layout. Even though the two are only 20Ω difference, but the FW traces are much thinner and loss is much higher. Also you have to match the length of the two pairs on the FW. That's why you often see one pair of traces zip zagging to increase the length to match the other pair. TI was the main chip set maker, they never have embedded controller with FW interface. At the time Cypress dominated USB, they used 8051 core with USB interface. This make it a lot easy and simpler to implement a controller. The only one good thing I saw was the peer to peer of FW. You can do things with FW that you cannot do with USB because any FW module can talk to any other FW module on the bus. It is really like a true bus rather than like USB where everyone talk only to the master.
    Last edited: Jul 10, 2012
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