Question on wiring fire wire to usb wire?

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Discussion Overview

The discussion centers around the feasibility of wiring a Firewire cable to a USB cable, exploring the technical implications and alternatives for connecting devices that utilize these different interfaces. The conversation includes considerations of electrical characteristics, compatibility, and practical solutions.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant questions whether it is possible to wire Firewire and USB cables together, suggesting that this may not work due to differences in electrical characteristics.
  • Another participant notes that Firewire has a differential impedance of 110Ω while USB has 90Ω, indicating potential issues with signal reflection if improperly connected.
  • Some participants suggest that using adapters to connect USB to Firewire is a more practical solution, pointing out that these adapters are often cheaper than modifying cables.
  • There is a claim that Firewire and USB operate on fundamentally different protocols, with Firewire being peer-to-peer and USB being master-slave, which complicates direct connections.
  • One participant shares their experience of needing to install a Firewire card to support an older video camera, highlighting the ongoing relevance of Firewire for certain devices.
  • A participant with design experience expresses a preference against Firewire due to its layout challenges and complexity compared to USB, while acknowledging Firewire's peer-to-peer capabilities as an advantage.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of directly connecting Firewire and USB cables, with some arguing against it due to technical incompatibilities, while others suggest using adapters as a viable alternative. The discussion remains unresolved regarding the practicality of direct wiring.

Contextual Notes

Participants mention various technical specifications and operational differences between Firewire and USB, indicating that assumptions about compatibility may depend on specific use cases and device requirements.

slee95
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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?
 
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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!
 
Why do people want to use adapter? Get a real USB or Firewire cable!
 
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.
 
vk6kro said:
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.

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.
 
I have had to install a firewire card in my desktop to support my old video camera.
 
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.
 
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