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  • powering a usb cable

    I was wondering..
    I have not used any powered usb hubs in my setup.
    I have passed one usb cable to my hand brake (3m) to connect my ipod or mouse or whatever.. I am using the other 3 usb ports for my touchscreen, my GPS, and a remote control..

    When I connect my ipod or my creative mp3 player.. they do not work.. device has mulfunctioned...etc. if i connect it back in the trunk (where i keep my pc) directly in the pc it works fine.. so there is a voltage drop i guess in the cable..

    what i was wondering is can i cut the red wire on the usb extention cable and give it 5 volts directly from my DSATX? and not using the power from the mobo, instead of buying a hub which is useless to me?

  • #2
    if you splice into the hub like that, it'll put power back into the mobo, which is probably a bad thing

    just get a powered hub, and use the 5v from the dsatx

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    • #3
      I think an active USB cable will sort your problem. I think your probably using cheap USB cables that cant cope with the electrical noise of the car. An active cable should work a treat for you.
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      • #4
        you can do this no problem, just send power twards the front & not connected to the motheboard.... this may or may not be your issue... some devices just don't like long cable runs... there are usb extenders that can help if the power doesn't, worth a shot though..
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        • #5
          Originally posted by FC3S
          if you splice into the hub like that, it'll put power back into the mobo, which is probably a bad thing
          If he cuts the +5v wire in the extension cable and only applies +5v to the wire going to the device-side plug, and leaving the +5v wire coming from the computer disconnected, then it wouldn't harm anything.

          The computer does have control of the +5v line on its USB ports, ie - it can shut off devices as it wishes... so there is a chance that the computer might be unhappy that you are powering the device all the time, taking control away from it... but during normal operation that probably wouldn't be an issue.

          Though, that would only solve it if it is in fact a power issue; it's also quite likely that it is a signal issue, in which case you would need either a hub or an active USB repeater cable as others have suggested. The USB spec for maximum cable length is something like 5 meters, and I think that that is probably assuming the cable is used in a "normal" household environment, as opposed to a car where there is a lot more interference, etc, so if you are using a cable that is anywhere near to that long, signal problems might very well be your issue.
          But don't take it from me! here's a quote from a real, live newbie:
          Originally posted by Viscouse
          I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.
          eegeek.net

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          • #6
            thanks for the answers.. i think it will work but as evendude said the pc would not be very happy of losing control.. it is probably a power issue. as if i connect my mouse it works fine... it is just devices that draw a lot of current that have a problem.

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            • #7
              you can run a jumper wire from the ps to the hub because its all coming from the same power source.

              i also heard that if you have a hub and are using usb 2.0 and 1.0 devices at the same time it goes to 1.0 disabling the 2.0 device. havent ever proved this theory though.
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              • #8
                each motherboard header for usb can only provide about 500ma before it's overloaded, but then again, for a device to be usb compliant it should be able to be run on 500ma or less, unless they provide an external power source...

                I'm guessing your issue isn't power related, but worth ruling out anyway by testing this...
                MY NEWEST INSTALL:modded infiniti fx with big screen

                first windows carpc install........my liquid cooled LVDS screen :D

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                • #9
                  Originally posted by albysure
                  I also heard that if you have a hub and are using usb 2.0 and 1.0 devices at the same time it goes to 1.0 disabling the 2.0 device. havent ever proved this theory though.
                  no, that's not the case. in fact, in case you're interested, the system is pretty cool: all communication between the PC and the usb 2.0 hubs is done at usb 2.0 speeds; even if the PC is trying to communicate with a usb 1.x device on a hub. the hub gets data from the PC at high speed, "dumbs it down" to low speed to communicate with the device, and then gets the device's response and transmits it back to the PC at high speed. while the hub is communicating with the device at low speed, the rest of the hubs and devices on the bus can continue operating at high speed, even those on the same hub, so the low-speed transaction isn't wasting valuable bus time. consequently, all this extra conversion and control is why usb 2.0 hubs are usually a lot more expensive than 1.x hubs; they're not just faster, but also a lot 'smarter' and have to do a lot more than simply pass data straight through.

                  sorry for going off on a tangent, can you guess who's been spending too much time reading about USB?
                  But don't take it from me! here's a quote from a real, live newbie:
                  Originally posted by Viscouse
                  I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.
                  eegeek.net

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                  • #10
                    see, now I thought the oposite was true, & that only special hubs can share both without reducing the 2.0 to 1.X.... I didn't think just any 2.0 hub can support both speeds simultaniously???
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                    first windows carpc install........my liquid cooled LVDS screen :D

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                    • #11
                      Originally posted by turbocad6
                      see, now I thought the oposite was true, & that only special hubs can share both without reducing the 2.0 to 1.X.... I didn't think just any 2.0 hub can support both speeds simultaniously???
                      The book I've read this from (USB Complete by Jan Axelson) doesn't make any distinctions about any different 'types' of usb 2.0 hubs, it speaks in terms that imply they're referring to ALL usb 2.0 hubs. since this book is my primary reference, if there's something they're leaving out then I'd be ignorant of it as well :P

                      but, at http://www.everythingusb.com/usb2/faq.htm it says:
                      "Hi-Speed and Full/Low-Speed USB devices can coexist nicely on USB 2.0 hubs. Connecting such a hub to a USB 2.0 port is recommended." which seems to support the idea.

                      Reading the actual usb 2.0 specification, it sounds like 2.0 devices attached to the hub along with the 1.x device might have to wait while the low speed transaction is taking place, but it still sounds like they can operate at 2.0 speeds when the 1.x device is not being communicated with. if that is the case, the 1.x device would be slowing the 2.0 devices down when it is communicating, I don't think it would be nearly as severe as actually forcing them to 1.x speeds...

                      with a usb 2.0 hub, an external usb 2.0 storage device, and any usb 1.x device, it should be pretty easy to test. transfer a large file to/from the storage device without the 1.x device plugged in, and then test it again with it plugged in... i'll try giving it a shot when i'm not at work and have some free time (which is rare )
                      But don't take it from me! here's a quote from a real, live newbie:
                      Originally posted by Viscouse
                      I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.
                      eegeek.net

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                      • #12
                        I know I've seen a few hubs that specificaly advertized that they can do both simultainiously, & I think I've seen plenty of references to the speed dropping to the lower if any one device is 1.X... I just assumed this was the case, which is why I'm using 2 hubs... maybe that's not necissary..... cool... I gotta test this..
                        MY NEWEST INSTALL:modded infiniti fx with big screen

                        first windows carpc install........my liquid cooled LVDS screen :D

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                        • #13
                          Okay, I found some info that sorta relates to your mention of different types of hubs, in the wikipedia entry for USB.

                          hubs have "transaction translators" which handle communication between a low/full speed (1.x) device and a high speed (2.0) bus; cheaper ones have one for the whole hub, better ones have one per port. The difference is that with only one, all the 1.x devices are sharing the same 1.x bandwidth, ie - only one 1.x speed device can communicate with the hub at a time; with one TT per port, all the 1.x devices can communicate with the hub at the same time, and then from there each TT is only competing for high-speed (2.0) bandwidth, which is much greater. basically with one TT per hub, all the 1.x devices would work like they were plugged into a single hub; with one TT per port, they would act like they each had their own dedicated hub, so your 1.x devices would run faster on a TT-per-port hub...

                          the article still doesnt give much detail about how this pertains to mixing 2.0 and 1.x devices on one hub; since it does mention TT's competing for 2.0 bandwidth in the TT-per-port hubs, that leads me to believe that any 2.0 devices attached to a hub would be competing with the 1 or more TT's for 2.0 bandwidth as well, and thus still run at 2.0 speeds.

                          the article says:
                          "The Transaction Translator in a Hi-Speed hub (or possibly each port depending on the electrical design) will function as a completely separate Full Speed bus to Full Speed and Low Speed devices attached to it."
                          since that says "to full speed and low speed devices attached to it" and does not include high speed devices, that also leads me to believe that high speed devices function independently of the low/full-speed devices running through the transaction translator.

                          I also just turned up this diagram from a tom's hardware guide article that someone was using to illustrate the opposing view, even though it seems to support my thought:
                          http://images.tomshardware.com/2003/.../single-tt.gif
                          as you can see, the usb 2.0 device is NOT passing through the TT, so it is running at full speed and thus only competing for usb 2.0 bandwidth with the output of the TT, which even with 3 or more usb 1.x devices plugged in, would only be a small fraction of the full usb 2.0 bandwidth.
                          the full article:
                          http://www.tomshardware.com/2003/09/...ogy/page7.html
                          in the article they run speed tests with a usb 2.0 hard drive and usb 1.1 webcam plugged into the two different hubs (one with one TT per hub, one with one TT for each port) and the transfer speeds for the usb 2.0 hard drive do not change very much (16.2 MB/s vs 16.6 MB/s)

                          I think that kind of proves it (although i'd still like to test it out on my own), because 16.2 MB/s is well above the maximum speed of usb 1.x, but that's the speed they were getting with a usb 2.0 HD and usb 1.1 webcam in the same, single TT usb 2.0 hub.
                          But don't take it from me! here's a quote from a real, live newbie:
                          Originally posted by Viscouse
                          I am learning buttloads just by searching on this forum. I've learned 2 big things so far: 1-it's been done before, and 2-if it hasn't, there is a way to do it.
                          eegeek.net

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