USB hubs and long runs

[SavannahLion]

With all things being equal and staying withing specs.

Am I to understand that one can indeed use a powered hub to extend a connection longer than the spec'ed 5 meter limit? Reading the FAQ's at usb.org, it does seem to imply that this is the case and it does seem to make sense if the issue has to do with the signal timing.

I'd try this out but I don't want to invest in a pair 5 meter long cables at the moment.

[Le Chuck]

I thought that they made specialty booster for that up to 100m.  You're not using a regular off the shelf powered hub for that but a more specialized type of range extender ie the followin:  This one has an integrated buffer but the power delivery at the far end is not that great for a lot of arcade peripherals.  This page has cables with separate power, some have dual ported ends for $30. 

If you get one or find a better solution let us know.

[drventure]

5 meters? You might be better off with a Wireless USB extender

http://www.google.com/search?q=Wireless+USB+extender

Never used one, though I came close to picking one up to allow me to relocate a printer at one point (I ended up using a Wireless router that I could install DWRT on, turn it into a bridge and then connect the printer via ethernet instead of USB, but that's another story)

[DillonFoulds]

Out of curiosity, what's the application that requires a 30m usb cord?

[smalltownguy]

Just use a Cat5 extension:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250792101786

[MonMotha]

You can cascade powered repeaters (aka hubs, possibly with only one port) quite a ways before you run into any problems, but there is a flat distance limit imposed by the speed of light and repeater delays combined with the speed at which USB devices are required to respond at the most basic level to messages sent by the host.  I don't remember what it is off the top of my head, but my recollection is that it's fairly long.  Something like 100m.

The unrepeated cable length limit is imposed by the cable specs and capacitive loading.  It would be possible to make a USB cable capable of going farther than the spec allows while maintaining basic compatibility with the USB physical layer, but in practice most people just use media converters and CAT5.  Since this doesn't introduce the timing delay and skew caused by a whole mess of repeaters, you can go quite far before you hit the timing problem described above.

USB really was never designed to go beyond the desk, though.  If you need to go beyond about 10-15m, I'd generally recommend some sort of protocol level extender.  While the USB spec has very stringent requirements on how fast slaves have to acknowledge receipt of things (bit level timing on the wire), the protocol allows for fairly slack timing of the actual messages that make up data responses.  Basically, you can receive some message, and while you have to acknowledge that you got it very quickly, you can take quite some time in preparing your actual response.  I know extenders in this flavor are available, and I'm guessing that's what most wireless ones are.  It may mess up isochronous mode operation, though, but that's only really used on multimedia devices.

[smalltownguy]

You can cascade powered repeaters (aka hubs, possibly with only one port) quite a ways before you run into any problems, but there is a flat distance limit imposed by the speed of light and repeater delays combined with the speed at which USB devices are required to respond at the most basic level to messages sent by the host.  I don't remember what it is off the top of my head, but my recollection is that it's fairly long.  Something like 100m.

The unrepeated cable length limit is imposed by the cable specs and capacitive loading.  It would be possible to make a USB cable capable of going farther than the spec allows while maintaining basic compatibility with the USB physical layer, but in practice most people just use media converters and CAT5.  Since this doesn't introduce the timing delay and skew caused by a whole mess of repeaters, you can go quite far before you hit the timing problem described above.

USB really was never designed to go beyond the desk, though.  If you need to go beyond about 10-15m, I'd generally recommend some sort of protocol level extender.  While the USB spec has very stringent requirements on how fast slaves have to acknowledge receipt of things (bit level timing on the wire), the protocol allows for fairly slack timing of the actual messages that make up data responses.  Basically, you can receive some message, and while you have to acknowledge that you got it very quickly, you can take quite some time in preparing your actual response.  I know extenders in this flavor are available, and I'm guessing that's what most wireless ones are.  It may mess up isochronous mode operation, though, but that's only really used on multimedia devices.

Did you stay at a Holiday Inn last night?

[Le Chuck]

You can cascade powered repeaters (aka hubs, possibly with only one port) quite a ways before you run into any problems, but there is a flat distance limit imposed by the speed of light and repeater delays combined with the speed at which USB devices are required to respond at the most basic level to messages sent by the host.  I don't remember what it is off the top of my head, but my recollection is that it's fairly long.  Something like 100m.

The unrepeated cable length limit is imposed by the cable specs and capacitive loading.  It would be possible to make a USB cable capable of going farther than the spec allows while maintaining basic compatibility with the USB physical layer, but in practice most people just use media converters and CAT5.  Since this doesn't introduce the timing delay and skew caused by a whole mess of repeaters, you can go quite far before you hit the timing problem described above.

USB really was never designed to go beyond the desk, though.  If you need to go beyond about 10-15m, I'd generally recommend some sort of protocol level extender.  While the USB spec has very stringent requirements on how fast slaves have to acknowledge receipt of things (bit level timing on the wire), the protocol allows for fairly slack timing of the actual messages that make up data responses.  Basically, you can receive some message, and while you have to acknowledge that you got it very quickly, you can take quite some time in preparing your actual response.  I know extenders in this flavor are available, and I'm guessing that's what most wireless ones are.  It may mess up isochronous mode operation, though, but that's only really used on multimedia devices.

Did you stay at a Holiday Inn last night?

     I was thinking the same thing!

[MonMotha]

No, I actually make USB devices for a living.  I really am a professional in that field.  No Holiday Inn Express needed.

[Le Chuck]

Can you make aimtraks wireless?  I'll send you $$.  Seriously, not kidding. 

[smalltownguy]

Can you make aimtraks wireless?  I'll send you $$.  Seriously, not kidding. 

BIG +1 to that. Amen brotha.

[SavannahLion]

Thank MonMotha, that was what I was looking for.  I think I'm safe to say I'll be staying under 10-15 meters I haven't measured my garage, but I think it's unlikely I'll exceed that length.

The powered hub idea is really desirable because that means I can break out the single port into 4/7/10/... extra ports as I need them, get the distance I think I would want, and still stay with off the shelf parts. Even if I end up daisy chaining more than one hub, the additional hubs wouldn't go any farther than the first hub.

To keep runs as short as possible and to help keep costs low (a cursory glance on Google shows 5 meter A/B cables run about $11 a piece) is it conceivable to obtain bulk uncut USB cable and fashion a USB panel or even use cat cable? I see a ton of discussions about using cat in lieu of USB cable but very little about just how the two differ other than being stranded/unstranded. That's what I was trying to figure out USB.org.

[SavannahLion]

Out of curiosity, what's the application that requires a 30m usb cord?

I would love to share but that would make it a project announc ement and I've only got a 1/3 of it planned in Sketchup and I just finally settled on the control layout. I don't want a still born on my hands if you understand.

[drventure]

Can you make aimtraks wireless?  I'll send you $$.  Seriously, not kidding. 

BIG +1 to that. Amen brotha.

And another. I've searched for some small wireless USB adapter but no joy...

[MonMotha]

There's no off the shelf device that will do this?  Is it just a formfactor issue of existing "wireless USB" products?

[Note: there is actually a Wireless USB standard, but nobody uses it - most are just proprietary wireless extenders with a USB port on each end]

[drventure]

I haven't found anything, but I'm definitely not an industry insider or anything, so my knowledge of USB in general is pretty limited.

I guess my main thing is I'd like to see a wireless aimtrak that could be battery operated, much like a wiimote. That would make for some fantastic lightguns...

[Howard_Casto]

There's no off the shelf device that will do this?  Is it just a formfactor issue of existing "wireless USB" products?

[Note: there is actually a Wireless USB standard, but nobody uses it - most are just proprietary wireless extenders with a USB port on each end]

Well I've searched for similar things for doing a computerized xmas display (I don't like the idea of having an expensive computer directly connected to outdoor lights.)  Your typical wireless usb module is like 100 bucks, for one device.  So I don't think it's a form factor thing so much as it's cost-prohibitive

[Le Chuck]

There's no off the shelf device that will do this?  Is it just a formfactor issue of existing "wireless USB" products?

[Note: there is actually a Wireless USB standard, but nobody uses it - most are just proprietary wireless extenders with a USB port on each end]

Well I've searched for similar things for doing a computerized xmas display (I don't like the idea of having an expensive computer directly connected to outdoor lights.)  Your typical wireless usb module is like 100 bucks, for one device.  So I don't think it's a form factor thing so much as it's cost-prohibitive

I've seen similar and they are always fairly large and require external supply.  What we need is a dongle sized transmitter with a 5v battery setup to power the peripheral.  It seems to be very easy to make for wireless mice and presentation clickers but apparently it doesn't translate well for the data packets that the aimtrak sends.  Shame really.