USB Extension cable and performance

[Chunce DeLeone]

Would a 6ft USB extension cable reduce performance for joysticks and interfaces like Ram controls yoke interface, or Ultimarc rotary interface? 

[MonMotha]

Passive USB extension cables are technically against the specification and therefore never guaranteed to work, but I've used them without much issue in the past.  As long as the total length of cable is <15ft, you're probably not going to encounter problems especially for devices that are not high-speed USB 2.0.

[Chunce DeLeone]

Would a hub be better?  I just want my pc to be down where the coin door is and the usb connection up where the control panel will be. 

[MonMotha]

If you get a good hub, yes.  That should work great.  Problem is, there's a lot of really crappy hubs floating around.  I'd almost be inclined to say that the extension cable is less likely to cause problems.

[WhereEaglesDare]

a powered hub would be best, but it really depends on your board, I have fabricated 35-45 foot USB and PS2 cables before for a customer of mine that wanted a keyboard here and the pc there and they always worked on newer boards (say about 2007-present), but anything older than that was always hit and miss.  Make one and give it a try.

[kegger]

If I had to do it again I would go with a powered hub for all my USB controls as I have had issues with U360's dropping out because of power. Currently I have U360's plugged into powered hub with no problems but I had another hub not being powered externally and it gave me issues   

[WhereEaglesDare]

keep in mind though that good powered hubs are pricey, check out ebay.

[Beretta]

like was said powered hubs eliminate problems.. however you should'nt have any preformance degridation wiht an extention..

with that said it may not work at all or only half the time.. i believe it's from voltage drop.

usb is so crappy, they should have went with 12v, it's bad enough being stuck on wimpy 5v but even then you only get like .5 amp's.. total weak sauce.

[MonMotha]

Well, there's a few problems associated with extensions.

As has been noted, the first is power.  Excessively long cables can cause voltage drop on the cable.  This is also seen with unpowered hubs.  The spec allows for some voltage drop, but not all devices properly accommodate it.

The second is excessive capacitive loading on the data lines.  This distorts the data signal and can make recovery impossible.  This tends to result in all sorts of intermittent problems or it just won't work at all even though the device gets power.  This is the principle reason the spec disallows long cable runs and extension cables (since they can be used to create an excessively long cable run).  You're usually OK as long as the total cable length does not exceed 12ft even if an extension is present, but it's technically against the spec.

You're right, USB is a terrible standard.  The 5V thing is annoying, and the fact that you only get 2.5W is also annoying.  It's enough to cause damage, but it's not enough to actually run anything big.  It should have been limited to either ~1W (low power devices like flash drives) for safety reasons or extended to about 25W to be able to run things like hard drives, printers, scanners, etc.  This is of course unrelated to the driver/software model it uses which I won't even begin to get into   About the only thing USB got right was the HID standard.  It's not too bad, and it's very flexible.

[R0UNDEYEZ]

It should have been limited to either ~1W (low power devices like flash drives) for safety reasons or extended to about 25W to be able to run things like hard drives, printers, scanners, etc.

as nice as that would be, where is all this power coming from? i think the average user probably uses stock power supplies that have 350w tops that is already running everything (processor, motherboard,harddrives,optical drives, fans etc) having a standard that would allow them to draw over 100 watts  off a single run of the mill hub seems like asking for problems to me, plus you know how people are with extension cables and adding extensions to extensions haha

[Blanka]

If it works, it is OK. I guess a hub adds delay, an extension not really.

[WhereEaglesDare]

bottom line, cut open the usb cable you wanna use, splice in some cat5e to make it long enough, and see if it works.  dont waste money unless you have to, if it is inside your cab nobody will see it.  Use butt splices to connect the wires,  and make sure you tape it real good so it dont come loose.

[MonMotha]

bottom line, cut open the usb cable you wanna use, splice in some cat5e to make it long enough, and see if it works.  dont waste money unless you have to, if it is inside your cab nobody will see it.  Use butt splices to connect the wires,  and make sure you tape it real good so it dont come loose.

Ug.  DON'T do that.  That makes everything way worse.

Just use one of those really common USB extension cables.  If it works.  Great.  They often do.  If it doesn't work, get a quality hub, and be done with it.

It should have been limited to either ~1W (low power devices like flash drives) for safety reasons or extended to about 25W to be able to run things like hard drives, printers, scanners, etc.

as nice as that would be, where is all this power coming from? i think the average user probably uses stock power supplies that have 350w tops that is already running everything (processor, motherboard,harddrives,optical drives, fans etc) having a standard that would allow them to draw over 100 watts  off a single run of the mill hub seems like asking for problems to me, plus you know how people are with extension cables and adding extensions to extensions haha

USB has almost excessive provisions for power budgeting as it is.  It would be nice to have a reasonably high maximum that the host can then dole out as needed.  It's unlikely most people would need to pull the full 25W from each port at the same time.  Most ports will just have things like flash drives, mice, etc. hung off them, and devices like scanners and printers don't pull that much juice when inactive.

Dell (king of tiny power supplies) actually was onboard for a "USB+Power" that extended the power available via a USB port to like 50W using an extra connector chunk.  It didn't catch on, unfortunately.

IEEE1394 allows for some excessive amount of power to be moved around, too.  Some posit that's why Apple calls it "Firewire"

[Ed_McCarron]

splice in some cat5e to make it long enough, and see if it works

I bump into this constantly.  People assume "Well, cat5 is rated to 100Mhz, so it must be good cable to use for -X-" -- but the truth is that cat5 (and most UTP cables) are useless without the differential drivers at each end.

A nice low cap shielded cable would fit the bill better.

[phatmeat]

I use 2 six foot extension USB cables in my Dynamo plugged directly from the pc to the Minipac and a USB track Ball ( so its like a 10ft run ).  I have no issues.

[WhereEaglesDare]

splice in some cat5e to make it long enough, and see if it works

I bump into this constantly.  People assume "Well, cat5 is rated to 100Mhz, so it must be good cable to use for -X-" -- but the truth is that cat5 (and most UTP cables) are useless without the differential drivers at each end.

A nice low cap shielded cable would fit the bill better.

I am pretty sure that Cat5e (e = enhanced) is rated for 350MHz.  I have used it several times for this purpose and no problems when the PC can handle that long of an extension.

[MonMotha]

CAT5e is rated for 350MHz.  However, the characteristic impedance does not match USB specifications, and the splices will introduce all sorts of nastiness.  Also, high-speed USB 2.0 is >350MHz.  Just use a real USB cable.  USB *is* differentially signaled, but the cable characteristics it expects are not those of CAT5e.  USB cables are also shielded, which standard UTP CAT5e is not (the 'U' means unshielded).

There's a difference between "yeah, this often works" and "this should always work".  The specification is deliberately conservative so that things should always work.  The physical electrical/cabling section is quite informative.  I suggest reading it if you're interested.

All this said, you're not likely to damage anything messing around with this stuff.  Feel free to experiment.  Just remember that everything you're doing is against the specification and by no means guaranteed to work right.

[Ed_McCarron]

CAT5e is rated for 350MHz.

Heh, my TDR only tests out to 100 Mhz -- it was around before 5e existed.

Just remember that everything you're doing is against the specification and by no means guaranteed to work right.

This is very true -- that ethernet run won't mysteriously stop working at 329 feet -- just don't call me back to run new cable if it doesn't.