Am having an annoying problem getting a USB 2.5" HDD enclosure working with my
ASUS P4P800 Deluxe motherboard in USB 2.0 mode.
The enclosure is recognised as a USB Mass Storage Device on bootup and can be
written and read from as a USB 1.0 device ok (but slow of course).
But when ports are configured for USB 2.0 then on plugging in the enclosure
(front or rear ports) the message "USB Device Not Recognized" pops up bottom
right of XP and "Unknown Device" later shows up in XP's Device Manager.
The USB 2.5" HDD enclosure is a (UHH-AL2) and uses an ALI (M5621 A1) chipset if
that is any help to anybody.
Motherboard is running latest BIOS (1014) and XP has SP1 and all patches etc
installed.
The same enclosure has been tried on a friends computer with the same ASUS
motherboard and operating system but the same problem happens to him.
Anyone know what might be going wrong?
I've emailed ASUS but no response as yet.
Summary Info:
Motherboard is: P4P800 Deluxe
USB 2.5" HDD enclosure is (UHH-AL2) as at:
http://www.ecs.com.tw/products/peripherals.htm?submenu_id=17&function_id=14
Operating System: Windows XP with SP1 installed.
thanks in advance
Tony
You've already proved it is not a protocol problem, since the device works
at USB 1.0 speeds. And, the ALI website has a press release, stating they've
just passed some kind of protocol compliance test.
Here are a list of possible problems:
1) Protocol compliance - this includes having full config data so that
Windows can install the right driver, PHY level transmission protocol
etc.
2) Enclosure powering problem, either due to insufficient sized "wall
wart" or enclosure has some problem with excess current flow either
to or from the enclosure. As you are probably aware, sometimes use
of an externally powered USB hub, can help devices that are bus
powered, such as Alcatel "Frog" USB ADSL modems, that draw more than
the allowed 500ma from the cable. If your enclosure uses a wall wart,
this is not likely to be a problem.
3) Transmission line matching problem. At USB 1 rates, the cable can
be pretty crappy, and it will still work. But at USB 2.0 rates, there
must be careful attention to PCB copper track transmission line
impedance, as well as impedance match and proper loss characteristics
of the cable. Not all original USB 1 cables can pass USB 2 signals.
Most recently purchased cables should work with either, as now
cabling manufacturers are more aware of the spec they have to meet.
Some case manufacturers, and their front panel connector schemes, still
haven't figured out how to implement USB 2.0 compatible connectorization.
4) There could be an error inside the enclosure, in terms of resistor
strapping. The resistors are part of the power up and reset protocols,
and help either end of the link determine what kind of device is
connected.
5) There have been problems with excessive jitter in clock sources, when
doing USB 2.0. There was one motherboard chipset, that doesn't seem
to be very jitter tolerant, so if a jittery device is connected to
the motherboard, it won't work properly. The solution was to place a
_USB 2.0_ hub between the USB device and motherboard. The reason
this helps, is USB 2.0 hubs reclock the data, before sending it on.
This data regeneration gives the hub silicon a chance to handle the
jitter, and reduce it before the data is sent to the motherboard.
Note that the USB 2.0 hub even reclocks USB 1.0/1.1 data, and helps
get a bad USB 1 signal to the motherboard.
The jitter comes from processes like clock multiplication. A chip can
use a crystal to get 12MHz, and then use clock synthesis to get a
480MHz signal for making cable data. If the layout of the bridge
chip is bad and noise is coupled into the clocking circuitry, this
causes modulation of the clock, otherwise known as jitter.
6) Finally, have a look inside the enclosure. I bought a few enclosures
before Christmas, and the build quality inside is terrible. I found
a ribbon cable on crooked, loose screws on assemblies etc. The usual
cheap sleeve bearing fans. In fact, the ribbon cable didn't even
seem to match the header it connected to (2.5mm versus
0.1" dimensions). So, have a look inside. But, be careful, as in
disassembling one of my enclosures, I managed to get one of the
unkeyed cables on a header, with a displacement of one pin.
Nearly fried the damn thing.
You can disprove a lot of these possibilities, by finding a computer
that the enclosure will work with. Then, you can verify your cables
are good etc.
With the cost of enclosures, if all else fails, I'd get a self powered,
USB 2.0 capable hub, and give that a try.
HTH,
Paul
