weird USB issue - low/high power mode problem

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icantux · #1 Post by **icantux** » Tue Apr 18, 2006 11:40 pm

Hi all,

I'd like to ask your opinion and seek some advice on this strange issue I have with one of the USB ports on my T42 (2378-reu).

Ever since I tried using a HDD (40GB 5400rpm) in an enclosure that I connected to the USB port, I'm having a problem with that port (the bottom one). When I connect a mouse or memory stick, sometimes windows presents me with a notice stating that there's a problem with the USB port (not recognized) but most of the time there's simply no output whatsoever and the device doesn't work.

It just seems that there's no power at all for single devices...

Here's the strange part. If I connect a mini 4-port USB hub (no additional external power source), windows detects it right away and I'm able to connect the same mouse, memory stick, etc, and windows recognizes that as well. All work at USB 2.0 when hooked up through the USB hub.

Why would a single device not work, but the mini 4-port hub and all devices hooked through that work without any problems? Oddly enough, when I plug in the external HDD enclosure in that bottom USB port, it works and the drive letter pop up. But no single device (memory stick, mouse) will work on it unless it's plugged in through the USB 4 port hub!

I'm led to believe it's a hardware problem and not a software issue - here's why:
- I uninstalled the USB devices (device manager), rebooted windows, drivers re-install without any problems = port still doesn't work with single devices.
- in linux I tried to plug in a single device and it gets no power. If I plug in the 4-port hub it works without problems and all other USB devices work when plugged into the hub.. at USB 2.0 as well!

What gives? Is the USB port foobared?

Is there a way to reset it (hard reset)?

DavidNZ · #2 Post by **DavidNZ** » Wed Apr 19, 2006 1:51 am

I've had my fair share of USB problems myself. Given what you say, i'm not convinced it's a hardware issue as the port just wouldn't work period, with or without a USB hub. What is really odd is that the hub itself isn't powered. So, I'm of no real help, but just didn't think it would be a hardware issue.

jonnnny · #3 Post by **jonnnny** » Wed Apr 19, 2006 9:20 am

I really have no idea about these things but just a guess...
maybe the usb is over powered, so when you plug in the hub, it lowers the power output to each port?

Probably doesn't make sense.. wild guess lol

kam_ · #4 Post by **kam_** » Wed Apr 19, 2006 10:44 am

USB has 2 power modes 100mA and 500mA. On a hardware level this is probably gated from two internal power sources providing different current. This may be with transistors inidivdually mounted on the MB, but more likely some USB controller chip.

I imagine the hardware relating to the 100mA power source for that port has blown, and only 500mA is available.

A hard drive will switch to 500mA immediately as it needs alot of current. Same with a HUB, it will use 500mA mode and provide 100mA mode to each of the ports on the HUB.

A single low power device like a mouse will only use 100mA - low power mode. I guess there is a problem there and the device is detected during the handshake, but as soon as it selects 100mA mode it drops out.

jsmit86 · #5 Post by **jsmit86** » Wed Apr 19, 2006 11:44 am

Another thought.....

Try a differnet USB cable. I have had times where a certain USB cable will work for one device (Blackberry) and not work properly for MP3 player or hard drive. One cable I have is intermittent with my HDD, and for some reason I never seem to just throw the cable out.

icantux · #6 Post by **icantux** » Wed Apr 19, 2006 1:42 pm

Hmmm... thanks for your replies.

The low/high power explanation is the most plausible. That means that the low power mode USB is fried and I can only make use of the mini hub to access the USB port for any peripherals.

Interestingly, by using an USB extension cable I am able to use the port with only one low-power requirement peripheral (such as a USB stick or mouse), but a direct connection by either a mouse of USB stick will not work.

kam_ · #7 Post by **kam_** » Wed Apr 19, 2006 5:00 pm

How long and thin is the cable? DC current drops quite rapidly along long wires, and with it so does the voltage. It may be switching up to high power mode to maintain the 5volts.

OR it may be a physical connection problem. Perhaps the USB hub's connector happens to fit more snugly and so it works.

lithium726 · #8 Post by **lithium726** » Wed Apr 19, 2006 5:40 pm

When you connect a device, push the end of the connector (the part where the cable goes out of it) away from you. I say this becase the casing around the USB ports is angled such that the USB connectors go in at a slight angle, and if they are angled too much towards YOU they will not work. Give that a shot... works for me

icantux · #9 Post by **icantux** » Wed Apr 19, 2006 11:41 pm

Well, the cable's rather thin and about a metre long. Doesn't really make sense that peripherals attached to the cable work, yet they won't without either a hub or that patch cable. This is really strange.

Either way any connector is fairly snug and all the connectors (mouse, stick, cable, hub) are all the same size. There is no significant wiggle, no more than in the top USB port.

Gah... Now the connection is becoming intermittent. Time to call Lenovo for a fix - better be covered in the extended warranty.

weird USB issue - low/high power mode problem

weird USB issue - low/high power mode problem

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