# [solved] External USB drive &  USB ports

## BlueFusion

Hi all,

Yesterday when I tried to plug my external harddrive (a 2.5" notebook drive in an external USB case) into my media desktop, I heard it began clicking.  At first I thought I had lost the data to a dead drive.  To be sure, I hooked it up to my desktop computer.  Same thing.  For giggles, I hooked it up to my laptop and it worked like a champ.  No clicking or errors of any sort.  So I took it back to the desktop.  Still clicking and spitting out the following in dmesg:

 *Quote:*   

> usb-storage: device found at 4                                                          
> 
> usb-storage: waiting for device to settle before scanning                               
> 
> scsi 9:0:0:0: Direct-Access     HTS54101 0G9AT00          A60A PQ: 0 ANSI: 2 CCS        
> ...

 

I then tried plugging it into the direct motherboard USB ports on the back of the case on my desktop.  Worked fine.  Did the same with the media desktop and also worked fine.  I figured that's why it worked on the laptop in the first place since the USB ports are directly on the motherboard.  I find it odd that the case USB ports on BOTH desktop systems failed to properly function with this device when they have both worked fine in the past.  Furthermore, to test the case ports, I used my 8GB flash drive in each front/case port on both systems and functioned flawlessly on both.

So what can cause this?  I had been looking through my kernel config wondering if something in there could have changed how they function.  And for what it's worth, all three systems used support USB 2.0 and the external drive is powered by USB only.

Here's all the pertinent info I can think of...

 *Quote:*   

> rich@area51 ~ $ emerge --info
> 
> Portage 2.1.6.13 (default/linux/x86/10.0, gcc-4.3.4, glibc-2.9_p20081201-r2, 2.6.31-gentoo-r6 i686)                                                                             
> 
> =================================================================                       
> ...

 

 *Quote:*   

> rich@area51 /etc/kernels $ grep -i usb kernel-config-x86-2.6.31-gentoo-r6 
> 
> # USB Network Adapters
> 
> # CONFIG_USB_CATC is not set
> ...

 

 *Quote:*   

> area51 ~ # lspci -v 
> 
> 00:00.0 Host bridge: Intel Corporation QuickPath Architecture I/O Hub to ESI Port (rev 12)
> 
>         Subsystem: ASUSTeK Computer Inc. Device 836b                                      
> ...

 

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## NeddySeagoon

BlueFusion,

Post your /proc/bus/usb/devices   when the drive is connected but not working/making clicking sounds

I suspect its a power issue and the above file will hold the evidence.

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## BlueFusion

Hi, as requested:

 *Quote:*   

> rich@area51 ~ $ cat /proc/bus/usb/devices
> 
> T:  Bus=08 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
> 
> B:  Alloc=  0/900 us ( 0%), #Int=  0, #Iso=  0                   
> ...

 

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## NeddySeagoon

BlueFusion,

Your external storage device is not listed there

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## BlueFusion

Hmm, I retrieved that info after the drive was attached for atleast 15 seconds while it was clicking and dmesg giving the same errors as above.

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## eccerr0r

I'm sure it is a power issue.

I have a external 2.5" HDD that would simply not work with many USB ports, it ends up clicking horribly when plugged in using bus power.  I ended up having to hack an external 5V PSU to it to get it to reliably work.

Most 2.5" HDDs require a clean 5V at 500mA to spin up the disk.  This is exactly the limit of USB, however, a lot of "expensive" USB host adaptors use what's known as a "polyfuse" (self-healing fuse, PPTC) that basically can't sustain the full 5V at 500mA.  Some of the cheaper USB omit the fuse entirely (few devices use real regular fuses) and these will tend to power the hard drives fine.  I'm not sure of the long term characteristics of these "poly" fuses, they may degrade over time when used.

In any case, I think the max power will be reported as a hardcoded number by the usb-ata bridge chip,

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## NeddySeagoon

BlueFusion, 

That the device was connected but not listed points to a power issue.

The workaround is a powered external USB hub.

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## BlueFusion

Thanks guys.  The external enclosure has a power adapter, but it is not currently with me.  I'm fine with having to plug it into the back of the motherboard, but just wanted to make sure nothing else is awry.  Is this a usual scenario with case-mounted USB ports and USB-powered devices such as disks?

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## NeddySeagoon

BlueFusion,

Its a feature more than a problem.  The USB spec says that each root hub must provide 500mA for all connected devices.

A root hub is a pair of stacked USB connecors on the back of the PC.

Some devices need all of that 500mA, 3G modems, disks, adsl modems, webcams and other things.

Some USB powered disks have two USB connectors, one to power the drive spin motor and another for the the electronics and data.

This means that some arrangements of USB devices work and some don't because of the 500mA limit.

Look at your USB tree with usbview - it shows the power requirements of each device.

A powered external USB hub, resets the 500mA limit, as they normally provide 500mA per USB port.

Add into the mix the variation on current limits on USB ports and some devices will not work with some ports.

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## BlueFusion

Thanks a bunch for your help and sharing your knowledge!  I'll rest a little easier knowing there's nothing technically wrong  :Smile: 

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## BlueFusion

Just wanted to verify that it was indeed a power issue.  I found a second USB cable that goes into a small power port on the external enclosure for this very problem.  Plugged it in and worked beautifully on all ports.

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