Re: Force USB low speed on an specific port.
On 2011-12-21, Marc Aymerich <glicerinu@gmail.com> wrote:
> On Tue, Dec 20, 2011 at 2:59 PM, Alan Greenberger <alanjg@ptd.net> wrote:
>> On 2011-12-18, Marc Aymerich <glicerinu@gmail.com> wrote:
>>> Hi,
>>> Today I've tried to connect my mouse through +10meters USB cable.
>>> Seems that it works pretty well despite of what the RFC says about
>>> maximum cable lenght :) the only problem I have is that ~5% of mouse
>>> clicks are lost. I want to try putting the bus speed to a lower rate.
>>> Is this posible ? for example, can I force a USB2.0 bus to work in
>>> USB1.0 mode or something like that?
>>>
>>> Thanks!
>>
>> Mice don't do USB2. They are Low Speed USB1 devices. To see this, type
>> lsusb to get the bus and device numbers of the mouse and then lsusb -t
>> which should show something like:
>> |__ Port 1: Dev 2, If 0, Class=HID, Driver=usbhid, 1.5M
>> showing that it is running at 1.5 Mbits/sec
>
> Acctually i didn't mention that between the cable and the mouse there
> is a usb2.0 hub (lcd monitor with usb)
>
> /: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/8p, 480M
> |__ Port 2: Dev 9, If 0, Class=hub, Driver=hub/4p, 480M
> |__ Port 1: Dev 10, If 0, Class=HID, Driver=usbhid, 1.5M
>
> So the cable speed is 480M.
>
During the time slice that the hub in your monitor is talking to the
mouse, the hub's hardware is communicating via USB low speed. Due to
poor signal quality, too many packets are getting CRC errors. No
software will alter this.
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