Re: [gentoo-user] [OT]: "Reset" of USB when switching to console and back to X?

[Paul Hartman <paul.hartman+gentoo@gmail.com>]

On Wed, Aug 17, 2011 at 1:42 PM,  <meino.cramer@gmx.de> wrote:
> Paul Hartman <paul.hartman+gentoo@gmail.com> [11-08-17 18:02]:
>> On Tue, Aug 16, 2011 at 10:01 PM,  <meino.cramer@gmx.de> wrote:
>> > Hi,
>> >
>> > I have attached an old keyboard (PS/2-connector) via an
>> > USB-PS/2-adaptor to my PC.
>> >
>> > When typing too fast (...) the three LEDs of the keyboard flashes
>> > and everything typed then is typed as if the CTRL-Key constantly
>> > locked (I am using the X-window-system with openbox as windowmanager.
>> > There is no session management.)
>> >
>> > It is possible to revert back to normal when I switch
>> > from X-windows to the Linux console (CTRL-ALT-F1) and back
>> > to X (CTRL-ALT-F7).
>> >
>> > My question is:
>> > What part (PC? Adapator? Keyboard?) gets out of sync here is
>> > "resetted" (somehow), while switching between console and
>> > X-windows?
>> >
>> > How can I reset the behaviour without switching? How can I
>> > prevent the behaviour completly?
>>
>> FWIW I have experienced that same behavior with several PS/2 to USB
>> adapters, in Windows, in Linux, etc. I think it's a common problem
>> with those adapters in general. I've never used one that didn't "go
>> crazy" a few times a day.
>>
> Hi Paul,
>
> after some recursive investigations :) via internet I found some
> interesting things:
> 1) Yes, your are completly right: It is the USB-PS2-adapter, which
> goes crazy.
> 2) No, you are wrong, the reason is different.
> ;) :)
> 3) The answer is 41.999998 (calculated by a P90). ;)
>
> The reason for stuck CTRL/SHIFT keys is a missing pull-up
> resistor from the clock and the data line to the +5V line
> of the PS2 connection. Or in other words: Adding these resistors
> seem to fix the problem in most cases.
> See the link below (which describes the process for a IBM Model M keyboard. Seems true
> for other old PS2 keyboards as mine, too):
> http://ps-2.kev009.com:8081/ohlandl/keyboard/modify_keyboard/Model_M_Modifications.html
>
> The PS2 goes crazy because the high level gets too low without the
> additonal pull up resistors. But the "origin of the reason" is not
> the adapter, but the low high levels of the old PS2 line as such.
>
> I did find these information that late (after posting to this list)
> by searching for informations about certain different usb-PS/2-adapter.
> Sorry, when answering the other half of my own question.... :)

Very interesting info, it's good to know the real reason why it always
seems like a "universal" problem with those adapters.

In the end, to solve my own problem, I bought two Unicomp keyboards
which are the same as the old heavy IBM keyboards but with USB
built-in. ;)