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

[meino.cramer@gmx.de]

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.... :)