On Wed, Aug 17, 2011 at 1:42 PM, <meino.cra...@gmx.de> wrote: > Paul Hartman <paul.hartman+gen...@gmail.com> [11-08-17 18:02]: >> On Tue, Aug 16, 2011 at 10:01 PM, <meino.cra...@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. ;)
