Gentoo Archives: gentoo-user

From: meino.cramer@×××.de
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] [OT]: "Reset" of USB when switching to console and back to X?
Date: Wed, 17 Aug 2011 18:43:28
Message-Id: 20110817184221.GE13752@solfire
In Reply to: Re: [gentoo-user] [OT]: "Reset" of USB when switching to console and back to X? by Paul Hartman
1 Paul Hartman <paul.hartman+gentoo@×××××.com> [11-08-17 18:02]:
2 > On Tue, Aug 16, 2011 at 10:01 PM, <meino.cramer@×××.de> wrote:
3 > > Hi,
4 > >
5 > > I have attached an old keyboard (PS/2-connector) via an
6 > > USB-PS/2-adaptor to my PC.
7 > >
8 > > When typing too fast (...) the three LEDs of the keyboard flashes
9 > > and everything typed then is typed as if the CTRL-Key constantly
10 > > locked (I am using the X-window-system with openbox as windowmanager.
11 > > There is no session management.)
12 > >
13 > > It is possible to revert back to normal when I switch
14 > > from X-windows to the Linux console (CTRL-ALT-F1) and back
15 > > to X (CTRL-ALT-F7).
16 > >
17 > > My question is:
18 > > What part (PC? Adapator? Keyboard?) gets out of sync here is
19 > > "resetted" (somehow), while switching between console and
20 > > X-windows?
21 > >
22 > > How can I reset the behaviour without switching? How can I
23 > > prevent the behaviour completly?
24 >
25 > FWIW I have experienced that same behavior with several PS/2 to USB
26 > adapters, in Windows, in Linux, etc. I think it's a common problem
27 > with those adapters in general. I've never used one that didn't "go
28 > crazy" a few times a day.
29 >
30 Hi Paul,
31
32 after some recursive investigations :) via internet I found some
33 interesting things:
34 1) Yes, your are completly right: It is the USB-PS2-adapter, which
35 goes crazy.
36 2) No, you are wrong, the reason is different.
37 ;) :)
38 3) The answer is 41.999998 (calculated by a P90). ;)
39
40 The reason for stuck CTRL/SHIFT keys is a missing pull-up
41 resistor from the clock and the data line to the +5V line
42 of the PS2 connection. Or in other words: Adding these resistors
43 seem to fix the problem in most cases.
44 See the link below (which describes the process for a IBM Model M keyboard. Seems true
45 for other old PS2 keyboards as mine, too):
46 http://ps-2.kev009.com:8081/ohlandl/keyboard/modify_keyboard/Model_M_Modifications.html
47
48 The PS2 goes crazy because the high level gets too low without the
49 additonal pull up resistors. But the "origin of the reason" is not
50 the adapter, but the low high levels of the old PS2 line as such.
51
52 I did find these information that late (after posting to this list)
53 by searching for informations about certain different usb-PS/2-adapter.
54 Sorry, when answering the other half of my own question.... :)

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Subject Author
Re: [gentoo-user] [OT]: "Reset" of USB when switching to console and back to X? Paul Hartman <paul.hartman+gentoo@×××××.com>