making a KVM switch without keyboard/mouse

[Andy Fish]

Hi,

I have a cheap kvm switch (it's unbranded but the model number appears to be
K-14-E) which switches ps2 keyboard and mouse and d-sub video. This switches
the one of my monitors between a number of test machines.

Separately to this I have my main PC with a dedicated monitor attached to
the primary output on a dual-head video card.

So far so good, but I would like to use the monitor that's connected to the
KVM as the secondary display on the dual-head card - just running the
secondary dual head output into one of the KVM inputs (for the sake of
argument we'll say input #3). so when the KVM is switched to position 3 I
have dual head operation.

Obviously in this case the keyboard and video are connected to the PC with
the main display, and not to the KVM, and this is the problem - the KVM
switch will not recognise input #3 as active because there is no keyboard
connection, so I can't switch the KVM to position #3.

The only solution I've found is to connect the keyboard and mouse inputs for
#3 to an otherwise unised PC which I have to power on when I want to use
dual-head mode.

I was wondering whether anyone else has come up against this problem and
whether there are any easy solutions. I guess the KVM just needs to detect a
5v supply on one of the pins to decide it is connected, so maybe it is
possible to knock up something easy with a bit of soldering?

thanks for any brainwaves

Andy

 

[Mike Brown - Process Manager]

Hi,

I have a cheap kvm switch (it's unbranded but the model number appears to be
K-14-E) which switches ps2 keyboard and mouse and d-sub video. This switches
the one of my monitors between a number of test machines.

Separately to this I have my main PC with a dedicated monitor attached to
the primary output on a dual-head video card.

So far so good, but I would like to use the monitor that's connected to the
KVM as the secondary display on the dual-head card - just running the
secondary dual head output into one of the KVM inputs (for the sake of
argument we'll say input #3). so when the KVM is switched to position 3 I
have dual head operation.

Obviously in this case the keyboard and video are connected to the PC with
the main display, and not to the KVM, and this is the problem - the KVM
switch will not recognise input #3 as active because there is no keyboard
connection, so I can't switch the KVM to position #3.

The only solution I've found is to connect the keyboard and mouse inputs for
#3 to an otherwise unised PC which I have to power on when I want to use
dual-head mode.

I was wondering whether anyone else has come up against this problem and
whether there are any easy solutions. I guess the KVM just needs to detect a
5v supply on one of the pins to decide it is connected, so maybe it is
possible to knock up something easy with a bit of soldering?

thanks for any brainwaves

Andy

Would it be easier to just hook up your main PC to the KVM?

 

[Andy Fish]

Would it be easier to just hook up your main PC to the KVM?

Alas no.

I often need to use 2 PCs at the same time (for client/server testing
or whatever) and this only works sensibly when I have separate
keyboards and mice for the two setups.

one option I am considering is to run all the test systems and linux
boxes on vmware, then I could dispense with all the extra PCs and the
KVM

 

[Mike Brown - Process Manager]

"Mike Brown - Process Manager"

Alas no.

I often need to use 2 PCs at the same time (for client/server testing
or whatever) and this only works sensibly when I have separate
keyboards and mice for the two setups.

one option I am considering is to run all the test systems and linux
boxes on vmware, then I could dispense with all the extra PCs and the
KVM

VMWare may be a good option. I would also look into buying one of the
"old-style" KWM switches that you switch manually. Or maybe you could
find/make a keyboard splitter. I see a lot of them that take 2 KBs into a
single port. Haven't seen one that would take 1 KB into 2 ports, but I
don't see a problem with it operating.

 

[Rob Stow]

VMWare may be a good option. I would also look into buying one of the
"old-style" KWM switches that you switch manually. Or maybe you could
find/make a keyboard splitter. I see a lot of them that take 2 KBs into a
single port. Haven't seen one that would take 1 KB into 2 ports, but I
don't see a problem with it operating.

I just gave this a try with a Belkin KVM:

Main system:
- USB mouse and keyboard *not* connected to the KVM
- PS/2 mouse and keyboard ports connected to the KVM
- Primary port on video card *not* connected to the KVM -
connected directly to primary monitor.
- Secondary video port on video card connected to the KVM.

Second and Third systems:
- PS/2 mouse and keyboard ports connected to the KVM
- Video port connected to the KVM

KVM: connected to PS/2 mouse and keyboard
connected to "secondary" monitor

This left me with the USB mouse and keyboard working in conjunction
with the primary monitor. The secondary monitor took its display
signal as determined by the KVM, with the PS/2 mouse and keyboard
working in conjunction with that secondary display.

It is not a perfect solution, but you just might have the parts
on hand already to test it out and see if it does the job for you.

 

[Andy Fish]

I just gave this a try with a Belkin KVM:

Main system:
- USB mouse and keyboard *not* connected to the KVM
- PS/2 mouse and keyboard ports connected to the KVM
- Primary port on video card *not* connected to the KVM -
connected directly to primary monitor.
- Secondary video port on video card connected to the KVM.

Second and Third systems:
- PS/2 mouse and keyboard ports connected to the KVM
- Video port connected to the KVM

KVM: connected to PS/2 mouse and keyboard
connected to "secondary" monitor

This left me with the USB mouse and keyboard working in conjunction
with the primary monitor. The secondary monitor took its display
signal as determined by the KVM, with the PS/2 mouse and keyboard
working in conjunction with that secondary display.

It is not a perfect solution, but you just might have the parts
on hand already to test it out and see if it does the job for you.

Thanks for the idea Rob. I don't have a USB keyboard to hand but your
suggestion inspired me to a bit of lateral thinking

I discovered that my KVM only requires the keyboard input to be "present"
i.e. it works with no mouse. I don't have a USB keyboard but I do have a USB
mouse, so I connected the PS2 mouse input on the PC to the keyboard input on
the KVM.

So now my setup is the same as yours except the top two lines read:

Main System:
- USB mouse and PS2 keyboard *not* connected to the KVM
- PS/2 mouse connected to keyboard port of the KVM

I guess that cross-connecting the mouse and keyboard could theoretically be
causing a problem with hardware or interrupts. However, since the KVM is
only using it to detect a voltage, and the PSU mouse input is disabled in
windows, I reckon I'm probably OK

Andy

 

[Rob Stow]

Thanks for the idea Rob. I don't have a USB keyboard to hand but your
suggestion inspired me to a bit of lateral thinking

I discovered that my KVM only requires the keyboard input to be "present"
i.e. it works with no mouse. I don't have a USB keyboard but I do have a USB
mouse, so I connected the PS2 mouse input on the PC to the keyboard input on
the KVM.

So now my setup is the same as yours except the top two lines read:

Main System:
- USB mouse and PS2 keyboard *not* connected to the KVM
- PS/2 mouse connected to keyboard port of the KVM

I guess that cross-connecting the mouse and keyboard could theoretically be
causing a problem with hardware or interrupts. However, since the KVM is
only using it to detect a voltage, and the PSU mouse input is disabled in
windows, I reckon I'm probably OK

Andy

Glad I could help, even if only indirectly.