Re: USB keyboard

Claude Hopper wrote:
Franc Zabkar wrote:
On Fri, 24 Oct 2008 09:32:19 -0400, Claude Hopper
<boobooililililil@xxxxxxxxxxxxxx> put finger to keyboard and composed:

I just bought a USB keyboard and didn't really want that type. I bought
an adapter (USB to PS/2). For some reason that does not work at all
where a previous PS/2 keyboard worked just fine. What could be the problem?
It could be that your keyboard doesn't support dual protocols, ie it
may know how to "talk" USB but not PS/2. The USB signal pins are Data+
and Data-, whereas for PS/2 they are Data and Clock. The USB keyboard
needs to recognise that it is connected to Data and Clock, not Data+
and Data-, and change its protocol to suit.

- Franc Zabkar

What does "adapter" mean?????????????

There are "active" and "passive" adapter devices. A passive one,
is a mechanical adapter, and it just wires the pins through to
different pins on a different shaped connector.

Examples of passive adapters are -

1) DVI-I to VGA adapter for video cards (selects the analog signals
on the DVI-I connector and puts them in the familiar 15 pin VGA
2) S-video to composite adapter. Takes the four pin S-video signal
from a video card, and makes a two signal composite output. That
adapter isn't completely passive, as it has a single capacitor
inside the adapter, to join the Y-C signals together and
make composite.
3) The green PS/2 to USB mouse adapter for my Logitech mouse. As Franc
said, it connects DATA+/DATA- to DATA/CLK. To work, it requires
that the mouse support both protocols. When the power comes on,
the mouse has the ability to tell whether USB signals are
present (DATA+/DATA-) or whether DATA/CLK are present. The green
adapter has no components inside (my assumption, based on the
size of the adapter). The mouse works all the magic. Only some
mice have that kind of dual logic inside. Other USB mice
will be USB only, and if connected to the green adapter, they
wouldn't know what to do.

An example of an active adapter.

This one takes a computer equipped with a USB port, and allows a
PS/2 mouse and PS/2 keyboard to be connected. Inside the adapter,
is a pretty complicated chip. It includes a processor and firmware.
The early versions used to freeze after about ten minutes of usage.
Presumably that has been fixed by now. The device would be pretty
simple inside, consisting of a single chip and perhaps a quartz
crystal for timing. (I had a datasheet for the chip at one time,
but cannot remember right off hand who makes it.)

I'm not aware of an active adapter that goes the other way.
So if you had a USB keyboard, and the computer had only PS/2
ports, I don't know of a device to do the conversion. Maybe
something like a universal KVM might do the conversion, but
at a level of expense that would make a new keyboard a bargain
by comparison.

Just buy another keyboard.