USB2 to PS2 adaptors?

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Mon Jan 14 14:25:37 SAST 2013

I've got a USB keyboard which was OK on a netbook, which
has now been stolen. And I've been using a USB-to-PS2
small adaptor for my mouse. So both items tested are OK.

I'm trying to test a mother-board which tests ok with a PS2
keyboard, by using the USB-keyboard via the same USB-to-PS2

Why does the mother board NOT detect the USB-keyboard via the
USB-to-PS2 adaptor?

I'm guessing that PS2 is NOT an electrical/protocol standard.
It's just a mechanical standard. And probably the USB mouse also
just uses a primitive non-full-usb protocol.

So then, did the netbook have the ability to detect a <fake-USB>
keyboard/mouse ?

== TIA.

Re: USB2 to PS2 adaptors?

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Mouse and Keyboard adaptors are different

the adaptor should be marked

Re: USB2 to PS2 adaptors?

philo wrote:

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I have a usb to ps2 adaptor in my hand right now and it has a mouse symbol
on it.

Why do you think that is?

Re: USB2 to PS2 adaptors?

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It's marked 'CHINA'; but being green tells all.

Pen wrote:-
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It's unlikely that a USB-mouse is especially PSU compatible.
Probably the USB-mouse protocol, just copied the existing
PS2, so that a plain passive adaptor could fake it.

Now the USB keybrd runs, but I haven't got time, before overheating
to test the mouse.

BTW. the system shuts down after 1 minute, with this unconfirmed PSU
and inadequate CPU cooling.

Is it the CPU or the PSU which initiates the shutdown ?

== TIA.

Re: USB2 to PS2 adaptors?

On 1/15/2013 7:04 AM, wrote:
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You have your facts wrong about the USB/PS2 situation.

Re: USB2 to PS2 adaptors?

Pen wrote:
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A mouse can be dual protocol.

You can design the four wire interface on a mouse, such that
it can sense the difference between USB and PS/2. USB for example,
senses what is there via strap resistors. PS/2, as far as I know,
pulls clock and data high, except when signaling is going on.

When a mouse supports dual protocols, it comes with the passive
turquoise adapter in the box. My mouse comes with one of these.
My mouse supports both USB and PS/2, and I plug on this adapter
when connecting to a PS/2 computer. A mouse does not have to be
dual protocol, and some USB mice will be USB only. Plugging
one of these on, will do nothing for such a USB-only mouse.

That adapter does not have a chip inside. Instead, it
simply passes the correct USB (4 pin side) to PS/2 DIN (6 pin

The USB DATA- pin, functions as PS/2 Data  (DIN, Pin 1)
The USB DATA+ pin, functions as PS/2 Clock (DIN, Pin 5)

The choice of Pin 1 and Pin 5, correspond to the first table
on this page. (PS/2)

When a checked the 875P reference schematic from Intel,
the mouse PS/2 and keyboard PS/2, have the same pinout.
So Data on Pin 1, and Clock on Pin 5.

(Go to PDF page 70 for a look... File is 25281202.pdf)


This, on the other hand, is an active adapter. It
converts PS/2 only keyboards or mice, to work with
a USB only computer. So when your motherboard lacks
PS/2 connectors, and you don't have a dual protocol mouse,
you buy one of these so you can use your older PS/2
keyboard and PS/2 mouse.

The "blob" in the middle of the cable, contains an 8 bit
processor with its own firmware, and that is how mouse/keyboard
protocol is converted to USB packets.


Re: USB2 to PS2 adaptors?

On 1/14/2013 7:49 AM, wrote:
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In suspect that the mouse was USB/PS2 compatible. The small
adapters have no parts in them so the mouse or keyboard has
to be labeled PS2/USB compatible as the protocols are different.

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