question about keyboard controllers

[Mike Hollywood]

HI,
How do keyboards work? Is there a controller on the motherboards, or is the
controller in the keyboard?
When you loose the keyboard, what causes it, assuming it's plugged in.
Can you get a pci card that you can plug a ps2 keyboard into?
Can you convert a ps2 keyboard to a USB keyboard?
Do ps2 and usb keyboards use the same controller? Where is it.
Does the operating system have anything to with it?

As you can see, I've been having keyboard problems.
Thanks for any insights.

Mike

 

[David Maynard]

HI,
How do keyboards work?

You push on a key and a character appears.

Is there a controller on the motherboards,
yes

or is the
controller in the keyboard?
yes

When you loose the keyboard, what causes it,

Forgetting where you put it.

assuming it's plugged in.

Follow the cord to find it. Or, if it's really just loose, tighten it back up.

Can you get a pci card that you can plug a ps2 keyboard into?

Trick question. To do what?

Can you convert a ps2 keyboard to a USB keyboard?

No but you can get an adapter so a PS2 keyboard can be plugged into a USB port.

Do ps2 and usb keyboards use the same controller?
No

Where is it.

The keyboard controller is in the keyboard.

Does the operating system have anything to with it?

Only in running the hardware driver, receiving the characters, and sending
them to whatever is in use.

As you can see, I've been having keyboard problems.

How are you typing?

Thanks for any insights.

Might help if you explained exactly what the symptoms are in more detail
that simply 'loose'.

 

[Mike Hollywood]

Hi David,
thanks for taking the time to reply.
I'm typing on my computer, the problem is on my
girlfriend's. Last night I took over another keyboard,
and it worked. (that's 3 of them)
Today she left a msg on my tape saying it didn't work today.
So, I'm trying to fix her computer. That makes 3 keyboards that worked when
I left, and later didn't work.
I'm starting to think whatever is powering the keyboard is frying them, but
not knowing how they work it's all just
guesswork on my part, hence my post.

If i understand what you were tyring to tell me, it was that there are
controllers both on the mobo and inside the keyboard, and in addition to the
controllers there is also software drivers that run the keyboard. is that
it?

Mike

 

[David Maynard]

Hi David,
thanks for taking the time to reply.
I'm typing on my computer, the problem is on my
girlfriend's. Last night I took over another keyboard,
and it worked. (that's 3 of them)
Today she left a msg on my tape saying it didn't work today.
So, I'm trying to fix her computer. That makes 3 keyboards that worked when
I left, and later didn't work.
I'm starting to think whatever is powering the keyboard is frying them, but
not knowing how they work it's all just
guesswork on my part, hence my post.

If i understand what you were tyring to tell me, it was that there are
controllers both on the mobo and inside the keyboard, and in addition to the
controllers there is also software drivers that run the keyboard. is that
it?

Yes, and it's unlikely that the motherboard power is frying the keyboards
as it's the same 5 volt power the motherboard itself uses and would likely
fry itself first.

Have you taken any of the three keyboards back and tried them on a working
system to see if they really are bad?

What is she doing just before it "doesn't work" any more?

 

[JAD]

Hi David,
thanks for taking the time to reply.
I'm typing on my computer, the problem is on my
girlfriend's. Last night I took over another keyboard,
and it worked. (that's 3 of them)
Today she left a msg on my tape saying it didn't work today.
So, I'm trying to fix her computer. That makes 3 keyboards that worked when
I left, and later didn't work.
I'm starting to think whatever is powering the keyboard is frying them, but
not knowing how they work it's all just
guesswork on my part, hence my post.

If i understand what you were tyring to tell me, it was that there are
controllers both on the mobo and inside the keyboard, and in addition to the
controllers there is also software drivers that run the keyboard. is that
it?

Mike

you.ve tried un plugging and plugging them in? could be a bad port.
you can use usb keyboards as long as the bios is fairly new
some adapters will work ps2toUSB

 

[Mxsmanic]

How do keyboards work?

Since nobody has covered this part:

Keyboards send signals to the computer each time you press or release
a key. These signals include a number indicating the position of the
key on the keyboard (NOT the character printed on the key), and a flag
to indicate whether the key has been depressed or released. The
operating system running on the computer collects these numbers
(called scan codes) as they arrive from the keyboard, and uses tables
and some other logic to translate the scan codes into actual
characters.

Keyboard repeat, which is handled by the keyboard, sends multiple "key
depressed" signals if you hold a key down for more than a certain
amount of time. This is called typematic behavior.

N-key rollover refers to the ability of a keyboard to send a signal to
the computer for a second, third, or nth key when it is depressed even
before preceding keys are released. Four-key rollover means that you
can do this with up to four keys; once four keys are simultaneously
depressed, pressing additional keys without releasing a key has no
effect. Sometimes rollover applies only to alphabetic or certain
other keys. N-key rollover is common today, but not universal, and
may not apply to all keys.

Some keys are handled in a special way. Instead of the keyboard
generating a single scan code for the key, it generates codes for some
other key (usually a shift key), followed by the actual key changing
state, followed potentially by another code for another (shift) key.
This allows a bit more flexibility in the way the keyboard behaves,
but it also requires more complex keyboard drivers, and it requires
that the keyboard keep the shift states (capitals, numeric lock,
function keys on some keyboards, etc.) memorized locally.

Many keyboards have indicators for shift lock and other states. These
can be controlled by the computer and may or may not correspond to the
keyboard's own internal state memory (if any). Additionally, the
keyboard driver may or may not respect these state indicators (they
can get out of sync, or the OS may simply not care about them).

Keys are assigned scan codes roughly from left to right and from top
to bottom. Scan code 00 is not used.

The keyboard sends data serially to the keyboard controller in the
computer. Two-way communication is possible on recent keyboards
(setting shift status and so on). A BIOS interface simplifies reading
scan codes and/or characters from the keyboard.

 

[larry moe 'n curly]

How do keyboards work? Is there a controller on the motherboards, or is the
controller in the keyboard?

www.bilimonline.8k.com/hardware.htm has info about all sorts of
computer hardware, including keyboards (see bottom of page).

The keys are arranged in a grid of rows and columns, and the keyboard's
microprocessor scans each row, one at a time, and checks all the
columns to see if any keys have been pressed in that row. The
microprocessor translates key presses and releases into data, converts
it to serial form, and transmits it to the computer. The computer's
south bridge chip contains another controller to decode that data.

Sometimes the computer quits responding to the keyboard because the
socket on the computer becomes loose or unsoldered, or the wiring
breaks next to the keyboard. But don't underestimate the trouble that
can be caused by a dirty keyboard because dirt can prevent key presses
from registering, and liquids can create permanent shorts. And it
seems that some keyboards are simply built cheaply and wear out their
contacts.

 

[larry moe 'n curly]

N-key rollover refers to the ability of a keyboard to send a signal to
the computer for a second, third, or nth key when it is depressed even
before preceding keys are released. Four-key rollover means that you
can do this with up to four keys; once four keys are simultaneously
depressed, pressing additional keys without releasing a key has no
effect. Sometimes rollover applies only to alphabetic or certain
other keys. N-key rollover is common today, but not universal, and
may not apply to all keys.

I once wired a bare keyboard, consisting of just switches and no
electronics, into a matrix and connecting it to a parallel printer port
and reading the I/O ports directly. I first had lots of trouble with
key bounce until I added a debounce time delay to the key releases as
well as to the key presses. The typing felt really awful because I had
no rollover. I added 2-key rollover by simply storing the previous key
pressed. That was good enough for normal typing, but I read about
n-key rollover and implemented that by storing the whole key matrix.
That made the typing feel even better, but I'd sometimes get phantom
keys, even when I typed very slowly, so I had to check for when more
than two keys were pressed simultaneously in different columns. I
first simply locked those out but later did something I can't remember
that decoded those keys properly. Later, I wired a diode in series
with each key switch, and it gave me 100% reliable n-key rollover even
without any programming tricks. I've seen a couple of PC keyboards
made with mechanical switches that containes spaces for adding such
diodes.

 

[~1AMD Tower~]

you.ve tried un plugging and plugging them in? could be a bad port.

yes, or bent pins, etc. I am starting to thin it may be the port.
The ps2 mouse port may also
be involved in this because I worked on the system this morning, and
couldn't get a ps2 mouse to work, but a USB mouse does work.
I tried 2 more keyboards, and both work, both ps2, but when the
system boots it says the keyboard is not properly plugged in or
something like that, press F1 to continue, and then after pressing
F1, it boots to windows, and both keyboards work.
It is an amd duron system running a 1.2 gigs, on a cheap mobo, but
I forgot who make the mobo. I put this together about 3 years ago,
and had no problems until recently.

 

[~1AMD Tower~]

Hi "Mxsmanic"

Thank you for taking the time to explain all of this.
I'm starting to get a "feel" for it.

Mike



....

 

[~1AMD Tower~]

Hello "larry moe 'n curly"

I want to thank you, too, for helping me with this.
I spent some time last night at the link you provided
and I now know more about keyboards then I thought
was possible! Truly informative. thanks.

Mike

 

[Bob M]

HI,
How do keyboards work? Is there a controller on the motherboards, or is the
controller in the keyboard?
When you loose the keyboard, what causes it, assuming it's plugged in.
Can you get a pci card that you can plug a ps2 keyboard into?
Can you convert a ps2 keyboard to a USB keyboard?
Do ps2 and usb keyboards use the same controller? Where is it.
Does the operating system have anything to with it?

As you can see, I've been having keyboard problems.
Thanks for any insights.

Mike

Are you hot swapping the keyboards? In other words are you shutting
the computer off, unplugging the keyboard, plugging in the new one, and
then restarting the computer? My roomate has a computer where the
keyboard sometimes stops working. If he unplugs the keyboard while the
computer is running and plugs another one in, it won't work. I always
tell him to shut the computer off first and when he does like he's told,
a reboot usually fixes the problem. Not sure why the keyboard fails at
random in the first place. But we've always gotten the keyboard or
another one to work after shutting the system down first. Good luck and
I hope this helps.

Bob