[chuck-users] odd hid issue (touchpad)

Hans Aberg haberg at math.su.se
Sat Jul 18 13:48:21 EDT 2009


On 18 Jul 2009, at 16:14, Kassen wrote:

>> Though some older protocols like SCSI have advantages over more  
>> modern, consumer friendly ones like USB, I  don't there are any  
>> system bus issues for these, as one has some intermediate hardware  
>> that provides the communication. In the 1970s I assembled a  
>> computer, that wrote the keyboard characters directly into memory,  
>> which the CPU checked in a loop. This is highly inefficient way to  
>> handle it.
>
> Ah, yes, I would indeed imagine that would be fast. For all I know  
> that's what Apple is doing now...

A development now is that the GPus become usable as extra CPUs.

> This might also be limited by factors like maximum poll-rate and  
> resolution;
>
> For the USB keyboards I have checked, this seems to be limitation of  
> the keyboard, that is, even before the data is sent to the computer.  
> This is because it differs with the keyboard. The computer is so  
> fast that it easily can handle any human typed key roll-over. The  
> slow USB 1 bus is on about 12 Mb/s, which should admit for tens of  
> thousands of key stroke in a tenth of a second.
>
> I meant PS/2 might be limited there.

Oh, I thought you meant the other way around.

> In recent years the quality of high performance mice has gone up  
> quite a bit, probably originally inspired by games like Quake. It  
> was chiefly mouse signals that I was refering to.

I haven't checked that out.

> Sadly (I feel) the quality of keyboards hasn't made the same  
> progression and keyboard ghosting is now typically worse then it was  
> on keyboards from the 80's.

On the Mac side, this was a problem in the 1990s - they would wear out  
after awhile - but not lately.

> I think I tried a Mac keyboard once on a Windows, finding it not  
> working. One needs to have a driver installed. Each device may  
> require its own. The USB HID interface unifies those, so that only  
> one driver is needed, which then can be supplied by the OS. The  
> latest version of this USB HID interface or standard was issued this  
> year. So perhaps it was not available when 'chuck' was written.
>
> Odd. I've never seen a keyboard not work, I think. Special keys  
> (like volume or "sleep" ones) may need a driver in my experience but  
> the keyboard itself always worked. I think you can even take a ps/2  
> keyboard, use a USB adapter and plug it straight into a Mac,  
> provided you are willing to remap some stuff to the "Apple" and  
> related keys.

Windows is notorious for letting users install drivers on their own.  
On Mac OS X, they are usually supplied with the OS installation ("plug  
and play"). One exception was printer drivers when the Intel Macs were  
new - then, for awhile, they were only supplied with the OS  
installation on the PPC side.

But when I looked on the Spacenavigator there was an article, in 2007  
perhaps, about how to get it working on a Mac by finding some USB  
numbers. So this unified HID interface may be rather new.

The USB HID key number assignment is also different an older and a  
newer Mac keyboard I have. The numbers of key above the <tab> and the  
key to the right of <left-shift> are swapped, I think it was. You  
might try those keys in the diatonic.ck I made - they are made for the  
more recent keyboard from 2009, which is the same as on a third one  
from 2002.

So for correct translation, one needs to look up the name of the  
device, and choose a key map for that one.

also, the Mac short keyboards have a special "function" key, that lets  
one to supply some of the keys of an extended keyboard, plus some for  
special Mac use. The function key was not reported at all, and  
pressing it did not report the extended keyboard key values. So it has  
some USB function not covered by the HID standard, it seems.

   Hans




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