9 Dec
2008
9 Dec
'08
9:47 a.m.
On Tue, Dec 9, 2008 at 7:38 AM, Jules Richardson
<jules.richardson99 at gmail.com> wrote:
There must presumably be a USB keyboard protocol standard though (otherwise
every USB-connected keyboard out there would need proprietary drivers) - so
I assume that the more expensive PS/2-USB adapters really do interpret the
PS/2 protocol and convert it to such a standard, and are primarily designed
for keyboards which aren't natively USB-aware...
USB keyboards and mice are HID (Human Interface Device) devices and
there is a standard specification for these devices. The active
PS/2-USB adapters appear to the host to be a standard HID which
unknown to the host speaks PS/2 to the keyboard and/or mouse.
http://www.usb.org/developers/hidpage/
http://www.usb.org/developers/devclass_docs/HID1_11.pdf
These specs are hard to understand but the actual device firmware
implementation isn't hard.