On 17.09.2008 02:06, Peter Stuge wrote: > Carl-Daniel Hailfinger wrote: > >> All of them have PS/2. However, some only have one PS/2 port which >> is either a pure keyboard or a combined keyboard/mouse connector. >> The latter may pose challenges regarding pinouts and/or electrical >> interfaces (multiplexing?). >> > > PS/2 uses four signals; power, ground, clock and data. Dual-purpose > mini-DINs (e.g. page 10 in http://www.pcengines.ch/schema/alix1c.pdf) > use the two last pins in a 6-pin connector for the second clock and > data pair. > > Y-cables are simple splitters. > > The 6-pin connector is backwards compatible with 4-pin plugs, so > plugging a keyboard directly into it will work without a splitter. >
Thanks for the info. > Carl-Daniel Hailfinger wrote: > >> Short version: Some keyboards are dual USB+PS/2 keyboards and have >> an USB connector by default. They often come with a pure passive >> adapter which will convert the USB pinout to a PS/2 pinout. >> http://us.st12.yimg.com/us.st.yimg.com/I/directron_2019_60686738 is an >> example image of such a female USB -> male PS/2 adapter. >> > > The image shows a mouse adapter. > > Did you actually take one apart to verify that it is nothing more > than a passive adapter? > No. > As you know, USB signals are much faster than PS/2, and I would be > very surprised to see electronics in keyboards clever enough to > support both over the same wires. That's not a simple trick. > > I would however not be at all surprised to learn that those green and > purple adapters actually have electronics in them to translate > between USB and PS/2. > Would checking connectivity with a multimeter suffice? >> Some time ago, a few pranksters (myself included) suggested to use >> such an adapter to plug USB flash drives into legacy PCs without >> USB ports. Of course that wouldn't work due to the passive nature >> of the adapter (electrical and protocol mismatch). >> > > I would instead guess that it will not work because the electronics > in the adapter was designed and implemented to support one specific > type of USB HID device. (Keyboard, or mouse, but not both. Oh, and if > it was a passive adapter there would be no difference between > keyboard and mouse adapters.) > One of the adapters in my collection supports keyboard and mouse (tested). I didn't check the others (they all look the same). >> The PS/2 port is generally seen as a pure input "device" and using >> it for complex output (i.e. not just switching keyboard lights) >> will certainly baffle lots of people and confuse those "of course >> that won't work" experts. >> > > Those experts might be well served by reading up on the PS/2 > protocol. The signalling is very much bidirectional between the > keyboard controller on the mainboard, and the microcontroller in the > actual keyboard itself. > True. Regards, Carl-Daniel -- http://www.hailfinger.org/ -- coreboot mailing list: [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
