Re: a USB for the Apple II smoke test

["josephoswaldgg@hotmail.com" <josephoswald@gmail.com>]

The Wizard of Oz wrote:
> 	The point I was trying to make was there is a cheap device which can be
> bought which will allow a USB mouse to be connected to the 9 pin
> connector. It works. I seen it. If there is circuitry on the mouse to
> detect the eventual connection to the computer then it's not in the
> device. This means a USB mouse will work with a 9 pin connection. I've
> seen it. I can't remember if I've seen the reverse.

Things are not as simple as they appear. Some mice have very
intelligent circuitry that makes them "combo" mice, which can adapt to
different signalling voltages and conditions.

http://www.pcguide.com/buy/des/compMouse-c.html

I would guess the adapter is simply a wiring converter, and the mouse
is smart enough to notice what voltages it sees coming through the
wires, and recognize that it must be looking through the adapter. The
ones I see are PS/2+serial combo mice.

http://users.tkk.fi/~then/mytexts/mouse.html

describes the serial mice; the PS/2 mice use only 5 V. So a mouse can
check +12 V-->serial, +5 V-->PS/2 signalling.

For your USB--9 pin connector model, I can't find any documentation or
product info for such a mouse or converter, but is is conceivable the
mouse has a fall back to serial mode when it sees +12 V on a USB pin
instead of the normal +5 V from a USB port.

The other possibility is that the adapter has a very small integrated
circuit inside it; 9-pin serial mice, from what I can gather, get their
power because the serial interface drives a line (TX PC-->mouse?) with
+12 V. That means there is also +12 V for a special purpose IC to use,
which could implement enough of the USB controller protocol to make the
mouse wake up and talk, and for the IC to send Microsoft
mouse-compatible signals to the interface. This seems a bit of a
stretch; USB is pretty damn complicated on the host side, but
microcontrollers are getting smarter all the time.

> 	I've used a 9pin to 25pin adaptor to get a mouse to work on an older
> computer. I've done this. It works.

That adapter is pretty much a simple pin-to-pin wiring.

> 	Therefore, if he were to put the 25pin plug back on his SSC and make
> appropriate adjustments for baud rate and data format he could get data
> ...long scenario deleted...

yes, but in this case, the USB device is almost certainly not speaking
USB. It has fallen back to speaking a serial protocol. So you've really
connected a 9-pin serial mouse to the Apple II serial port.

Not impossible to decode, either; assert the RTS line to give the mouse
power, listen at 1200 baud, and you should see mouse data coming back.
But I don't think any GS software knows what to do with that data.