Re: a USB for the Apple II smoke test

[The Wizard of Oz <wizard@emeraldcity.gov>]

On Fri, 29 Jul 2005 20:34:25 -0700, Michael J. Mahon wrote:

> The Wizard of Oz wrote:
>> On Thu, 28 Jul 2005 11:09:11 -0700, Michael J. Mahon wrote:
>> 
>> 
>>>The Wizard of Oz wrote:
>>>
>>>>On Wed, 27 Jul 2005 09:47:49 -0700, pilgrimer wrote:
>>>>
>>>><snip>
>>>>
>>>>>I wonder,
>>>>>could it be the baud rate on the SSC?  could it be something else? could
>>>>>it be God never  intended this sort of thing?  Do I really wanna take
>>>>>this one any further?  Not really, but it was interesting.
>>>>
>>>>
>>>>	I think you may be on to something. I seem to recall the early days of
>>>>the mouse on the PC there used to be problems with baud rates. As I recall
>>>>anything above 9600 was fine. It might be cool to see the GS with two
>>>>mice. Since the PC mice are serial devices (the "S" in USB) I see no
>>>>reason why it wouldn't work in theory. Perhaps the problem with the SSC
>>>>could be related to it allowing one connection instead of the three
>>>>available on the backplate. Since there were mice available which didn't
>>>>use the ADB connector, it seems logical there would be drivers for them in
>>>>GSOS.
>>>
>>>Actually, USB has about as much in common with RS-232 as a
>>>giraffe has with a grapefruit.
>> 
>> 
>> 	Bad analogy. A better one would be like what a bison has to do with a
>> cow. The hardware protocols can't be a lot different. After all there is a
>> direct path from RS-232 to USB. I bought a couple of RS-232 to RS-232-C
>> (25 pin to 9 pin) adaptors. Friends have bought RS-232-C to USB adaptors.
>> None of these adaptors required circuitry. It was all a matter of wiring.
> 
> The analogy is not so bad as you think.
> 
> Those are not "adapters"--they only permit connections to the adaptive
> capability already in certain specific devices.  There is no such thing
> as a passive USB-to-RS-232 adapter.
> 
> USB is a multipoint network, using complex protocols just to set up a
> data transfer.  Its lowest data rate is 1.5Mbits/second, way out of
> RS-232's league.
> 
> RS-232 and USB have almost nothing in common that would allow
> interoperation.
> 
> Read the USB spec--it is easily 20x more complex than RS-232
> to do _anything_.
> 
> -michael

	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.

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

	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
signals through the 25pin plug. From the 25pin plug he could use the 9pin
to 25pin adaptor to connect with a 9pin mouse. Remember it is the data
which is important. If instead of connecting to a 9pin mouse he were to
connect to a 9pin to USB adaptor, the data on both sides of the 9pin
connection would have to match up. Otherwise the USB to 9pin adaptor would
not work on PCs either (which they do). The USB mouse would plug in to the
USB to 9pin adaptor. This is the whole purpose behind the adaptor.

	Now to go through in the reverse direction. The USB mouse detects it is
connected to a USB to 9 pin adaptor. Fine, it thinks it's a 9pin mouse.
This is the only point where the USB spec or the circuitry in the mouse is
relevant. It outputs signals which eventually appear as the appropriate
signals at the 9pin plug. It can now connect to a 9pin serial port.
Instead of a serial port lets connect it with a 9pin to 25pin adaptor. We
(I) know a 9pin mouse can use this adaptor to connect to a 25pin serial
port. Does the SSC have a 25pin connector? I think it does. Is it the same
as the PC 25pin serial port? If it weren't then external modems wouldn't
behave the same way. There may be an issue with maximum baud rate, but
that's another issue. If it were a PC, at this point we should have a
functional mouse. All we have to do is see if it is possible to match the
baud rate and data format of the SSC to that of the mouse. IF all this is
possible then in this narrow application we have a path to connect a
single USB device (in this case the mouse) to a GS.

	Would this work with other devices like printers? I don't know. I'm only
talking about a mouse here. Maybe there is something in THEIR circuits
which would make them think they are 9pin devices if connected to a USB to
9pin adaptor.

	As to software, it doesn't matter if Apple made a serial mouse. If Bart
got movement on the screen - ANY movement - by moving the mouse then the
GS is willing to accept mouse output from a serial device other than the
ADB port. This means the software is at least partially there. Bonus! Is
there anything in the mouse toolbox or the serial toolbox which says a
mouse has to be connected to the ADB port and ONLY the ADB port?

	In the end I think a functional USB card would be the better way to go.
I'm just saying this specific hack should theoretically work and is worth
looking in to. Since working adaptors ARE being sold, getting into the
specs is overthinking the situation a little.

	Now to the specs... Both basically transmit information one bit at a
time. That's the definition of a serial device. One deals only with a
single device and the other deals with a single device at one time. So USB
has a higher baud rate... That's only to be expected. It's newer
technology. Bi-directional and uni-directional lines can be dealt with by
software and wiring. Others have dealt with synchronous versus
asynchronous better than I could. As long as both are dealing with serial
information then they are related. I'd say they are more related to each
other than they are to a parallel protocol. Well, maybe not... I don't see
why we can't apply the USB paradigm (I hate that word) to a parallel
protocol and come up with a UPB.

				Later
				Mike