On Wed, 14 Nov 2001 at 21:37:26, Phoebus R. Dokos wrote:
(ref: <[EMAIL PROTECTED]>)
>>One _very_ good idea Keith Mitchell had was to use the 'spare' input
>>socket as a PS/2 mouse port - _all_ it would need is a suitable driver.
>>That would make sH LITE a better product at the cost of a connector.
>>I must find time (and help) to investigate that.
>
>I did use a PS/2 mouse when I had my Aurora/sH :-) It's a standard serial
>port apart from the difference in the packaging (mini din instead of
>Sub-D9). I was thinking it wouldn't work at first but I was influence from
>the PC which uses the PS/2 port as a different kind of serial port with its
>own IRQ and only one baud setting. However from an electrical standpoint
>its 100% the same :-)
No it isn't. COM mice need nominal +12v/-12V (RS232C) - sH works with
+- 10V approx.
Ps2 mouse only needs a single 5V rail - much easier. Also the PS2 data
lines are TTL. ie 0V and >1.75V. Electrically it is the same as a
keyboard. It worked for you because an RS232 port will accept TTL
input. RS232C spec defines logic change a fraction above 0V.
Marginal, but works at low speed.
I remember using a Diablo daisy wheel printer from the Compukit UK101 (
still have it). I generated TTL output to the RS232C printer input -
timed carefully from basic as the printer had a limited line only
buffer. It was though, thankfully, very flexible on line speed. It was
an awful lot easier than the previous set up - driving an IBM golfball
printer direct with hardware. .... but a lot less fun.
All COM mice use a +5V rail internally, but must have the negative
reference voltage to generate the data out. Oddly we found a few COM
mice that worked off 5V - it depends on their method of chopping the
12v. They must have used 5V approx Zener diodes. A lot though don't.
.... but they all needed the -VE reference voltage.
Quite a lot of circuitry had to be put into sH (charge pump) to double
the 5V rail, only for the mice to chop it back to 5V (8-)#
> Just a D-9 to mini din converter suffices :-)
Yeah - drivers are the only issue - the converter lead is trivial.
(Nasta will correct the above I am sure - he knows far more than me
(8-)# )
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