[OT] USB KVM switches

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Feb 2 19:36:30 2005

> They actually make a USB->RS232 single-chip interface. YMMV, as I've never

If that's the chip I think it is, it's actually USB to TTL-level async.
You need to add a MAX232 or similar to get RS232 levels out of it. But
anyway...

And of course this is no solution to useing USB devices on a host that
only has RS232 ports...

[CoCo Serial Port]
> *DIN-4*. And rather made of unobtanium as well... I *wish* it was DIN-5, as

I wish the 4 pin DIN plug was the most difficult part I had to find. It's
darn easy to get over here.

Actually, there are 2 different 4 pin DIN plugs. The one used on the
CoCo, and another one with the pins at the corners of a rectangle -- the 2
pins furthest from the keyway are further apart in this version and have
a plastic peg between them which opens a contact on the socket when the
plug goes in.

There's a similar 2 pin one -- not the flat + round speaker DIN plug, but
a normal looking DIN plug with 2 pins and a plastic peg -- that was used
for the power/remote control connector on some tape recorders. Now that
one _is_ unobtainium!

> those are still available (or at least findable).

Which 5 pin DIN? There are at least 3 -- the 180 degree one (like a CoCo
cassette socket), the 240 degree one (like a 6 pin one without the middle
pin, can be used for a CoCo joystick if you don't want the second fire
button) and the quincuncial one, used foe the BBC serial port.

There are also 2 different 8 pin DIN plugs. One is a 7 pin one with an
extra pin i nthe middle, the other has the 2 outside pins offset from the
circle. Both are used on classic computers (In fact I think the Epsom
QX10 uses both of them, they are not interchangeable).

Now I guess I should mention the HS20's RS232 port. It's on a 8 pin DIN
socket, and the pinout follows the RS232 numbering with 2 exceptions :

Pin 1 is ground (it would be protective ground on a RS232 port, on this
machine there's only one ground)

Pin 7, which would hav been signal ground, gets the DTR signal.

It's actually a very sensible pinout. The 8 pin DIN socket will take 8
pin, 7 pin, 5 pin and 3 pin DIN plugs. And on the HX20 all of them give a
useful subset of the signals :

3 pin gives you ground, TxD, RxD
5 pin adds RTS, CTS
7 pin adds DSR, DTR
8 pin adds DCD.

-tony
Received on Wed Feb 02 2005 - 19:36:30 GMT