[linux-audio-user] [OT] DIY serial input devices?

[Paul Coccoli]

On 5/6/05, Rob Fell <robin.fell at ntlworld.com> wrote: 
> 1.  RS232 is nominally a +/- 13v (ish) system - you don't want to ground
> anything.
> 2.  It's an I/O port, and should be safe against short circuits, but I'd
> recommend using at least 1K series resistance when you're poking around
> there :)
> 3.  The RS232 inputs should have pull-ups/downs to bring them to valid
> levels when disconnected.
> 
> In summary - with 99% of normal sane hardware, it should work (but I'd
> recommend the precaution of a 1K resistor).
> 

Hmm...so if DTR is set to +13V (0) and RTS is set to -13V (1) for
example, then I can use switches connected to CD, DSR, and CTS so that
each pin can read 0 or 1.  Is that correct?  Where do the resistors
go?  Between DTR and the 3 switches and RTS and the 3 switches?

I'm going to refrain from making an ASCII diagram and hope I've made
myself clear.

Thanks for the suggestions, Rob.

As for the other suggestions, my box does not have a parallel port or
a gameport (Shuttle XPC).  I think I can add a parallel port, but that
would cost money.  I've seen a number of DIY parallel port digital
joystick interfaces, and apparently some of them even have kernel
support.  A joystick port would be great, since it gives you four
analog signals (expression pedals/MIDI CCs).  Alas, all I have is the
lowly serial port.