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

[Paul Coccoli]

I've been thinking about a way to interface a footswitch to my
computer for triggering things like sooperlooper and fweelin.  I've
got a sustain pedal for my MIDI controller on the way, but it got me
thinking.  I've got a perfectly good serial port on the back of my
computer, doing nothing.  I'd like to put it to work, but my hardware
skillz are, well, lacking.

I've figured out this much: you can wire a simple loopback by
connecting DTR to DCD and DSR and connecting RTS to CTS.  What if you
insert a switch between these?  E.g. connect RTS to the sleeve pin of
a female 1/4" TS jack and CTS to the tip pin.  Could you then plug in
a sustain pedal?

I've seen software that monitors the state of the pins on the serial
port, so I'm not worried about that part.  I'm just not sure if the
hardware would work.  Like when the switch is open, do you connect CTS
to ground?  I don't know enough about this stuff.

Any hardware hackers out there?  Am I crazy?  I suspect there's more
to it than what I've said here.  Could I wire up a TRS jack and a TS
jack and plug in my amp footswitch (2 switches) and a sustain pedal?