[LAU] DIY digital control surfaces

[Len Ovens]

I seem to have gotten an itch to make some control surfaces for my home 
recording system.

The first thing I find is that hardware is expensive and software is cheap 
(money wise, time is something else). Fewer pots and switches costs less 
and so they need to be multi-functional. This means momentary switches 
with coloured lights in them, rotary encoders, and motorized faders.

So, how about a touch surface? 7inch android things don't cost much and 
have wireless and stuff... and play games when we are bored ;)  with a 
touch surface you have to watch what you are doing all the time, real 
knobs and sliders let you feel.

digital mixers use a mix of things... but no mouse that I have seen. 
Generally at least one touch screen though. It is used for all the stuff 
that is hard to use controls for. But also for remote control. The diy 
sites show the rotary encoders with light strips to show position, but I 
don't see this on the mixers... they give feedback through the touch 
screen instead. The encoder is $2, the light strip is $15. I am not sure 
what the interface is like, but it would seem simpler than a pot.

Encoders are fine for starting from where I am and moving, but for some 
things a fader is still needed. If it is going to be used for more than 
one thing, it needs to be motorized. This doesn't seem too bad at $20 for 
the fader/motor combination.... but the support stuff has to be there too. 
It needs a motor driver, encoder and (so they say) touch sensing so the 
motor won't fight against your finger.

There seem to be "brains" out there with switch and analog inputs with USB 
or midi ports. (and led outputs) Ya the stuff is all there.

Some other ideas: for faders on a touch pad (screen or drawing pad or 
whatever) The point where the fader is right now does not matter, only 
that it can be moved in the right direction without jumping to whereever 
the finger first touches, tactile feel could be added plastic template 
that has slots where the faders are supposed to be. This would be cheap to 
try (compared to building just about anything) and I have wanted a drawing 
tablet to try other things anyway.

For switches the keyboard has got to be the cheapest thing... only one 
thing is focus changes. Linux is very nice in recognizing and using new 
USB things. If I plug in a second keyboard, I now have two keyboards that 
do the same thing (mice work this way too). I want to use the second 
keyboard as direct input for my own program that takes key presses in and 
puts midi messages out to a jack port. In fact it may be an interesting 
tool to make a keyboard driver that uses one key to switch modes between 
midi mode and keyboard mode on the main keyboard even. (that strange flag 
key for example)

Anyway, is there an easy way to grab a keyboard device before the system 
does? This looks to be /dev/input/event7. There is a utility called actkbd 
that reads this. And I guess it can run a script for any one key or just 
output to stdout the key press. Anyone have a better idea?

--
Len Ovens
www.ovenwerks.net