I stumbled on this last night when I was working on my TiGR Guitar Rack HID stompbox (that I have mentioned elsewhere).
The stompbox includes 3 controls/buttons on the top which are to be used to change a single parameter on a single guitar effect, for instance frequency or delay on my chorus effect.
I am calling the feature The Bender. Because as I play I will be able "bend" individual parameters on individual effects. (Very cool, I think. And am VERY MUCH looking forward to using this feature!)
So...on to the chase.
The patch below includes 2 versions: the Mobmuplat one, which "receive"s from GUI and then feedbacks into "send to GUI" and a pd version which is quite different because feeding numbers into themselves on pd causes a stack overflow. So it uses v/vals to rectify the issue and only sends updates on bangs.
So what does it do:
If you click Up, it starts and slowly (or quickly depending on how you set the "Rate of Change") moves a slider (could be any value) up its curve. Stop stops the motion and Down sends the value slowly back down (at the same rate of change as the Up).
So it automatically changes the value over time. Which to me is Way cool.
Hope you find it useful or at least interesting.
Peace, Good Will and Plenty of Spirit.
p.s. making HIDs is even waaay more fun than making GUIs. :---)