For my android app DJPad I originally implemented knob control as linear. Move up or right and the value increases, move down or left and the value decreases.

For my android app DJPad I originally implemented knob control as linear. Move up or right and the value increases, move down or left and the value decreases. I realized this was a mistake when I gave my app to friends to test and had to stop myself from saying "no! you're moving the knob wrong!" and went back to the drawing board :)