anyway, there's no need to look at the tft side of the project (basically it's an "IF button pressed"), in fact now I just made up a couple of physical buttons for testing pourpose.
my doubt are all in the pot side of the project.
also there's a digital interface with 4 buttons that can be used instead of the pot, it has on off + and - and every button has 2 pin on the interface (open/close circuit) but the only think that comes in my mind ti digitally to it is to add relay but they are too slow
Hook up the device, Measure the voltage across the two pins on each button. Do you see no voltage difference or maybe a 5V across the two pins. I suspect you will see a voltage maybe 5V. A button is usually pulled up to avoid random state changes. If that is the case, you can connect the 5V pin to an arduino pin to output 0V and 5V to "press" the button. Then see if the other pin on all 4 buttons are indeed all connected (common). Connect the common to arduino gnd.
I see 5V (4,9v to be precise) when the button is unpressed and it goes to 0v when pressed
can I plug the 5v pin to an arduino pin and the other pin to ground to make an HIGH/LOW thing?
Or I could use a transistor as a switch in order to open/close the ciruit or a solid state relay (faster than a normal relay).
basically, I measured a continuous current flow on all the pins on the board, and if I short the ON pins (measure = 0v) as soon as I "un-short" them it does turn on (and it goes back to 5V)...how does it work? I can't really figure it out
The way they work is by pulling one pin to 5V using a pull-up resistor. If you have a multimeter, select current mode (mA range) and connect the meter between the two pins. You will read a current probably in the mA range. Let me know what you got. I have a hunch you don't need a transistor, just using the arduino pin is good enough.