What values should I expect to read for each of this trills when I don't touch it? Is it 0 or -1?
Assuming you are using the Linux library (e.g.: on Bela), then you should use getNumTouches() / getNumHorizontalTouches() to verify how many touches are currently detected and do not call touchLocation() or touchHorizontalLocation() with an index higher than the one returned by the getNum... call.
uzi_hs It seems that I keep getting values that are bigger than 0, even if I don't touch them. Touching them - I see values from 0 to 1. But one I take off my hand it still show me bigger values (specifically for the Square and Ring).
Is this due to interference/noise?
Keep in mind that every time a Trill device is initialised (e.g.: every time a Bela program starts), the device's baseline is recomputed, so you should make sure you are not touching the device while the program starts, or it will assume a different baseline from the real one, which can cause "ghost" touches to be detected later on (although it should resolve itself after a few seconds of not touching the device). Also, make sure your hands are not wet and more in general that the device does not get condensation on it, as that would also increase the capacitance reading and could result in a ghost touch being detected.
If the device is glued onto a surface, make sure there are no air bubbles beneath it and more in general that it doesn't move when pressed, as that could cause unexpected changes in the baseline if the surrounding material is capacitive. Probably worth mentioning that if resting it on a surface, this surface shouldn't be metallic or conductive.
If you still get "ghost" touches, try using the Trill/general-settings example in the Bela IDE and see if you can visualise the "ghost" touch in the GUI when the device is set to DIFF mode. If that's the case, compare the readings between the BASELINE and RAW mode: during normal operation and with no fingers on the device's sensing surface, the two should be very similar. Any difference there may be read as a ghost touch. See here for more details.
