I don‘t know about wahahas code (will Check it When i get on my pc), But my code should Display the Point correctly (Even if the coordinate System is pretty ugly, it should do what it should), so i assume that there is a Problem When receiving the coordinates from your arduino. Try printing out the coordinates to See if they get updated. You can do that by just printing x and y after you set it to the respective list[].
Ok, i just checked it and it works just fine… the only thing is that the point is drawn way to small and can be hidden behind the lines. So you can just set strokeWeight(0) after background and then strokeWeight(10) just before the point is drawn, or just draw an ellipse…
If this still doesn’t work, then it is pretty much guaranteed that you don’t receive correct coordinates from your arduino. Just add after
x = list[0];
y = list[1];
println(x, y);
But since you already print out the val, i assume that it should really give out a vector, else you’d have noticed, so i’m 99% sure you’re just not seeing the point because its too small.