Why can I not draw in the serialEvent() function?

[GoToLoop]

Alternatively, if you just need to refresh the canvas when new data arrives, you can use the noLoop() / redraw() technique:

Map function worked in Processing 2 and early 3.. But broke in 3.5.3. Need guidance

Mutating the sketch’s main canvas outside the “Animation Thread” crashes the program! Callback serialEvent() is run by the Serial’s Thread btW. So even calling something like background() can be fatal! Actually, due to a bad design, any Processing function which depends on color() will get wrong results when they’re multithreading invoked! So any canvas mutating operations should be moved to draw() or called by it. Here’s a post link for…