Quote:Accordingly, I downloaded SC code
--which I presumed to be Working Perfectly, like in its Video--
Well, there is your first mistake.
Quote:The program runs smoothly, leaving a clearly debugged Sub,
There is your second.
Quote:Is there a way to use the debugger to step-by-step, See the next step (Next Sub) where the code goes to Die?
And the third one.
Just because a method doesn't fall over immediately, just because it seems to work in a video (particularly a YouTube video) doesn't mean it does what you want it to, or what you need to to in order to work with your code. Debugging is a much more complicated process than "it didn't crash when it ran".
And one of the problems with serial communications is that received data does not "arrive" on the main thread - it uses a totally different thread to pass you each character as it arrives. So "predicting the next sub" the code will execute is meaningless, because as soon as you introduce serial data, your thread becomes multithreader, and the concept of "next" because very vague: the next executed code could happen before, during, or after the current line of code and you can't control that.
And debugging multithreaded apps is a lot more complicated! Start here: Learn to debug multithreaded applications - Visual Studio | Microsoft Docs
] and here: Debug multithreaded applications - Visual Studio | Microsoft Docs
] and begin reading!