Some hosts like Pronterface use continuous M105 commands to poll temperature, this causes a software halt when the heating via M109 or M190 is finished. Flushing the rx buffer fixes this.
As reported in #15, thanks to @rug156 for the feedback!
Using TMC2208 in standalone mode, I've inverted the stepper direction to match Anycubics pin layout. M110 memory watcher was removed due to redundancy and - ironically - to save memory.
David Ramiro