Without seeing the whole context of the error… dunno
But you will not get far controlling a stepper like this… the driver will require a proper library and nearly the full MCUs attention in order to properly pulse the needed signals.
Since Blynk also needs to be running constantly in the background doing it IoT stuff, well, there can be a timing conflict.
I have worked this out with a dual MCU approach… one for running the stepper and one for overseeing the control via Blynk.
And also with a single MCU and semi-fancy timing… but it will limit the maximum rotational speed of the stepper.
