You haven't explained how an AC audio TONE (TONE is a word used to describe an audio sound) has anything whatsoever to do with a PWM 0 to 5V DC SWITCHING signal (not AC, NOT AUDIO) . Does that explain the confusion ? How does the link to the stepper driver explain the TONE part ?
FYI-I know that it is possible to convert an audio tone to a PWM duty cycle through various methods but it is up to you to state that you are doing this. Simply saying all you have to do is generate a tone without stating "I have a tone to pwm circuit to generate my stepper PWM" is not enough.. I didn't see that, and we therefore have to ask why you would say that. Without knowing your background we have no idea if you have any idea what it means to say that.
Also- You never identified this:
to a parallel breakout board
What breakout bd ? Vendor link ?
Datasheet ?