Hi,
you say "not need an H Bridge or complex drivers"
but then use a switch mode regulator. Isn´t this complex, too?
If you don´t want to waste the (30V-24V) * 0.5A = 3W then the next simple solution is a Mosfet and a free wheeling diode.
Almost any microcontroller has a PWM ouptut. So code is very simple: just a couple of lines for PWM setup ...
Enabling/disabling the PWM will be as simple as switching a port pin ON/OFF. (one simple line of code)
Try 75% duty cycle.
Klaus
Added:
This does not mean that the switch mode solution is bad.
Btw: there are dedicated simple DC motor control ICs, which include the free wheeling diode and also include features like soft start, overcurrent protection, overheat protection....