Let’s build a simple differential-drive robot.

drive the motors via the shift register.

HW-130 Motor Control Shield (also widely known as the L293D Motor Shield

D5 and D10 are unused on most HW-130 boards – they are remnants of other shield designs. Stick to D6 and D9 for PWM.

The datasheet never mentions this, but the shield works fine for light stepper loads (NEMA 17 size max).