How to control a motor driver (BTS7960) without PWM
You need to drive one of the direction lines (E or F) high at the same time that you drive the corresponding PWM line (G or H, repsectively) high. These two signals are effectively ANDed together by how the driver chips are wired together. My guess would be that E and F control the two high-side switches (one on each chip) and that G and H control the two low-side switches.