How can I use a MC33926 Motor Driver like it is offered for Arduino to drive forwards, backwards with a PWM and a direction control.

The problem is that the MC33926 has Inputs IN1 and IN2 and not PWM and DIR as usual. How can IN1 and IN2 be directly used with a Arduino. Such as it is done in the ArduMower project.

I'm also wondering under which conditions this is controller is energy efficient? If the load has a flywheel effect (e.g. high RPM mower disk) reducing RPM would waste energy?

I know there are different shields that have logic to drive the inputs with PWM and DIR, but the ArduMower PCB 1.4 decided to hook it up directly. Here is a hardware solution by pololu (I wish i would understand these two NAND gates and the Q2, but that's another problem):

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I have figured this so far:

  • If the PWM frequency is too low, the load-free power consumption (100% PWM 200mA) of the motors increases(!) rapidly when driving slowly, e.g. 33% to 1A.
  • From a certain PWM frequency (>2kHz), the power consumption normalizes and driving more slowly requires less power.
  • MC33936 has IN1 and IN2, which are normally connected with IN1 = LOW and IN2 = PWM or IN1 = PWM and IN2 = LOW (not good for most MCs)
  • Alternatively you can use IN1 = PWM and IN2 = LOW / HIGH BUT you must INVERT the PWM SIGNAL when running reverse, i.e. IN1 = PWM and IN2 = LOW or reverse IN1 = ~PWM (inverted PWM) and IN2 = HIGH. Otherwise you start driving at 0 PWM with 100% motor power. This is quite tricky, too.
  • MC33936 has no freewheel (except if ENABLE = LOW) and brakes the motor to 0 when IN1 = IN2
  • MC33936 is a braking motor controller that actively sets the output RPM. of the motor according to PWM.

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