Brushless Air Fan Reverse Turn

Job ID: 39239223

Budget: $10 – $30 CAD

I have a 12V brushless air fan that operates at 0.7A and has four wires:

Red – +12V

Black – GND

Yellow – PWM Speed Control

Purple – Feedback

The manufacturer informed me that to reverse the fan’s rotation, I need to send a signal to the PWM (yellow) wire.

Could you please guide me on how to generate the correct PWM signal to achieve a reverse turn? Do I need a specific duty cycle, frequency, or additional control?

Thank you for your help!