Hi everyone,

I am using a 80C552 microcontroller for my school project. I need a 50Hz PWM signal to drive my servo, and a 20KHz PWM signal to drive the motor speed control circuit. However, 80C552 is common frequency for both PWM channels. It cannot program with different frequency for each channel. Can anyone help me to solve this problem? I am thinking to use a Timer 555 to generate a 20KHz PWM signal for the motor speed control; however, I cannot change the motor speed (I can't change the duty cycle of 555 without changing the value of resistor).

Please help. Thank you

Michael