Using micropython on ESP32, how to have 2 PWM pins with different frequencies?

Question

When I initialise two PWM pins on ESP32 using micropython I found the two pins are always on the same PWM frequency.

motorPin1 = machine.PWM(Pin(21, mode=Pin.OUT))
motorPin1.duty(512)
motorPin1.freq(10)
motorPin2 = machine.PWM(Pin(22, mode=Pin.OUT))
motorPin2.duty(300)
motorPin2.freq(200)

In the above example, both motorPin1 & motorPin2 end up on the same frequency. Also if the frequency on one pin is updated, it will also update the frequency on the other (to the same frequency). Duty cycle can be controlled separately but not frequency.

I eventually found ESP32 has pwm 'channels' which are driven/timed in pairs. So for example, if you have two PWM pins assigned to channels 0 & 1, they will always run at the same frequency. The micropython PWM interface doesn't expose the PWM channel assigned to a pin.

How do people setup PWM pins in micropython with the appropriate PWM channels to allow separate control of the frequency?

Oliver.R Oliver.R · Accepted Answer · 2020-05-19T23:55:56

Unfortunately this hardware functionality is not currently available in MicroPython - there is an open PR to add this: https://github.com/micropython/micropython/pull/3608

You could look into bit-banging or utilising timers if your needs are more basic, otherwise you could provide support for getting the PR merged!

Using micropython on ESP32, how to have 2 PWM pins with different frequencies?

1 Answers