Seeed XIAO NRF52840 PWM Frequency

Products & Technology XIAO
#1

Is there any way to adjust the PWM frequency on the XIAO NRF52840, I am trying get the frequency up to 20KHZ so that my motor driver doesn’t make any audible noise.

I found this in the library folder
AppData\Local\Arduino15\packages\Seeeduino\hardware\mbed\2.9.1\cores\arduino\wiring_analog.cpp

void analogWrite(PinName pin, int val)
{
  pin_size_t idx = PinNameToIndex(pin);
  if (idx != NOT_A_PIN) {
    analogWrite(idx, val);
  } else {
    mbed::PwmOut* pwm = new mbed::PwmOut(pin);
    pwm->period_ms(2); //500Hz
    float percent = (float)val/(float)((1 << write_resolution)-1);
    pwm->write(percent);
  }
}

I have also tried an specific PWM library

Which I was able to get to work, but it is causing issues with other parts of my program.

Any help is appreciated.

#2

I figured it out somewhat
C:\Users\Matt\AppData\Local\Arduino15\packages\Seeeduino\hardware\mbed\2.9.1\cores\arduino\mbed\drivers\include\drivers\PwmOut.h

 /** Set the PWM period, specified in seconds (float), keeping the duty cycle the same.
     *
     *  @param seconds Change the period of a PWM signal in seconds (float) without modifying the duty cycle
     *  @note
     *   The resolution is currently in microseconds; periods smaller than this
     *   will be set to zero.
     */
    void period(float seconds);

    /** Set the PWM period, specified in milliseconds (int), keeping the duty cycle the same.
     *  @param ms Change the period of a PWM signal in milliseconds without modifying the duty cycle
     */
    void period_ms(int ms);

    /** Set the PWM period, specified in microseconds (int), keeping the duty cycle the same.
     *  @param us Change the period of a PWM signal in microseconds without modifying the duty cycle
     */
    void period_us(int us);

    /** Read the PWM period
     *  @returns
     *   The PWM period, specified in microseconds (int)
     */

So in the wiring_analog.cpp from above I changed the period from period_ms(2) to period_us(50). No more motor noise from my motor driver. I have not verified the actual frequency with a scope, but It’s out of my hearing range now.