code: func (g *Driver) SetPWMFreq(port Grove, freq uint16) error {
  	if freq < 3 {
  		freq = 3
  	}
  	if freq > 48000 {
  		freq = 48000
  	}
  	return g.writeBytes([]byte{
  		goPiGo3Address,
  		SET_GROVE_PWM_FREQUENCY,
  		byte(port),
  		byte((freq >> 8) & 0xFF),
  		byte(freq & 0xFF),
  	})
  }
docs: // SetPWMFreq setst the pwm frequency for the given pin/port.