code: func (m *MotorDriver) Speed(value byte) (err error) {
  	if writer, ok := m.connection.(PwmWriter); ok {
  		m.CurrentMode = "analog"
  		m.CurrentSpeed = value
  		return writer.PwmWrite(m.SpeedPin, value)
  	}
  	return ErrPwmWriteUnsupported
  }
docs: // Speed sets the speed of the motor