S2 motor speed control

How can change the motor to something like 15 Hz instead of the default 10 Hz?

Here is the output of getMotorInfo:

max_speed: 1200
min_speed: 480
desired_speed: 600

But no matter what value I provide by calling setMotorSpeed, the desired_speed remains at 600. (600 seems to mean 600 RPM, which is 10 Hz)

/// Attempt to set the motor speed:
if (opt_channel_type == CHANNEL_TYPE_SERIALPORT) {
            std::cout << "Set motor speed to " << settings.get_motor_speed() << std::endl;
            //drv->setMotorSpeed();
            // Trying to change the motor speed:
            sl_result setSpeedResult = drv->setMotorSpeed(settings.get_motor_speed());
            std::cout << "Set speed? ";
            switch (setSpeedResult) {
            case SL_RESULT_OK:
                std::cout << "ok" << std::endl;
                break;
            case SL_RESULT_OPERATION_FAIL:
                std::cout << "fail" << std::endl;
                break;
            case SL_RESULT_OPERATION_NOT_SUPPORT:
                std::cout << "not support" << std::endl;
                break;
            case SL_RESULT_OPERATION_STOP:
                std::cout << "stop" << std::endl;
                break;
            case SL_RESULT_OPERATION_TIMEOUT:
                std::cout << "timeout" << std::endl;
                break;
            }
            LidarMotorInfo motorInfo;
            drv->getMotorInfo(motorInfo);
            std::cout << "max_speed: " << motorInfo.max_speed << std::endl;
            std::cout << "min_speed: " << motorInfo.min_speed << std::endl;
            std::cout << "desired_speed: " << motorInfo.desired_speed << std::endl;
            std::cout << "motorCtrlSupport: " << motorInfo.motorCtrlSupport << std::endl; //0=none, 1=pwn, 2=rpm
        }

Slamtec / rplidar_sdk

S2 motor speed control #114