Add selectable scanmode for RPLIDAR

Testing if scanmode could be used to better detect tires etc.

Also testing if the strange "tails" (when there is an object nearby, objects farther away get some measurement nearer or farther than they are (hard to explain in words...)) as mentioned in #7 could be somehow prevented. Quick tests showed very strange behavior:
- If using "standard" (4 ksps)-mode and 20 rpm, there are no tails.
- Lowering RPM to about 5 the tails appear
- If using "express" (8 ksps)-mode and 20 rpm there are no tails
- Lowering RPM to 10 the tails appear
- Any 16 ksps mode seems to have tails whatever the RPM (can not get more than 20 RPM)

Doesn't make much sense. Seems like the RPLIDAR starts to mangle the measured points if "angular resolution" is good enough... But anyway, using "express" (8 ksps)-mode and 20 RPM there are no tails. So maybe use that and forget the strangeness...

Scanmode affects sampling rate and max distance (found from https://download.slamtec.com/api/download/rplidar-protocol/2.2?lang=en , page 12):
Standard: 4 ksps, 16m
Express: 8 ksps, 25m
Boost: 16 ksps, 25m
Sensitivity: 16 ksps, 25m
Stability: 16 ksps, 25m

"Sensitivity" mode does not work. "Stability" seems to be 10 ksps so maybe it is the so much advertised "outdoor-mode"(?)

Lidar/rplidarthread.cpp

@@ -22,11 +22,12 @@
 
 #include "rplidarthread.h"
 
-RPLidarThread::RPLidarThread(const QString& serialPortFileName, const unsigned int serialPortBPS, const unsigned short motorPWM)
+RPLidarThread::RPLidarThread(const QString& serialPortFileName, const unsigned int serialPortBPS, const unsigned short motorPWM, const short scanMode)
 {
     this->serialPortFileName = serialPortFileName;
     this->serialPortBPS = serialPortBPS;
     this->motorPWM = motorPWM;
+    this->scanMode = scanMode;
 
     terminateRequest = false;
     suspended = false;
@@ -177,9 +178,17 @@ void RPLidarThread::run()
             {
                 suspendIfNeeded();
 
-                emit infoMessage("Starting scan...");
-
-                rpResult = lidarDriver->startScan(false, true);
+                if (scanMode == -1)
+                {
+                    // Use startScan-call when scanmode is "standard"
+                    emit infoMessage("Starting scan using startScan-call...");
+                    rpResult = lidarDriver->startScan(false, true);
+                }
+                else
+                {
+                    emit infoMessage("Starting scan using startScanExpress-call, mode: " + QString::number(scanMode) + "...");
+                    rpResult = lidarDriver->startScanExpress(false, scanMode);
+                }
 
                 if (IS_FAIL(rpResult))
                 {

Lidar/rplidarthread.h

@@ -35,8 +35,9 @@ class RPLidarThread : public QThread
      * @brief Constructor
      * @param serialPortFileName File name of com port to open
      * @param serialPortBPS Speed (Bits Per Second) of the serial port
+     * @param scanMode Value used in startScanExpress-call's scanMode-parameter or -1 (use startScan-call instead)
      */
-    RPLidarThread(const QString& serialPortFileName, const unsigned int serialPortBPS, const unsigned short motorPWM = 660);
+    RPLidarThread(const QString& serialPortFileName, const unsigned int serialPortBPS, const unsigned short motorPWM = 660, const short scanMode = -1);
     ~RPLidarThread() override;
 
     void run() override;            //!< Thread code
@@ -56,6 +57,7 @@ class RPLidarThread : public QThread
     QString serialPortFileName;
     unsigned int serialPortBPS;
     unsigned short motorPWM = 0;
+    short scanMode = -1;
 
     bool terminateRequest = false;
     bool suspended = false;

mainwindow.cpp

@@ -172,6 +172,7 @@ MainWindow::MainWindow(QWidget *parent) :
     ui->lineEdit_SerialPort_RPLidar->setText(settings.value("SerialPort_RPLidar", "\\\\.\\COM").toString());
     ui->spinBox_SerialSpeed_RPLidar->setValue(settings.value("SerialSpeed_RPLidar", "256000").toInt());
     ui->spinBox_MotorPWM_RPLidar->setValue(settings.value("MotorPWM_RPLidar", "660").toInt());
+    ui->comboBox_ExpressScanMode->setCurrentIndex(settings.value("ExpressScanMode_RPLidar", "0").toInt());
 
     // Why is this needed? Q_ENUM should do the job? Different threads causing the need for this?
     qRegisterMetaType<SerialThread::DataReceivedEmitReason>();
@@ -188,6 +189,7 @@ MainWindow::~MainWindow()
     settings.setValue("SerialPort_RPLidar", ui->lineEdit_SerialPort_RPLidar->text());
     settings.setValue("SerialSpeed_RPLidar", ui->spinBox_SerialSpeed_RPLidar->value());
     settings.setValue("MotorPWM_RPLidar", ui->spinBox_MotorPWM_RPLidar->value());
+    settings.setValue("ExpressScanMode_RPLidar", ui->comboBox_ExpressScanMode->currentIndex());
 
     delete messageMonitorForm_Base_Serial;
     delete messageMonitorForm_Base_NTRIP;
@@ -1086,7 +1088,7 @@ void MainWindow::on_pushButton_StartThread_RPLidar_clicked()
 {
     if (!thread_RPLidar)
     {
-        thread_RPLidar = new RPLidarThread(ui->lineEdit_SerialPort_RPLidar->text(), ui->spinBox_SerialSpeed_RPLidar->value(), ui->spinBox_MotorPWM_RPLidar->value());
+        thread_RPLidar = new RPLidarThread(ui->lineEdit_SerialPort_RPLidar->text(), ui->spinBox_SerialSpeed_RPLidar->value(), ui->spinBox_MotorPWM_RPLidar->value(), ui->comboBox_ExpressScanMode->currentIndex() - 1);
         if (ui->checkBox_SuspendThread_RPLidar->isChecked())
         {
             thread_RPLidar->suspend();
@@ -1113,6 +1115,7 @@ void MainWindow::on_pushButton_StartThread_RPLidar_clicked()
         ui->lineEdit_SerialPort_RPLidar->setEnabled(false);
         ui->spinBox_SerialSpeed_RPLidar->setEnabled(false);
         ui->spinBox_MotorPWM_RPLidar->setEnabled(false);
+        ui->comboBox_ExpressScanMode->setEnabled(false);
         ui->pushButton_StartThread_RPLidar->setEnabled(false);
         ui->pushButton_TerminateThread_RPLidar->setEnabled(true);
     }
@@ -1150,6 +1153,7 @@ void MainWindow::on_pushButton_TerminateThread_RPLidar_clicked()
         ui->lineEdit_SerialPort_RPLidar->setEnabled(true);
         ui->spinBox_SerialSpeed_RPLidar->setEnabled(true);
         ui->spinBox_MotorPWM_RPLidar->setEnabled(true);
+        ui->comboBox_ExpressScanMode->setEnabled(true);
         ui->pushButton_StartThread_RPLidar->setEnabled(true);
         ui->pushButton_TerminateThread_RPLidar->setEnabled(false);
     }