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what does the rssi of bluetoothdeviceinfo mean

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  • MihanM Offline
    MihanM Offline
    Mihan
    wrote on last edited by
    #1

    Hi
    I want to know how should I understand the rssi value. It's qint16. Does the value show me the signal strength like -100 dbm -> rssi() == -100?
    Regards
    Mihan

    jsulmJ 1 Reply Last reply
    0
    • MihanM Mihan

      Hi
      I want to know how should I understand the rssi value. It's qint16. Does the value show me the signal strength like -100 dbm -> rssi() == -100?
      Regards
      Mihan

      jsulmJ Offline
      jsulmJ Offline
      jsulm
      Lifetime Qt Champion
      wrote on last edited by
      #2

      @Mihan Maybe this explains https://www.bluetooth.com/blog/proximity-and-rssi/

      https://forum.qt.io/topic/113070/qt-code-of-conduct

      MihanM 1 Reply Last reply
      1
      • jsulmJ jsulm

        @Mihan Maybe this explains https://www.bluetooth.com/blog/proximity-and-rssi/

        MihanM Offline
        MihanM Offline
        Mihan
        wrote on last edited by
        #3

        @jsulm So what are the range of rssi about good signal and no good signal

        jsulmJ 1 Reply Last reply
        0
        • MihanM Mihan

          @jsulm So what are the range of rssi about good signal and no good signal

          jsulmJ Offline
          jsulmJ Offline
          jsulm
          Lifetime Qt Champion
          wrote on last edited by
          #4

          @Mihan According to the article I provided above this is not standardised. Also you should maybe ask in some other forum more related to Bluetooth.

          https://forum.qt.io/topic/113070/qt-code-of-conduct

          MihanM 1 Reply Last reply
          0
          • jsulmJ jsulm

            @Mihan According to the article I provided above this is not standardised. Also you should maybe ask in some other forum more related to Bluetooth.

            MihanM Offline
            MihanM Offline
            Mihan
            wrote on last edited by
            #5

            @jsulm But why I always get the rssi zero after scanning? How to get the true rssi?

            jsulmJ 1 Reply Last reply
            0
            • MihanM Mihan

              @jsulm But why I always get the rssi zero after scanning? How to get the true rssi?

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #6

              @Mihan said in what does the rssi of bluetoothdeviceinfo mean:

              But why I always get the rssi zero after scanning?

              That you did not say before.
              Can you show how you're scanning?

              https://forum.qt.io/topic/113070/qt-code-of-conduct

              MihanM 1 Reply Last reply
              0
              • jsulmJ jsulm

                @Mihan said in what does the rssi of bluetoothdeviceinfo mean:

                But why I always get the rssi zero after scanning?

                That you did not say before.
                Can you show how you're scanning?

                MihanM Offline
                MihanM Offline
                Mihan
                wrote on last edited by Mihan
                #7

                @jsulm
                This code is used on Qt 5.6.2, so it doesn't have QBluetoothDeviceDiscoveryAgent::deviceUpdated()

                CBluetoothManager::CBluetoothManager()
                {
                    m_BluetoothLocalDevice = new QBluetoothLocalDevice(this);
                    m_BluetoothLocalDevice->powerOn();
                    m_BluetoothLocalDevice->setHostMode(QBluetoothLocalDevice::HostConnectable);
                
                    m_BluetoothScanner = new QBluetoothDeviceDiscoveryAgent(this);
                    connect(m_BluetoothScanner,SIGNAL(finished()),this,SLOT(BluetoothScanFinished()));
                }
                
                CBluetoothManager::BluetoothScanFinished()
                {
                    auto list = m_BluetoothScanner->discoveredDevices();
                
                    for(int n = 0; n < list.count(); n++)
                    {
                          // add items into QTableWidget (QString is name, QIcon is signal strength) 
                    }
                }
                
                jsulmJ 1 Reply Last reply
                0
                • MihanM Mihan

                  @jsulm
                  This code is used on Qt 5.6.2, so it doesn't have QBluetoothDeviceDiscoveryAgent::deviceUpdated()

                  CBluetoothManager::CBluetoothManager()
                  {
                      m_BluetoothLocalDevice = new QBluetoothLocalDevice(this);
                      m_BluetoothLocalDevice->powerOn();
                      m_BluetoothLocalDevice->setHostMode(QBluetoothLocalDevice::HostConnectable);
                  
                      m_BluetoothScanner = new QBluetoothDeviceDiscoveryAgent(this);
                      connect(m_BluetoothScanner,SIGNAL(finished()),this,SLOT(BluetoothScanFinished()));
                  }
                  
                  CBluetoothManager::BluetoothScanFinished()
                  {
                      auto list = m_BluetoothScanner->discoveredDevices();
                  
                      for(int n = 0; n < list.count(); n++)
                      {
                            // add items into QTableWidget (QString is name, QIcon is signal strength) 
                      }
                  }
                  
                  jsulmJ Offline
                  jsulmJ Offline
                  jsulm
                  Lifetime Qt Champion
                  wrote on last edited by
                  #8

                  @Mihan said in what does the rssi of bluetoothdeviceinfo mean:

                  Qt 5.6.2

                  You should really at least try with a more recent Qt version.

                  https://forum.qt.io/topic/113070/qt-code-of-conduct

                  MihanM 1 Reply Last reply
                  0
                  • jsulmJ jsulm

                    @Mihan said in what does the rssi of bluetoothdeviceinfo mean:

                    Qt 5.6.2

                    You should really at least try with a more recent Qt version.

                    MihanM Offline
                    MihanM Offline
                    Mihan
                    wrote on last edited by
                    #9

                    @jsulm but the system root provided by the main board supplier (based on freescale(NXP)) is Qt 5.6.2 . Is there something wrong in Qt5.6.2? Because the connection of bluetooth (QBluetoothLocalDevice::requestPairing(...)) also doesn't work in this version until Qt5.12.0.
                    I had tested it. It seem to have some problems between the bluetooth protocol(Bluez) and this function.

                    jsulmJ 1 Reply Last reply
                    0
                    • MihanM Mihan

                      @jsulm but the system root provided by the main board supplier (based on freescale(NXP)) is Qt 5.6.2 . Is there something wrong in Qt5.6.2? Because the connection of bluetooth (QBluetoothLocalDevice::requestPairing(...)) also doesn't work in this version until Qt5.12.0.
                      I had tested it. It seem to have some problems between the bluetooth protocol(Bluez) and this function.

                      jsulmJ Offline
                      jsulmJ Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by
                      #10

                      @Mihan said in what does the rssi of bluetoothdeviceinfo mean:

                      Is there something wrong in Qt5.6.2?

                      It is possible that some Bluetooth related issues where fixed since Qt5.6.2

                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                      MihanM 1 Reply Last reply
                      0
                      • jsulmJ jsulm

                        @Mihan said in what does the rssi of bluetoothdeviceinfo mean:

                        Is there something wrong in Qt5.6.2?

                        It is possible that some Bluetooth related issues where fixed since Qt5.6.2

                        MihanM Offline
                        MihanM Offline
                        Mihan
                        wrote on last edited by Mihan
                        #11

                        @jsulm Okay now I use Qt 5.12.0 to complie, it works. But I still don't know how to use these rssi(),all are 127 I received. It seems that this rssi() is different from the bluetooth's rssi(e.g. -65dbm).
                        In other words, what's the unit of this rssi();

                        Also, I find that the bin of 127 is 0111 1111. Does Qt use each bit to signify the signal strength?

                        jsulmJ 1 Reply Last reply
                        0
                        • MihanM Mihan

                          @jsulm Okay now I use Qt 5.12.0 to complie, it works. But I still don't know how to use these rssi(),all are 127 I received. It seems that this rssi() is different from the bluetooth's rssi(e.g. -65dbm).
                          In other words, what's the unit of this rssi();

                          Also, I find that the bin of 127 is 0111 1111. Does Qt use each bit to signify the signal strength?

                          jsulmJ Offline
                          jsulmJ Offline
                          jsulm
                          Lifetime Qt Champion
                          wrote on last edited by
                          #12

                          @Mihan As explained in the link I posted before there is no standardised unit for this. It just indicates whether the signal is getting stronger (higher values) or weaker (lower values).

                          https://forum.qt.io/topic/113070/qt-code-of-conduct

                          MihanM 1 Reply Last reply
                          1
                          • jsulmJ jsulm

                            @Mihan As explained in the link I posted before there is no standardised unit for this. It just indicates whether the signal is getting stronger (higher values) or weaker (lower values).

                            MihanM Offline
                            MihanM Offline
                            Mihan
                            wrote on last edited by Mihan
                            #13

                            @jsulm Oh, I didn't notice that the example the link said "For example, Manufacturer A could have an RSSI max value of 100 while Manufacturer B will return RSSI values anywhere from 0 to 127. "

                            So,maybe rssi() == 127 means this signal is the best.

                            Thank you so much!

                            1 Reply Last reply
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