.. _cb_tonmonitoringmodbuscb:

TOnMonitoringModbusCB
------------------------------------------
This callback function is used to check the **Modbus I/O state data** registered in the robot controller.

See :ref:`Rules for callback functions <callback_rules>`.

**Defined in:** ``DRFLEx.h``

.. code-block:: cpp

   // typedef (DRFL.h)
   typedef void (*TOnMonitoringModbusCB)(const LPMONITORING_MODBUS);

   // registration API (internal + wrapper)
   DRFL_API void _set_on_monitoring_modbus(LPROBOTCONTROL pCtrl, TOnMonitoringModbusCB pCallbackFunc);
   void set_on_monitoring_modbus(TOnMonitoringModbusCB pCallbackFunc)
   {
       _set_on_monitoring_modbus(_rbtCtrl, pCallbackFunc);
   };

**Parameter**

.. list-table::
   :header-rows: 1
   :widths: 20 25 15 40

   * - Parameter Name
     - Data Type
     - Default Value
     - Description
   * - pModbus
     - :ref:`MONITORING_MODBUS <struct_MONITORING_MODBUS>`
     - -
     - Pointer to structure containing Modbus register symbols and values.

**Return** |br|
None

**Example**

.. code-block:: cpp

   #include "DRFLEx.h"
   #include <iostream>
   #include <thread>
   #include <chrono>
   using namespace DRAFramework;
   using namespace std;

   // Callback: invoked when Modbus monitoring data updates
   void OnMonitoringModbusCB(const LPMONITORING_MODBUS pModbus)
   {
       if (!pModbus) return;

       cout << "[MODBUS] register count = " << pModbus->_iRegCount << endl;

       // Each entry contains a symbol (name) and its current value
       for (int i = 0; i < pModbus->_iRegCount; ++i)
       {
           // Example fields based on structure naming
           //   _tRegister[i]._szSymbol  → register name
           //   _tRegister[i]._iValue    → register value
           cout << "  " << pModbus->_tRegister[i]._szSymbol
                << " : " << pModbus->_tRegister[i]._iValue << endl;
       }
   }

   int main()
   {
       CDRFLEx drfl;

       // Connect to the controller
       if (!drfl.open_connection("192.168.137.100")) {
           cout << "Failed to connect to controller." << endl;
           return -1;
       }

       // Register Modbus monitoring callback
       drfl.set_on_monitoring_modbus(OnMonitoringModbusCB);

       // Keep process alive to receive Modbus updates
       while (true)
           std::this_thread::sleep_for(std::chrono::seconds(1));

       drfl.close_connection();
       return 0;
   }

**Notes**

- Use this callback to build **Modbus dashboards**, **alarm rules**, or **data logging** pipelines.  
- For I/O state (GPIO) monitoring, see :ref:`TOnMonitoringCtrlIOCB <cb_tonmonitoringctrliocb>` and its EX variants.  
- Each callback receives the most recent data. If the callback takes longer than the data period (100 ms before DRCF 3.5, 20 ms from DRCF 3.5), intermediate samples are not delivered. Do not rely on receiving every sample (for example for integration or differentiation).