This topic guides you through the steps to create and build the application's backend using GHS MULTI IDE. The backend enables the application's UI to communicate with the platform and get the required information from the hardware. In this case, the device interface gets the status of the on-board user button. The following diagram describes the interaction between the two components:

Export application and platform sources

This section provides you step-by-step instructions to create a GHS MULTI IDE project from a QmlProject, complete with application and platform sources exported by the Qt for MCUs tools.

1. Create a batch script with the following commands, which calls the qmlprojectexporter to generate a GHS Multi IDE project

   set QUL_ROOT=C:\path\to\QtMCUs\2.8.2
   set QMLPROJECT_FILE=C:\path\to\YourProject.qmlproject
   set BOARDDEFAULTS=%QUL_ROOT%\platform\boards\renesas\rh850-d1m1a-baremetal\cmake\BoardDefaults_32bpp.qmlprojectconfig
   set RGL_DIR=C:\path\to\rgl_ghs_D1Mx_obj_V2.1.0a
   set PROJECT_DIR=C:\path\to\PROJECT_DIR
   
   %QUL_ROOT%\bin\qmlprojectexporter.exe %QMLPROJECT_FILE% --platform=rh850-d1m1a-baremetal --toolchain=GHS --boarddefaults=%BOARDDEFAULTS% --outdir=%PROJECT_DIR% --project-type=ghs --include-ide-generated-hw-code --board-sdk=%RGL_DIR%

   Before running the script, make sure that the following variables are set:

   • RGL_DIR to the Renesas Graphics Library (RGL) 2.1.0a install path,
   • QUL_ROOT and QMLPROJECT_FILE.
   • PROJECT_DIR to the output directory where you want to place the GHS project files.

   Now, run the script from the command prompt to generate the following:

   • C++ sources generated from QML in %PROJECT_DIR%/QtMCUs/generated
   • The exported platform sources in %PROJECT_DIR%/QtMCUs/platform
   • A top-level project file with subproject files in %PROJECT_DIR%/GHS.

   The generated GHS project includes the following:

   • %PROJECT_DIR%/GHS/project.gpj: The top-level project file.
   • %PROJECT_DIR%/GHS/prj/program.gpj: The program compile definitions, include directories, compiler and linker options.
   • %PROJECT_DIR%/GHS/prj/drivers.gpj: List of the RGL sources.
   • %PROJECT_DIR%/GHS/prj/QtMCUs/qul_platform.gpj: List of the RH850-D1M1A platform sources.
   • %PROJECT_DIR%/GHS/prj/QtMCUs/qul_app.gpj: List of the generated sources from the qmlproject export.
   • %PROJECT_DIR%/GHS/prj/QtMCUs/qul_module_<ModuleName>.gpj: One subproject for each module, including the sources generated for the corresponding QmlProject module.
   • %PROJECT_DIR%/GHS/prj\application.gpj: A convenience empty subproject for the application, which you will edit in the next section.
   • %PROJECT_DIR%/GHS/mcu_<YourProject>_qul_workspace.gmb: A workspace with some added commands for convenience. See GHS Multi IDE QUL Workspace for more details.
   • %PROJECT_DIR%/GHS/qul_probe_E1.con: Contains metadata for making a connection to the E1 probe.
   • %PROJECT_DIR%/GHS/qul_probe_E2.con: Contains metadata for making a connection to the E2 probe.

For more information, refer to Exporting a Qt for MCUs project with platform sources.

Build application in GHS MULTI IDE

The following instructions guide you through the GHS project adaptation steps needed to build the application:

1. Launch the GHS MULTI Launcher (mstart.exe)
2. Select File > Load Workspace from File... and navigate to %PROJECT_DIR%/GHS as exported in the previous section. Select the workspace file mcu_<YourProject>_qul_workspace.gmb.
3. Double click the Project Manager entry in the workspace to open the project in the Project Manager.
4. Create a new file named main.cpp in any directory. The directory will be referred to as BACKEND_DIR:

   #include "YourProject.h"
   
   #include <qul/application.h>
   #include <qul/qul.h>
   
   int main()
   {
       Qul::initHardware();
       Qul::initPlatform();
       Qul::Application app;
       static YourProject item;
       app.setRootItem(&item);
       app.exec();
       return 0;
   }

   This contains the default entrypoint for the application. You will extend this entrypoint later with extra configuration steps to use the LED and user button. Refer to the running Qt Quick Ultralite in applications for more information. Make sure to use the same project name (YourProject) that you chose in the earlier chapter.

5. Right-click application.gpj and select Edit. Replace its contents with the following.

   #!gbuild
   
   macro APPLICATION_EXPORT_DIR=C:/path/to/PROJECT_DIR/QtMCUs/generated
   macro BACKEND_DIR=C:/path/to/BACKEND_DIR
   
   [Subproject]
       -DQUL_STD_STRING_SUPPORT
       -I${APPLICATION_EXPORT_DIR}
   
   # ----- backend -----
   ${BACKEND_DIR}/main.cpp

   Make sure to set the APPLICATION_EXPORT_DIR macro to the directory that has the exported UI sources, and the BACKEND_DIR macro to the directory containing main.cpp and the backend sources you created earlier.

   Note: Indentation is important in .gpj project files. Make sure there is no whitespace in the beginning of the line including the source file. Refer to the MULTI IDE documentation for more information

6. The application binary name is application.elf by default. To use a different name, change -o application.elf to -o YourProject.elf in the program.gpj project file.
7. At this point, to verify that the steps so far have been followed correctly, you can build and flash your partially implemented application to the RH850 board to run it on the target hardware.

   Before flashing, make sure that the board is connected to the target board and the computer. For more information, see connecting Renesas RH850 to the probe.

   Once the connection is established, you can use GHS MULTI IDE to flash the application onto the board and debug using the capabilities in the IDE.

In the next section, you will add the low-level logic to enable interaction between UI and hardware with the user button.

Develop the C++ backend

The following instructions guide you through the process of developing the C++ backend for your application:

1. Create new C++ source and header files and name them deviceinterface.cpp and deviceinterface.h respectively. Save these files in the BACKEND_DIR directory that you just created.
2. Replace the contents of deviceinterface.h with the following:

   #ifndef DEVICEINTERFACE_H
   #define DEVICEINTERFACE_H
   
   #include <qul/signal.h>
   #include <qul/singleton.h>
   #include <qul/eventqueue.h>
   
   typedef int HWButtonEvent;
   
   class DeviceInterface : public Qul::Singleton<DeviceInterface>, public Qul::EventQueue<HWButtonEvent>
   {
   public:
       Qul::Signal<void(int button)> buttonEvent;
       void onEvent(const HWButtonEvent &inputEvent);
   
       void toggleLED();
   };
   
   #endif //DEVICEINTERFACE_H

   The header declares the DeviceInterface class, which inherits from Qul::Singleton and Qul::EventQueue. It also declares the buttonEvent Signal and the HWButtonEvent event type. This allows the Singleton object instance to be globally available. It provides an interface between C++ and QML, to emit the changed signal on receiving the HWButtonEvent input event. For more information, refer to Defining Singletons in QML and Transferring data from Interrupt Handlers to QML.

3. Similarly, replace the contents of deviceinterface.cpp with the following:

   #include "deviceinterface.h"
   #include "boardutils.h"
   
   void DeviceInterface::onEvent(const HWButtonEvent &inputEvent)
   {
       buttonEvent(inputEvent);
   }
   
   void DeviceInterface::toggleLED()
   {
       BoardUtils::toggleLED();
   }

4. Create a new C++ source and header files pair and name them boardutils.cpp and boardutils.h respectively. Save these files in the BACKEND_DIR directory.
5. Replace the code in boardutils.h with the following:

   #ifndef BOARDUTILS_H
   #define BOARDUTILS_H
   
   namespace BoardUtils {
   void configure();
   void toggleLED();
   } // namespace BoardUtils
   
   #endif //BOARDUTILS_H

6. Add the RH850-D1M1A-specific implementation of BoardUtils::configure() and BoardUtils::toggleLED() to boardutils.cpp:

   #include "boardutils.h"
   #include "deviceinterface.h"
   #include "r_typedefs.h"
   #include "r_bsp_hmi_api.h"
   
   #define LED_NR 0
   #define LED_BRIGHTNESS_ON 100u
   #define LED_BRIGHTNESS_OFF 0u
   
   void button_handler()
   {
       DeviceInterface::instance().postEventFromInterrupt(0);
   }
   
   namespace BoardUtils {
   void configure()
   {
       R_BSP_HMI_Init();
       R_BSP_SetButtonCallback(BSP_BTN_CENTER_PRESS, button_handler);
       R_BSP_HMI_SetLed(LED_NR, LED_BRIGHTNESS_OFF);
   }
   
   void toggleLED()
   {
       static bool isOff = true;
       R_BSP_HMI_SetLed(LED_NR, isOff ? LED_BRIGHTNESS_ON : LED_BRIGHTNESS_OFF);
       isOff = !isOff;
   }
   } // namespace BoardUtils

   The configuration function calls BSP-specific initialization functions from the RGL library for the user LED and button. It then registers button_handler() as the interrupt request handler for the user button events. The interrupt request handler propagates the low-level interrupt events to the QML context using the DeviceInterface Singleton object.

7. To properly configure the RH850 LED and button, change main.cpp to include the boardutils.h header and to call BoardUtils::configure() after the normal platform initialization:

   #include "boardutils.h"
   ...
   
   int main()
   {
       Qul::initHardware();
       Qul::initPlatform();
       BoardUtils::configure();
       ...
   }

8. Add the new source files to application.gpj:

   #!gbuild
   ...
   
   # ----- backend -----
   ${BACKEND_DIR}/main.cpp
   
   ${BACKEND_DIR}/boardutils.cpp
   ${BACKEND_DIR}/deviceinterface.cpp

9. Finally, add the RGL library sources needed for LED and user button interaction to application.gpj:
   • ${QUL_BOARD_SDK_DIR}/vlib/bsp/board/d1mx_mango/src/hmi/r_bsp_hmi_knob.c
   • ${QUL_BOARD_SDK_DIR}/vlib/bsp/board/d1mx_mango/src/hmi/r_bsp_sys_hmi.c
   • ${QUL_BOARD_SDK_DIR}/vlib/bsp/hmi/src/r_bsp_hmi_main.c

Integrate UI and backend in Design Studio

Use the DeviceInterface Singleton object from Qt Design Studio, to access the low-level backend functions that you implemented in the earlier section.

1. Open your project in Qt Design Studio and select the Connections view.
2. Select the button in the Connections tab to add a new connection.

   

3. Select the new connection and use the Connection panel to jump to the Code view.

   

4. In Code view, add the first connection with statusRect as the target, and DeviceInterface.toggleLED() as the action for the onPressedChanged signal.

   

5. In Code view, add the second connection with DeviceInterface as the target, and statusRect.pressed = !statusRect.pressed as the action for the onButtonEvent signal.

   

   Now when you press the button, the event propagates to the QML context, which changes the statusRect.pressed property. This results in changing the color of the UI item. In response to the statusRect.pressed property change, the DeviceInterface.toggleLED() method toggles the LED.

6. Use a text editor to change yourproject.qmlproject to generate the necessary C++/QML interfaces needed for the singleton object:

   InterfaceFiles {
       files: ["C:/path/to/BACKEND_DIR/deviceinterface.h"]
   }

   Change the BACKEND_DIR path to the directory containing the deviceinterface.h file.

   For more information, refer to QmlProject InterfaceFiles.

Update the GHS project after making changes to the UI

Since you have made changes to the UI parts of your application, export the UI sources again using qmlprojectexporter.

Use the --update-project command-line argument to apply new changes in UI code to an existing GHS project. Use one of the methods listed below:

1. Use the predefined command under Sync Qmlproject files in the workspace in the GHS MULTI Launcher. Double click it in the UI to update the project files.
2. Manually invoke qmlprojectexporter using the following batch script:

   set QUL_ROOT=C:\path\to\QtMCUs\2.8.2
   set QMLPROJECT_FILE=C:\path\to\YourProject.qmlproject
   set PROJECT_DIR=C:\path\to\PROJECT_DIR
   set QMLPROJECT_DIR=%PROJECT_DIR%\QtMCUs\generated
   
   %QUL_ROOT%\bin\qmlprojectexporter.exe %QMLPROJECT_FILE% --update-project=%PROJECT_DIR%/GHS/project.gpj

Your application is now ready. Build your GHS MULTI project and flash it to the RH850 board to test that everything works as intended. Next, you can try to experiment and add support for another LED.