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:

Develop the C++ backend

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

1. 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 entry point to Qt Quick Ultralite applications for more information. Make sure to use the same project name (YourProject) that you chose in the earlier chapter.

2. 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.
3. 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.

4. 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();
   }

5. 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.
6. 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

7. 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.

8. 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();
       ...
   }

Integrate UI and backend in Design Studio

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

1. Open your project in Design Studio and select the Connections pane.
2. Click + in the Connections tab to add a new Connection, and set DeviceInterface as Target and onButtonEvent as Signal Handler. Right-click the new connection and select Open Connection Editor as shown below:

   

3. Add the following code in the Action field:

   {
       statusRect.pressed = !statusRect.pressed
       DeviceInterface.toggleLED()
   }

   This is the QML event handler for the buttonEvent you defined earlier. Now on press of the button, the event propagates to the QML context, which changes the statusRect.pressed property. This results in changing the color of an UI item.

4. 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.

Export application and platform sources

This section provides you step-by-step instructions to create a GHS MULTI IDE project, and integrate 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\2.5.4
   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: program compile definitions, include directories, compiler and linker options
   • %PROJECT_DIR%\GHS\prj\drivers.gpj: list of RGL sources
   • %PROJECT_DIR%\GHS\prj\QtMCUs\qul_platform.gpj: list of RH850-D1M1A platform sources
   • %PROJECT_DIR%\GHS\prj\QtMCUs\qul_app.gpj: list of 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

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 IDE Project Manager (multi.exe)
2. Select File > Open Project and select the top-level project.gpj file exported in the earlier section.
3. Right-click application.gpj and select Edit. Replace its contents with the following to add the source files from BACKEND_DIR:

   #!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
   ${BACKEND_DIR}/boardutils.cpp
   ${BACKEND_DIR}/deviceinterface.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. Refer to the MULTI IDE documentation for more information

4. 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.
5. Finally, add the RGL library sources needed for LED and user button interaction to application.gpj:
   • ${SDK_DIR}/vlib/bsp/board/d1mx_mango/src/hmi/r_bsp_hmi_knob.c
   • ${SDK_DIR}/vlib/bsp/board/d1mx_mango/src/hmi/r_bsp_sys_hmi.c
   • ${SDK_DIR}/vlib/bsp/hmi/src/r_bsp_hmi_main.c

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.

If you make changes to the UI, you have run qmlprojectexporter again to generate new UI sources. The following section describes how to update your project with the newly generated sources.

Making changes to the UI

If you make any changes to the UI parts of your application, export the UI sources again using qmlprojectexporter.

Automatically updating an existing project with new UI sources is not currently implemented. To apply changes made to the UI, you have to update the project files manually.

1. Use qmlprojectexporter to generate new UI source files with the following batch script:

   set QUL_ROOT=C:\path\to\QtMCUs\2.5.4
   set QMLPROJECT_FILE=C:\path\to\YourProject.qmlproject
   set BOARDDEFAULTS=%QUL_ROOT%\platform\boards\renesas\rh850-d1m1a-baremetal\cmake\BoardDefaults_32bpp.qmlprojectconfig
   set PROJECT_DIR=C:\path\to\PROJECT_DIR
   set QMLPROJECT_DIR=%PROJECT_DIR%\QtMCUs\generated
   
   %QUL_ROOT%\bin\qmlprojectexporter.exe %QMLPROJECT_FILE% --platform=rh850-d1m1a-baremetal --toolchain=GHS --boarddefaults=%BOARDDEFAULTS% --outdir=%QMLPROJECT_DIR%

2. Update the existing project files with the new sources. There is one subproject for the main .qmlproject file, called qul_app.gpj and one subproject for each module, with the naming scheme qul_module_<QmlProjectName>.gpj.

   You can find a list of generated source files in %APPLICATION_EXPORT_DIR%\config\<QmlProjectName>.1.compiler_outputs.txt, where QmlProjectName corresponds to the name of a QmlProject. Add the C++ source files from each compiler_outputs.txt file to its respective subproject in GHS MULTI IDE.

3. If you have added new modules since the initial generation, add them manually as a subproject. To do this, right-click application.gpj and select Add Item into application.gpj. Select Subproject from the popup, and place the new file in %PROJECT_DIR%\GHS\prj\QtMCUs with the name qul_module_<ModuleName>.gpj.

   Find the list of generated sources in the compiler_outputs.txt file for this module, and add them to the subproject you just created.

4. Update linked libraries as they might have changed since the last update. You will find the list of required libraries in the <QmlProjectName>.1.libraries.txt file(s) in the %APPLICATION_EXPORT_DIR\config directory. For example, they might list the following libraries:
   • Qul::MonotypeUnicode
   • Qul::MonotypeUnicodeEngineShaperDisabled
   • Qul::PNGDecoderNull

   Identify the corresponding libraries for your build type and platform in the ${QUL_DIR}/lib folder and add them to program.gpj with the -l directive if they are not already listed. For the example libraries listed above, these are the corresponding library files to link against in program.gpj:

   • -l${QUL_DIR}/lib/libQulMonotypeUnicode_rh850-d1m1a-baremetal_Windows_ghs-arm_MinSizeRel.a
   • -l${QUL_DIR}/lib/libQulMonotypeUnicodeEngineShaperDisabled_rh850-d1m1a-baremetal_Windows_ghs-arm_MinSizeRel.a
   • -l${QUL_DIR}/lib/libQulPNGDecoderNull_rh850-d1m1a-baremetal_Windows_ghs-arm_MinSizeRel.a

   Note: If any of the libraries.txt files list Qul::PNGDecoderLodePNG, you must NOT link against Qul::PNGDecoderNull.