C

Qt Quick Ultralite instrument_cluster Example

Demonstrates how to control user interface elements from a C application.

Overview

This example demonstrates how to control user interface elements from a C application.

Target platforms

RH850 D1M1A AUTOSAR

Project structure

The instrument_cluster example consists of the following files:

src/VehicleStatus.cpp
src/VehicleStatus.h
CMakeLists.txt
mcu_instrument_cluster.qmlproject
instrument_cluster.qml

The CMake project file contains a basic build script, instrument_cluster.qml which defines the application's UI. The project configuration is defined in mcu_instrument_cluster.qmlproject.

In addition to these files, the src/simulation folder contains a simple simulator to provide input data for the instrument cluster on non-AUTOSAR platforms:

src/simulation/baremetal/main.cpp
src/simulation/freertos/main.cpp
src/simulator.cpp
src/simulator.h

The fonts folder contains the font files of the application:

fonts/TitilliumWeb-Light.ttf
fonts/TitilliumWeb-SemiBold.ttf

CMake project file

Note: Simulation files are added only for non-AUTOSAR targets.

cmake_minimum_required (VERSION 3.21.1)

project(instrument_cluster VERSION 0.0.1 LANGUAGES C CXX ASM)
if (NOT TARGET Qul::Core)
    find_package(Qul)
endif()

set(TARGET_SOURCES src/VehicleStatus.cpp)
set(INCLUDE_DIRECTORIES ${CMAKE_CURRENT_SOURCE_DIR}/src)
set(GENERATE_ENTRYPOINT_ARG "")

if(NOT QUL_PLATFORM MATCHES "autosar")
    set(SIMULATOR_DIR src/simulation)
    set(TARGET_SOURCES
        ${TARGET_SOURCES}
        ${SIMULATOR_DIR}/simulator.cpp
        ${SIMULATOR_DIR}/${QUL_OS_LOWERCASE}/main.cpp
    )
    set(INCLUDE_DIRECTORIES
        ${INCLUDE_DIRECTORIES}
        ${CMAKE_CURRENT_SOURCE_DIR}/src/simulation
    )
else()
    set(GENERATE_ENTRYPOINT_ARG GENERATE_ENTRYPOINT)
endif()

qul_add_target(instrument_cluster
    ${TARGET_SOURCES}
    QML_PROJECT mcu_instrument_cluster.qmlproject
    ${GENERATE_ENTRYPOINT_ARG}
)
app_target_setup_os(instrument_cluster)

target_include_directories(instrument_cluster PRIVATE
    ${INCLUDE_DIRECTORIES}
)

if(NOT CMAKE_CROSSCOMPILING AND NOT WIN32)
    add_custom_command(TARGET instrument_cluster
        COMMAND strip instrument_cluster -o instrument_cluster.stripped
        DEPENDS instrument_cluster)
endif()

QmlProject file

import QmlProject 1.3

Project {
    mainFile: "instrument_cluster.qml"

    MCU.Config {
        defaultFontFamily: "Titillium Web"
    }
    FontFiles {
        files: [
            "fonts/TitilliumWeb-Light.ttf",
            "fonts/TitilliumWeb-SemiBold.ttf"
        ]
    }
    QmlFiles {
        files: [
            "instrument_cluster.qml"
        ]
    }
    InterfaceFiles {
        files: ["src/VehicleStatus.h"]
    }
}

VehicleStatus singleton

The VehicleStatus singleton is responsible for storing the vehicle parameters for the user interface. It inherits from Qul::Singleton to expose the public signals and properties to QML. It also inherits from Qul::EventQueue to provide an event queue to trigger user interface update when the property values are changed.

    ...
    Qul::Property<int> speed;
    Qul::Property<double> tripMeter;
    Qul::Signal<void(bool leftBlinkerState)> leftBlinkerStateChange;
    Qul::Signal<void(bool rightBlinkerState)> rightBlinkerStateChange;
    ...

The QML code accesses these values via VehicleStatus singleton:

    ...
    Text {
        id: speedometer
        color: "#2CDE85"
        anchors.centerIn: parent

        font.weight: Font.DemiBold
        font.pixelSize: 90
        text: VehicleStatus.speed
    }
    ...

The repainting of the instrument cluster is triggered by using a dummy event queue. Event handling requires Qt Quick Ultralite engine to do an update.

...
void qul_application_send_value_change_event()
{
    VehicleStatus::instance().postEvent(true);
}
...

The actual event handler does nothing:

    ...
    void onEvent(const bool &value)
    {
        // Dummy event queue to trigger UI updates
        (void) value;
    }
    ...

C linkage functions are exposed to the non-GUI code to control instrument cluster content:

...
extern "C" {
void qul_application_set_speed(int speed)
{
    VehicleStatus::instance().speed.setValue(speed);
}
...

AUTOSAR example

In an AUTOSAR project, the Qt Quick Ultralite Complex Device Driver calls the C linkage APIs as shown below:

#include "VehicleStatus.h"
...
// QUL Complex Device Driver Runnable with a periodic trigger
void Cdd_Qul_Update(void)
{
    int changedValuesCount = 0;

    static int previousSpeed = 0;
    int speed;

    // Read the speed value via the AUTOSAR Interface
    // Rte_Read_Cdd_Qul_Speed(&speed);

    if (speed != previousSpeed) {
        changedValuesCount++;
        qul_application_set_speed(speed);
        previousSpeed = speed;
    }
    ...
    if (changedValuesCount > 0) {
        // Send an event to trigger repainting of the UI
        qul_application_send_value_change_event();
    }

    qul_update_engine(); // Calls Qul::Application::update()
}

Files:

See also Integrating C++ code with QML.

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