Hardware Design

For the Modbus RTU part, a self-developed Modbus RFID reader is applied, as shown in the figure below. It is designed based on the STM32F0 chip and supports Modbus RTU communication and RS485 interface.

 

Software Design

Open-Source Protocol Stack Software

project(imgui)

message("imgui cmake..")

add_library(imgui
    lib/imgui/imgui.cpp
    lib/imgui/imgui_demo.cpp
    lib/imgui/imgui_draw.cpp
    lib/imgui/imgui_tables.cpp
    lib/imgui/imgui_widgets.cpp
    lib/imgui/backends/imgui_impl_sdl2.cpp
    lib/imgui/backends/imgui_impl_opengl3.cpp
)

find_package(SDL2 REQUIRED)
find_package(OpenGL REQUIRED)

target_link_libraries(imgui PUBLIC SDL2::SDL2)
target_link_libraries(imgui PUBLIC OpenGL::GL)

include_directories(lib/imgui)
include_directories(lib/imgui/backends)

The project’s CMakeLists.txt is shown below. Core dependencies: SOEM, SDL2, OpenGL, ImGui, libmodbus, and pthread.

# project info
cmake_minimum_required(VERSION 3.28)
project(master VERSION 0.1.0 LANGUAGES C CXX)

# set some option
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
set(SOEM_BUILD_SAMPLES ON)

# libs
add_subdirectory(lib/SOEM)
include(lib/imgui.cmake)

add_executable(master master.cpp imgui_main.cpp fieldbus.c)

# link libraries
target_link_libraries(master PRIVATE soem)
target_link_libraries(master PRIVATE imgui)
target_link_libraries(master PRIVATE modbus)
target_link_libraries(master PRIVATE pthread)

Code Development

1. One thread is responsible for EtherCAT communication with a synchronization cycle of 5ms;
2. Another thread handles Modbus RTU communication with a cycle of 10ms;
3. The third thread is the UI thread, which runs the interface developed with ImGui.

void ImGui::mywindow(void)
{
    main_window();
    DrawModbusSerialPanel();
}

// 线程函数
void * thread_func_ecat(void *arg)
{
    for (;;)
    {
        op_loop();
        usleep(5000);
    }
    return NULL;
}

// 线程函数
void * thread_func_modbus(void *arg)
{
    for (;;)
    {
        if (g_connected && g_modbusCtx)
        {
            uint16_t regs[2];

            /* 固定站号 2 */
            modbus_set_slave(g_modbusCtx, 2);

            /* 写保持寄存器 1 = 0 */
            modbus_write_register(g_modbusCtx, 0, 0);

            /* 读保持寄存器 2、3 */
            if (modbus_read_registers(g_modbusCtx, 1, 2, regs) == 2)
            {
                g_reg2 = regs[0];
                g_reg3 = regs[1];
            }
        }
        usleep(10000);
    }
    return NULL;
}

// 线程函数
void * thread_func_ui(void *arg)
{
    imgui_init();
    return NULL;
}

int main(int argc, char *argv[])
{
    printf("EtherCAT Debug Tool\n");
    printf("A GUI tool for debugging EtherCAT networks\n");
    pthread_t tid1, tid2, tid3;
    int id1 = 1, id2 = 2, id3 = 3;

    // create thread
    if (pthread_create(&tid1, NULL, thread_func_ui, &id1) != 0) {
        perror("thread_func_ui is created.");
        return 1;
    }

    if (pthread_create(&tid2, NULL, thread_func_ecat, &id2) != 0) {
        perror("thread_func_ecat is created.");
        return 1;
    }
    if (pthread_create(&tid3, NULL, thread_func_modbus, &id3) != 0) {
        perror("thread_func_modbus is created.");
        return 1;
    }
    // wait for threads to finish
    pthread_join(tid1, NULL);
    pthread_join(tid2, NULL);
    pthread_join(tid3, NULL);

    return 0;
}

Yassin