项目目标：实现Linux程序和codesys应用程序之间的数据读写

实现方法：使用共享内存的方式

使用codesys软件，使用ST编程语言，编写IDE程序：

PROGRAM PLC_PRG

VAR

tt: Ton;

hShMemRead: RTS_IEC_HANDLE;

ResultRead: RTS_IEC_RESULT;

deInstRead : DataExchange;

ReadResult: RTS_IEC_RESULT;

iRead: __UXINT;



hShMemWrite: RTS_IEC_HANDLE;

ResultWrite: RTS_IEC_RESULT;

deInstWrite : DataExchange;

WriteResult: RTS_IEC_RESULT;

iWrite: __UXINT;

ulSize: UDINT := SIZEOF(DataExchange);

END_VAR



tt(IN := TRUE,PT:=T#500MS);

IF tt.Q THEN

// Read structure from Shared Memory.

hShMemRead := SysSharedMemoryCreate('_CODESYS_SharedMemoryTest_Read', 0, ADR(ulSize), ADR(ResultRead));

iRead := SysSharedMemoryRead(hShMemRead, 0, ADR(deInstRead), SIZEOF(deInstRead), ADR(ReadResult));

iRead := SysSharedMemoryClose(hShm := hShMemRead);



// Write structure to Shared Memory.

hShMemWrite := SysSharedMemoryCreate('_CODESYS_SharedMemoryTest_Write', 0, ADR(ulSize), ADR(ResultWrite));

deInstWrite.diValue1 := deInstWrite.diValue1 + 1;

deInstWrite.diValue2 := deInstWrite.diValue2 - 1;

iWrite := SysSharedMemoryWrite(hShMemWrite, 0, ADR(deInstWrite), SIZEOF(deInstWrite), ADR(WriteResult));

iWrite := SysSharedMemoryClose(hShm := hShMemWrite);



tt(IN:=FALSE);

tt(IN:=TRUE);

END_IF

将程序下载到控制器之中

采用shm内存共享的方式，编写c语言程序：

#include <stdio.h>

#include <stdlib.h>

#include <sys/mman.h>

#include <sys/stat.h>

#include <fcntl.h>

#include <string.h>



struct DataExchange {

    int i1;

    int i2;

};



int main(int argc, char **argv)

{

    struct DataExchange *pRead, *pWrite;

    char sSharedMemReadName[100] = "_CODESYS_SharedMemoryTest_Write";

    char sSharedMemWriteName[100] = "_CODESYS_SharedMemoryTest_Read";



    int fdRead = shm_open(sSharedMemReadName, O_CREAT | O_RDWR, S_IRWXU | S_IRWXG);

    printf("Shared Memory Read: %s %d\n\n",sSharedMemReadName, fdRead);

    ftruncate(fdRead, sizeof(*pRead));

    pRead = mmap(0, sizeof(*pRead), PROT_READ | PROT_WRITE, MAP_SHARED, fdRead, 0);

    close(fdRead);



    int fdWrite = shm_open(sSharedMemWriteName, O_CREAT | O_RDWR, S_IRWXU | S_IRWXG);

    printf("Shared Memory Write: %s %d\n\n",sSharedMemWriteName, fdWrite);

    ftruncate(fdWrite, sizeof(*pWrite));

    pWrite = mmap(0, sizeof(*pWrite), PROT_READ | PROT_WRITE, MAP_SHARED, fdWrite, 0);

    close(fdWrite);



    do

    {

        sleep(1);

        printf("pRead->i1: %d pRead->i2: %d pWrite->i1: %d pWrite->i2: %d\n",

               pRead->i1, pRead->i2, pWrite->i1, pWrite->i2);

        printf("Press 'Enter' to increment values or 'q' and then 'Enter' to quit\n");

        pWrite->i1++;

        pWrite->i2--;

    } while (getchar() != 'q');



    munmap(pRead, sizeof(*pRead));

    shm_unlink(sSharedMemReadName);



    munmap(pWrite, sizeof(*pWrite));

    shm_unlink(sSharedMemWriteName);

    exit(0);

}

根据使用的硬件平台，用gcc编译成可执行文件，便能够同时在系统和IDE上看到共享数据，如下图所示

由于刷新频率并不同步，两边的数值显示上有点差别。

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