Read or Write a list of variables with one single ADS-command

[Satheesh-satz]

This is regarding writing a list of variables with one single ADS-command as referred in the following link. http://infosys.beckhoff.com/english.php?content=../content/1033/tcsample_labview/html/tcsample_labview_overview.htm&id=

From the provided sample application "ADS_Demo_SumReq.cpp" it has used data structure

typedef struct dataPar { unsigned long indexGroup1; // index group in ADS server interface unsigned long indexOffset1; // index offset in ADS server interface unsigned long length1; // count of bytes to read unsigned long indexGroup2; // index group in ADS server interface unsigned long indexOffset2; // index offset in ADS server interface unsigned long length2; // count of bytes to read unsigned long data1; // count of bytes to read unsigned long data2; // count of bytes to read } TDataPar;

But with this data structure it is limited to only two variables right? And also i am not finding this data structure defined any where on the ADS library header files.

My question here is :

1. How to modify the data structure and use it to write multiple variables?
2. Can we have this data structure captured on any of the ADS header files

Thanks, Satheesh

[pbruenn]

Are you sure your link is correct? I think you are looking for this one: http://infosys.beckhoff.com/content/1033/tcsample_vc/html/tcadsdll_api_cpp_sample17.htm?id=20654114132734386906

[Satheesh-satz]

Hi Patrick, You are right, That the link i am talking about.

[pbruenn]

Okay, there you find this example: http://infosys.beckhoff.com/content/1033/tcsample_vc/Samples/API/CPP/Sample17/Sample17-C-ADS-DLL-SumRequests.zip

There is this struct used:

typedef struct dataPar {
    unsigned long       indexGroup; // index group in ADS server interface
    unsigned long       indexOffset;    // index offset in ADS server interface
    unsigned long       length;     // count of bytes to read
} TDataPar;
TDataPar parReq[2];

And AdsSyncReadWriteReq() called like this:

nErr = AdsSyncReadWriteReq(pAddr, 
                        0xf080, 
                        reqNum, 
                        4*reqNum+reqSize,   // we request additional "error"-flag(long) for each ADS-sub commands
                        (void*)(mAdsSumBufferRes), 
                        12*reqNum,          // send 12 bytes (3 * long : IG, IO, Len) of each ADS-sub command
                        &parReq);

[Satheesh-satz]

Hi Patric,

I referring to the Multiple write sample, in that the structure is define just to write only two variable at a time

typedef struct dataPar { unsigned long indexGroup1; // index group in ADS server interface unsigned long indexOffset1; // index offset in ADS server interface unsigned long length1; // count of bytes to read unsigned long indexGroup2; // index group in ADS server interface unsigned long indexOffset2; // index offset in ADS server interface unsigned long length2; // count of bytes to read unsigned long data1; // count of bytes to read unsigned long data2; // count of bytes to read } TDataPar; TDataPar parReq;

So, my question here is, what if i want to write more than two variable at a time.

Thanks, Satheesh

[pbruenn]

Did you try:

typedef struct dataTriple {
    unsigned long indexGroup1; // index group in ADS server interface
    unsigned long indexOffset1; // index offset in ADS server interface
    unsigned long length1; // count of bytes to read
    unsigned long indexGroup2; // index group in ADS server interface
    unsigned long indexOffset2; // index offset in ADS server interface
    unsigned long length2; // count of bytes to read
    unsigned long indexGroup3;
    unsigned long indexOffset3;
    unsigned long length3;
    unsigned long data1; // count of bytes to read
    unsigned long data2; // count of bytes to read
    unsigned long data3;
} TDataTriple;

Personally I would reuse TDataPar from the read example:

template <class T, size_t N>
struct AdsWriteTuple {
    TDataPar header[N];
    T data[N];
};

And use it like this:

static const size_t reqNum = 3;
AdsWriteTuple<unsigned long, reqNum> parReq;

nErr = AdsSyncReadWriteReq(pAddr,
                           0xF081, // ADS list-write command
                           reqNum, // number of ADS-Sub commands
                           4*reqNum, // we expect an ADS-error-return-code for each ADS-Sub command
                           (void*)(mAdsSumBufferRes), // provide space for the response containing the return codes
                           sizeof(parReq),
                           &parReq);   // buffer with data

As we are on suggestions. I highly recommend to use uint32_t instead of unsigned long, when you expect to work with an unsigned 32-Bit value, because unsigned long could be 64-Bit on different compilers.