Read PLC variable declaration

Download: 'Read PLC Variable Declarations'

The following information is transferred when accessing the variable declaration:

All the information listed above is transmitted in a data stream. Before this can be read, the first AdsSyncReadReq() is used to obtain the length. The data itself is transferred with the second AdsSyncReadReq(). The pchSymbols variable is a pointer, pointing to this region. The FOR-loop copies the corresponding data region into the pAdsSymbolEntry structure for each individual PLC variable. The individual information items in the PLC variables are stored in this structure. The macros PADSSYMBOLNAME, PADSSYMBOLTYPE and PADSSYMBOLCOMMENT simplify the evaluation of this data.

#include <iostream.h>
#include <windows.h>
#include <conio.h>
#include <assert.h>

// ADS headers for TwinCAT 3
#include "C:\TwinCAT\3.0\AdsApi\TcAdsDll\Include\TcAdsDef.h"
#include "C:\TwinCAT\3.0\AdsApi\TcAdsDll\Include\TcAdsAPI.h"

void main()
{
 long         nErr, nPort; 
 char         *pchSymbols = NULL; 
 UINT         uiIndex; 
 AmsAddr     Addr; 
 PAmsAddr     pAddr = &Addr; 
 AdsSymbolUploadInfo tAdsSymbolUploadInfo; 
 PAdsSymbolEntry pAdsSymbolEntry; 

 // Open communication port on the ADS router
 nPort = AdsPortOpen();
 nErr = AdsGetLocalAddress(pAddr);
 if (nErr) cerr << "Error: AdsGetLocalAddress: " << nErr << '\n';
 
 // Select Port: TwinCAT 3 PLC1 = 851
 pAddr->port = 851;

 // Read the length of the variable declaration
 nErr = AdsSyncReadReq(pAddr, ADSIGRP_SYM_UPLOADINFO, 0x0, sizeof(tAdsSymbolUploadInfo), &tAdsSymbolUploadInfo);
 if (nErr) cerr << "Error: AdsSyncReadReq: " << nErr << '\n'; 
 pchSymbols = new char[tAdsSymbolUploadInfo.nSymSize]; 
 assert(pchSymbols); 

 // Read information about the PLC variables 
 nErr = AdsSyncReadReq(pAddr, ADSIGRP_SYM_UPLOAD, 0, tAdsSymbolUploadInfo.nSymSize, pchSymbols); 
 if (nErr) cerr << "Error: AdsSyncReadReq: " << nErr << '\n'; 

 // Output information about the PLC variables 
 pAdsSymbolEntry = (PAdsSymbolEntry)pchSymbols; 
 for (uiIndex = 0; uiIndex < tAdsSymbolUploadInfo.nSymbols; uiIndex++)
 { 
 cout << PADSSYMBOLNAME(pAdsSymbolEntry) << "\t\t" 
     << pAdsSymbolEntry->iGroup << '\t' 
     << pAdsSymbolEntry->iOffs << '\t' 
     << pAdsSymbolEntry->size << '\t' 
     << PADSSYMBOLTYPE(pAdsSymbolEntry) << '\t' 
     << PADSSYMBOLCOMMENT(pAdsSymbolEntry) << '\n'; 
 pAdsSymbolEntry = PADSNEXTSYMBOLENTRY(pAdsSymbolEntry); cout.flush();
 }
 getch();

 // Close communication port
 nErr = AdsPortClose(); 
 if (nErr) cerr << "Fehler: AdsPortClose: " << nErr << '\n';

 // Release memory
 if (pchSymbols) delete(pchSymbols);
}