Read flag synchronously from the PLC

Download: 'Read flag synchronously from PLC'

In this example program the value in flag double word 0 in the PLC is read and displayed on the screen.

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

// ADS headers for TwinCAT 3
#include "C:\TwinCAT\AdsApi\TcAdsDll\Include\TcAdsDef.h"
#include "C:\TwinCAT\AdsApi\TcAdsDll\Include\TcAdsAPI.h"
void main()
{
 long nErr, nPort;
 AmsAddr Addr;
 PAmsAddr pAddr = &Addr;
 DWORD dwData;
 // Open communication port on the ADS router
 nPort = AdsPortOpen();
 nErr = AdsGetLocalAddress(pAddr);
 if (nErr) cerr << "Error: AdsGetLocalAddress: " << nErr << '\n';
 
 // TwinCAT3 PLC1 = 851
 pAddr->port = 851;
 // Read value from MD0 and display
 do
 {
 nErr = AdsSyncReadReq(pAddr, 0x4020, 0x0, 0x4, &dwData);
 if (nErr) cerr << "Error: AdsSyncReadReq: " << nErr << '\n';
 cout << dwData << '\n';
 cout.flush();
 }
 while (getch() == '\r'); // Read the next value (use Carriage return as delimitter), stop otherwise
 // Close communication port
 nErr = AdsPortClose();
 if (nErr) cerr << "Error: AdsPortClose: " << nErr << '\n';
}