Accessing an array in the PLC

An array, located in the PLC, is to be read by means of a read command. The variable is addressed here by its variable name. The procedure is only slightly different from that for reading discrete variables:

Unpack the sample program 'Access an array in the PLC': sample03.zip

• To execute the *.jar sample, the command 'java -classpath "Sample03.jar;[path to TcJavaToAds.jar] Main' must be executed in the console in the correct directory (example path: "C:TwinCAT\Ads Api\AdsToJava\*"). For this, java must be entered in the environment variables.

import de.beckhoff.jni.Convert;
import de.beckhoff.jni.JNIByteBuffer;
import de.beckhoff.jni.tcads.AmsAddr;
import de.beckhoff.jni.tcads.AdsCallDllFunction;

public class Main
{
    public static void main(String[] args)
    {
    long err;
    AmsAddr addr = new AmsAddr();
    JNIByteBuffer dataBuff = new JNIByteBuffer(200);

    // Open communication        
    AdsCallDllFunction.adsPortOpen();
    err = AdsCallDllFunction.getLocalAddress(addr);
    addr.setPort(AdsCallDllFunction.AMSPORT_R0_PLC_RTS1);

    if (err != 0) {
        System.out.println("Error: Open communication: 0x"
            + Long.toHexString(err));
    } else {
        System.out.println("Success: Open communication!");
    }

    // Read value by IndexGroup and IndexOffset
    err = AdsCallDllFunction.adsSyncReadReq(addr,
                        0x4020,     // Index Group
                        0x0,    // Index Offset
                        200,
                        dataBuff);
    if(err!=0)
    {
        System.out.println("Error: Read by handle: 0x" 
            + Long.toHexString(err));
    }
    else
    {
        for (int i = 0; i < dataBuff.getUsedBytesCount(); i=i+2)
        {
        // PLC datatype int consists of two bytes. Get them.
        byte lowByte = dataBuff.getByteArray()[i];
        byte highByte = dataBuff.getByteArray()[i+1];
        // Create new byte[]. Little endian!
        byte[] valBytes = { lowByte, highByte };
        // Integer value: byte[] to int
        int valInt = Convert.ByteArrToShort(valBytes);
        System.out.println("Value of PLCVar[" + i/2 + "]: " + valInt);
        }
    }

    // Close communication
    err = AdsCallDllFunction.adsPortClose();
    if(err!=0) { 
        System.out.println("Error: Close Communication: 0x" 
            + Long.toHexString(err)); 
    }

    try{
        System.in.read();
    }
    catch (Exception e){
        System.out.println("Error: Close program");
    }
    }
}