ADS sum command: read and write multiple variables
This sample shows how to read or write many variables using the ADS sum command. Set up as TcAdsClient.ReadWrite it serves as a container in which the subcommands are transported in an ADS stream.
System requirements:
- TwinCAT v2.11 Build >= 1550
Unpack the sample program 'ADS sum command: read and write multiple variables': sample13.zip
- To execute the *.jar sample, the command 'java -classpath "Sample13.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.
Fetch symbol information of the PLC variables
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import de.beckhoff.jni.JNIByteBuffer;
import de.beckhoff.jni.tcads.AdsCallDllFunction;
import de.beckhoff.jni.tcads.AmsAddr;
public class Main {
private final static RequestData[] REQ_DATA = new RequestData[]{
new RequestData("uintValue", 0x4020, 0x0, 0x2),
new RequestData("boolValue", 0x4020, 0x8, 0x1),
new RequestData("dintValue", 0x4020, 0x10, 0x4)
};
// The data that is going to be written in the third step
private final static char CHAR_VAL = Character.MAX_VALUE;
private final static byte BOOL_VAL = 1;
private final static int INT_VAL = Integer.MIN_VALUE;
private final static int DATA_LEN = 7;
private final static int RESP_ERR_LEN = 4;
public static void main(String[] args) {
long err;
AmsAddr addr = new AmsAddr();
try {
// 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!");
}
If variables are to be written or read in the PLC without resorting to handles, then IndexGroup and IndexOffset must be known. To get these values from all relevant variables, usually the symbol information has to be read out. In this sample, the values are assumed to be constant and defined in REQ_DATA.
Read values
The RequestBuffer is now written with the data from REQ_DATA according to the scheme below. Here IG1 stands for the IndexGroup of the first subcommand. IO2 for the IndexOffset of the second subcommand and L3 for the length of the expected response of the third subcommand.
As a response of the sum command we receive an Ads error code (Err) per subcommand, as well as the requested value (Data). Accordingly the length of the buffer in this case is: 3 * 4 bytes (Error) + 7 bytes (The sum of all lengths of the expected responses).
The sum command itself is called with the parameters IndexGroup: 0xF080 (sum command read), IndexOffset: 0x3 (number of subcommands), ResponseBuffer length, ResponseBuffer, RequestBuffer length, RequestBuffer.
// Create request buffer (see picture 1)
JNIByteBuffer jniRequestBuffer = null;
ByteBuffer requestBuffer =
ByteBuffer.allocate(RequestData.SIZE * REQ_DATA.length);
requestBuffer.order(ByteOrder.LITTLE_ENDIAN);
for (int i = 0; i < REQ_DATA.length; i++) {
requestBuffer.put(REQ_DATA[i].toByteArray());
}
// Need to let a JNIByteBuffer wrap the byte[] to be able to send it
jniRequestBuffer = new JNIByteBuffer(requestBuffer.array());
// Create response buffer (see picture 2)
JNIByteBuffer jniResponseBuffer = new JNIByteBuffer(
REQ_DATA.length * RESP_ERR_LEN + DATA_LEN);
// Read the values via sum command
err = AdsCallDllFunction.adsSyncReadWriteReq(
addr,
0xF080,
REQ_DATA.length,
jniResponseBuffer.getUsedBytesCount(),
jniResponseBuffer,
jniRequestBuffer.getUsedBytesCount(),
jniRequestBuffer);
if (err != 0) {
System.out.println("Error: Get values: 0x"
+ Long.toHexString(err));
} else {
System.out.println("Success: Get values!");
// Evaluate the sub commands error codes and response values
// (see picture)
ByteBuffer responseBuffer =
ByteBuffer.wrap(jniResponseBuffer.getByteArray());
responseBuffer.order(ByteOrder.LITTLE_ENDIAN);
// In each loop the errPosition is increased by the Size of an
// error (int) and the valPosition by the size of the
// corresponding data type
int[] respErrs = new int[REQ_DATA.length];
for (int i = 0; i < respErrs.length; i++) {
respErrs[i] = responseBuffer.getInt();
}
for (int i = 0; i < REQ_DATA.length; i++) {
String varName = REQ_DATA[i].getVarName();
int val = 0;
if (respErrs[i] == 0) {
switch (REQ_DATA[i].getLength()) {
case 1:
val = (int) responseBuffer.get();
break;
case 2:
val = responseBuffer.getChar();
break;
case 4:
val = responseBuffer.getInt();
break;
default:
break;
}
System.out.println(varName + ": " + val + "\t");
} else {
System.out.println(varName + ": Error: 0x"
+ Long.toHexString(err) + "\t");
}
}
}
Write values
To be able to write data, this data must only be appended to the RequestBuffer from the upper part (see picture). All other parameters remain unchanged. Only an adjustment of the sum command is necessary (see below).
As a response of the sum command we get an Ads error code (Err) per subcommand, but this time no data, because we executed a write operation. Accordingly the length of the buffer in this case is: 3 * 4 bytes (Error).
For the sum command, the value for the IndexGroup must now be changed to 0xF081 (sum command write).
//// Write values
// Construct buffers. Fill request buffer with the data from above
// and append the data that is going to be written (see picture 3)
byte[] requestBufferCopy = requestBuffer.array();
requestBuffer = ByteBuffer.allocate(
requestBuffer.capacity()
+ DATA_LEN);
requestBuffer.order(ByteOrder.LITTLE_ENDIAN);
requestBuffer.put(requestBufferCopy);
requestBuffer.putChar(CHAR_VAL);
requestBuffer.put(BOOL_VAL);
requestBuffer.putInt(INT_VAL);
// Need to let a JNIByteBuffer wrap the byte[] to be able to send it
jniRequestBuffer.setByteArray(requestBuffer.array(), true);
// Adjust the length of the response buffer (compare pictures 2 & 4)
jniResponseBuffer.setUsedBytesCount(8 * REQ_DATA.length, true);
// Write the values via sum command
err = AdsCallDllFunction.adsSyncReadWriteReq(
addr,
0xF081,
REQ_DATA.length,
jniResponseBuffer.getUsedBytesCount(),
jniResponseBuffer,
jniRequestBuffer.getUsedBytesCount(),
jniRequestBuffer);
if (err != 0) {
System.out.println("Error: Write values: 0x"
+ Long.toHexString(err));
} else {
System.out.println("Success: Write values!");
// Evaluate the sub command error codes
ByteBuffer responseBuffer =
ByteBuffer.wrap(jniResponseBuffer.getByteArray());
responseBuffer.order(ByteOrder.LITTLE_ENDIAN);
for (int i = 0; i < REQ_DATA.length; i++) {
String varName = REQ_DATA[i].getVarName();
err = responseBuffer.getInt();
if (err == 0) {
System.out.println(varName + ": Success\t");
} else {
System.out.println(varName + ": Error: 0x"
+ Long.toHexString(err) + "\t");
}
}
}
System.out.println("\nPress enter to continue..");
System.in.read();
} catch (Exception ex) {
ex.printStackTrace();
} finally {
// Close communication
err = AdsCallDllFunction.adsPortClose();
if (err != 0) {
System.out.println("Error: Close communication: 0x"
+ Long.toHexString(err));
} else {
System.out.println("Success: Close communication!");
}
}
}
}