How can assign a new variable to an array in TwinCAT?
in TwinCAT you can initialize all your array's argument directly for example for array a we can use:
a : ARRAY [1..3] OF INT := [3(0)];
or
a : ARRAY [1..3] OF INT := [0,0,0];
but if you want to assign the array in the main program(not initializing part) for example
a:=[2,8,5];
you will face this error tip: Unexpected array initialisation.
any help would be appreciated.
You cannot directly initialize arrays inside the program part.
That beeing said, the best option is porbably to define a constant containing the desired initialization values and then assigning the value of that constant to your array:
VAR
aiMyArray : ARRAY [1..2] OF INT;
END_VAR
VAR CONSTANT
aiInitializerMyArrayOptionA : ARRAY [1..2] OF INT := [1,2];
aiInitializerMyArrayOptionB : ARRAY [1..2] OF INT := [3,4];
END_VAR
IF bCondition THEN
aiMyArray := aiInitializerMyArrayOptionA;
ELSE
aiMyArray := aiInitializerMyArrayOptionB;
END_IF
The other option would be to manually initialize each index one by one which easily gets impracticale with decent array sizes:
IF bCondition THEN
aiMyArray[1] := 1;
aiMyArray[2] := 2;
ELSE
aiMyArray[1] := 3;
aiMyArray[2] := 4;
END_IF
Looping thorugh all elements and assigning values might be an option too. But that would only be usefull when the values are no arbitrary constatns but you are able to calculate the values from some formula.
Related
I need to change the length of the array dynamically.Right now the code looks like this:
VAR
arrData : ARRAY[1..200] OF INT;
length : INT := 200;
END_VAR
The size of the array depends on the length variable.Here the value of length variable can be changed during runtime using the VISU(gui). So if I change the value of the length = 180 then 20 bytes of arrData are unused.Is there a way to declare the array as variable length similar to vectors in c++ such that the memory is not assigned during declaration but during runtime.
Edit:
How to deallocate the memory safely?
PROGRAM MAIN
VAR
arrData : POINTER TO INT;
length : INT := 200; // can be changed at runtime
bNew : BOOL := TRUE;
oldLength : INT; // to hold the old length variable
isInit : BOOL := FALSE;
END_VAR
IF NOT isInit THEN
oldLength := length; // initialise only once
isInit := TRUE;
END_IF
// if length is changed during runtime then delete the array
IF oldLength <> length THEN
IF arrData <> 0 THEN
__DELETE(arrData);
bNew := TRUE;
END_IF
oldLength := length;
END_IF
// during the first run or when the length is changed
IF bNew THEN
arrData := __NEW(INT,length);
bNew := FALSE;
END_IF
// deallocate the memory when the MAIN program goes out of scope
// as we are not deleting the array when the length variable is not
// changed during runtime
END_CASE
The way to do it is to use __NEW __NEW in Infosys
pMyPointer := __NEW(INT, length);
__NEW will return a pointer to first element of an array. You can access latter elements by offsetting this pointer.
You can check if length was changed by comparing value from this and previous cycle. If so, __DELETE the old array and initialize a new one.
Edit:
I think, that you get your error the moment TwinCAT runtime is stopped, as the momory allocated by __NEW is not freed at that point.
Your code should be placed not in a Program (PRG) but in a Function Block (FB). The reason for that is that you need to implement FB_exit method (This method is called implicitly when FB instance is destroyed, i.e. when stopping TwinCAT runtime like you do by activating configuration). There is no equivalent method for a PRG as far as I know.
To do this:
Create a new FB, instantiate it and call it in your MAIN and move your code from MAIN to the FB
Add a FB_exit method to this FB. Exact naming is crucial
In your FB_exit method write the following code:
IF __ISVALIDREF(arrData) THEN
__DELETE(arrData);
END_IF
This method will be called every time you stop your runtime and free the memory.
Links to Infosys:
__ISVALIDREF - equal to pMyPointer <> 0 but more readable
FB_exit
I have structure declared like this:
TYPE board:
STRUCT
number: INT;
color: DWORD;
END_STRUCT
END_TYPE
And i want to declare array of these structures with starting values in POU. I do it like this:
Program PLC_PRG
VAR
arr1: ARRAY[1..61] OF board;
board: board;
arr1[1].color := 16#FF0000;
END_VAR
But i get an error which say: "Error 4024: PLC_PRG(10): Expecting ':' before '['".
Do anybody know how to solve this problem?
You didn't specify a platform but I'll assume TwinCAT. To initialize an array of structures, you have to do it all in the variable declaration line.
arr1: ARRAY[1..61] OF board := [(number:=7, color:=16#FF0000), (number:=5, color:=16#FF0001)];
This example will initialize elements 1 and 2 of the array. To my knowledge you can't selectively initialize individual array elements as you are maybe wanting to do. You could use statements like arr1[17].color := 16#FF0000 of course but it would have to be outside of your variable declaration block.
Is it possible to store a variable value in each PLC cycle? I need the first 10 values each time to perform some calculations. I am using the OpenPCS platform and ST for programming.
You can create an array of values and then store as array values
VAR
aBuffer : ARRAY[1..32] OF WORD;
init:BOOL; (* Init array *)
rest:BOOL; (* Reset *)
val:WORD; (* Value *)
iCount:INT; (* Array index *)
END_VAR
VAR_TEMP
iTmp : INT;
END_VAR
iTmp := UINT_TO_INT(N) - 1;
IF NOT init OR rest THEN
init := TRUE;
FOR iCount := 1 TO iTmp DO
aBuffer[iCount] := val;
END_FOR;
END_IF
iCount := INC1(iCount, 32);
aBuffer[iCount] := val;
This is a code example that created 32 elements array and every new PLC cycle assign new element and rotates.
After that, you can calculate the average or min and max.
INC1 increments given value by one until it reaches 32 and then reset to 1.
In my project I have a type like:
TYPE myDataStruct :
STRUCT
A : UINT;
B : WORD;
C : REAL;
D : Custom_Obj;
END_STRUCT
END_TYPE
And I need to keep an array of this type for persistent memory. I can't just use VAR RETAIN because this particular piece of memory needs to persist through a download. The controller I am using has a way to do this but in order for it to work I need to be able to set the array equal to an initial value. So if I have declared
myarray := ARRAY[0..20] OF myDataStruct;
How do I then initialize this array to a blank array? What is the equivalent of new in other languages?
I have guessed
myarray := [21(A := 0,
B := '',
C := 0.0,
D := ??? )];
But that doesn't appear to be right. It could be simplified if there were only one level deep of custom structs and for this application I could do that. However, I still don't think I have the syntax right.
What is the equivalent of new in other languages?
The analog of this is
VAR
EmptyArray : ARRAY[0..20] OF myDataStruct;
END_VAR
If you want to pre-populate it with default values
VAR
EmptyArray : ARRAY[0..20] OF myDataStruct := [
(A := 100, B := 200, С := 0.0, D := ???),
(A := 34, B := 45, С := 0.1, D := ???),
..... etc
];
END_VAR
For CoDeSys 2.3 delete [ and ].
What you have to understand that EmptyArray is not a prototype of data you need but already initialized variable.
There is no way to initialize it in "x = new struct()" way. You also can't assign the whole array in the code with something like myarray = [1, 2, 3] etc, as far as I know.
If you just want to set it empty with values like 0, '', etc, then there are two ways that I would use:
1. Use MEMSET function to set all bytes to 0
Link to the online help
//Something like
MemSet(
pbyBuffer := ADR(myarray), //Address of the variable
byValue := 0, //Byte that address is filled with
dwSize := SIZEOF(myarray) //How many bytes? (variable size)
)
2. Create a dummy variable and assign it to the myarray
The variable is always initialized to zeros, so EmptyArray values are all 0/empty etc.
VAR
EmptyArray : ARRAY[0..20] OF myDataStruct;
END_VAR
//In the code
myarray := EmptyArray;
I hope I understood your question correctly.
I know I can write
a := Object()
a[1] := "textA"
a[2] := "textB"
a[3] := "textC"
Can I write something like
a := {"textA", "textB", "textC"}
?
You can define an indexed array using the bracket syntax:
a := ["textA", "textB", "textC"]
or the array creation function:
a := Array{"textA", "textB", "textC"}
An indexed array is an object representing a list of items, numbered 1 and up. In this example, the value "textA" is stored in object key 1, the value "textB" in object key 2 and the value "textC" in object key 3.
https://autohotkey.com/docs/Tutorial.htm#s7