Hi,

I am trying to cleanup some variable mapping. I have an I/O device that has its points defined as BIT. I would like to map these into an array of something but I cannot use an array of BIT. Mapping to an array allows me to access bits through a common FB so I only need to map the points once.
I have created a Union based on a Forum response (https://forge.codesys.com/forge/talk/Engineering/thread/9613d49992/) and it seems to do what I would like. However, when I map the bits to my device, I get a C0355 warning (A single bit cannot be referenced. A reference to the complete byte will be stored.).

What does this warning mean and is there a better way to map this?

Thank you

My code:

TYPE Output_Byte :
STRUCT
   Bit0 : BIT;
   Bit1 : BIT;
   Bit2 : BIT;
   Bit3 : BIT;
   Bit4 : BIT;
   Bit5 : BIT;
   Bit6 : BIT;
   Bit7 : BIT;
END_STRUCT
END_TYPE

TYPE Output_Union :
UNION
   //Note: I added the array here as a test. I get the same C355 warning even without.
   aByte : ARRAY[0..9] OF BYTE;
   Bytes : ARRAY[0..9] OF Output_Byte;
END_UNION
END_TYPE

Usage in Global:

   testBytes    : Output_Union;

Usage in my device map:

Application.Global.testBytes.Bytes[0].Bit2

Try

testBools : ARRAY [0..9] OF BOOL;

Thank you @i-campbell. Using testBools[x] in the mapping does work.

I am trying to pass these points along to a client over a network and I would like to just send a bunch of Bytes (without manually converting them). The BOOL type does not map nicely to Bytes.

I would like to do something like:

InputBytes : ARRAY[0..9] OF BYTE;

and then use 'InputBytes[0].2' in the mapping. However, this will not even compile.

Using an array of BOOL makes the network sending messy.

The benefit of the Union is that the value of the 8 BITS is exposed in through the BYTE object (aByte in the example). If I use BOOL in the Output_Byte structure, this relationship breaks.

I will look at it more with your suggestion in mind and see if I am approaching this wrong.

Thank you again.

As you have 4 distinct parameters, it will not be possible to map them to a BIT variable from the mapping dialog.
You could try
testBytes AT %QB200 : Output_Union;
OR
testBytes AT %QB400 : Output_Union;
Depending on which addressing mode your PLC uses.

You could also use Util.Pack() / Util.Unpack() somewhere in your code