Extract 4 bytes from array of bytes to save in decimal value (int?)

2022-01-11T14:35:08.843000Z

The focus is on the readability, almost everyone can roll a (de)serialization code.

A library function which is already made and does everything right and aptly named is way better than something that would be copypasted all over the place and quickly gets messy.

Besides that, your code is broken on 16-bit processors. Yes, they still exist, run Codesys and continue to be deployed.

Extract 4 bytes from array of bytes to save in decimal value (int?)

2022-01-11T13:55:57.782000Z

Oh good catch! I didn't notice the system endianess. Typically, I would avoid adding additional libraries just to use a single function.

Let's get back to the basics where packing bytes is simply bit shifting. In this case, the output could be computed via (assuming receiving system is little endian):

dwOutput := SHL(Application.GVL_IO_LINK.Port1_inputs[4], 24) + SHL(Application.GVL_IO_LINK.Port1_inputs[3], 16) + SHL(Application.GVL_IO_LINK.Port1_inputs[2], 8) + Application.GVL_IO_LINK.Port1_inputs[1];

Bit shifting is the equivalent of multiplying by orders of 2 (e.g. shift left by 1 means multiply by 2).

Extract 4 bytes from array of bytes to save in decimal value (int?)

2022-01-07T15:10:23.976000Z

This works only if you have a big endian machine.
The easiest way would be using the dedicated functions from CAA Memory.

Extract 4 bytes from array of bytes to save in decimal value (int?)

2022-01-02T19:10:25.032000Z

@alberth007,

Probably the easiest and most efficient way is to use pointer. Just create a pointer to DWORD since it's 4 bytes. For example:

// create variable
pdwValue : POINTER TO DWORD;

// map variable to memory address
pdwValue := ADR(Application.GVL_IO_LINK.Port1_inputs);

// dereference pointer to get value and operate on it directly
IF (pdwValue^ > 500) THEN
    // do something
END_IF

// less efficient way would be to copy value to another variable
myValue := pdwValue^;

Extract 4 bytes from array of bytes to save in decimal value (int?)

2021-12-02T10:46:13.329000Z

Here you are: https://help.codesys.com/webapp/JMeheH6MvY4aZSJh5TgzrbLOrZE%2FPackBytesToDword;product=CAA%20Memory;version=3.5.17.0
It is just the Codesys WebHelp, you could have searched for PackBytesToDword.

Extract 4 bytes from array of bytes to save in decimal value (int?)

2021-11-29T17:51:47.652000Z

Hi, can you re-share the link. This one seems to be inactive at the moment.

Extract 4 bytes from array of bytes to save in decimal value (int?)

2021-04-26T06:00:59.238000Z

You should recheck your coefficients. Or just use the PackBytesToDWord function which is more explicative in source code.

Extract 4 bytes from array of bytes to save in decimal value (int?)

2021-04-24T22:50:17.032000Z

065536+04096+1*256+182=437

Extract 4 bytes from array of bytes to save in decimal value (int?)

2021-04-23T10:27:21.159000Z

Use CAA Memory PackBytesToDword function: https://help.codesys.com/webapp/s6roH8o4mLnj5nlRX9QvTFobNAo%2FPackBytesToDword;product=CAA_Memory;version=3.5.12.0
optionally followed by a DWORD_TO_DINT cast if you have a signed value in two's complement.

Also, INT is two bytes. You want DINT (4 bytes).

Extract 4 bytes from array of bytes to save in decimal value (int?)

2021-04-22T16:09:56.835000Z

Hello,

I have a question, maybe easy for you, but I cannot solve it and maybe you can help. I have a sensor that provides me the data in an array of 16 bytes. I need to take the 4 first bytes and save it in an INT value which is a distance value, so I have in the four first bytes [0,0,1,181,..] which is 437 mm that my sensor is displaying I need these 437 into a variable (INT I suppose). How can I do it easily?

Thanks for your help!

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