The string function LEN returns the current # of characters in the string.

Are you peeking into a string's bytes rather than looping through the characters within the string from 0 to LEN(your string) - 1?

Where are your string values getting assigned?

PEEK is not appropriate for working with string data within the PLC.  PEEK/POKE _can_ be useful when dealing with imported / exported data outside the PLC to a non-Siemens device.  However, there are instructions that convert between packed array of characters and siemens strings automatically - without requiring peek/poke.

MRCordova

Thanks for your Answer, the thing is i dont know the lenght of the string i will read, the only thing i know i will have at least fixed lenght of 16 (string[16]), but the string in there will be dynamic, so for example some times the value of that string will be= 'Test 1' and some times will be='This is a Test', so  since im reading that with peek instruction with a For loop instruction (char by char) i really dont know the lenght.

But thinking a little more, maybe i can just fix the times the for loop will iterare reading first the first 2 bytes and knowing the real lenght of the string, will test it, and let you know.

Use the string to char array and char array to string instructions to convert between external (AB/CIP and JSON) and internal (Siemens S7) "string" data structures.

No need to use peek/poke which is very inefficient way to mess around, and very low-level code.

Use higher level code and use what's built into the PLC to save you work and make the code more future proof.

MRCordova

Yes im reading other Allen Bradlley tags via CIP communication, and some of them are strings. and then i send them to an movile app, where i structure a JSON file on my PLC, so im working a lot with strings, and almost all  are dynamic, and we wanted to make the program reusable, so we are doing dynamic Addressing. 

Basically we need to use PEEK and POKE to have dynamic adressing.