Siemens S7-1200 and Weintek HMI String display problem

Hello tedpan,

you have to consider byte 2 of the string tag. That is indicating the length of the current string.

In case of 'ABC':

- first byte: 8 (total length)

- second byte: 3

- bytes 3-5: ABC

- bytes 6-8: $00 (empty)

Regards,

Frink

tedpan

The workaround works as Cookie_M0nster suggested.

To further test this, I created an ASCII object in EBPro, allow input, and created MyData variable, data type String[8] in Siemens.

Strange things happen after I typed in 'ABCD' (without quotes)

MyData contains 'ABCD$00$00$00$00' (without quotes)

If I type 'ABC'

MyData contains 'ABC$00$00$00$00$00' (without quotes)

I contacted Weintek and this is their response:

"Hi,

In the early days, we had a mechanism to add zeros to the back of String, but later found that it would cause some additional problems.
We tend not to change the data content in the driver, so this is the current phenomenon for String behavior.

In the future, the need to judge the end character of ASCII objects will be added.
At present, it may still need to be processed by the alternative method of manually filling in 0.

Best Regards,"

Well I don't want the additional $00 added. I will update when I get a reply.

Prof. Frink posted an appropriate response. Do you know that STRING[8] actually has a memory footprint of 10 bytes? The first byte represent the capacity (8 in this case). The second byte is the occupied length (3 when the string contains 'ABC').

That is what makes STRING[8] and Array [1..8] of Char different. What does the HMI actually handle? You need to test this with a tag stored in not optimized memory so that all the bytes can be checked. That will point to the direction you need to go.

Might I suggest a string update FC that accepts the string to be changed as an InOut, the new text to assign as an IN.  Inside, it fills the InOut string with ' ' using string fill command, then assigns the input text to the string.  At the exit of the FC, the InOut string does exactly what you want every time.

If you use an array of char, it's easier to first convert to a string, then pass through the above FC, then convert to array of char.  Portal offers instructions for all these tasks, so it should be very efficient.

Guillaume Monnot

Greettings Everyone !

I had the same issue with a weintek screen cMT2158X to display strings. (it display it well, but the olders last(s) char of the previous string was still display if the new string was shorter than the previous one on the same ASCII object on weintek Easybuilder pro.

It didn't work for me even with array of char in TIA, and tried all configurations in Weintek screen of Unicode...

So I did it this way, which works with strings, not the best, but it works ! :

Define a string[20] for example, and then measure his lenght. (For me my input was from an real time SQL data base, let's say string[20]:="Example' and then I just replace with the replace function all last char which are empty to the rest of the string with a space char ' ' with a for loop, so the string[20] will change and be ('Example            ')

And then no more problem in Weintek screen to display it.

for i:=LEN(IN:=Mystring) TO 20 DO

Mystring:=REPLACE(IN1:=Mystring, IN2:=' ', L:=1, P:=#i+1);

END FOR;

I do this loop only when I got a new input on my screen from my ERP.

Hope it can help someone.

Have a good day