CODEWITHSUNDEEP
rs485st
Toxic Me
Toxic Me

Reputation: 11

Separating out frames from Serial Communication Data using STL

There is a keyboard which is connected to PLC controller. The keyboard is sending frames to the controller.

Below is the frame send by Keyboard.

$ 200103001<000000008000000000000000000009$ 3$ 200103001<000000008000000000000000000009$ 3$ 200103001<000000008000000000000000000009$ 3$ 200103001<000000008000000000000000000009$ 3$ 200103001<000000008000000000000000000009$ 3$ 200103001<000000008000000000000000000009$ 3$ 200100?1$ 3

The single frame is structured with STX (02) and then useful data and then ETX(03). In above frame, you can see STX as $2 and ETX as $3.

What does '$' sign represents here?

I am trying to use Structured Text IEC programming language. How to extract the data in between $2 and $3?

Btw, the received frame is saved as STRING(255).

I tried using FIND function to locate STX and ETX position. However, because of $ sign, it is not finding STX and ETX.

FIND (StringWhereDataIsSaved, '$3') -> Does not work

FIND (StringWhereDataIsSaved, '03') -> Would find 03 in the data section of frame instead of the ETX

FIND (StringWhereDataIsSaved, '3') -> Would find 3 in the data section of frame instead of the ETX.

Upvotes: 1

Views: 23

Answers (1)

kolyur
kolyur

Reputation: 514

Look at the received data in a text editor that allows you to see hidden characters, such as Notepad++. There is something in between the $ and the digit, looks to be a space but could be something else such as carriage return. Revise your FIND command to search for the correct string and it should work.

Upvotes: 0

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