Open and write into TXT File

bododonath · August 2020

Hi Team,

We have the controller AXC F 1152 with a little program.

Now we want to write a little error log into a text file.

I need some help how I can write the code therefore.

Maybe someone was creating something like this before and can give some tipps.

Thanks & BR

Bodo

Martin PLCnext Team · August 2020

Hi Bodo,

Here is an example of how to write text to a file in in PLCnext Engineer.

https://www.plcnext-community.net/en/discussions-2-offcanvas/example-for-saving-data-in-a-file.html

The example uses Structured Text, but you can use the same FBs in other IEC 61131 languages, if you want.

Hope this helps.

~ Martin.

bododonath · August 2020

Hi Martin,

what a great and very fast solution.

I've tried the code and it works fine.

I have an other question. It is possible to write the file on a local PC System or maybe on file server?

BR

Bodo

Martin PLCnext Team · August 2020

Hi Bodo,

I don't think there is a standard solution to this problem from PLCnext Engineer on its own, but this could probably be achieved using standard Linux utilities.

Possibilites include:

Using rsync to copy the contents of local file(s) to a remote machine.
Using syslog-ng for decentralised system logging.
Using a cloud service to log messages (via MQTT, for example).
Looking for solutions from vendors in the PLCnext Store.

You should be able to try most options on a standard Linux system, and once you have a solution working the way you want, you can try porting that solution to the PLCnext Control.

Hope this helps.

~ Martin.

bododonath · August 2020

Hi Martin,

Thanks again for your support.

I have a last question fot this topic.

How can collect a String ('hello World') with the actual date?

Do you have an idea.

BR

Andy

Martin PLCnext Team · August 2020

Hi Andy,

There is a function block called "RTC_S" that retrieves the current date and time as a string.

~ Martin.

bododonath · September 2020

Hi Martin,

I have a last question (hope so).

In your example : https://www.plcnext-community.net/en/discussions-2-offcanvas/example-for-saving-data-in-a-file.html

I work with a ByteArray35 and if I understand right, that means no more characters like 34.

Now I need the oppertunity for more characters - is this possible?

Thanks

Andy

Martin PLCnext Team · September 2020

Hi Andy,

I only used ByteArray35 in that example because that was already a defined data type in PLCnext Engineer. But you can use a byte array of any length. To do that:

In a DataType worksheet, create a new data type as a byte array of any fixed length (the declaration templates - accessible using right-click - are handy for this).
In your program, declare a variable of that type, instead of type ByteArray35.

Hope this helps.

~ Martin.

bododonath · September 2020

Hi Martin,

sounds good, but I need more help.

Did you have a short example for me?

Thanks a lot for your support.

BR
Andy

Martin PLCnext Team · September 2020

Hi Andy,

Hope this helps.

(video has no sound)

Note that the array actually contains 421 elements (0 to 420), so I could have called it ByteArray421, or else declared the array bounds as either [0 .. 419] or [1 .. 420].

~ Martin.

bododonath · September 2020

Hi Martin,

That's great - it works fine. ?

Thank you so much for your help.

BR
Andy

jacob · November 2021

Hi Martin,

Can I get that sample code? I want to do test with PLCnext 2152. Thank you,

Jacob

Martin PLCnext Team · November 2021

Hi Jacob, unfortunately this new forum has broken all the links to old threads, and deleted all the attachments on those old threads.
For the record, here is the new link to the old thread mentioned above:
https://www.plcnext-community.net/forum/#/discussion/1446/example-for-saving-data-in-a-file
... but of course since the attachments are gone, that doesn't help.
On Monday I will see if the site admins can restore the old attachments, otherwise I will try to recreate the example.

Martin PLCnext Team · November 2021

OK, the admins are looking at the option of restoring images in old forum posts.

Here are the details of the earlier example, which writes a string to a text file on the PLC's file system:

Program variables:

// Name         Type
FILE_OPEN1      FILE_OPEN
STRING_TO_BUF1  STRING_TO_BUF
FILE_WRITE1     FILE_WRITE
FILE_CLOSE1     FILE_CLOSE
OpenCommand     BOOL
CreateByteArray BOOL
WriteCommand    BOOL
CloseCommand    BOOL
FileHandle      UINT
StringToWrite   STRING
NumChars        INT
CharsToWrite    ByteArray35

Program code:

// Here is the string we will write to file.
StringToWrite := 'hello world';
NumChars := LEN(StringToWrite);

// Go online, open this program instance and 
// set OpenCommand to TRUE.
// This will open the file.
FILE_OPEN1(
  Execute := OpenCommand,
  Name := '/opt/plcnext/my-file.txt',
  Done => CreateByteArray,  // Immediately create the byte array when the OPEN command is finished.
  Handle => FileHandle      // We need the file handle for other operations on this file.
);

// Convert the string to an array of bytes
STRING_TO_BUF1(
  REQ := CreateByteArray,
  BUF_CNT := NumChars,
  DONE => WriteCommand,  // Immediately set WriteCommand when the buffer is ready.
  SRC := StringToWrite,
  BUFFER := CharsToWrite
);

// Add CR LF to the end of the string, just for the craic.
CharsToWrite[NumChars] := BYTE#16#D;    // CR = 0x0D
CharsToWrite[NumChars+1] := BYTE#16#A;  // LF = 0x0A

// Write the array of bytes to file
FILE_WRITE1(
  Execute := WriteCommand,
  Handle := FileHandle,
  Done => CloseCommand,   // Immediately set CloseCommand when the file write is finished.
  Buffer := CharsToWrite,
  Length := NumChars + 2  // Remember CR LF !
);

// Close the file
FILE_CLOSE1(
  Execute := CloseCommand,
  Handle := FileHandle
);

// Now use ssh (or PuTTY) to check that the file has been created, and that it contains the expected text.

jacob · November 2021

Hi Martin,
I found "Data Logger" library on PLCnext store and it's working well. Also I tested the example code. Thank you,

Jacob

Martin PLCnext Team · November 2021

Great, thanks for the feedback.
If you're interested in the Datalogger library, you might also want to look at:
- Simple Logger, which (as the name suggests) is a simpler version of the DataLogger library.
- The built-in DataLogger, which stores data in a SQLite database rather than a text file.

These are each useful for different scenarios, so hopefully one suits your project.
-

rookie · December 2022

https://forum.plcnext-community.net/discussion/comment/9795#Comment_9795

How can i test the programm with putty? what is the needed configuration?

Thank you.

rnsas · March 2023

https://forum.plcnext-community.net/discussion/comment/6379#Comment_6379

file path '/opt/plcnext/my-file.txt'  can be changed or not?

Martin PLCnext Team · March 2023

https://forum.plcnext-community.net/discussion/comment/11614#Comment_11614

Yes, the NAME parameter on the FILE_OPEN function block takes a STRING as a parameter, and this can be a literal or a variable.

Martin PLCnext Team · March 2023

https://forum.plcnext-community.net/discussion/comment/11383#Comment_11383

(better late than never?)

In the window shown in the screen shot, just enter the IP address of the PLC, and press the "Open" button. It should ask for the username and password, which are the same as the ones you used to send the PLCnext Engineer project to the PLC.

kurt.klingbeil · March 2023

so ByteArray35 is a specific arbitrarily pre-defined array ?

I haven't yet figured out how to declare arrays in general such as INT(2) WORD(5) etc...

Does one require a secret incantation ? ;-)

Is it correct to assume that a STRING is a byte array with the first element containing the string length ?

I believe BASIC strings are like this

And when the STRING_TO_BUF is executed, is the result a null-terminated "unix" string ?

or an open-ended byte-array which requires the length to be specified in an external variable ?

kurt.klingbeil · March 2023

Oh... I meant to also inquire about the mechanism of multiple sequential file writes...

On the other platform I am familiar with, the actual WRITE command must be always executed

and an ENABLE boolean controls the actual operation...

To write multiple files sequentially, one had to one had to monitor the status of the currently active

write command, and when it had completed, then disable that write command and enable the next one

and sequentiallly propagate the enables while checking the statuses

Is there an equivalent paradigm here ?

One must create one write "package"/program for each filename and then juggle the enables ?

dwi · January 30

Hello Martin,

I also tested your code, and it worked. However, I need to write multiple strings to the file for my application. Unfortunately, this hasn't worked as expected—only the first string is being written to the file.

Here is the code I have so far. The StringsToSave[] array is already populated beforehand:

// Datei öffnen

FILE_OPEN(

Execute := OpenCommand,

Name := '/opt/plcnext/my-file.txt', // Pfad zur Datei

Done => str_to_buf,

Handle => FileHandle);

// Strings in einer Schleife schreiben

FOR i := 1 TO NumStrings DO

// Länge des Strings ermitteln

NumChars := LEN(StringsToSave[i]);

// String in den Puffer umwandeln

STRING_TO_BUF(

REQ := str_to_buf,

SRC := StringsToSave[i],

BUF_CNT := NumChars,

DONE => WriteCommand,

BUFFER := CharsToWrite);

// CRLF hinzufügen

CharsToWrite[NumChars] := 16#0D; // CR

CharsToWrite[NumChars + 1] := 16#0A; // LF

// In die Datei schreiben

FILE_WRITE(

Execute := WriteCommand,

Handle := FileHandle,

Buffer := CharsToWrite,

Done => write_done,

Length := NumChars + 2); // Stringlänge + CRLF

END_FOR

// Datei schliessen

FILE_CLOSE(

Execute := CloseCommand,

Handle := FileHandle,

Done => file_closed);

Tim Phoenix Contact Deutschland Support · January 30

Hello dwi,

please try to combine the strings of the array with CONCAT blocks into one.

The write commands may be sent faster than the Linux system can / may react.

dwi · January 31

Hello Tim,

Thanks for your quick reply!

I tried it with the concat block and it worked.

Thank you very much for your help!

David

Open and write into TXT File

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