Differents records in Datalog File

Hello
In LV, how to create a dtalog file containing two (or more) differents
sequences of identically structured records?
I want to save in the same file 10 cluester (made of 1 string and 1
Boolean) and 3 double-precision reals.
Thanks.

Hi Zen,
I attach a LLB in which you find 2 vis to write and read DLG files,and relative sub-vis.
If you change the cluster structure, you must change it also in all sub-vis.
Good luck,
Alberto
Attachments:
datalog.zip ‏117 KB

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How to random write in to specific record in datalog file

lab view

patibandla wrote:
please go through Examples avilabe in the Help Menu.
Help<< Find Examples..
Forums is for new issues not for learing..
see the attachment ex:
Shame on you. This forum is dedicated to learning. What we don't (normally) do is provide ready-made code for people so people wander away from this forum with no better understanding of LabVIEW than when they came.
Besides, probably the user was asking how to do a random access write to a datalog file. Which I have no idea why you would do that - except to fudge data - which defeats the purpose of a log file - and could get you into legal trouble if the data is guaranteed to be untampered with.

Writing Datalog Files with record length

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Each I16 number in LabVIEW that you write uses 2 bytes because 8 bits equals 1 byte. If you write 128 numbers, the file will be 256 bytes long. You can modify the VI to write I32 (4 bytes) or I8 (1 byte) just by changing the representation of the number. You also need to change the subVI that does the actual writing (Write File+ [I16].vi). Be sure to rename the VIs that you change. I would think that your Fortran program would work as long as the data types match.

"Error 1 when trying to open and read datalog file from several subVi's

So, I've been coding up this model based controller and have hit a snag:
The program starts and opens a datalog file and passes the refnum to two loops.
At a regular time interval (every 2 minutes), one loop (that's iterating once per second) writes the current information to a datalog file.
Meanwhile, another loop (that's iterating continuously) checks to see if the file is big enough to support training of the model, if it is, then the training process begins. Once this happens a period of recent information is read from the file. Initially, this read would fail and return 0 data. However, this problem was fixed by passing in the data file path rather then the refnum and having the vi open,
read, and close the data file. With the path, the vi was able to read all the data. However, still in the same loop, another vi downstream tries to read the file and returns error code 1, and no data is read. I tried passing that vi the path and seeing if it made any difference to open, read and close the file. But even then the read failed (with error code 1).
I don't understand why it can read in one vi and not the other!
Does anyone know what is going on here? It seems that semaphores would probably solve the problem, but would prefer a simpler solution. Thank you very much.

Try passing the data to the continuous loop through a LV2-style global. That way you are only access the file in one place. But then that begs the question, if the data is passed internally, do you really need the file at all?
Mike...
Certified Professional Instructor
Certified LabVIEW Architect
LabVIEW Champion
"... after all, He's not a tame lion..."
Be thinking ahead and mark your dance card for NI Week 2015 now: TS 6139 - Object Oriented First Steps

How Do I Convert LV7.1 Datalog Files to LV8 Format?

I have several LabVIEW 7.1 datalog files that generate Error 71 (File data type conflict) when I try to open them in LabVIEW 8 using the new Open/Create/Replace Datalog vi with my original typedef constants wired to the record type terminal. Likewise, my original LV7.1 code recompiled in LV8 often generates error 116 (unflatten or byte stream read operation failed due to corrupt, unexpected, or truncated data) or error 4 (end of file encountered) when randomly accessing records in the LV7 datalog files, presumably due to changes made to the datalog file structure in LV8. I recall one time when a dialog box popped up asking if I would like to convert the file to LV8 format. Since this was a file currently in use on the server by LV7.1 clients, I had to reply no. With copies of the datalog files now on my hard drive ready for conversion, I haven't seen the conversion dialog box pop up again.
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Thanks,
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Good afternoon Larry,
Thanks for posting!
The Datalog file support in LabVIEW has changed, but the underlying
principles of the technology remains the same.
Converting to the new format should just involve converting a few VIs to the new Datalog-specific versions. As you can see, the new Datalog VIs appear in
their own sub palette in 8 which will help keep things simple.
Before we address the concerns with the errors, let’s first
make sure that the code has been properly converted.
To convert your VI to the new format:
1)      Replace
the Open File VI from LabVIEW 7 with an “Open/Create/Replace Datalog” VI in LabVIEW
8. Keep your type constant or control
wired to the “Datalog Type” input.
2)      Replace
any “Write File” VIs in LabVIEW 7 with “Write
Datalog” and triple check that your data matches the datatype wired into the
open exactly.
3)      Replace
any “Seek” VIs with “Set Datalog Position”. The input to this VI is the number of records
to advance (check the mode set by the “from” parameter).
4)      Replace
any Reading VIs with the corresponding “Read Datalog” VI.
I suspect that if you are receiving errors saying that the
end of file has been encountered it is a result of a bad input to the “set Datalog
position” VI. I attached a basic example
of writing a Datalog file in LabVIEW 8, and reading the results. The rest of the functions in the new Datalog palette
should be pretty straightforward.
Does this help? I
would be more than happy to answer any other questions on this if you need any
additional clarification, or if this response does not address your question.
Travis M
LabVIEW R&D
National Instruments
Attachments:
Datalog8.zip ‏30 KB

How can I deny write access to datalog files for all but one process in LV8?

In LabVIEW 7.1, wiring the deny mode terminal of Open File.vi with a Deny Write Only enum constant was an effective means for ensuring that only one process could write to a datalog file at a time. In LabVIEW 8.0, Open File.vi is no longer available and the new Open/Create/Replace Datalog vi does not provide a deny mode terminal. Also, the new Deny Access vi does not support datalog files. Furthermore, the Set Permissions vi is an unsatisfactory solution because under the Windows operating system, it simply sets the Read Only file attribute. This is inadequate because I have demonstrated that it is still possible for two processes to open a datalog file with read/write access before either one has had a chance to set the Read Only file attribute in order to lock out the file. If a process sets the Read Only file attribute first, then it can't open the file with read/write access for itself.
Does anyone understand the file mechanism by which deny mode used to work with the old Open File.vi? I wish to restore the functionality I had in LV 7.1 in my LV 8 programs.
Thanks!
Larry

Larry Stanos wrote:
I appreciate the
empathy from Rolf, but I'm hoping that someone may have written one or
more vi's containing CINs that call Windows 2000/XP file access control
library routines. At least I'm assuming that is how the deny mode
input to Open File.vi used to work in LV7.1. The Microsoft
Developers Network on-line documentation on Access Control http://msdn.microsoft.com/library/default.asp?url=/library/en-us/secauthz/security/access_control.as... is
daunting to put it mildly. But even if a set of CINs has not
already been coded, perhaps someone could point me to the specific set
of calls I need to make to absolutely guarantee that no two
clients can simultaneously open the same file with write privileges. Unfortunately
the elimination of deny mode functionality for datalog files in
LV8 has sabotaged my commitment to a March 1 release date because it
would also be impractical to convert everything back to LV7.1 at
this point. Sincere thanks to anyone who can help me out here!
Unfortunately
the functionality you mention does not work in the way the deny mode in
the LabVIEW nodes works. Basically that deny mode is converted to an
according FILE_SHARE_READ/FILE_SHARE_WRITE value and passed to the
Win32 API CreateFile function. This is more or less the only place
where you can define a global share (or deny) access to a file. That is
also why the Deny Access node online help is talking about that the
file is reopened.
But I just retried what you had tried to do, and low and behold it
works with wiring a datalog refnum to Deny Access. What is important
here however is that you do need to wire a datatype to the record type
input of the Open/Create/Replace Datalog node. Otherwise you can't
connect the resulting datalog refnum to any other file function, since
it is an incomplete datatype.
Rolf Kalbermatter
Rolf Kalbermatter
CIT Engineering Netherlands
a division of Test & Measurement Solutions

A programme that will extract particular records from a file

Let's assume that there is a text file containing arround 50 records in the following format:
ABCDEFGH:AB:12345:-09876:567:876
The file to be read by the programme consist of a sequence of records each of which is split into fields using separator characters just like as we have in the Unix. The command line arguments should be given to execute the programme
The most important part of the programme is that the condition for extracting a particular record from that file will be that specified fields shall contain a particular string of characters.
The command line arguments to be given are:
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-<num> This flag introduces a match requirement for field "num". Fields are numbered starting at 1. This flag may be followed by further flags and then by the string to look for.
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-d A differ match. A match is recorded even if the two strings differ by one letter. For example: "gest and rest" will be recorded as a match.
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And your question is??

Same data wire (source and sink are listed as "datalog file reference of") will not connect

I am trying to write a short program that will convert a string spreadsheet file into a datalog file with the numbers turned back into numbers. I have a case structure for each type of spreadsheet (different types per columns and different number of columns). I use a 'for loop' to process all records (rows). And I use a 'sequence structure' to individually process each column item into its original format (string or number), then group together into a bundle and then write the results to the datalog file format.
The first two (case structures) worked but the second pair of case structures would not allow me to connect the datalog file reference number from the 'write to datalog file' to the 'close datalog file' through the 'for loop' wall.
I am using 8.2
I am sure it is an stupid issue, but the error message just did not point me towards a solution.
con-fUsed, DogFace.
Attachments:
PROCESS SH TO DLOG.vi ‏84 KB

The problem is that you are creating a different type of datalog file in cases 2 and 3 than you are in cases 0 and 1.
The structure of a datalog file is the same as an array of clusters. All of the clusters must be of the same structure. Only the values of the individual cluster elements can vary.
You are trying to write three different cluster structures to a single datalog file. You just can't this.
You'll either need to write to three different files, or come up with a structure that everything will fit into.
One other quick hint. NEVER use a variable to pass data when you can wire the terminal directly to the function.
Ed
Message Edited by Ed Dickens on 03-19-2007 11:39 AM
Ed Dickens - Certified LabVIEW Architect - DISTek Integration, Inc. - NI Certified Alliance Partner
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.

How can you read datalog files in LabVIEW?

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Hi,
when you read from a datalog file you have to wire to the datalog type input of the Open File function a cluster of the same type as the clusters when you created the file; each cluster is a record.
In the example Write Datalog File Example.vi you see that each record consists of a cluster containing a string and 1D array of DBL; in the Read Datalog File Example.vi a cluster of exactly the same type is wired to the datalog type inputs.
You can use this example to read your datalog files but you must wire to the datalog type input a cluster containing the time data and a waveform data; pratically you have to tell how the data are saved in your file.
I hope I have been clear enough, eventually if you tell me how you save the time data (string, numeric) I
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Alberto

Opening my datalog file errors out with error 42 generic error

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Certified LabVIEW Embedded Systems Developer
Endigit

Greetings FlamingYawn!
I apologize for the trouble you're having opening some of your saved datalog files. Unfortunately, as you have already mentioned, Error 42 is a general error and as such, provides us with little information that we can use in troubleshooting the issue. From all the research I have done, it seems that the two most common causes of this type of problem are from a logic error in the writing section of the code or from the files being corrupted by some other means during the write (i.e., from bad sectors on a hard disk). Unfortunately, the file type is a proprietary binary format and the structure is not publicly known. We currently do not have any tools for use in reading these files outside of LabVIEW. This is not necessarily to prevent the files from being read by other software but simply because it is a file type that was designed specifically for LabVIEW. The best information I can provide you with is related to the file header. This can be found in the following KnowledgeBase article:
LabVIEW Data Logger: Binary Header File Format
http://digital.ni.com/public.nsf/allkb/747B83B6C8E4A6218625669100563B61
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Best Regards,
Michael G
Michael G.
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National Instruments
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Hi,
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Hello,
Thanks for answering my question. I downloaded LV6.02 as you suggested but the problem persists.
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Attachments:
WriteLV5.vi ‏65 KB
OpenLV5.vi ‏74 KB
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Hi SapAll.
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> segment 3-occurs for 3 times so here PI Need to create a file with 3 records as segment 3 repeats for 3 times, here segment 1 and segment 2 field values repeats for all the 3 records int the file and segment 3 fields values will have to be mapped respectively for each record of all the 3 records from each segment 3.
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Differents records in Datalog File

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