binary file

[michael bsc]

hi

i write in labview to binary file the data is double i suppose the default mode is without any headers i have succed to read it back in labview

the problem is that i cant read the file from other places

in matlab i recieve garbage

fid = fopen(filename,'bin')

data = fread(fid,....)

fclose(fid)

[EdDickens]

The binary data that LabVIEW writes is going to be readable only by LabVIEW because there is no "standard" binary file format. Each application that can handle binary files has it's own method of creating the file format.

If you want the data to be available to read in other applications, you should save it as an ASCII (text) file. Most applications can read an ASCII file is some standard format like comma separated values or tab delimited files.

If writing speed is an issue, try first writting the files as binary, then convert them to ASCII when needed.

Ed

[altenbach]

Many application CAN read plain binary data if you tell them the binary format and data type. One complication under Windows is the fact that LabVIEW writes big-endian binary format, while most other W32 programs are little-endian. You need to reverse the bytes in each DBL.

Unfortunately my matlab knowledge is limited, but you should be able to read it with the right commands. Good luck! 🙂

[alipio]

Hello
You should have no problem to read labview binary files in Matlab. Matlab "bin" is little endian , but you can instruct it to read big endian,

Just try the options for fread.

Cheers
Alipio

[Chris Reyerson]

Yes, the problem is most likely with the endian, LabView was developed for the Mac, as such it reads big endian (or little endian, i get them mixed up), and Intel machines are the opposite (or course).  I have had this problem repeatedly.  I have written a small program which will correct the endian, I have attached it.  You will have to put this endian swap program inside a for loop and swap every single word.

You can rewite the program for signed intergers and floats too. 

Please let me know if this works for you.

Chris

[GTPUMA]

Thanks for this post, I was trying to import data into matlab and was getting garbage, turns out it was the endianness. Here's what I used in matlab to read an array of double that I wrote using the 'write to binary file' VI.

example for a 1D array of 5 elements of double type

fid = fopen('c:\test.dat','r','b');

f = fread(fid, [5],'double',0,'b')

it's the 'b' parameter that specifies to read the file as big endian

Thanks!