How to define "byte stream type" for "open file"?

[FElicia]

Hello,

I created some numbers (type "double") in Matlab and stored in a file. What value should I use to specify the "byte stream type" for "open file" in Labview? Should I put something like "DBL" or "I32". I don't know where to find the list of legal "types" in Labiew help.

Thanks so much!

Felicia

[altenbach]

You would create a diagram constant of the desired type and wire it to the type input of "read binary file". If you don't get a broken wire, it's legal. :D
Since you wrote DBL data, you would read it as DBL. Most likely, you need to also specify little endian.
Can you attach a small sample file and tell us what kind of data you expect?
What is your LabVIEW version? I don't see any "bytestream type" input. If your version is ancient, you might not even have the byte order input.

[smercurio_fc]

Looks like 7.1:<img src="Loading Image..."> The Matlab "double" is 64 bits (8 bytes). It doesn't make much sense to use an integer datatype to read a floating point value, so you would use DBL in LabVIEW. The numeric data types table can be found <a href="http://zone.ni.com/reference/en-XX/help/lv/71/lvhelp/Numeric_Data_Types_Table/" target="_blank">here</a>. By the way, this assumes you saved the file as raw binary, as opposed to a .mat file, which is something different. Message Edited by smercurio_fc on 08-08-2008 11:21 AM


read file 7.png:
http://forums.ni.com/attachments/ni/170/347924/1/read file 7.png

[FElicia]

Thank both of you!


I'm using Labview 6.1 base "Read File", just like the picture above. I've specified the byte stream type as DBL; however, the output is an array of string. What should I do with the string? I've tried to use "Decimal String To Number" but I got an output of "0".


I've also tried the "Read From SGL File" in Labivew and specified type "single" in Matlab, the output numbers were extremely large and wrong.

[altenbach]

Read the entire file as a plain string. No need to specify byte stream and such.
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Now simply typecast it to an array of DBL. Most likely, you need to convert to little endian, meaning you need to swap some bytes.
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[smercurio_fc]

I no longer have 6.1, but you can try to do the following:<img src="Loading Image..."> I did this in 7.1 with a file generated by Matlab and the file was read correctly, but I didn't do a whole lot of testing with it, so you have been forewarned.:smileywink:Message Edited by smercurio_fc on 08-08-2008 02:20 PM


read matlab dbl file.png:
http://forums.ni.com/attachments/ni/170/347960/1/read matlab dbl file.png

[FElicia]

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[altenbach]

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[smercurio_fc]

There is an array constant in the Array palette. Place it on the block diagram and then place whatever you need inside the container. For a DBL array place a numeric constant in there, and then right-click on the array element and set the representation to DBL.