Why are some 1394 Camera Attributes Writable in MAX yet Enumerate in LabVIEW Vision as unwritable

[MGould]

I know this board sees its fair share of camera attribute setting questions but hopefully this one is different enough to warrent some discussion.

I am in the middle of porting a piece of code that used to use IMAQ Legacy 1394 to IMAQdX since NI decided to drop the unique 1394 support.  I have run into an interesting problem.  When working with a DCAM 1.3 complient camera (Prosilica E1360C, firewire)  I am finding that is possible to set the gain in MAX manually, yet when you enumerate the camera attributes in LabVIEW using the Enumerate Attributes.vi,  CameraAttributes::Gain::Value comes up as not writable.  How is NI MAX getting around this?  I've tried writing the gain register using the writing the gain register manualy by referencing the DCAM 1.3 Spec document and then using the Write Register.vi but I've had no luck.  The same was true when just trying to write the CameraAttributes::Gain::Value using the write attribute property node.

Does anyone have a suggestion? 

[A_Person]

From your description it sounds like you're viewing the boolean output in the Attribute Information Array off of the Enumerate Attributes function, is this correct?

Although I would expect this to work, can you try the Grab and Attributes Setup example program in LabVIEW (under Hardware Input and Output»IMAQdx»High-Level)?  Its operation is basically the same as what you are doing but does have some differences like the use of property nodes.  I just want to verify that you see consistent results with the different programs.

Please try this and let us know if you have any further information.

[BlueCheese · Accepted solution]

Hi MGould,

Have you checked that the Mode of the attribute in question is set to the appropriate setting first? I believe the Value attributes will be read-only if the mode of the associated feature is set to Auto, OnePush, or Ignored.

Eric

[MGould]

Well, using the example recommended above I can set the gain programatically.  I'll have to delve into what the difference between my code and the example is.

[MGould]

This was correct.  I needed to set the mode first.  I thought I was doing that but on inspection of my code I realized I had messed that portion of it up.  Thanks everyone.  A Person, that example VI was very helpfull to see what I was doing wrong.