vestman

I still haven't found a way to read/write Single-Process Variables except putting a Shared Variable structure on the block diagram. Is this really the only possible way?

Hi

Is it possible to access a Single-Process Shared Variable using DataSocket?

When I try it DataSocketOpen throws Error 1184 (Path not found, FTP login incorrect, or no FTP write permission.)

If I change the variable to Network-Published it works fine.

/Emil

Thank you for your replies.

I understand that SV might not be the fastest way to communicate but the giant time increase still puzzles me.

Earlier tests have shown that both read and write operations take virtually no time at all so having to wait that long for the data to arrive is just frustrating.

I also made an .exe of my test-VI and saw no positive change at all.

The intended use is to monitor data from a compactRIO 9012 on a PC.

Unfortunately the use of Shared Variables is not longer optional. Padding the data might be a solution although not the prettiest.

Our original goal was to detect data changes on the cRIO within 10ms on the PC but this might have to be revised.

Thanks

Hi,

I am trying to achieve as high speed as possible when sending data over the network using shared variables.

I have created a small test application as seen below.

The test sequence consists of writing an array of I32 to a shared variable (so far located on my local machine) and then measure the time it takes before the same array can be read back from the variable.

When I run tests I observe a behavior related to the size of the array. When writing an array larger than 2033 elements the average read+write time is around 0.8ms but when using a smaller array this time increases to a whopping 31ms.

This behavior must be related to the built-in transmit buffer which holds 8kB, but why is the difference over 30ms? If the buffer isn't full the data should still be sent within 10ms? there has to be some additional delay related to smaller amounts of data?

In my project the data will rarely fill the buffer and I do not have access to the Flush.vi of LV 8.5.1.

Is there another way to speed up the transfer?

Thank you. I was afraid that would be the case.

Do you know if there are limitations when creating Express VIs for the FPGA-palette?

hi

I'm building a set of FPGA subVIs for use in our future cRIO applications. The subVIs will be of type "8 channel DO", "8 channel DI", "8 channel PWM" et.c, with an array as input.

I want the user to be able to place a subVI on the block diagram, connect an input, open the front panel of the subVI and select which 8 channels to use (from an I/O name control).

This is not a problem to implement, but what about using multiple instances of the same VI? All subVIs point to the same file and hence changes to one equals changes to all.

Is there a way around this, to be able to save changes made to every subVI placed on the block diagram independently?

/Emil

Thanks! Don't know how I missed that one.

Hi,

I am trying to create a number of Shared Variables programmatically. My plan is to read a configuration file and create the number of variables needed.

I understand (from the excellent Shared Variable FAQ) that this is possible "with a VI server interface to the LabVIEW project".

I have found a method called AddItem that requires "Name", "Path" and "Type" inputs. Is this the method to use and if so, how do I specify path and type? The documentation on this topic is really non-existent.

/Emil