HELP! LabView: Calculating Time of a process in nanoseconds

[ACiDuser]

Hello Developers! I have PCI-express board and VI based on CIN which reads data from board memory. I need to calculate data transfer speed, so I decided to calculate Time-1 for the first byte that is passed into Labview array, and Time-2 for the last byte. In nanoseconds, cause transfer speed is rather hight, then get difference and calculate Transfer speed MB/s. Is there any methods how to do this in LabView? Thank you in advance!

[Hillary_C_E]

Hi ACiDuser,

I think what you're looking for is the Get Date/Time in Seconds VI. This is in the Functions Palette»Programming»Timing Palette. You can use it to get the current time. You might also want to consider the Elapsed Time Express VI that is located in the same palette.

[ACiDuser]

In seconds or miliseconds - not enough. I need measure time in microseconds or better with nanosecond precision. Is it possible to do in LV ?

[parthabe]

I dont think so. It is neither impossible for LV nor for the OS? What is your OS?

You should use LV RT, I think...

[mishklyar]

Hello ACiDuser,from my experience about similar issue:

    We used the next sequence: Generate signal-Record Signal-Generate again,and measured at the scope the

time between two generations.If you are using Windows,the time interval may vary very rapidly,it may be microseconds,

and rarely even miliseconds.

[ACiDuser]

My OS is Ubuntu Linux Kernel-2.6, I use LabView 7.1 Real-Time

[Hillary_C_E]

Hello,

What PCIX board do you have? The transfer rate is a property of the board. However, I think you are limited to milliseconds. You could of course convert to nanoseconds. Have you tried using the suggestions above? Is your transfer fast enough that you really need nanoseconds?

[TWGomez]

Agreed. Anything below milliseconds in todays OS's is a calculation to get you there and not actual timing.

[ACiDuser]

So.. I Have Altera development board Stratix II GX and I do read and write data through PCIe x8, so It seems that transfer speed should be great, but I need actualy measure it. As I understood for measuring time in nanoseconds I can only use OS specific functions?

[Hillary_C_E]

Hi ACDuser,

So, you can't measure or regulate the hardware timing of the PCIe bus from LabVIEW. There are limitations of the PCIe x8 bus (around 1 GB/sec). You might want to contact Altera about the capabilites of their board with regards to transfer speed.