EPWR Error

[JBredeson]

I have a simple CVI app that has been running for years on various GPIB devices. I recently added it to a couple of new machines and now I get an EPWR error message after the program runs for a couple of minutes. It occurs only on the machines with the new installation. All of the machines are XP using GPIB-USB-HS interfaces. The app was rebuilt using CVI 8.0.1, but I did install the August 2007 version of LabView.

[A_Ryan]

JBredeson,

A couple of items to consider for this specific issue: it could be the USB bus is losing power or your computer is going into sleep mode.  I know you mention that the program only runs for a couple of minutes, but here are a couple of links to consider.  GPIB Error Codes and Common Solutions, and VISA Drivers and Updates

I have some additional questions for you:
1.  What version of the VISA driver do you have?
2.  Have you tried the GPIB-USB-HS in a different USB port?
3.  What are the differences between the computers that work and those that don't?
4.  Does this error happen in the same section of code?
5.  Next time your run the code, please use NI-SPY to capture what commands are being sent/received?

[JBredeson]

The VISA version is 4.2.

This problem occurs on multiple computers and only started after the source code was recompiled with LabWindows 8.1.1.

The problem is now universal across all machines that had the recompiled software installed. All are XP Professional.

The problem occurs in the same section of code. This is what happens in the code

Delay(.05)

ibrsp                                //generates the data read

ibrd                                  //read the data

process the data and display. This is just an infinite loop until the operator tells it to stop. It will operate for 4 minutes to 5 hours seemingly at random. The NI-SPY will show successful operations and suddenly, the EPWR error will occur and will continue to occur from that point on.

[Song_M]

Hey Jbredeson!

The first thing I would recommend is to install the latest version of the 488.2 and VISA drivers:

They can be found here

488.2

http://joule.ni.com/nidu/cds/view/p/id/335/lang/en

Visa

http://joule.ni.com/nidu/cds/view/p/id/1070/lang/en

Aaron was correct in that EPWR stands for a loss of power by the bus.  This usually happens if Windows enters a power conserving or hibernation mode.