LabVIEW
Why does Lab View code work through USB and sometimes it does not?
Hello,
Please see the attachment, this code when 1936-c is connected to PC through USB does not have any error.
If I run the vi, it does not have any error either yet, it does not read power (does not display power).
In Block diagram if I activate the Highlight Execution, I can see the correct instrument address travels to the while loop, passes through Send Cmnd, and then "error -1. or error -2" comes out, this is the only way I can find there is an error. I opened each individual sub vi, I can not find any errors.
All these sub vi are part of the instrument driver of 1936-C that I got them from Newport Corp's website. I mean I di not wrote them.
If I turn power meter on and off, and run the code it start reading power, when I stop the vi, and run it again, it does not read power.
As Dennis said it is their dll. USB may stand for "Universal Serial Bus", but the only thing universal about it is the description of the interface, each bit of hardware has its own implementation of what the messages sent are and do. Many companies do use the same .dll drivers, from the company that manufactured the particular USB interface chipset, particularly those that are using it like an old "serial" port, but even then they sometimes encapsulate the calls to that lower level .dll in a .dll of their own, some of which I have found don't play nicely with LabVIEW. I haven't any experience with your specific instrument.
Another thought is that you are loosing the usb connection from your computer, as you mention a problem with an XY stage? Is that also part of the power meter code or seperate? I had problems about a year ago where occasionally the USB on the test computer would "glitch", causing, in my case, the USB to Serial adapter I was using to be "reinstalled" by Windows, resulting it this case in a new com port #. My program had no way of knowing that this had happened, or what the new port mapping was. The final resolution, with NI's support telling me that they had seen problems with certain motherboard's USB, was to plug a USB adapter board into the computer's motherboard for my instruments and comm ports. Since your problem seems to be corrected by power cycling the instrument I'm wondering if Windows is intermittently loosing communications with it. Here is a fairly lengthy discussion about what I went through to find the problem.
Good Luck, let us know of your progress so we can help, or learn.
