Sorry for just mentioning ibfind earlier, because the same thing can occur using ibdev. When you use ibdev, it opens a handle to the device, or a device descriptor. From the NI-488.2 help file, you can use ibdev in C code like this:
ud = ibdev (BdIndx, pad, sad, tmo, eot, eos)
where the inputs are described as follows (they are all data type int):
BdIndx Index of the access board for the device
pad The primary GPIB address of the device
sad The secondary GPIB address of the device
tmo The I/O timeout value
eot EOI mode of the device
eos EOS character and modes
The output of the function, which I have labeled ud, is an integer which is the device descriptor. Every time ibdev (or ibfind) is called, it creates a new device descriptor as an output. If you run this in a loop, and never close the handle, it will keep creating new device descriptors and keep them all open, until the driver cannot handle any more. It looks like we're running into a limit at 1024.
To fix this, you need to discard the handle using ibonl. Simply call ibonl with your device descriptor and the value 0 as inputs. In this case:
ibonl (ud, 0)
This should keep the program from having too many device descriptors open at once.
John M
Applications Engineer
