Problem(s) Encountered:

...we met a problem at midnight: the readout time was too short when the fit file was written (~1.12sec). The output image looks wrong. Most of pixels are zero. I restarted Owl software and we lost the connection to Owl, it shows: 'ERROR - Driver  PCI Device 0  failed to open ERROR - ( CArcPCI::Open() ): Failed to open device ( /dev/astropci0 ) : ( errno: 16 ) - Device or resource busy'. I tried an exposure. It shows an Error as: 'ERROR - Not connected to any controller!' Then, I followed the solution of Eric: click 'Setup' -> 'Apply'. Then it shows another Error as: 'ERROR - SetupThread error: java.lang.Exception: Not connected to any device!'

Justin rebooted the mdmarc2 and restarted Owl software. Then we tried an exposure. But the readout time is still not correct (too short, ~2 sec). Justin has tried reseating the fiber connections, rebooting mdmarc2, restarting owl, and power cycling the ccd electronics. They all didn't work.

Solution:

It appears that the issue stemmed from some debris in one of the fiber connector housings.  After removal, things seem to be working again.  More extensive tests are forthcoming...