When a cDAQ (I'm using both a 9184 and 9188) chassis is energized (or the host computer is rebooted) it is programmatically read as reserved (by either MAX or LAbVIEW program). To gain control of the chassis, one has to either use MAX (MAX deosn't save or remember the previous reservation) and reserve it or programmatically force the reservation in the LabView code. In addition, if a chassis is reserved by a different host, another host can force the reservation by itself programmatically. Both of these can be accomplished by using the reserve chassis function with the 'Override Reservation' input set to True. This really is not a good method - it's effectively a hostile-takeover of the hardware (I've tried this and I can literally reserve hardware that is actively being used by another host).
I would recommend the following firmware/driver/software updates/corrections:
- When a chassis is power-up it should be in an ‘unassigned’ state. Basically it will be in 'standing-by' waiting for a job/task.
- When a host interrogates the chassis it should only be able to ‘reserve’ it if it is in the ‘unassigned’ state. Once the chassis is reserved by a host it is locked to it until it is either unreserved by the host or power is cycled to the chassis and it reboots, returning it to the unassigned state.
- When interrogated, a ‘reserved’ chassis should provide the identification of what host has reserved it. This would allow redundant or multi-host configurations to find each other and do things like handing-over a chassis between hosts. This is useful if a host error is detected (redundant host system) or a host needs to be taken offline for service and the process can’t tolerate extended interruption (and it's useful to do this programmatically).
- The chassis firmware and functions in DAQmx should be updated or augmented consistently to support 1,2, and 3.
- There should be example code showing how to implement these features
