Hi Dan,
Check your Timeout on the DAQmx Read. Error -200284 is a timeout error. By default this is 10 seconds, you can make it wait infinitely with a -1 in the timeout field.
Here's a KnowledgeBase article that discusses Error 200284. Finally, here is another related KnowledgeBase article that discusses
.
Timeout with Change Detection.
Have a great morning,
MatthewW
Applications Engineer
National Instruments