You still have not answered my question about the Error Message -- there appears to be no error message with the number 200077. I do not have a myDAQ in front of me, so I cannot directly test your code and see what the error is, but you can ...
I understand that you want to learn how to use the DAQmx functions directly without using the DAQ Assistant. This is a worthy goal, since you can do much more, and have much more direct control, when you control the loops and use just the DAQmx functions that you need. A very powerful tool is the concept of a Task, which you can create in MAX or in the LabVIEW Project.
The LabVIEW Project provides a framework to wrap around your project. It may not make sense to a LabVIEW Beginner, who writes a single Giant VI (yours isn't that big, don't worry) that takes 3-10 screens to view. But one very important technique that applies across all programming languages is Divide and Conquer, or Write Subroutines/Functions/Sub-VIs That Do One Thing. Indeed, all but the most trivial LabVIEW program may involve tens, hundreds, even thousands of VI. How to manage them?
Before LabVIEW 8, the answer was "Let Windows Do It", meaning place them in Folders and sub-Folders with Helpful Names. So you might have an all-encompassing top folder called "My Big Project", with sub-folders "Interaction with User", "Interaction with Hardware", and "Data Communication", inside of which were "Type Defs", "Utility VIs", etc. When LabVIEW Project was introduced, it added the ability to include additional Project-related information, such as "What DAQmx Devices am I using", "How do I want to build an Executable", and "How do I manage code split between two or more Targets" (important in Real-Time and RIO architectures).
There are excellent tutorial materials available on the Web. One place to start is here, Advanced Programming in DAQmx (there also the main Getting Started with DAQmx page which will point you to the Advanced page). On the Advanced page, the first article is especially useful.
Notice the concept of a Task, which can be defined both in MAX and in the Project. Defining a Task handles a lot of the "messy details" in configuring DAQmx, as it binds such things as the Sampling Rate, Channel Choice, type of sample (e.g. Voltage or Temperature or Force), special Scales, etc. into a single thing, the Task. With a properly configured Task constant, many DAQmx routines will need only a few functions -- Start Task, Read/Write, Stop Task, and Close.
Do some reading and thinking. And find out what the real Error Message is, please ...
Bob Schor
