NI-DAQmx Base - "Read or Write task without first setting line states"

Question

I am writing an application to interface with the USB-6501 hardware platform. In my application, I am first initializing all the lines on each digital port to be either read or write lines. After these lines have been initialized to the correct state, I would like to write data to a specific port, or read data from that port, without having to again define the line states (i.e. I'd like to write data to the port based on the already configured lines).
Here's how I approach the problem. On initialization, my program will create a DAQmxBase task which will set the lines I specify as "Write" lines for port0, following this is another task which specifically sets the "Read" lines for port0. When I create a task to simply read or write data to a port (without again defining which lines are write and which lines are read) I receive the error "-200428 - Value passed to the Task/Channels In control is invalid.". If I define the read and write lines as a step in the same task which reads or writes data (respectively), the process seems to work ok.
Can anybody offer any insight to whether or not I should be able to accomplish this task using this approach?
Thank you for your help.

Answer 1

Hello DarkCloud. Thank you for contacting National Instruments. If you create a task in the DAQmx Base Configuration Utility and set the direction of the line, you don't need to reset the direction in LabVIEW. There are some examples of how to do this at Start>>All Programs>>National Instruments>>NI-DAQmx Base>>Examples>>LabVIEW 7.1. Open the static example for DIO>>Write Dig Port. Please let me know if you have any questions. Have a great day!
Marni S.
National Instruments