LabVIEW
digital output for NI6009
What McDan said was ture. Your error is due to you configuring an entire port (8 lines) and then sending only one bit. His solution will work.
However, when dealing with digital lines, I prefer to use booleans instead of a U8. It is easier to see what state each line gets. With a U8, you have to break down the number to its bits to see each line state. But for the purpose of just setting everything to a low state, the U8 will work fine.
Sticking to my preference of using booleans, see the attached picture for the proper way to initialize all lines low. Create a list of lines for the physical channel input. PXI-6225/port0/line0:7 will describe all lines on port 0 (notice the colon between line0 and 7). You could also list the channels separated by a comma (xxx/lport0/line0, xxx/port0/line1, and so on). Since you are using the lines individually later one (by looking at the code at the right in your picture), you would be better to setup the DAQmx Channels for "one channel for each line" at the very beginning, and using the task output for all subsequent actions. You would not have to create the channels again, as you are doing on the right side. Just pass the task wire to the next stage.
Also, in your picture you have the Start vi before the write vi. This is backwards. You need to write first, then start. Normally the write vi will not perform an output. It just loads the internal buffer with data in preparation for the start command. Now if you look at my picture below, you will see a True constant called auto start. This will tell the Write vi to start writing as soon as it gets its data. By using this, you don't even need the start vi.
