USB 6210 Using counter as an external clock

Question

I was referencing an old post for how to read and write data from a quadrature encoder. I am using a USB 6210 card along with Labview 8.2.1. In the previous post it describes needing to:
"You will have to create an external clock using the other counter on
the board then route the signal either externally or internally"
I do not know what this means and I do not understand what is required to do such (Changes to wires, change the Vi...etc). If someone could please shed some light on this I would really appreciate it.
I am basing my approach on the following NI example:
Meas Angular Position-Buffered-Cont-Ext Clk.vi

Answer 1

Hi rose8,
The example you are referencing requires an external clock to basically take samples of the angular position based on time.  For instance, you can rotate your angular encoder all you want, but it will not save which position you are at until a sample clock rising edge is seen.  When the sample clock rising edge is seen, then it places that position into a buffer, and continues to wait for the next sample clock rising edge to happen.  Every time the rising edge happens, the position of your angular measurement is recorded one point at a time, stored in a 1D or 2D array. 
The sample clock cannot be an on board clock that is already created.  So now, we look at what sources we can use for our external clock to sample the position of our encoder and save it in our memory buffer.  We can use an external source and bring it into the board, or we can create a clock using another counter on the board.  Since you are looking to do this, I'll assume you want to create a clock from there.
In software, you specify two counter tasks; one to measure your angular position and one to generate a pulse train.  The pulse train you generate will be the sample clock for the buffered angular position measurements you are taking.  Now, you can route this externally or internally, based on your application.  The easiest way is internally, because it doesn't require any additional wires to accomplish.
To route internally, all you have to do is for your DAQmx Timing VI, specify CtrXInternalOutput from your USB 6210 as the source, where X is the counter you generate your pulse train on.  To see this source as an available selection, right click your Resource Name and select I/O Name Filtering from the shortcut menu, and then be sure that Include Advanced Terminals is checked. 
In programming, you would want to start your angular position task first, and then start your clock generation from your second counter.  They will run in parallel and just be sure to clear both threads at the end of your program.  Hopefully this clears up some confusion for you.
Kyle A.
National Instruments
High Speed Digital I/O Product Support Engineer - R&D