There are probably several ways to measure these characteristics. I suggest you post the diagram to the Multifunction DAQ forum: http://forums.ni.com/t5/Multifunction-DAQ/bd-p/250 to get some other engineers to weigh in as well.
Assuming the 6229 is required, the semi-period measurement provides the base information necessary. If you add a start trigger, you can differentiate between HIGH/LED ON and LOW/LED OFF. From there, decisions will have to be made in software about how to interpret the information. Please refer to Figure 7-9 on page 7-8 of the M-Series User Manual.
Use two adjacent semi-period measurements to calculate the duty cycle of the brightness (that's the easy part).
From the original post, it's necessary to measure the flash rate; however the diagram shows the frequency is 1Hz with a 50% duty cycle. If how I'm interpreting the diagram is correct, then the blink rate is always 1Hz, and only the brightness changes. I still have some ambiguities:
Scenario 1) The LED is either constantly on/off, or it's blinking once per second, and the duration of the blink varies within 1s.
Scenario 2) The LED is either constantly on/off, or it's blinking at an arbitrary rate.
In other words, a bound must be placed on the fastest and slowest blink rates. Then the on and off conditions are specified by semi-period measurements that exceed those bounds.
I highly recommend you program and test this as a stand-alone DAQmx task before porting it into VeriStand, because VeriStand's going to add a layer of complexity to the solution. Buffered semi-period tasks are usually read within loops. However, the VeriStand engine is a loop. You don't want to put a loop within VeriStand's loop without understanding the programming paradigms and caveats.
If I had my way, I'd use an R-Series PXI card and design my own instrument to measure this signal.
Steve K
