Hi franciscoo,
If I am understanding your application correctly you need to generate 4 pulses of a frequency sweep, once a second. Please let me know if I have misunderstood your post.
With the 6229, you would be able to load a waveform into memory that you can output at different clock rates. This waveform would consist of your 4 pulses. You would have to consider the number of samples in the waveform and the clock rate needed to generate the frequency you desire. Each pulse would have to be represented by many samples and then you would need to generate each sample at a fast rate to reach your desired frequency. You would have to stop and restart the task for each clock rate and though this is system dependent it is usually on the order of several milliseconds, which is less than your 1 second down time. The task would be set up for a start trigger and you could connect up a 1Hz signal to a trigger line and this would ensure that your waveform begins precisely once a second. This 1Hz frequency could be generated with the onboard counter. There would be an issue with setting the exact clock rates for your generation. The clock rates on an M Series will be coerced to the nearest integer division of the 80MHz timebase, regardless of what you have set. For example, if you try to set your clock rate to 31kHz, it will actually be running at 80MHz/2581 = 30.99574kHz.
There are many examples in the Example Finder (Help>>Find Examples) that would get you started with a finite voltage task with a start trigger and also a counter frequency generation.
I would recommend that you take a look at our function generators for this type of application because they take advantage of direct digital synthesis (DDS). This allows for frequencies to be changed on the fly and to have 0.355uHz of resolution. Principally, it would function similar to what I described above where you would load a waveform into memory and generate it ad different rates. With DDS you will not have to stop and start the task each time and you can choose the frequency you want your waveform to be and the driver will make the appropriate adjustments. The available generation rates would be more than enough for the application and can be well suited for future developments. You can refer to the link below for more information on our signal generators, specifically the Understanding Direct Digital Synthesis (DDS) article for more information on how it works.
Signal Generator Fundamentals
http://zone.ni.com/devzone/cda/tut/p/id/4089
Steve B
