Example: "Digital - Conitinuous Output" How does it work?

Question

I have to generate a sequence on three channels (with my NI 9375 Digital Output card on a cDAQ9188).
In 1 second, the sequence consists of, for example:
channel 1: starting low .. on 15 ms high .. on 865 ms low again
channel 2: starting high .. on 115 ms low .. on 650 ms high again
channel 3: starting low .. on 85 ms high .. on 920 ms low again
This have to be conituously generated and hardware timed.
For this application, they advised me to work with the example "Digital - Continuous Output". Can anyone explain to me how I get this sequence with the "Data To Write" Controls-box on the Front Panel? And how can I visualise my generated sequence?
Thanks in advance!
Solved!
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Answer 1

Hello Hannes,
There are 2 major things that you have to keep in mind in this case regarding the example you're using:
- The sample rate you're going to use has to be high enough.
In your case the minimum sample rate has to be 200 Hz (seeing that your smallest step is 5 ms).
Of course you could also use any multiple of this.
- At the other side you have to check how the array of unsigned integers in the Data to Write is related to your digital outputs.
Depending on which Digital Outputs you're using one of the bits in your unsigned integer will correspond to one of your Digital Ouputs.
This mentioned the "difficult" part starts:
Seeing the period is 1 second and if you have selected 200 Hz (5 ms period sampleclock) as the sample rate, then:
- For channel 1:
the first 3 bits should be 0, the next 170 [= (865-15)/5] should be 1, the remaining 27 (200-173) bits should be 0.
- For channel 2:
the first 23 bits should be 1, the next 107 [= (650-115)/5] should be 0, the remaining 70 (200-130) bits should be 1.
- For channel 3:
the first 17 bits should be 0, the next 167 [= (920-85)/5] should be 1, the remaining 16 (200-184) bits should be 0.
To represent this visually the best thing you can do is to use 3 arrays of 200 booleans for the 3 channels.
These arrays can be easily shown in a Digital graph
You then have to make a very simple conversion algorythm to convert these 3 arrays of 200 bits/booleans to 1 array of 200 unsigned integers.
Is my explanation a bit clear to you?
Note: Here we took 1 as high and 0 as low.
Kind Regards,
Thierry C - Applications Engineering Specialist Northern European Region - National Instruments
CLD, CTA
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