How to Create Digital Array?

[Mark_Yedinak]

I thought they were bytes too but when I use the Boolean to 0,1 VI it returns a U16. This is why I thought they may be storing them as U16. I agree though that storing them as bytes would be the normal and effecient way to store them.

[theodyssey12]

Hi,

I tried to use initialize array and tried to output it to a digital waveform but theres no output - is there any way I can output it successfully to a digital waveform so I can then append/insert other arrays into the waveform?

Thanks a lot,

Mitchell

[crossrulz]

Can you show us the code you have made?  It helps to add context.

[theodyssey12]

Attached is the program I've been working on - the digital array part I am having trouble with is inside the true part of the case structure - I put a boolean false value to represent 0 and wired it to an initialize array, where I tried to build an array and make create a digital waveform out of it.

I am hoping to create a long digital array/data list of 0s and insert 1's at specific points to create a digital waveform.  Could you please look at it and tell me what I'm doing wrong?

Thanks a lot,

Mitchell

[altenbach]

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@Mark_Yedinak wrote:

I thought they were bytes too but when I use the Boolean to 0,1 VI it returns a U16. This is why I thought they may be storing them as U16. I agree though that storing them as bytes would be the normal and effecient way to store them.

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Yes, they are stored as bytes and anything !=0 is a TRUE. An illustrative example is JeanPierre's Hello World program (posted here).

Note that arrays of booleans were stored as 8 booleans/byte prior to LabVIEW 5.0. This made some sense with the very limited memory in those ancient times. You can still set typecast to 4.x mode if you need to operate on flattened data compressed this way.

Today, a boolean array takes the same memory per element as a U8 array.

[altenbach]

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@theodyssey12 wrote:

Attached is the program I've been working on - the digital array part I am having trouble with is inside the true part of the case structure - I put a boolean false value to represent 0 and wired it to an initialize array, where I tried to build an array and make create a digital waveform out of it.

I am hoping to create a long digital array/data list of 0s and insert 1's at specific points to create a digital waveform.  Could you please look at it and tell me what I'm doing wrong?

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You seem to be aimlessly coverting 1D arrays to 2D arrays and vice versa.

You want to initilize the 2D boolean array on one step as all false, then use "replace array subset" in a FOR loop to edit certain locations. Keep the array in a shift register.

Here's a quick example (LabVIEW 8.6).

[theodyssey12]

Thanks a lot! 

I think I have a much better understanding of how it works now.  For the purposes of my project, I have two more questions:

1. Since I have 50,000 samples, how can I insert a function/algorithm to insert true values at specific points?

2. After I have this array, how can I have it shown on the front diagram and change it to a digital waveform format (for outputting to my DAQ board)?

I really appreciate the help,

Mitchell

[crossrulz]

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@theodyssey12 wrote:

1. Since I have 50,000 samples, how can I insert a function/algorithm to insert true values at specific points? Use the Replace Array Subset

2. After I have this array, how can I have it shown on the front diagram and change it to a digital waveform format (for outputting to my DAQ board)? Use the Boolean Array to Digital Waveform like you already have in your VI

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[altenbach]

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@theodyssey12 wrote:

1. Since I have 50,000 samples, how can I insert a function/algorithm to insert true values at specific points?

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Instead of the fixed "TRUE positions" in my example, you can calcuate TRUE or false based on the valie of the iteration terminal, for example. What kind of function do you have in mind?

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@theodyssey12 wrote:

2. After I have this array, how can I have it shown on the front diagram and change it to a digital waveform format (for outputting to my DAQ board)?

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It does not sound reasonable to show 50000 elements on the front panel. I don't use digital waveforms, but is whatever you were doing in your code working in principle?

[theodyssey12]

I am trying to use T_n = T_0 (sqrt(n+1) - sqrt(n)) where:

T_n = time between pulses, which I can convert to distance between samples

T_0 = sqrt (pi/(250n))

n = pulse number (0,1,2, ...)

The pulses are responsible for causing a potential difference which I am using to drive a stepper motor, and I need a digital waveform with a shortening period (as given by the equation) in order to accelerate it.

Yes, what I have been was working in the attachment you gave me, but when I tried to run it in my program (to test whether it would work in my case structure) the edited array indicator didn't seem to light up.  Is there a reason why this happened?

Also, when I tried to use the vi to convert it from array to digital waveform it didn't seem to accept it (see wiring in attached doc).  How can I convert 2d boolean to true/false boolean and vice versa so the wiring can be accepted?

Thanks a lot for all of the help and explaining, I have been working on this program for several days now and have made a lot more progress in these few hours than I've had in the last few days.  I'd really like to get my program up and running so I can finish my project!

Mitchell