Take Data from a hardware and plot on graph

[Nayan]

Hello..

I want to take a sample data from a microcontroller based hardware and plot it on a waveform graph.

The hardware is communicating in serial.

If I will send wavform points of a sin wave of 1kHz in 1sec, so I should get 1 complete wave.

But even after increasing the baud rate the wave will not have a perfect time scale.

So I should send time values also.

In which format should I send and recieve the commands to or from the Microcontroller ???

[GerdW]

Hi Nayan,

that question is to be discussed with the vendor of this "microprocessor based hardware"!

If I will send wavform points of a sin wave of 1kHz in 1sec, so I should get 1 complete wave.

What is a complete wave (aka period) to you? The wave will be complete even with just 10 samples…

[Nayan]

If I will set sampling frequency as 8k then It will be a complete wave (1k freq).

But if I wil send only the single array of points (not timestamp), it dont know the graph will show the exact wave.

So I need to send timestamp also,

I just want to know in what format (String commands to VISA) should I send and receive the data....

[GerdW]

Hi Nayan,

timestamp format isn't exactly defined. LabVIEW has it's own format, but your µP will probably use something completely different. You need to define the format on your own - or depend on the capabilities of the µP board.

Why do you thin you need a timestamp? When your DAQ hardware uses a constant sample rate the dt between the samples is fixed and known! The graph will show the "exact wave" in this case!

If I will set sampling frequency as 8k then It will be a complete wave (1k freq).

You will have 8 samples per sine period, when the sine has a frequency of 1kHz and you read samples at 8kS/s…

[Nayan]

Okay Thanks..

Means you are saying that I can set 'dt' of the waveform in 'Build waveform' function ??

[GerdW]

Hi Nayan,

yes, you can!

[Nayan]

Thanks Buddy..

I will try..

[Nayan]

Hey..

I tried a little.. I got another problem..

I am setting a sin wave of 10Hz frequency to have 1000 samples..

The sine values before sending is showing the full wave.. 

Also when I recieve the points by VISA, total points are recieved.

But when I am trying to use Build Waveform function, I am getting only 200 points in a wave.

Please refer the attached vi.

[GerdW · Accepted solution]

Hi Nayan,

But when I am trying to use Build Waveform function, I am getting only 200 points in a wave.

That's because you're using the shift register (and the array it holds) wrong!

You made several mistakes:

- your array constant is set to contain just 201 elements. Why did you use that arbitrary value?

- you used the ReplaceArraySubset function. The approach is nice, but with your limited array constant it fails: you want to replace 1000 elements in an array, that only contains 201 elements. This will never work…

You need to learn to use AutoIndexing of loop tunnels!

Possible solution:

P.S. using a timeout of 1000s is most often just wrong…

[Nayan]

Thak you very much.. It worked