txt file in real time 
Author Message
 txt file in real time

Hi all,

I have a txt file with 7 signals and is tab delimited.
I am able to load the file but I have all the waveform at once.
I would like to play the wakeform in real time.
I know that I had a sampling frequency of 2K so each of my points is
1/2000 seconds.
Any ideas or examples will be helpful!

Thanks



Sat, 10 Dec 2005 23:24:04 GMT  
 txt file in real time
Now I am reading all the waveform at one the problem is that the file
is like 100megs and is about 2 minutes of real time so I want to see
the power spectrum in real time.
I was also trying to do it with delays but the wait for next
milisecond function accepts 1 as the smallest input so my sample
frequency is smaller that 1ms.
I know that it won't be really accurate becasuse it will depend on the
processor adn the time it takes to do the calculations.
Do you have an example with a single little file on how to read it
line by line?
Thanks a lot


Sun, 11 Dec 2005 00:33:40 GMT  
 txt file in real time
Ok, but why you can not just read all the waveform at once and then
supply values sequentally at a given rate (using delays, or, better,
wait for multiple function)? Or, If the waveform is huge and you don't
want to load it at once you can read your text file line by line,
converting each line to waveform data and, as earlier, suppling this
data to the graph at the given rate? (But beware, that in this case
you will be much more dependent of your OS reading file speed, and,
may be, not able to achieve given rate).


Sun, 11 Dec 2005 00:11:59 GMT  
 txt file in real time
And about high playback sampling rates... I must admit, that labview
just simply not fast enough :(
The wait functions are also limited by OS time-quants.


Sun, 11 Dec 2005 01:05:30 GMT  
 txt file in real time
Thanks for your vi.
I will try to pass then a set of points at once and then play them.
It is a shame that you don't have the ability to play the waveforms as
they were aquired.
Merci!


Sun, 11 Dec 2005 01:58:41 GMT  
 txt file in real time
Yes, but when you acquire waveform it usually uses some kind of
harware buffering. And this is not the case when you analyse or
display them on a graph...


Sun, 11 Dec 2005 02:39:32 GMT  
 txt file in real time

Quote:
> I will try to pass then a set of points at once and then play them.
> It is a shame that you don't have the ability to play the waveforms as
> they were aquired.

On recent versions of LV running on OSes with threading, controls and
indicators automatically do buffering, to update at a rate that makes
sense for the human eye, and letting the diagram run at the rate that it
wants to.  So, that means the real problem is that you want a .5ms
delay, and that just isn't supported by the OSes LV runs on.  maybe this
will change, but you can approximate this for a combination of 0's and
1's.  So one way of doing this is to measure how many ms have elapsed
since your loop began, compare this to the computed data timestamp and
wait the difference, or zero if behind.  This will work about as well as
anything does since you aren't going to see 2,000 distinct pictures in
one second anyway.

Greg McKaskle



Sun, 11 Dec 2005 21:39:17 GMT  
 
 [ 7 post ] 

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