Reading DMA FIFO using Invoke method node

Hi
I am trying to read a DMA FIFO using invoke method node to read the data in the FIFO on RT.
It works fine but the problem is that it consumes a lot of CPU if the timeout is increased. Can
anyone tell why this is happening and if this is the desired behaviour then what other methods i can
use to avert this.
Please help at the earliest
Regards
Amit

Hi
Can anybody help me as it is urgent ,
What i further found out is that is that it is eating up a lot of meory when continuosly polled up in a looop....
Regards
Amit Ahuja

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I'm not quite sure why that is happening, but I
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application_pic.jpg ‏27 KB

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Get image invoke method gives blank image when I try to capture waveform graph picture

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I am facing problem when try to capture waveform graph picture using invoke method Get image and write JPEG function, some times it gives blank images.I am using these functions inside nested loops.
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(1) Sometimes I found it captures images correctly when i run labview program first time but after that it starts writing blank images.
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Attachments:
image_capture_problem.lvproj ‏6 KB
image capture problem.JPG ‏149 KB
0.0_10__3.jpg ‏2 KB

Hi,
I have tried sequence structure.But sometimes it also gives blank images. I have attached new vi which is using flat sequence. Run this vi 7-8 times then you will observe blank images. I don't know why?Any help will be greatly appreciated.
Attachments:
image_capture_problem.vi ‏69 KB

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Error -50400 occurred at Invoke Method: FIFO.Read in Host.vi

Hey there,
we have sensors on an Engine which are connected to a NI cRIO 9014 board (with a NI9411 6-channel digital input modul) and go from there via network to a host computer.
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Error -50400 occurred at Invoke Method: FIFO.Read in Host.vi
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The transfer did not complete within the timeout period or within the specified number of retries.
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When I press the start button (boolean 3) in the host.VI to start the reading of the data from the board AFTER I pressed the run button of the host VI.
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We tried to increase the time out, but it still did not work, the error occurs!
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We included the VI's in the attachement!
Thanks in advance!
Solved!
Go to Solution.
Attachments:
Host.vi ‏152 KB
C_RIO.vi ‏92 KB
Cyl_Pres.lvproj ‏196 KB

Chrisse,
There are a few things wrong in your application, if I may offer some suggestions.
First, your while loops are not running in parallel. In fact, they are in while loops with a true constant wired to them. I am not sure if this is by design for debugging, or on accident. I would put the Polling(read pulling zero elements) outside your main while loop.
Your second nested while loop (the one polling the # of elements and then pulling them out) is going to run just once, and may pull only a few samples. I don't think that is what you are looking for here, and there are a couple ways we can go here. You could continuously poll until you have 0 elements available for x amount of time, then you know you have no more samples available and you can process all the data OR you can put all of your data processing as part of that loop and just always write to file immediately as x samples are pulled.
Also, your main loop's stop condition is (i <= 3) Therefore, it will run once and then stop. Maybe you mean >=3?
Also, you have 'append to file' disabled on your write to spreadsheet, so everytime you write you are overwriting old data. If you want to continuously write, you will be losing data. This can be cured by either setting this to true(requiring a new file name or programatically deleting the old spreadsheet every time you run the vi) OR you can collect all of your data in a shift register, and only write to file once you have all your data available.
The error you are seeing is because you try to close your FPGA reference twice. You only need to close it once.
After seeing your overall picture, I think this can all be cured by simply hardwiring your Read to get your 1440X4 elements, but as we have seen, this does not work. Something is happening in your system....this is what I want you to do...run just the following code...and let me know how many elements remaining it gives you...Once the number has settled(I hope it does and your engine doesn't keep running), hit stop, and all the values will be put on a graph for you. My broken wires are because I do not have the FPGA VI.
Message Edited by Robbob on 04-21-2009 01:48 PM
Rob K
Measurements Mechanical Engineer (C-Series, USB X-Series)
National Instruments
CompactRIO Developers Guide
CompactRIO Out of the Box Video
Attachments:
numelements.jpg ‏39 KB

How can i decide the depth of all3 DMA fifo's are used as target to host at RT contoller side(host)?

Hello,
I am using all DMA fifos,I want to acquire data from 3 AI modules upto 50 khz frequency.Sampling rate can be varied according to application.
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*****************Certified LabView Associate Developer****************************

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I am trying to pass a parameter to a vi running in parallel with my main vi. I am using invoke nodes to do this without any problems. In server.vi I want to respond to a change in the control using an event structure. I have found that when passing the value to the vi using the invoke node from client.vi the event structure does not respond to the change in value. Is this correct behaviour? In the attachment run client and server, any change in the client panel is reflected in server without a response from the event structure. Running server by itself a change in the cluster causes the event structure to respond as expected. Thanks in advance for any help on this.
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Test Invoke Node.llb ‏47 KB

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DMA FIFO number of elements to read mismatch in FPGA and RT

Hi all
I am using myRIO , LV14 to run my application.
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Attachments:
cRIOdevguide_FIFOreadwrite.PNG ‏107 KB
FPGA_FIFO_write.PNG ‏41 KB
RT_FIFO_read.PNG ‏39 KB

Hi Nathan
Yes, I could have replaced it with an OR. Regarding my application, I want to acquire data in chunks of 2000 samples. If at all I receive a timeout error, I want to discard that chunk of 2k samples and start all over again. So my logic was like this, I acquire the data, if there is a timeout, the reset is triggered, and the system waits to comeback from reset, and it starts acquiring again. Btw, I tried removing the multiple FIFO reads in RT, but the error is still the same.
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Reading DMA FIFO using Invoke method node

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