Real-Time Measurement and Control

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Using stacked shift registers

Hi there,


The aim is to perform cross correlation in the time domain pt by pt.  This entails 2 arrays of data which 'slide' across each other getting multiplied and added.


I can do this easy enough but my problem is that during the next time instance I want to add a pt to each of the arrays and delete the first point in the array then perform the cross correlation again. I have found that the majority of the multiplications in the first time instance are the same as in the second instance. I want to utilise this fact.


I have been told to try playing  round with stacked shift registers but am stuck..... I hope this picture kind of explains what I want to do as I'm battling with words at the moment.


If anyone could help me I would be much appreciated!!!



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Is there any reason why you cannot use the cross available in Signal Processing>>Sig Operation palette? There is also a pt by pt vi available is Signal processing>>pt by pt>>Sig Operation pt by pt palette.

"A VI inside a Class is worth hundreds in the bush"
യവന്‍ പുലിയാണു കേട്ടാ!!!
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Yeah Because I am coding of FPGA. There is a FFT algorithm and could hence perform the xcorr in the freq domain but I have been hitting issues when it comes to space so thought I would try a differerent approach.
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SORRY for forgetting to mention FPGA in first place.Seems a silly question whithout it!
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If you are running out of FPGA space, be sure that you do not have any array indicators or controls on the front panel, this could use up a lot of space.


Have you seen our ipnet page? It is a collection of user and employee submitted FPGA calls, and a quick look at it shows there is a cross-correlation and an auto-correlation.  Looking at these may help you architect your code better (

Message Edited by Rob_K on 02-09-2009 10:40 AM
Rob K
Measurements Mechanical Engineer (C-Series, USB X-Series)
National Instruments
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