Real-Time Measurement and Control

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can hardware and software measure input differently?

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hi i'm making an application that measures the speed of wind using crio-9012 and NI 9423(DIO)


I have the sensor that outputs voltage at different orientations so when it gets rotated it generates a 50% duty-cycle pwm-like wavefrom

when it's measured with higher wind speed, it will generates signal with greater frequency


Now by using labview i'm trying to see whether it can show me the right signal like i've seen from oscilloscope but it doesn't show me a proper output

When I rotate the sensor, the led from NI 9423 seem to blink at the right frequency(it means working) but the led I made from labview doesn't blink at different frequency, not really working


I don't see how this is happening when both of the leds are run by the same code, the diffrenece is one is hardware and the other one is software


What should i do?

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Where are you seeing the LED blink? Is it on the FPGA or RT VI? You need to be careful of how you design the user interface when dealing with FPGA or RT (you shouldn't be really designing a user interface for both targets in the first place). Post your code, if possible, and we can offer suggestions and advice.
Adnan Zafar
Certified LabVIEW Architect
Coleman Technologies
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it's fpga vi


my code is very simple i don't think it's need to be complicated since i only want to see whether it gets signals ok

메시지가 12-29-2008 05:23 AM
에 rlagksquf에 의해 편집되었음
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Accepted by topic author rlagksquf

I think that's the problem. Your code is really simple and there is nothing going on there really. Which means that the LED is going to change really quick in the resolution of ns. The way you are looking at the FPGA VI front panel is done using what's called the Interactive Front Panel Communication which is not deterministic. This means that as the FPGA target block diagram continues to run, the host computer updates values on the FPGA VI front panel window as often as possible. But, it's not possible to update at the rate the FPGA VI running nor is it possible to transfer that data to the host at that rate since both are running at different speeds (Your FPGA code runs at ns while the user interface might be updating in ms). Let me know if you don't understand this.

Interactive Front Panel Communication


If I were you, I would test the blinking by placing some sort of counter and counting the number of state changes. 

Adnan Zafar
Certified LabVIEW Architect
Coleman Technologies
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thanks for the explanation
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