FPGA 7831R analog period measurement express vi

[Schlenker]

Hello,

I'm new to LabView and using the PCI-7831-R FPGA.

First I want to send a pattern to set a device into oscillation mode, which works very well.

Afterwards I want to measure the frequency of the oscillation with one of the analog inputs of the FPGA card.

I thought about using the "ANALOG PERIOD MEASUREMENT EXPRESS VI" which seems very helpful as it lets me set the threshold and a hysteresis.

With the oscilloscope I can measure the signal at the input of the FPGA connector box.

Attached you'll find my HOST VI and the part of interest of my FPGA VI.

The entire FPGA VI is running in a while loop, whereas it includes a flat sequence with a timed loop in the first "part" to trigger the pattern.

Btw: The signal to measure is a 0-5V swing with a frequency from 20kHz - 70kHz.

Threshold 3V

Hysteresis 1V

I can actually get a result in the HOST VI but it varies from every time I resend the pattern, but the result on the scope is still the same.

I guess my fault is something with the clock, but I can't figure it out. 

Would be very pleased if somebody could help me.

Thanks,

Michael

[Schlenker]

No one who has ever used the analog period measurement express vi?

Would really appreciate some help!

[RuedigerE]

Hello,

there is a very good example for signal period measurement included in the lv example finder.

"Measuring Signal Period - R-Series"

Please have a close look at this example.

Regards

Rüdiger

[sunu]

How to measure the frequency of incoming analog signal into the FPGA from a photo detector?Is this possible??

[Hooovahh]

---

@sunu wrote:

How to measure the frequency of incoming analog signal into the FPGA from a photo detector?Is this possible??

---

The analog channel doesn't care where the signal is coming from, use the same example to read a frequency of any signal.

[Rajesh459]

I want to Find the Frequency of an analog signal which comes from NI5781 Module in LabVIEW FPGA.If anyone have an idea on that please suggest me.

[LocalDSP]

I assume your NI 5781 data is acquired inside a single-cycle-time-loop (SCTL) and therefore you cannot use the Analog Period Measurement FPGA Express VI directly. However if you configure the Express VI, then right-click on the icon and select Convert to SubVI, you'll have access to the generated code. As you'll see this code is inside an SCTL itself but you can try to move the code into your top-level loop (create a sub-VI without the SCTL and drop that subVI inside your own acquisition SCTL).