FPGA analog frequency measurement

[any thing]

Hi,

 

I am pretty new to labview..I need to change the frequency of my look up table in accordance with an analog input signal frequency....This can be done by changing my scan rate which is calculated as follows

 

scan rate=FPGA frequency(40 Mhz)/16*fin

 

I decided 2 possibilities to implement this...

 

1)I could simply measure the frequency of the incoming analog signal from the photo detector...

Please tell me how to measure this frequency on FPGA??

 

2)I could also measure the phases of the signals and thus update the frequency.

But I dont exactly know how to do this....

 

It would be really helpful if you can help me resolve this ASAP

 

Thank You

 

[rgwagner]

Hi Sunayana,

 

In the LabVIEW example finder there is a counter example. It is called "Edge Counter.lvproj" Frequency would be the number of counted edges per unit of time. The example should provide a starting point.

 

However, you will still need to convert the analog signal to digital using some sort of crossing detector. Hard to say how to do this without knowing your resources.

 

Kind regards,

 

Rick Wagner

[any thing]

I have a fpga, a pxi system and a daq.........My idea is to change the refresh rate 

 

I have to actually change therefresh rate with changes in input frequency frequency....My refresh
rate is calculated as follows.

scan rate=40Mhz/16*fin
for example for an incoming frequency of 10 khz, my scan rate would be 250
If suppose the incoming frequency is changed, I want the scan rate to be 
changed automatically so that the frequency of the look up table is updated.

 

How should this be done?

[hooovahh]

I don't know if I fully understand what you are talking about.  You have a look up table so I get the feeling you aren't reading an analog channel but instead are using that table as an output but your topic clearly states "measurement"

 

Please also try to use terms that are more appropriate.  The "Refresh Rate" can mean many things.  If instead you said your output rate, or sampling rate then it would be more clear what is going on.

 

We will need more information to understand what you are doing.  Post some code of what you are doing as well if you can.