Initialization of PtByPt Lilter

[jcannon]

Hi everyone,

I am acquiring a continuous waveform signal and would like to run a bandpass filter on prior to real-time display... I understand I need to use a ptbypt filter and that the "initialize" input t the ptbypt vi should be "true" for the first iteration of the while loop and "false" for the following loops within the same call.

Any suggestions for how I can do this?

Regards,

Jack

[GovBob]

Maybe you could use the first call? primitive and a T/F case structure inside your loop? Make sure you read the help for that primitive.

[crossrulz]

The easy way is to use a "Equal to 0?" function with the loop iteration counter.  The first iteration of the loop will have i == 0, so you only initialize on the first loop.

[jcannon]

Hi GovBob and Crossrulz,

Thank you for your replies... Very helpful... I was thinking something alone those lines....

However, my continuous daq vi will have an "idle" case in the loop that will keep the loop running but will "stop" the "read.vi" (so I can do some basic signal analysis, stop data to the graph so I can use the graph palette tools to zoom in etc)... When I start the "read.vi" again should the filter be re-initialized? How might I do this given that to loop has not stopped and the first call will not work and the loop iteration could be anything... Perhaps through a shift register?

Thanks,
Jack

[crossrulz]

Since you are using a state machine, I would use a boolean in a shift register.  Set the value to TRUE when you need to reset the filter, set it to FALSE when using the filter, and wire it straight through for all of the other cases.