Filter VI is not working fine if configured for a bandpass less than 1000Hz

[Vijith]

 I have attached an FIR filter form the examples that NI has given with Labview Embedded for Blackfin.This filter VI is working fine if configured for a bandpass greater than 1000Hz .But if we change the frequency to less than 1000Hz , say a a bandpass of 100Hz to 300Hz, the amplitude attenuation is not happening for frequencies less than 100Hz.

Hardware used: Balckfin eval board ADDS-BF537-EZLITE

Software Used: Labview Embedded for blackfin and VisualDSP++ 5.0

Please advice me why this is not working

[Rudi_N]

Vijith:

I hope all is well and sorry for the late response. I could not open the application that you attached in your post. Please send your project files again.

Thanks,

Rudi N.

[Vijith]

Hi Rudi,

I am attaching the VI again.

thanks

Vijith

[Nitin_T]

Hi Vijith,

The attached project is acting fine, but the file "FIR Filter.vi" still does not open up. It comes up as "File is not a resource file". There may be a case where there is something wrong with the program that is compressing the file. Please try to post the file once again, just the FIR Filter.vi

I was wondering if you've made any major changes to the FIR Filter Example available through the example finder. If not, then I can use the example as my reference. Also, let me know what kind of windowing method are you using in the project. Have you tried other types of Windows.

[Vijith]

Hi,

I have not made many changes in the FIR filter VI given in the examples. You may use the same example that is given in Blackfin section in the Toolkits and modules from the example finder.

thanks 

Vijith

[CharlieM]

The sample rate on the EZ-KIT is fixed at 48kHz (it can’t be changed). The number of samples should be a power of 2.  In order to get a narrow bandpass filter I believe the number of taps needs increased.  I ran the NI FIR Windowed Filter Design VI and I needed at least 150 taps to get a decent low freq cutoff.  I attached my modified VI which has good cutoff below 500Hz and above 1000Hz.