How to test the FIR II filter

[mitsvoid]

Dear All,

I hope this message finds you well. I am currently working on a project involving an Altera DE2-115 board, where I aim to pass stored 32-bit ADC data through a FIR filter. Specifically, I am capturing voice data from a microphone with an 8 kHz sampling rate at 32 bits. I designed a Low Pass filter using MATLAB with the following specifications:

• Filter Type: Low Pass
• Window: Hamming
• Order: 100
• Sampling Frequency (Fs): 8000 Hz
• Cutoff Frequency (Fc): 300 Hz

After designing the filter, I exported the coefficients and implemented them in the FIR II IP core. However, I encountered an issue where the output is 55 bits instead of the desired 32 bits. I attempted to handle this by truncating the 23 least significant bits, but this resulted in significant noise.

I am seeking advice on how to approach the truncation process effectively. Is there a method that can assist in determining which bits to remove?

Can i use the NCO IP core to generate a signal and to pass through the FIR filter in order to observe it with simualtion ?

Thank you.

[Kshitij_Intel · Accepted solution]

Hi,

You can use the NCO IP core to generate a signal and to pass through the FIR filter in order to observe it with simulation or on Signal Tap.

Thank you,

Kshitij Goel 

[FvM]

Hi,
you don't need NCO to test filter in simulation, just use sin() function in your testbench.

Another point, voice spectrum is about 300 Hz - to 3.4 kHz, applying a 300 Hz low pass leaves about nothing of speech signal. Do you mean high pass?

[mitsvoid]

Hi,

I didn't know about the sin() function, I will try it.

Yes, I was wrong about the cutoff frequency of the FIR filter.

Thank you.

[mitsvoid]

I would like to ask one more question. Can you let me know if it is possible to add, for example, the FIP II IP core inside to my custom IP core, which is based on the Avalon-MM interface?

[Kshitij_Intel]

Hi,

I think you mean to add in platform designer/QSYS. If Yes, you can.

Thank you,

Kshitij Goel