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FIR II core IP outputs incorrect data.

alperenpalp
Novice
2,922 Views

Hello,

It's my first time using intel's FIR filter IP and I'm having difficulties getting it working.

I basically want to low-pass filter the data coming from the ADC (LTC2387) using FIR II IP. The filter is fractional rate filter.

Here are some of the filter specs:

Input sampling rate: 15 MSPS

Filter clock : 60 MHz

Coeffs: 51 taps, 16-bit signed binary

Input 16-bit singed binary

Output: 36-bit signed binary.

The data coming from the ADC is in 2's complement, and therefore firstly I convert it to signed binary(bit magnitude) and feed the converted data to the filter's input.

To make sure that everything's working I make the input to the filter constant and observe the output, expecting that the output stays constant as well, but it doesn't.

The input is constant -256 (FF00h in 2s complement 8100h in signed magnitude) and the output looks quite random as you can see in the attachment.

I also attached the archieve file which include the filter I am using. The filter is in pre_process_20MSPS.vhd file along with the conversion from 2's comlement to singed magnitude process.

What am I doing wrong?

 

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CheePin_C_Intel
Employee
2,642 Views

Hi,

Would you mind to help opening a new thread on this. Thank you very much.

View solution in original post

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alperenpalp
Novice
364 Views

Hello CheePin,

I was going to ask another question about this, should I ask here or open another thread?

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CheePin_C_Intel
Employee
2,643 Views

Hi,

Would you mind to help opening a new thread on this. Thank you very much.

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