Ignorius
Newbie level 3
Hello guys,
I have been working on a project for a while and now stuck on a problem that annoys me. I am trying to fillter a wav file through a Low-Pass FIR filter on FPGA. When I send 8-bit samples to the FPGA it returns noisy output.
I have a receiver gets the 8-bit sample and passes it to the filter,
Filter then processes the sample and gives a 8-bit output to the transmitter.
Transmitter sends it to the PC in serial. You can see system in below figure.
**broken link removed**
I generated VHDL code of low pass filter with FDATool of MatLab with following spesifications.
Low-Pass - Equiripple (Direct Form I)
F sample: 44100Hz
F pass : 3500
Fstop : 4500
Order: 6
Filter Arithmetic: Fixed-point
Filter Precision: Specify all
Coefficients->
Numerator Word Length : 8
best precision fraction lengths: checked
use unsigned representation: cleared
scale the numerator coefficients...: cleared
Input/Output->
Input word length : 8
Input Fraction Length: 7
Output word Length: 8
Output Fraction length: 7
Filter Internals->
Product word length: 16
Product fraction length: 15
Accum word length : 18
Accum fraction length :15
Rounding mode: Nearest(convergent)
Overflow mode: Saturate
VHDL generation options are shown in figure
**broken link removed**
Wav file is sampled at 44100 khz and looks like
**broken link removed**
And the output wav file looks like this
**broken link removed**
When I zoom into both the first wav file and the filtered wav file, i see jumps and broken points in the wav file. as you can see below.
This one is wav file not filtered (zoomed in).
**broken link removed**
This one is filtered wav file (same zoomed as input).
**broken link removed**
This one is filtered wav file (with more zoom).
**broken link removed**
This one is filtered wav file (with much more zoom).
**broken link removed**
you can see sample points in this figure.
I will attach the wav file and the filtered one in audio.zip file.
I think i am doing something wrong about filter design but i could not find the actual problem. I tried, lots of variations with the given sipesifications.I hope this is a small mistake and can be solved easily. I would be gratefull for any answers. Please think about this problem and return me an idea.
Thanks
I have been working on a project for a while and now stuck on a problem that annoys me. I am trying to fillter a wav file through a Low-Pass FIR filter on FPGA. When I send 8-bit samples to the FPGA it returns noisy output.
I have a receiver gets the 8-bit sample and passes it to the filter,
Filter then processes the sample and gives a 8-bit output to the transmitter.
Transmitter sends it to the PC in serial. You can see system in below figure.
**broken link removed**
I generated VHDL code of low pass filter with FDATool of MatLab with following spesifications.
Low-Pass - Equiripple (Direct Form I)
F sample: 44100Hz
F pass : 3500
Fstop : 4500
Order: 6
Filter Arithmetic: Fixed-point
Filter Precision: Specify all
Coefficients->
Numerator Word Length : 8
best precision fraction lengths: checked
use unsigned representation: cleared
scale the numerator coefficients...: cleared
Input/Output->
Input word length : 8
Input Fraction Length: 7
Output word Length: 8
Output Fraction length: 7
Filter Internals->
Product word length: 16
Product fraction length: 15
Accum word length : 18
Accum fraction length :15
Rounding mode: Nearest(convergent)
Overflow mode: Saturate
VHDL generation options are shown in figure
**broken link removed**
Wav file is sampled at 44100 khz and looks like
**broken link removed**
And the output wav file looks like this
**broken link removed**
When I zoom into both the first wav file and the filtered wav file, i see jumps and broken points in the wav file. as you can see below.
This one is wav file not filtered (zoomed in).
**broken link removed**
This one is filtered wav file (same zoomed as input).
**broken link removed**
This one is filtered wav file (with more zoom).
**broken link removed**
This one is filtered wav file (with much more zoom).
**broken link removed**
you can see sample points in this figure.
I will attach the wav file and the filtered one in audio.zip file.
I think i am doing something wrong about filter design but i could not find the actual problem. I tried, lots of variations with the given sipesifications.I hope this is a small mistake and can be solved easily. I would be gratefull for any answers. Please think about this problem and return me an idea.
Thanks