scaling fixed point fft

Started by Bob in comp.dsp14 years ago 18 replies

Hello, I have constructed a 256 pt complex fft. My scaling is causing problems as the outputs from each stage are divided by 4 to...

Hello, I have constructed a 256 pt complex fft. My scaling is causing problems as the outputs from each stage are divided by 4 to avoid overflow. The input data and the twiddle factor coeffs are 16 bits wide (Q15). My problem is that when the data arrives at the last two butterfly stages of the FFT, it is non-existant, due to all the scaling beforehand. All inputs to these stages are zero....


Fixed Point Arithmetic resources

Started by Ashwin in comp.dsp14 years ago 9 replies

Hi, I'm looking for good links to information on Fixed Point Arithmetic. The only good resource I could find was - Fixed Point...

Hi, I'm looking for good links to information on Fixed Point Arithmetic. The only good resource I could find was - Fixed Point Arithmetic: An Introduction - by Randy Yates http://mel.interspace.dk/~sune/old-stuff/files/reading/fixed-point.pdf But, it is only an intro and does not deal with concepts like overflow, saturation and scaling. Are there any other good resources on the we...


floating point v fixed point

Started by Nick ELLIOTT in comp.dsp14 years ago 7 replies

My application is going to need a bit of fixed point, a bit of floating point calculations. Any advice as to whether a 720MHz fixed point...

My application is going to need a bit of fixed point, a bit of floating point calculations. Any advice as to whether a 720MHz fixed point processor (TI C64x) executing floating point libraries, can compete with a 225MHz floating point processor (TI C67x) ? Regards Nick


Fixed Point DSP Vs Floating Point DSP

Started by Sandeep Chikkerur in comp.dsp14 years ago 4 replies

Hi, I searched the internet to find out the difference between a fixed point & a floating point DSP. To my surprise, I did not find a well...

Hi, I searched the internet to find out the difference between a fixed point & a floating point DSP. To my surprise, I did not find a well defined difference. Plz, can anyone differentiate between the two so that a layman can also understand ? Thanx in advance...


Blackfin FFT precision

Started by Ed in comp.dsp14 years ago 1 reply

The 32 bit data types of the Blackfin processors should preserve more bits of precision than a 16 bit fixed point processor, if the FFT routines...

The 32 bit data types of the Blackfin processors should preserve more bits of precision than a 16 bit fixed point processor, if the FFT routines make use of the 32 bit data types. Can anyone comment on whether this is the case, and how well the precision is maintained in the calculations? How much precision would result from a library FFT routine of 2048 points of 10 bit data after an FFT i...


Fixed Point issues

Started by Xefteris Stefanos in comp.dsp14 years ago 4 replies

Hello, I am trying to implement an FIR and an IIR filter in fixed point arithmetic. The actual filter is of no importance(so I have implemented...

Hello, I am trying to implement an FIR and an IIR filter in fixed point arithmetic. The actual filter is of no importance(so I have implemented the simplest filter possible),as long as it is in fixed point,and moreover as I can give as input the desirable precision. I wrote the following piece of code,but the results are totaly bogus.. Can anybody suggest some help?I dont know if I have to ...


Floating point to fixed point conversion.

Started by Gowtham in comp.dsp14 years ago 9 replies

Hi, I am Gowtham, i am doing project on DSP in speech compression, i have written a program in C and i need to implement this on a fixed...

Hi, I am Gowtham, i am doing project on DSP in speech compression, i have written a program in C and i need to implement this on a fixed point chip,so now i have to convert the floating point numbers into fixed point and then implement the fixed point operations on the chip, i would appreciate if anyone can help me in this regard. Thanking all Gowtham


IIR on TI 55xx

Started by AntonZ in comp.dsp7 years ago 3 replies

I try to implement an IIR on a 16-bit fixed-point 5510 DSP. After calculating the filter in Matlab, I got the following coefficients: > > ...

I try to implement an IIR on a 16-bit fixed-point 5510 DSP. After calculating the filter in Matlab, I got the following coefficients: > > iir.tf.num ans = 1.0e-005 * 0.0868 0.3470 0.5205 0.3470 0.0868 > > iir.tf.den ans = 1.0000 -3.8373 5.5250 -3.5375 0.8498 Now I decompose the filter into two biqads: > > tf2sos(iir.tf.num,iir.tf.den) ans


Fixed Point Resonant Lowpass Filter C code required

Started by Malcolm Haylock in comp.dsp14 years ago 1 reply

Hi everyone, I'm a relatively newbie to DSP and would like to add a resonant lowpass filter to a simple sound application. I have a floating...

Hi everyone, I'm a relatively newbie to DSP and would like to add a resonant lowpass filter to a simple sound application. I have a floating point routine to do this but am wondering if this is possible in fixed point. I can't easily convert my existing floating point routine as this involves some very large gain multiplications not possible in the range of the fixed point values of t...


Problem with fixed point lowpass filter design

Started by Malcolm Haylock in comp.dsp14 years ago 3 replies

Hi Everyone, I'm a newcomer to DSP and am trying to write a Fixed Point implementation of the bilinear transform lowpass filter as outlined...

Hi Everyone, I'm a newcomer to DSP and am trying to write a Fixed Point implementation of the bilinear transform lowpass filter as outlined in the Audio EQ Cookbook (http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt): y[n] = (b0/a0)*x[n] + (b1/a0)*x[n-1] + (b2/a0)*x[n-2] - (a1/a0)*y[n-1] - (a2/a0)*y[n-2] where for a lowpass filter: b0 = (1 - ...


searching for a low power DSP, about 80 MIPS with flash and A/D's

Started by Fonze in comp.dsp14 years ago 10 replies

Hello everyone, So I'm lookig for a DSP with the following characteristics : - about 80-100 MIPS - 16 bits fixed point operations -...

Hello everyone, So I'm lookig for a DSP with the following characteristics : - about 80-100 MIPS - 16 bits fixed point operations - low-power for embedded application - on-chip flash (or EEPROM) - at least 8 12-bits A/D's As you see, my application doesn't require too much calculation power. But the problem is I just can't find what I need. All DSPs I find with all the peripherals are...


Fixed-point implementation of pow(0.5,x) and pow(x, 0.75)

Started by Anders Buvarp in comp.dsp14 years ago 17 replies

Hello, I need to implement in fixed-point pow(0.5,x) and pow(x, 0.75) and I was wondering if anyone has some pointers with regards to...

Hello, I need to implement in fixed-point pow(0.5,x) and pow(x, 0.75) and I was wondering if anyone has some pointers with regards to this? We are dealing with 32-bit words. Any help is greatly appreciated. -- Best regards, Anders Buvarp anders@lsil.com


Fixed point FFT

Started by Luca Baradel in comp.dsp14 years ago 1 reply

Hi, I have to implement the FFT for a vector long 2048 samples in a DSP which does not support floating point. Do you have any link to already...

Hi, I have to implement the FFT for a vector long 2048 samples in a DSP which does not support floating point. Do you have any link to already written code that computes the FFT with integer computation? Thank you in advance


Arranging biquads

Started by Curl in comp.dsp14 years ago 6 replies

Hello all ! Considering IIR filtering with fixed-point DSP : How to arrange biquads to reduce roundoff or quantization noise ? If anyone...

Hello all ! Considering IIR filtering with fixed-point DSP : How to arrange biquads to reduce roundoff or quantization noise ? If anyone has resources, advices or links ! Thank you.


Fixed point FFT in C

Started by Eric Meurville in comp.dsp14 years ago 1 reply

I am looking for an efficient fixed point FFT in C. Does someone know an implementation on PIC18 (I know that PIC18 is not a DSP but this...

I am looking for an efficient fixed point FFT in C. Does someone know an implementation on PIC18 (I know that PIC18 is not a DSP but this question is in the frame of a feasibility study with high constraints on costs) ? Thanks, EMe.


Fixed Point Library for Simulation?

Started by Alexander Peter in comp.dsp14 years ago 1 reply

Hi maybe I had the wrong keywords? I was gooling this group to find a fixed point class or library to simulate my target DSP arithmetic on a...

Hi maybe I had the wrong keywords? I was gooling this group to find a fixed point class or library to simulate my target DSP arithmetic on a Windows Platform. Any hints? Alexander


1.15 LMS problem ...please help

Started by rahul in comp.dsp14 years ago 1 reply

Hi friends, I am running an 1 tap complex tracker with an adaptive weight using a LMS algorithm. u-input d-ideal points y-filtered...

Hi friends, I am running an 1 tap complex tracker with an adaptive weight using a LMS algorithm. u-input d-ideal points y-filtered points w- coefficient y(i)=w*(i).u(i) e(i)=d(i)-y(i) w(i+1)=w(i)+mu.e(i).u(i) mu=0.01 The floating point algorithm works well with this value of mu. I have done a matlab fixed point 1.15 and 1.31 implementation of the above , and find that it ...


Fixed point implementation of 4'th order IIR filters

Started by Heureka in comp.dsp14 years ago 7 replies

Hi Does anyone have some guidelines on how to implement a 4'th order low-pass Butterworth IIR filter in fixed point. My cut-off frequency is...

Hi Does anyone have some guidelines on how to implement a 4'th order low-pass Butterworth IIR filter in fixed point. My cut-off frequency is relatively close to the DC frequency so high precision is needed for the coefficients. What about realization structure and so on! I have implemented the bit-flipping algorithm in http://www.cmsa.wmin.ac.uk/~artur/pdf/Paper16.pdf for quantization of...


Division

Started by Luca Baradel in comp.dsp14 years ago 6 replies

Does anybody know any efficient algorithm to compute the inverse of a number in a fixed point DSP? I have to perform the division and I have...

Does anybody know any efficient algorithm to compute the inverse of a number in a fixed point DSP? I have to perform the division and I have about 30 cicles to do it. I thought that a good way is to do a/b = a * inv(b). Right now the inverse is computed by series approximation exploiting the log properties, but I think there are far better ideas, like using somehow a lookup table. An...


Scaling to prevent overflow (Fixed Point)

Started by Heureka in comp.dsp14 years ago 3 replies

Hi, I've designed a fixed point filterbank based on cascaded second order sections. To this stage I have the filter coefficients, but finding...

Hi, I've designed a fixed point filterbank based on cascaded second order sections. To this stage I have the filter coefficients, but finding it hard to decide at which nodes the scaling should be done. Do any of you have some useful design rules? Some well-written litterature would be great too! Thomas:)