AnsweredAssumed Answered

Expert Code Generator

Question asked by Chadster1976 on Jul 18, 2016
Latest reply on Jul 27, 2016 by Kader.M



I am attempting to use the FFT Accelerator on an EZ Kit 21489 and I see in the documentation that there is an Expert Code Generator for assisting with Twiddles and configuration of pins available for the Visual DSP users. Is this available as a plugin for CrossCore users? I have searched the site as well as help documentation and cannot find reference to this for CrossCore. Am I missing something? Is there another equivalent option for CC users other than switching over to Visual DSP?


Just to clarify things a bit... I am a very novice user trying to implement an FFT and IFFT of 4096 points (or higher if I get to understand the process a little better). I have looked through the 256 and 512 point example talkthrough but I am a little confused about the best method of implementing a larger N-size FFT using the crosscore environment. I thought maybe the Expert Code Generator would be the answer, but after looking a bit deeper, I am thinking otherwise. I noticed that the twiddle files included in the ECG zip are not of the same resolution as the SpecialTwiddles2048.dat file included in the 512 example that has been circulated on this board and in the examples folder. I understand that the N>256 must be accomplished in a separate manner (Divide and Conquer as per instruction manual), but I am unsure of where I get the appropriate twiddles from? I considered making them myself using a MatLAB script, but I also noticed that the first 125+ lines in the SpecialTwiddles file were 1,0,-0,1,1,0,-0,1, etc,. which does not coincide with a normal twiddle cycle that I would generate from MatLAB.


I have just noticed some twiddle calls in the CrossCore help files (twidfftf_fr16_8k_table, accel_twidfft, etc.)

but I am unsure as to when to use these as opposed to the 512 example that used predefined twittles via a .dat file call? Would it be better to call the twiddles via a .dat file, or via the Run-Time Library method? Could anyone help steer me in the correct direction? An example even of the 512 point that uses the RTL for the twiddles, if appropriate, would be greatly appreciated - I could make the appropriate adjustments (I think) to get to a 4096 point version.


Any insights on this would be greatly appreciated.