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2D FFT in MPC5775K

Question asked by YANG TIANXI on Jun 28, 2016
Latest reply on Nov 14, 2017 by 磊 殷

I have some questions in writing  2D FFT code in MPC5775k by  using its SPT


1)  Use WIN instruction, failed.


   // Transfer input vector by PDMA
   // 128 x 64-bit real numbers(32bit real,32 bit image), 64-bit PDMA SRAM word holds 2 input points
   // Sign Extension,direct, 24 bit complex pack
   // VECTOR_LEN = 128 (128 x 2 input points in each), 128 = 0x0080
   // SRAM(input_addr) -> OPRAM (0x8000)
   0xA1040080, 0xDEADDEAD, 0x80000000, 0x01000001,    // test ,move data from SRAM to SPT OPRAM, ok

     // FFT 128 RDX4 instruction w/ complex input
     //  WIN instruction, multiply a constant complex, here is 2 + 0i;
    0x86000080, 0x80009000, 0x00000101, 0x00020000,    // WIN failed here

    // Stop Cmd
   0x10000000, 0x00000000, 0x00000000, 0x00000000,


what I  want to do is all the data  x 2,but failed, why?


2)  SPT is fixed point, when I do 2D FFT, the input data is comlex, and its range is  -2^23 to +2^23,

     Is SPT capable of doing such FFT?   I use the real FFT examples provided by NXP FAE, it supports

     input data range is 0 ~ 4096(with left shift, unsigned int)


I have implemented real FFT128/256/512/1024, supported  input data range is 0 ~ 4096, but get stuck in complex FFT when input data is very large.



3)  Where to find complex FFT example for MPC5775K in this forum?


Any help will be very appreciated..