To install the FFT MEX function, place the MEX file in your MATLAB software working directory, or in the MATLAB software, change directory to the directory containing the MEX file.
Note:
For Windows platforms, the correct
libIp_xfft_v9_1_bitacc_cmodel.dll
and
libgmp.dll
files must be copied to the directory where the FFT MEX function has been installed before running the MEX function.
Note:
For Linux platforms, the
libIp_xfft_v9_1_bitacc_cmodel.so
and
libgmp.so.11
files must be copied to the directory where the FFT MEX function has been installed before running the MEX function, or be visible using the $LD_LIBRARY_PATH environment variable. $LD_LIBRARY_PATH must be set correctly before starting MATLAB software.
The FFT MEX function is called
xfft_v9_1_bitacc_mex
. Enter this function name without arguments at the MATLAB software command line to see usage information. The FFT MEX function syntax is:
[output_data, blk_exp, overflow] = xfft_v9_1_bitacc_mex(generics, nfft, input_data, scaling_sch, direction)
The function inputs are shown in
Table: FFT MEX Function Inputs
.
Table 5-6:
FFT MEX Function Inputs
|
Input
|
Description
|
Permitted values
|
|
generics
|
Core parameters. Single-element, 9-field structure containing all relevant generics defining the core
|
|
|
generics.C_NFFT_MAX
|
log
2
(maximum transform length)
|
3-16
|
|
generics.C_ARCH
|
Architecture
|
1 = Radix-4, Burst I/O,
2 = Radix-2, Burst I/O,
3 = Pipelined, Streaming I/O,
4 = Radix-2 Lite, Burst I/O
|
|
generics.C_HAS_NFFT
|
Run time configurable transform length
|
0 = no, 1 = yes
|
|
generics.C_USE_FLT_PT
|
Core interface
|
0 = fixed-point
|
1 = single-precision floating-point
|
|
generics.C_INPUT_WIDTH
|
Input data width
|
8-34 bits
|
32 bits
|
|
generics.C_TWIDDLE_WIDTH
|
Phase factor width
|
8-34 bits
|
24-25 bits
|
|
generics.C_HAS_SCALING
|
Type of scaling
|
0 = unscaled, 1 = other
|
0
|
|
generics.C_HAS_BFP
|
Type of scaling if C_HAS_SCALING = 1
|
0 = scaled,
1 = block floating-point
|
0
|
|
generics.C_HAS_ROUNDING
|
Type of rounding
|
0 = truncation,
1 = convergent rounding
|
0
|
|
nfft
|
log
2
(transform length) for this transform. Single integer.
|
Maximum value is C_NFFT_MAX. Minimum value is 6 for Radix-4, Burst I/O architecture, or 3 for other architectures.
|
Maximum value is C_NFFT_MAX. Minimum value is 6 for Radix-4, Burst I/O architecture, or 3 for other architectures.
|
|
input_data
|
Input data. 1D array of complex data with 2nfft elements.
|
All components must be in the range of
-1.0
£
data < +1.0.
|
All components must be representable in the MATLAB software single datatype (equivalent to a float in C++).
|
|
scaling_sch
|
Scaling schedule. 1D array of integer values size S = number of stages. For Radix-4 and Streaming architectures,
S = nfft/2, rounded up to the next integer. For Radix-2 and Radix-2 Lite architectures,
S = nfft.
|
Each value corresponds to scaling to be performed by the corresponding stage and must be in the range 0 to 3. scaling_sch[1] is the scaling for the first stage.
|
N/A
|
|
direction
|
Transform direction. Single integer.
|
1 = forward FFT,
0 = inverse FFT (IFFT)
|
1 = forward FFT,
0 = inverse FFT (IFFT)
|
The following notes apply to the MEX function inputs.
1.
nfft
input is only used for run time configurable transform length (that is, generics.C_HAS_NFFT = 1). It is ignored otherwise and generics. C_NFFT_MAX is used instead.
2.
For fixed-point input FFTs (that is, generics.C_USE_FLT_PT = 0), to ensure identical numerical behavior to the hardware, pre-quantize the input_data values to have precision determined by C_INPUT_WIDTH. This is achieved using the MATLAB software built-in quantize function.
3.
scaling_sch
input is only used for a fixed-point input, scaled FFT (that is, generics.C_USE_FLT_PT = 0, generics.C_HAS_SCALING = 1, and generics.
C_HAS_BFP = 0). It is ignored otherwise.
4.
input_data
can be in natural or bit/digit-reversed sample index order. The MEX function produces samples in the same ordering format as they were input.
The function outputs are shown in
Table: FFT MEX Function Outputs
.
Table 5-7:
FFT MEX Function Outputs
|
Output
|
Description
|
Validity
|
|
output_data
|
Output data. 1D array of complex data with 2nfft elements.
|
Always valid.
|
|
blk_exp
|
Block exponent. Single integer.
|
Only valid if using block floating-point (if generics.C_HAS_SCALING = 1 and C_HAS_BFP = 1). Zero otherwise.
|
|
overflow
|
Overflow. Single integer. 1 indicates overflow occurred, 0 indicates no overflow occurred.
|
Only valid with a scaled FFT (if generics.C_HAS_SCALING = 1 and generics.C_HAS_BFP = 0) or an FFT with floating-point interfaces (that is, generics.C_USE_FLT_PT = 1). Zero otherwise.
|
The notes under the following headings apply to the MEX function outputs.
•
General
•
FFTs with Fixed-Point Interface
•
FFTs with Floating-Point Interface