/*******************************************************************************
Vendor: Xilinx
Associated Filename: window_fn_class.h
Purpose: Vivado HLS tutorial example
Revision History: March 13, 2012 - initial release
*******************************************************************************
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#ifndef WINDOW_FN_CLASS_H_
#define WINDOW_FN_CLASS_H_
#include <cmath>
using namespace std;
// Create a unique namespace which can help avoid name clashes
namespace xhls_window_fn {
// Enumerated type for window type
typedef enum {
RECT = 0, HANN, HAMMING, GAUSSIAN
} win_fn_t;
// The window_fn template class
// TI: input type - can be any floating or fixed point (ap_fixed<>) type
// TO: ouput type - same as TI
// TC: coefficient type - same as TI
// SZ: window size
// FT: function type - Hann, Hamming, etc; enumerated above
template<class TI, class TO, class TC, int SZ, win_fn_t FT = RECT>
class window_fn {
const int win_len;
const win_fn_t win_type;
public:
window_fn(void) : win_len(SZ), win_type(FT) {};
// The method that convolves indata w/ the window coeffs
void apply(TO *outdata, TI *indata);
// Get methods for polling class instance info - if not used, no hardware
// will be created for them
int get_len(void) { return win_len; };
win_fn_t get_type(void) { return win_type; };
};
// This template function selects the coefficient equation specific to the
// window function type chosen at class object instantiation.
template<int SZ, win_fn_t FT>
double coef_calc(int i)
{
double coef_val;
switch(FT) {
case RECT:
coef_val = 1.0;
break;
case HANN:
coef_val = 0.5 * (1.0 - cos(2.0 * M_PI * i / double(SZ)));
break;
case HAMMING:
coef_val = 0.54 - 0.46 * cos(2.0 * M_PI * i / double(SZ));
break;
case GAUSSIAN:
const double gaussian_sigma = 0.5;
double x = (i - SZ / 2) / (gaussian_sigma * (SZ / 2));
coef_val = exp(-0.5 * x * x);
break;
}
return coef_val;
}
// This template function is used to initialize the contents of the
// coefficient table. Currently, in order for the table to be mapped to
// a ROM it must be defined at file (global) scope, i.e. it cannot be
// a class method (member function).
template<class TC, int SZ, win_fn_t FT>
void init_coef_tab(TC *coeff)
{
for (int i = 0; i < SZ; i++) {
coeff[i] = coef_calc<SZ,FT>(i);
}
};
template<class TI, class TO, class TC, int SZ, win_fn_t FT>
void window_fn<TI,TO,TC,SZ,FT>::apply(TO *outdata, TI *indata)
{
TC coeff_tab[SZ];
// To ensure coeff_tab is implemented as a ROM on the FPGA, it must
// be initialized by a separate function. No hardware is synthesized
// for ROM initialization.
init_coef_tab<TC,SZ,FT>(coeff_tab);
winfn_loop:
for (unsigned i = 0; i < SZ; i++) {
//#pragma AP PIPELINE // implemented as TCL directive in this example
outdata[i] = coeff_tab[i] * indata[i];
}
}
}; // namespace xhls_window_fn
#endif // WINDOW_FN_CLASS_H_
