feat: Initial esp32-hacking project with firmware sources and docs

esp-crab/slave_recv/main/app/app_ifft.h

@@ -0,0 +1,26 @@
+
+#pragma once
+#ifdef __cplusplus
+extern "C" {
+#endif
+#include "IQmathLib.h"
+
+typedef struct {
+    float real;
+    float imag;
+} Complex;
+typedef struct {
+    _iq16 real;
+    _iq16 imag;
+} Complex_Iq;
+void IRAM_ATTR fft_iq(Complex_Iq *X,  int inverse) ;
+void IRAM_ATTR fft(Complex *X, int N, int inverse);
+
+float complex_magnitude_iq(Complex_Iq z);
+float complex_phase_iq(Complex_Iq z);
+float complex_magnitude(Complex z);
+float complex_phase(Complex z);
+
+#ifdef __cplusplus
+}
+#endif