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+/*!
+ * @file Adafruit_ZeroFFT.h
+ *
+ * This is an FFT library designed to run on ARM cortex M0 CPUs.
+ * It is based on FFT functions provided by ARM.
+ *
+ *
+ * Adafruit invests time and resources providing this open source code,
+ * please support Adafruit and open-source hardware by purchasing
+ * products from Adafruit!
+ *
+ * Written by Dean Miller for Adafruit Industries.
+ *
+ * BSD license, all text here must be included in any redistribution.
+ *
+ */
+
+#ifndef ADAFRUIT_ZEROFFT_ADAFRUIT_ZEROFFT_H_
+#define ADAFRUIT_ZEROFFT_ADAFRUIT_ZEROFFT_H_
+
+#include <Arduino.h>
+
+#define FFT_BIN(num, fs, size)                                                 \
+  (num *                                                                       \
+   ((float)fs / (float)size)) ///< return the center frequency of FFT bin 'num'
+                              ///< based on the sample rate and FFT stize
+#define FFT_INDEX(freq, fs, size)                                              \
+  ((int)((float)freq /                                                         \
+         ((float)fs /                                                          \
+          (float)size))) ///< return the bin index where the specified frequency
+                         ///< 'freq' can be found based on the passed sample
+                         ///< rate and FFT size
+
+#ifndef ALIGN4
+#define ALIGN4 __attribute__((aligned(4))) ///< align to 4 bytes
+#endif
+
+#ifndef q15_t
+#define q15_t int16_t ///< a q15 fractional data type
+#endif
+
+#ifndef q31_t
+#define q31_t int32_t ///< a q31 fractional data type
+#endif
+
+#ifndef float32_t
+#define float32_t float ///< 32 bit floating point data type
+#endif
+
+#define ZERO_FFT_MAX 4096 ///< the maximum allowed FFT size
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+/**************************************************************************/
+/*!
+    @brief  run an FFT on an int16_t array. Note that this is run in place.
+    @param source the data to FFT
+    @param length the length of the data. This must be a power of 2 and less
+   than or equal to ZERO_FFT_MAX
+    @return 0 on success, -1 on failure
+    @note The FFT is run in place on the data. A hanning window is applied to
+   the input data. The complex portion is discarded, and the real values are
+   returned.
+*/
+/**************************************************************************/
+extern int ZeroFFT(q15_t *source, uint16_t length);
+
+extern const q15_t window_hanning_16[];   ///< a hanning window of length 16
+extern const q15_t window_hanning_32[];   ///< a hanning window of length 32
+extern const q15_t window_hanning_64[];   ///< a hanning window of length 64
+extern const q15_t window_hanning_128[];  ///< a hanning window of length 128
+extern const q15_t window_hanning_256[];  ///< a hanning window of length 256
+extern const q15_t window_hanning_512[];  ///< a hanning window of length 512
+extern const q15_t window_hanning_1024[]; ///< a hanning window of length 1024
+extern const q15_t window_hanning_2048[]; ///< a hanning window of length 2048
+extern const q15_t window_hanning_4096[]; ///< a hanning window of length 4096
+
+#ifdef __cplusplus
+};
+#endif // __cplusplus
+#include "arm_common_tables.h"
+
+#endif /* ADAFRUIT_ZEROFFT_ADAFRUIT_ZEROFFT_H_ */