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/*
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 * Copyright (c) 2021, Texas Instruments Incorporated
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * *  Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 *
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 * *  Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 *
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 * *  Neither the name of Texas Instruments Incorporated nor the names of
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 *    its contributors may be used to endorse or promote products derived
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 *    from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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​
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#include "arm_const_structs.h"
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#include "arm_math.h"
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#include "ti_msp_dl_config.h"
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​
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/* Number of samples */
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#define NUM_SAMPLES 256
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/* Global variables and defines for FFT */
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#define IFFTFLAG 0
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#define BITREVERSE 1
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​
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/*
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 * This sample array contains a reference signal with two frequency components:
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 *   sine wave of amplitude of 0.5 and 2kHz frequency, and
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 *   sine wave of amplitude of 0.25 and 4kHz frequency
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 * The sample frequency of the signal is 100kHz.
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 */
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static uint32_t gDstBuffer[NUM_SAMPLES] = {0, 4091, 8021, 11639, 14810, 17421,
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    19391, 20671, 21246, 21137, 20397, 19109, 17378, 15325, 13078, 10767, 8513,
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    6421, 4577, 3040, 1839, 976, 424, 128, 16, 0, -16, -128, -424, -976, -1839,
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    -3040, -4577, -6421, -8513, -10767, -13078, -15325, -17378, -19109, -20397,
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    -21137, -21246, -20671, -19391, -17421, -14810, -11639, -8021, -4091, 0,
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    4091, 8021, 11639, 14810, 17421, 19391, 20671, 21246, 21137, 20397, 19109,
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    17378, 15325, 13078, 10767, 8513, 6421, 4577, 3040, 1839, 976, 424, 128,
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    16, 0, -16, -128, -424, -976, -1839, -3040, -4577, -6421, -8513, -10767,
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    -13078, -15325, -17378, -19109, -20397, -21137, -21246, -20671, -19391,
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    -17421, -14810, -11639, -8021, -4091, 0, 4091, 8021, 11639, 14810, 17421,
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    19391, 20671, 21246, 21137, 20397, 19109, 17378, 15325, 13078, 10767, 8513,
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    6421, 4577, 3040, 1839, 976, 424, 128, 16, 0, -16, -128, -424, -976, -1839,
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    -3040, -4577, -6421, -8513, -10767, -13078, -15325, -17378, -19109, -20397,
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    -21137, -21246, -20671, -19391, -17421, -14810, -11639, -8021, -4091, 0,
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    4091, 8021, 11639, 14810, 17421, 19391, 20671, 21246, 21137, 20397, 19109,
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    17378, 15325, 13078, 10767, 8513, 6421, 4577, 3040, 1839, 976, 424, 128,
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    16, 0, -16, -128, -424, -976, -1839, -3040, -4577, -6421, -8513, -10767,
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    -13078, -15325, -17378, -19109, -20397, -21137, -21246, -20671, -19391,
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    -17421, -14810, -11639, -8021, -4091, 0, 4091, 8021, 11639, 14810, 17421,
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    19391, 20671, 21246, 21137, 20397, 19109, 17378, 15325, 13078, 10767, 8513,
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    6421, 4577, 3040, 1839, 976, 424, 128, 16, 0, -16, -128, -424, -976, -1839,
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    -3040, -4577, -6421, -8513, -10767, -13078, -15325, -17378, -19109, -20397,
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    -21137, -21246, -20671, -19391, -17421, -14810, -11639, -8021, -4091, 0,
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    4091, 8021, 11639, 14810, 17421};
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​
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/* Expected Maximum amplitude and frequency index of FFT */
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#define GOLDEN_FFT_MAX_FREQ_INDEX (5)
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​
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/* Array with FFT results */
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volatile int16_t gFFTOutput[NUM_SAMPLES * 2];
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/* Maximum amplitude of FFT */
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volatile uint32_t gFFTmaxValue;
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/* Index of maximum frequency */
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volatile uint32_t gFFTmaxFreqIndex;
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​
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int main(void)
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{
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    SYSCFG_DL_init();
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​
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    /* Compute the FFT on the sampled data and then find the
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     * FFT point for maximum energy and the energy value */
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    arm_cfft_q15(
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        &arm_cfft_sR_q15_len256, (q15_t *) gDstBuffer, IFFTFLAG, BITREVERSE);
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    arm_cmplx_mag_q15((q15_t *) gDstBuffer, (q15_t *) gFFTOutput, NUM_SAMPLES);
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    arm_max_q15((q15_t *) gFFTOutput, NUM_SAMPLES, (q15_t *) &gFFTmaxValue,
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        (uint32_t *) &gFFTmaxFreqIndex);
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​
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    /*
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     * The following results are expected:
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     * gFFTOutput = FFT output of the signal
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     * gFFTmaxFreqIndex = 5
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     *  Note that bin 5 corresponds to ~1,953Hz +- ~195Hz, which represents
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     *  the 2kHz major component.
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     *  The next higher component in the FFT is bin 10 which corresponds to
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     *  the ~3,906Hz +- ~195Hz, representing the 4kHz component.
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     */
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    if (gFFTmaxFreqIndex != GOLDEN_FFT_MAX_FREQ_INDEX) {
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        __BKPT(0);
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    }
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​
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    while (1) {
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    }
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}
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​