[FAQ] CC2642R: FFT on CC13x2/CC26x2 devices

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/*
 *  ======== empty.c ========
 */

/* For usleep() */
#include <unistd.h>
#include <stdint.h>
#include <stddef.h>

/* Driver Header files */
#include <ti/drivers/GPIO.h>
// #include <ti/drivers/I2C.h>
// #include <ti/drivers/SPI.h>
// #include <ti/drivers/UART.h>
// #include <ti/drivers/Watchdog.h>

/* Driver configuration */
#include "ti_drivers_config.h"

#include "arm_math.h"
#include "arm_const_structs.h"

#define TEST_LENGTH_SAMPLES 4096

/* -------------------------------------------------------------------
* This is a fix for undefined __hardfp_sqrtf and __hardfp_sqrt symbols
* ------------------------------------------------------------------- */
int __hardfp_sqrt(int f){ return sqrt(f); }
float32_t __hardfp_sqrtf(float32_t f){ return sqrt(f); }

/* -------------------------------------------------------------------
* External Input and Output buffer Declarations for FFT Bin Example
* ------------------------------------------------------------------- */
extern float32_t testInput_f32_10khz[TEST_LENGTH_SAMPLES];
static float32_t testOutput[TEST_LENGTH_SAMPLES/2];

/* ------------------------------------------------------------------
* Global variables for FFT Bin Example
* ------------------------------------------------------------------- */
uint32_t fftSize = 2048;
uint32_t ifftFlag = 0;
uint32_t doBitReverse = 1;
arm_cfft_instance_f32 varInstCfftF32;
/* Reference index at which max energy of bin occurs */
uint32_t refIndex = 213, testIndex = 0;

/* ----------------------------------------------------------------------
* Max magnitude FFT Bin test
* ------------------------------------------------------------------- */
void MaxMagnitudeFFTBinTest(void)
{
  arm_status status;
  float32_t maxValue;
  status = ARM_MATH_SUCCESS;

  status=arm_cfft_init_f32(&varInstCfftF32,fftSize);


  /* Process the data through the CFFT/CIFFT module */
  GPIO_write(CONFIG_GPIO_LED_0, CONFIG_GPIO_LED_ON);
  GPIO_write(CONFIG_GPIO_LED_1, CONFIG_GPIO_LED_OFF);
  arm_cfft_f32(&varInstCfftF32, testInput_f32_10khz, ifftFlag, doBitReverse); // 2.587ms for 1024 points | 5.820ms for 2048 (280'411 clock cycles)
  GPIO_write(CONFIG_GPIO_LED_0, CONFIG_GPIO_LED_OFF);
  GPIO_write(CONFIG_GPIO_LED_1, CONFIG_GPIO_LED_ON);

  /* Process the data through the Complex Magnitude Module for
  calculating the magnitude at each bin */
  GPIO_write(CONFIG_GPIO_LED_0, CONFIG_GPIO_LED_ON);
  GPIO_write(CONFIG_GPIO_LED_1, CONFIG_GPIO_LED_OFF);
  arm_cmplx_mag_f32(testInput_f32_10khz, testOutput, fftSize); //22.020ms for 1024 points | 44.01 ms for 2048 points (2'128'459 clock cycles)
  GPIO_write(CONFIG_GPIO_LED_0, CONFIG_GPIO_LED_OFF);
  GPIO_write(CONFIG_GPIO_LED_1, CONFIG_GPIO_LED_ON);

  /* Calculates maxValue and returns corresponding BIN value */
  arm_max_f32(testOutput, fftSize, &maxValue, &testIndex);
  status = (testIndex != refIndex) ? ARM_MATH_TEST_FAILURE : ARM_MATH_SUCCESS;

  if (status != ARM_MATH_SUCCESS)
  {
      while (1); // something went wrong
  }
  else
  {
     // everything is working
  }
}


/*
 *  ======== mainThread ========
 */
void *mainThread(void *arg0)
{
    /* Call driver init functions */
    GPIO_init();
    // I2C_init();
    // SPI_init();
    // UART_init();
    // Watchdog_init();

    /* Configure the LED pin */
    GPIO_setConfig(CONFIG_GPIO_LED_0, GPIO_CFG_OUT_STD | GPIO_CFG_OUT_LOW);
    GPIO_setConfig(CONFIG_GPIO_LED_1, GPIO_CFG_OUT_STD | GPIO_CFG_OUT_LOW);

    /* Turn on user LED */

    MaxMagnitudeFFTBinTest(); // 24.77ms



    while (1) {
    }
}