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Hey I found the code in dsp library of the control suite ( in FPU folder). This code is supposed to find the real fft of the adc input. But I am unable to figure out which ADC pin to give the input for. There is no watch variable for it also.
// ========================================================================
// This software is licensed for use with Texas Instruments C28x
// family DSCs. This license was provided to you prior to installing
// the software. You may review this license by consulting a copy of
// the agreement in the doc directory of this library.
// ------------------------------------------------------------------------
// Copyright (C) 2010-2011 Texas Instruments, Incorporated.
// All Rights Reserved.
// ========================================================================
//
// File: Main.c -- Real-time RFFT with 12-bit ADC Input Test Example
//
// TITLE: DSP2833x Device Real-time Real FFT Test Program.
//
//=========================================================================
// DESCRIPTION:
//
// This program shows how to compute a real FFT with 12-bit real-time ADC
// input and associated spectrum magnitude, phase. The input data is
// collected by interrupt service routine function adc_isr(). The signal
// input (can be any signal from signal generator or sensor) is excerted
// in ADC input A0. The signal is sampled by epwm module and sampling
// frequency is defined in Lab.h. Here is 48kHz. The dynamic range of the
// input signal should be less than 0~3V. Real time real FFT is conducted
// frame by frame. As long as one frame of data is collected by adc_isr,
// it will set the FFTStartFlag. Whenever the main program detect the
// FFTStartFlag set, the FFT calculate starts. The FFTStartFlag is cleared
// after the calculation finished.
//
// The input buffer must be aligned to a multiple of the FFT size if using
// RFFT_adc_f32. If you do not wish to align the input buffer then use the
// RFFT_adc_f32u function. In this case, the section alignment #pragma can
// be commented. However, using this function will reduce cycle performance
// of the algorithm.
//
//
// FUNCTIONS:
//
// void RFFT_adc_f32 (RFFT_ADC_F32_STRUCT *)
// void RFFT_f32_mag (RFFT_F32_STRUCT *)
// void RFFT_f32_phase (RFFT_F32_STRUCT *)
//
// Where RFFT_ADC_F32_STRUCT is a structure defined as:
//
// typedef struct {
// Uint16 *InBuf;
// void *Tail;
// } RFFT_ADC_F32_STRUCT;
//
// Where RFFT_F32_STRUCT is a structure defined as:
//
// typedef struct {
// float32 *InBuf;
// float32 *OutBuf;
// float32 *CosSinBuf;
// float32 *MagBuf;
// float32 *PhaseBuf;
// Uint16 FFTSize;
// Uint16 FFTStages;
// } RFFT_F32_STRUCT;
//
// ASSUMPTIONS:
//
// * OutBuf of RFFT_F32_STRUCT has to be passed to Tail of
// RFFT_ADC_F32_STRUCT
// * Input signal is stored in Signal.asm
// * FFTSize must be a power of 2 (32, 64, 128, etc)
// * FFTSize must be greater or equal to 32
// * FFTStages must be log2(FFTSize)
// * InBuf, OutBuf, CosSinBuf are FFTSize in length
// * MagBuf and PhaseBuf are FFTSize/2+1 in length
// * MagBuf and PhaseBuf are not used by this function.
// They are only used by the magitude and phase calculation functions.
//
// Watch Variables:
//
// InBuf(RFFT_ADC_F32_STRUCT) Input buffer
// InBuf(RFFT_F32_STRUCT) Not used
// Tail Stored the address of OutBuf
// OutBuf Output buffer
// CosSinBuf Twiddle factor buffer
// MagBuf Magnitude buffer
// PhaseBuf Phase buffer
// j Index of normalized digital frequency component
// freq Real analog frequency of raw signal
//
//###########################################################################
// $TI Release: C28x Floating Point Unit Library V1.30 $
// $Release Date: January 04, 2012 $
//###########################################################################
#include "DSP28x_Project.h" // Device Headerfile and Examples Include File
#include "math.h"
#include "float.h"
#include "FPU.h"
#define RFFT_STAGES 9
#define RFFT_SIZE (1 << RFFT_STAGES)
#define ADC_BUF_LEN RFFT_SIZE // ADC buffer length
#define ADC_SAMPLE_PERIOD 3124 // 3124 = (3125-1) = 48 KHz sampling w/ 150 MHz SYSCLKOUT
#define F_PER_SAMPLE 48000.0L/(float)RFFT_SIZE //Internal sampling rate is 48kHz
RFFT_ADC_F32_STRUCT rfft_adc;
RFFT_F32_STRUCT rfft;
float32 RFFToutBuff[RFFT_SIZE]; //Calculated FFT result
float32 RFFTF32Coef[RFFT_SIZE]; //Coefficient table buffer
float32 RFFTmagBuff[RFFT_SIZE/2+1]; //Magnitude of frequency spectrum
//--- Global Variables
Uint16 AdcBuf[ADC_BUF_LEN]; // ADC buffer allocation
volatile Uint16 FFTStartFlag = 0; // One frame data ready flag
Uint16 DEBUG_TOGGLE = 1; // Used in realtime mode investigation
// Prototype statements for functions found within this file.
interrupt void adc_isr(void);
/**********************************************************************
* Function: main()
*
* Description: Main function for C2833x Real-time RFFT
**********************************************************************/
void main(void)
{
Uint16 i,j;
float32 freq; // Frequency of single-frequency-component signal
//--- CPU Initialization
InitSysCtrl(); // Initialize the CPU (FILE: SysCtrl.c)
InitGpio(); // Initialize the shared GPIO pins (FILE: Gpio.c)
InitPieCtrl(); // Initialize and enable the PIE (FILE: PieCtrl.c)
//--- Peripheral Initialization
InitAdc(); // Initialize the ADC (FILE: Adc.c)
// Interrupts that are used in this example are re-mapped to
// ISR functions found within this file.
EALLOW; // This is needed to write to EALLOW protected register
PieVectTable.ADCINT = &adc_isr;
EDIS; // This is needed to disable write to EALLOW protected registers
rfft_adc.Tail = &rfft.OutBuf; //Link the RFFT_ADC_F32_STRUCT to
//RFFT_F32_STRUCT. Tail pointer of
//RFFT_ADC_F32_STRUCT is passed to
//the OutBuf pointer of RFFT_F32_STRUCT
rfft.FFTSize = RFFT_SIZE; //Real FFT size
rfft.FFTStages = RFFT_STAGES; //Real FFT stages
rfft_adc.InBuf = &AdcBuf[0]; //Input buffer
rfft.OutBuf = &RFFToutBuff[0]; //Output buffer
rfft.CosSinBuf = &RFFTF32Coef[0]; //Twiddle factor
rfft.MagBuf = &RFFTmagBuff[0]; //Magnitude output buffer
RFFT_f32_sincostable(&rfft); //Calculate twiddle factor
//Clean up output buffer
for (i=0; i < RFFT_SIZE; i++)
{
RFFToutBuff[i] = 0;
}
//Clean up magnitude buffer
for (i=0; i < RFFT_SIZE/2; i++)
{
RFFTmagBuff[i] = 0;
}
//--- Enable global interrupts
asm(" CLRC INTM, DBGM"); // Enable global interrupts and realtime debug
//--- Main Loop
while(1) // endless loop - wait for an interrupt
{
if(FFTStartFlag) // If one frame data ready, then do FFT
{
RFFT_adc_f32u(&rfft_adc); // This version of FFT doesn't need buffer alignment
RFFT_f32_mag(&rfft); // Calculate spectrum amplitude
j = 1;
freq = RFFTmagBuff[1];
for(i=2;i<RFFT_SIZE/2+1;i++)
{
//Looking for the maximum valude of spectrum magnitude
if(RFFTmagBuff[i] > freq)
{
j = i;
freq = RFFTmagBuff[i];
}
}
freq = F_PER_SAMPLE * (float)j; //Convert normalized digital frequency to analog frequency
FFTStartFlag = 0; //Start collecting the next frame of data
}
asm(" NOP");
}
} //end of main()
interrupt void adc_isr(void)
{
static Uint16 *AdcBufPtr = AdcBuf; // Pointer to ADC data buffer
static volatile Uint16 GPIO34_count = 0; // Counter for pin toggle
PieCtrlRegs.PIEACK.all = PIEACK_GROUP1; // Must acknowledge the PIE group
//--- Manage the ADC registers
AdcRegs.ADCTRL2.bit.RST_SEQ1 = 1; // Reset SEQ1 to CONV00 state
AdcRegs.ADCST.bit.INT_SEQ1_CLR = 1; // Clear ADC SEQ1 interrupt flag
//--- Read the ADC result
*AdcBufPtr++ = AdcMirror.ADCRESULT0; // Read the result
//--- Brute-force the circular buffer
if( AdcBufPtr == (AdcBuf + ADC_BUF_LEN) )
{
AdcBufPtr = AdcBuf; // Rewind the pointer to the beginning
FFTStartFlag = 1; // One frame data ready
}
//--- Example: Toggle GPIO18 so we can read it with the ADC
if(DEBUG_TOGGLE == 1)
{
GpioDataRegs.GPATOGGLE.bit.GPIO18 = 1; // Toggle the pin
}
//--- Example: Toggle GPIO34 at a 0.5 sec rate (connected to the LED on the ControlCARD).
// (1/48000 sec/sample)*(1 samples/int)*(x interrupts/toggle) = (0.5 sec/toggle)
// ==> x = 24000
if(GPIO34_count++ > 24000) // Toggle slowly to see the LED blink
{
GpioDataRegs.GPBTOGGLE.bit.GPIO34 = 1; // Toggle the pin
GPIO34_count = 0; // Reset the counter
}
return;
} //end of main()
//===========================================================================
// End of File
//===========================================================================
