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<H1 class=aTitle>F2812 fft 源程序 TI例程</H1></DIV>
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<TD width=120>[日期：<SPAN id=TimeLabel>2005-4-18</SPAN>]</TD>
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<BR>/* */ <BR>/* fft.c */ <BR>/* */
<BR>/**************************************************************/
<BR><BR>/* <BR>Fast Fourier Transform (FFT). <BR>Using 8 points, takes
about 1.2 ms to execute one FFT. <BR>Sets up General Purpose Timer 1 to
generate events at 10 kHz. <BR>Will produce 10 kHz output on T1PWM and
T1PWM pins. <BR>*/ <BR><BR>#include "system.h" <BR>#include "eva.h"
<BR>#include "io2407.h" <BR>#include "adc.h" <BR>#include "interrup.h"
<BR><BR>#include "fftcmplx.h" /* Complex structure definition*/
<BR><BR>extern void FFT(COMPLEX *Y, int N); /* FFT Function */ <BR><BR>/*
The following define gives the number of samples. */ <BR>/* It should
divide exactly into 512 */ <BR>/* Should N be increased, to say to 32,
then the execution */ <BR>/* time of the FFT would increase */
<BR><BR>#define N 8 <BR><BR>unsigned int perform_fft = 0; /* Flag driven
by interrupt */
<BR><BR>/*************************************************************/
<BR>/* <BR>Initialise General Purpose Timers GPT1 and GPT2 <BR>*/
<BR>/*************************************************************/
<BR><BR>/* Initialise General Purpose Timer 1. */ <BR><BR>void
init_GPT1(void) <BR>{ <BR>MCRA |= T1PWM; /* Turn on T1PWM */ <BR>T1CON =
0x8142; /* Turn off GPT1 */ <BR>GPTCONA = 0x0041; /* Active low. */
<BR>T1PR = 1475; /* Sample at 10 kHz */ <BR>T1CMPR = 0; /* Duty = 0% */
<BR>T1CNT = 0xFFFE; /* Set to -2 */ <BR>T1CON = 0x9142; /* Start timer 1
*/ <BR><BR>EVAIFRA = 0xFFFF; /* Clear any pending interrupts */
<BR>EVAIMRA |= T1PINT_FLAG; /* Enable T1 period interrupt */ <BR>}
<BR><BR>/* Initialise General Purpose Timer 2 */ <BR><BR>void
init_GPT2(void) <BR>{ <BR>MCRA |= T2PWM; /* Turn on T2PWM */ <BR>T2CON =
0x8142; /* Turn off GPT2 */ <BR>GPTCONA |= 0x0008; /* Controlled from GPT1
*/ <BR>T2PR = 1475; /* Sample at 10 kHz */ <BR>T2CMPR = 0; /* Duty cycle
0% decimal */ <BR>T2CNT = 0xFFFE; /* Set to -2 */ <BR>T2CON = 0x9142; /*
Start timer 2 */ <BR>}
<BR><BR>/**************************************************************/
<BR><BR>void init_ADC() <BR>{ <BR>/* Non Cascade for 8 measurements. */
<BR>/* Will affect RESULT0 to RESULT7 only */ <BR><BR>ADCCTRL1 = (ADC_SOFT
| ADC_CPS /*| ADC_ACQ_PS3 | ADC_ACQ_PS2*/ ); <BR><BR>CHSELSEQ1 = 0x3210;
/* 8 measurements 0 */ <BR>CHSELSEQ2 = 0x0000; <BR>CHSELSEQ3 = 0xFFFF;
<BR>CHSELSEQ4 = 0xFFFF; <BR>MAX_CONV = 0x0007; /* 8 measurements, not 0 */
<BR><BR>/* Reset sequence at zero and software start of conversion */
<BR><BR>ADCCTRL2 = ( RST_SEQ1 | SOC_SEQ1); <BR><BR>} /* No semicolon here
*/ <BR><BR>/***********************************************************/
<BR><BR>int input_buffer[N] = {8191, 8191, 8191, 8191, 0, 0, 0, 0};
<BR><BR>COMPLEX y[N]; /* Variable passed to FFT and modified */
<BR><BR>/***********************************************************/
<BR>/* <BR>Shuffle input buffer along one place. <BR>Put latest input from
ADC into first buffer location. <BR>Input from ADCIN2 lies in range 0 to
FFC0h (65472 decimal). <BR>Divide by 8 to limit range from 0 to 8184.
<BR>*/ <BR>/***********************************************************/
<BR><BR>void shuffle_and_read(void) <BR>{ <BR>signed int i; <BR><BR>for (
i = N-1 ; i > 0 ; i--) <BR>{ <BR>input_buffer[i] = input_buffer[i-1];
<BR>} <BR><BR>input_buffer[0] = (RESULT2 >> 3); <BR>}
<BR><BR>/***********************************************************/
<BR>/* <BR>Copy from input buffer to complex structure. <BR>When FFT is
performed, the complex structure is overwritten <BR>by the return values.
<BR>*/ <BR>/***********************************************************/
<BR><BR>void copy_input_to_complex(void) <BR>{ <BR>unsigned int i;
<BR><BR>for ( i = 0 ; i < N; i++) <BR>{ <BR>(y[i]).real =
input_buffer[i]; <BR>(y[i]).imag = 0; <BR>} <BR>}
<BR><BR>/***********************************************************/
<BR>/* <BR>Main program <BR>Uses timers to read analog input on ADCIN2
into a buffer <BR>and then perform an 8-point FFT on it. <BR>*/
<BR>/**********************************************************/
<BR><BR>void main(void) <BR>{ <BR>signed int output1, output2; <BR>signed
int x; /* General purpose variable. */ <BR>signed int i; /* Counter */
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