/**************************************************************/ 
/* */ 
/*     fft.c */ 
/* */ 
/**************************************************************/ 

/* 
Fast Fourier Transform (FFT). 
Using 8 points, takes about 1.2 ms to execute one FFT. 
Sets up General Purpose Timer 1 to generate events at 10 kHz. 
Will produce 10 kHz output on T1PWM and T1PWM pins. 
*/ 

#include "system.h" 
#include "eva.h" 
#include "io2407.h" 
#include "adc.h" 
#include "interrup.h" 

#include "fftcmplx.h" /* Complex structure definition*/ 

extern void FFT(COMPLEX *Y, int N); /* FFT Function */ 

/* The following define gives the number of samples. */ 
/* It should divide exactly into 512 */ 
/* Should N be increased, to say to 32, then the execution */ 
/* time of the FFT would increase */ 

#define N 8 

unsigned int perform_fft = 0; /* Flag driven by interrupt */ 

/*************************************************************/ 
/* 
Initialise General Purpose Timers GPT1 and GPT2 
*/ 
/*************************************************************/ 

/* Initialise General Purpose Timer 1. */ 

void init_GPT1(void) 
{ 
MCRA = T1PWM; /* Turn on T1PWM */ 
T1CON = 0x8142; /* Turn off GPT1 */ 
GPTCONA = 0x0041; /* Active low. */ 
T1PR = 1475; /* Sample at 10 kHz */ 
T1CMPR = 0; /* Duty = 0% */ 
T1CNT = 0xFFFE; /* Set to -2 */ 
T1CON = 0x9142; /* Start timer 1 */ 

EVAIFRA = 0xFFFF; /* Clear any pending interrupts */ 
EVAIMRA = T1PINT_FLAG; /* Enable T1 period interrupt */ 
} 

/* Initialise General Purpose Timer 2 */ 

void init_GPT2(void) 
{ 
MCRA = T2PWM; /* Turn on T2PWM */ 
T2CON = 0x8142; /* Turn off GPT2 */ 
GPTCONA = 0x0008; /* Controlled from GPT1 */ 
T2PR = 1475; /* Sample at 10 kHz */ 
T2CMPR = 0; /* Duty cycle 0% decimal */ 
T2CNT = 0xFFFE; /* Set to -2 */ 
T2CON = 0x9142; /* Start timer 2 */ 
} 

/**************************************************************/ 

void init_ADC() 
{ 
/* Non Cascade for 8 measurements. */ 
/* Will affect RESULT0 to RESULT7 only */ 

ADCCTRL1 = (ADC_SOFT ADC_CPS /* ADC_ACQ_PS3 ADC_ACQ_PS2*/ ); 

CHSELSEQ1 = 0x3210; /* 8 measurements 0 */ 
CHSELSEQ2 = 0x0000; 
CHSELSEQ3 = 0xFFFF; 
CHSELSEQ4 = 0xFFFF; 
MAX_CONV = 0x0007; /* 8 measurements, not 0 */ 

/* Reset sequence at zero and software start of conversion */ 

ADCCTRL2 = ( RST_SEQ1 SOC_SEQ1); 

} /* No semicolon here */ 

/***********************************************************/ 

int input_buffer[N] = {8191, 8191, 8191, 8191, 0, 0, 0, 0}; 

COMPLEX y[N]; /* Variable passed to FFT and modified */ 

/***********************************************************/ 
/* 
Shuffle input buffer along one place. 
Put latest input from ADC into first buffer location. 
Input from ADCIN2 lies in range 0 to FFC0h (65472 decimal). 
Divide by 8 to limit range from 0 to 8184. 
*/ 
/***********************************************************/ 

void shuffle_and_read(void) 
{ 
signed int i; 

for ( i = N-1 ; i > 0 ; i--) 
{ 
input_buffer[i] = input_buffer[i-1]; 
} 

input_buffer[0] = (RESULT2 >> 3); 
} 

/***********************************************************/ 
/* 
Copy from input buffer to complex structure. 
When FFT is performed, the complex structure is overwritten 
by the return values. 
*/ 
/***********************************************************/ 

void copy_input_to_complex(void) 
{ 
unsigned int i; 

for ( i = 0 ; i < N; i++) 
{ 
(y[i]).real = input_buffer[i]; 
(y[i]).imag = 0; 
} 
} 

/***********************************************************/ 
/* 
Main program 
Uses timers to read analog input on ADCIN2 into a buffer 
and then perform an 8-point FFT on it. 
*/ 
/**********************************************************/ 

void main(void) 
{ 
signed int output1, output2; 
signed int x; /* General purpose variable. */ 
signed int i; /* Counter */ 
signed long temp; 

init_system(); /* Initialize variables and hardware */ 

init_ADC(); /* Initialise ADC */ 
init_GPT1(); /* Turn on timer 1 */ 
init_GPT2(); /* Turn on timer 2 */ 

MCRB &= 0xFFFE; /* I/O on IOPC0 for monitoring purposes */ 

IMR = INT2; /* Turn on INT 2 */ 

asm(" CLRC INTM"); /* Turn on maskable interrupts */ 

for ( ;; ) 
{ 
if ( perform_fft != 0 ) 
{ 
perform_fft = 0; /* Clear flag used to start fft */ 

PCDATDIR = 0x0101; /* IOPC0 high */ 

ADCCTRL2 = SOC_SEQ1; /* Start next conversion*/ 

copy_input_to_complex(); /* Copy inputs from receive buffer */ 


FFT(y,8); /* Calls generic FFT function*/ 

/* Determine magnitude of (y[0]).real */ 
/* output1 lies in range 0 to 32736 */ 

if ( (y[0]).real > 0) 
output1 = (y[0]).real; 
else 
output1 = -(y[0]).real; 

/* Determine magnitude of (y[0]).real */ 
/* output2 lies in range -32736 to 32736 */ 

if ( (y[2]).real > 0) 
output2 = (y[2]).real; 
else 
output2 = -(y[2]).real; 

/* Scale output in range 0 to 1475 */ 

temp = (signed long)(output1 * 2952); 
output1 = (signed int)(temp >> 16); 

T1CMPR = output1; 

temp = (signed long)( output2 * 2952); 
output2 = (signed int)(temp >> 16); 

T2CMPR = output1; 

shuffle_and_read(); /* Read in latest value from ADC */ 
/* and put into buffer */ 

PCDATDIR = 0x0100; /* IOPC0 low */ 

} /* End if */ 

} /* End for */ 

} /* End main() */ 

/************************************************************/ 

/* Interrupt routine */ 
/* The interrupt occurs once every 0.1 ms. 
/* Will make perform_fft = 1 once every 20 * 0.1 ms = 2 ms */ 

void c_int2(void) 
{ 
static unsigned int x; 

if ( 0x0027 == PIVR) 
{ 
EVAIFRA = T1PINT_FLAG; /* Clear GPT1 period interrupt */ 

if ( x < 19 ) /* Increase if FFT with more points */ 
{ 
x++; 
} 
else 
{ 
x = 0; 
perform_fft = 1; /* Global flag to start FFT */ 
} 

} 
} 

/* End of fft.c */ 

/************************************************************/