73 lines
2.3 KiB
C++
73 lines
2.3 KiB
C++
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#include <stdio.h>
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#include <stdlib.h>
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#include <math.h>
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#include <cstring>
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#include "pico/stdlib.h"
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#include "hardware/pio.h"
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#include "hardware/dma.h"
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#include "hardware/adc.h"
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#include "hardware/irq.h"
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typedef signed int fix15;
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// Helpers for 16.15 fixed-point arithmetic
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constexpr __always_inline fix15 multiply_fix15(fix15 a, fix15 b) {return (fix15)(((signed long long)(a) * (signed long long)(b)) >> 15);}
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constexpr __always_inline fix15 float_to_fix15(float a) {return (fix15)(a * 32768.0f);}
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constexpr __always_inline float fix15_to_float(fix15 a) {return (float)(a) / 32768.0f;}
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constexpr __always_inline fix15 int_to_fix15(int a) {return (fix15)(a << 15);}
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constexpr __always_inline int fix15_to_int(fix15 a) {return (int)(a >> 15);}
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constexpr unsigned int SAMPLE_COUNT = 512u;
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class ADCFFT {
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private:
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unsigned int adc_channel;
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unsigned int adc_pin;
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float sample_rate;
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unsigned int log2_samples;
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unsigned int shift_amount;
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int dma_channel;
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// Here's where we'll have the DMA channel put ADC samples
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uint8_t sample_array[SAMPLE_COUNT];
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// Lookup tables
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fix15 sine_table[SAMPLE_COUNT]; // a table of sines for the FFT
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fix15 filter_window[SAMPLE_COUNT]; // a table of window values for the FFT
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// And here's where we'll copy those samples for FFT calculation
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fix15 fr[SAMPLE_COUNT];
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fix15 fi[SAMPLE_COUNT];
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int max_freq_dex = 0;
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void FFT();
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void init();
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public:
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ADCFFT() : ADCFFT(0, 26, 10000.0f) {};
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ADCFFT(unsigned int adc_channel, unsigned int adc_pin) : ADCFFT(adc_channel, adc_pin, 10000.0f) {}
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ADCFFT(unsigned int adc_channel, unsigned int adc_pin, float sample_rate) :
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adc_channel(adc_channel), adc_pin(adc_pin), sample_rate(sample_rate) {
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log2_samples = log2(SAMPLE_COUNT);
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shift_amount = 16u - log2_samples;
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dma_channel = dma_claim_unused_channel(true);
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memset(sample_array, 0, SAMPLE_COUNT);
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memset(fr, 0, SAMPLE_COUNT * sizeof(fix15));
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memset(fi, 0, SAMPLE_COUNT * sizeof(fix15));
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init();
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};
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~ADCFFT();
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void update();
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float max_frequency();
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int get_scaled(unsigned int i, unsigned int scale);
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};
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