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75 lines
2.5 KiB
C
75 lines
2.5 KiB
C
/**
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* Baseband
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*
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* Various functions for baseband sample processing
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*
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* Copyright (C) 2012 by Benjamin Larsson <benjamin@southpole.se>
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* Copyright (C) 2015 Tommy Vestermark
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*/
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#ifndef INCLUDE_BASEBAND_H_
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#define INCLUDE_BASEBAND_H_
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#include <stdint.h>
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/// This will give a noisy envelope of OOK/ASK signals
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/// Subtract the bias (-128) and get an envelope estimation (absolute squared)
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/// @param *iq_buf: input samples (I/Q samples in interleaved uint8)
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/// @param *y_buf: output
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/// @param len: number of samples to process
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void envelope_detect(uint8_t const *iq_buf, uint16_t *y_buf, uint32_t len);
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// for evaluation
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void envelope_detect_nolut(uint8_t const *iq_buf, uint16_t *y_buf, uint32_t len);
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void magnitude_est_cu8(uint8_t const *iq_buf, uint16_t *y_buf, uint32_t len);
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void magnitude_true_cu8(uint8_t const *iq_buf, uint16_t *y_buf, uint32_t len);
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void magnitude_est_cs16(int16_t const *iq_buf, uint16_t *y_buf, uint32_t len);
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void magnitude_true_cs16(int16_t const *iq_buf, uint16_t *y_buf, uint32_t len);
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#define FILTER_ORDER 1
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/// Filter state buffer
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typedef struct {
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int16_t y[FILTER_ORDER];
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int16_t x[FILTER_ORDER];
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} FilterState;
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/// FM_Demod state buffer
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typedef struct {
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int32_t br, bi; // Last I/Q sample
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int32_t xlp, ylp; // Low-pass filter state
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} DemodFM_State;
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/// Lowpass filter
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///
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/// Function is stateful
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/// @param *x_buf: input samples to be filtered
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/// @param *y_buf: output from filter
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/// @param len: number of samples to process
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/// @param FilterState: State to store between chunk processing
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void baseband_low_pass_filter(uint16_t const *x_buf, int16_t *y_buf, uint32_t len, FilterState *state);
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/// FM demodulator
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///
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/// Function is stateful
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/// @param *x_buf: input samples (I/Q samples in interleaved uint8)
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/// @param *y_buf: output from FM demodulator
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/// @param len: number of samples to process
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/// @param DemodFM_State: State to store between chunk processing
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void baseband_demod_FM(uint8_t const *x_buf, int16_t *y_buf, unsigned long num_samples, DemodFM_State *state);
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// for evaluation
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void baseband_demod_FM_cs16(int16_t const *x_buf, int16_t *y_buf, unsigned long num_samples, DemodFM_State *state);
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/// Initialize tables and constants
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/// Should be called once at startup
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void baseband_init(void);
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#endif /* INCLUDE_BASEBAND_H_ */
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