mirror of https://github.com/wb2osz/direwolf.git
172 lines
4.3 KiB
C
172 lines
4.3 KiB
C
/* fsk_demod_state.h */
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#ifndef FSK_DEMOD_STATE_H
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/*
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* Demodulator state.
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* Different copy is required for each channel & subchannel being processed concurrently.
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*/
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typedef enum bp_window_e { BP_WINDOW_TRUNCATED,
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BP_WINDOW_COSINE,
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BP_WINDOW_HAMMING,
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BP_WINDOW_BLACKMAN,
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BP_WINDOW_FLATTOP } bp_window_t;
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struct demodulator_state_s
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{
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/*
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* These are set once during initialization.
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*/
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#define TICKS_PER_PLL_CYCLE ( 256.0 * 256.0 * 256.0 * 256.0 )
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int pll_step_per_sample; // PLL is advanced by this much each audio sample.
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// Data is sampled when it overflows.
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int ms_filter_size; /* Size of mark & space filters, in audio samples. */
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/* Started off as a guess of one bit length */
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/* but somewhat longer turned out to be better. */
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/* Currently using same size for any prefilter. */
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#define MAX_FILTER_SIZE 320 /* 304 is needed for profile C, 300 baud & 44100. */
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/*
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* FIR filter length relative to one bit time.
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* Use same for both bandpass and lowpass.
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*/
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float filter_len_bits;
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/*
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* Window type for the mark/space filters.
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*/
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bp_window_t bp_window;
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/*
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* Alternate Low pass filters.
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* First is arbitrary number for quick IIR.
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* Second is frequency as ratio to baud rate for FIR.
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*/
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int lpf_use_fir; /* 0 for IIR, 1 for FIR. */
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float lpf_iir;
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float lpf_baud;
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/*
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* Automatic gain control. Fast attack and slow decay factors.
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*/
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float agc_fast_attack;
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float agc_slow_decay;
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/*
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* Hysteresis before final demodulator 0 / 1 decision.
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*/
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float hysteresis;
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/*
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* Phase Locked Loop (PLL) inertia.
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* Larger number means less influence by signal transitions.
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*/
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float pll_locked_inertia;
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float pll_searching_inertia;
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/*
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* Optional band pass pre-filter before mark/space detector.
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*/
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int use_prefilter; /* True to enable it. */
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float prefilter_baud; /* Cutoff frequencies, as fraction of */
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/* baud rate, beyond tones used. */
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/* Example, if we used 1600/1800 tones at */
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/* 300 baud, and this was 0.5, the cutoff */
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/* frequencies would be: */
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/* lower = min(1600,1800) - 0.5 * 300 = 1450 */
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/* upper = max(1600,1800) + 0.5 * 300 = 1950 */
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float pre_filter[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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/*
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* Kernel for the mark and space detection filters.
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*/
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float m_sin_table[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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float m_cos_table[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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float s_sin_table[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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float s_cos_table[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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/*
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* The rest are continuously updated.
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*/
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signed int data_clock_pll; // PLL for data clock recovery.
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// It is incremented by pll_step_per_sample
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// for each audio sample.
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signed int prev_d_c_pll; // Previous value of above, before
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// incrementing, to detect overflows.
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/*
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* Most recent raw audio samples, before/after prefiltering.
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*/
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float raw_cb[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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/*
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* Input to the mark/space detector.
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* Could be prefiltered or raw audio.
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*/
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float ms_in_cb[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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/*
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* Outputs from the mark and space amplitude detection,
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* used as inputs to the FIR lowpass filters.
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* Kernel for the lowpass filters.
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*/
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int lp_filter_size;
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float m_amp_cb[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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float s_amp_cb[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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float lp_filter[MAX_FILTER_SIZE] __attribute__((aligned(16)));
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float m_peak, s_peak;
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float m_valley, s_valley;
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float m_amp_prev, s_amp_prev;
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int prev_demod_data; // Previous data bit detected.
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// Used to look for transitions.
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/* These are used only for "9600" baud data. */
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int lfsr; // Descrambler shift register.
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/*
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* Finally, try to come up with some sort of measure of the audio input level.
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* Let's try gathering both the peak and average of the
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* absolute value of the input signal over some period such as 100 mS.
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*
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*/
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int lev_period; // How many samples go into one measure.
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int lev_count; // Number accumulated so far.
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float lev_peak_acc; // Highest peak so far.
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float lev_sum_acc; // Accumulated sum so far.
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/*
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* These will be updated every 'lev_period' samples:
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*/
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float lev_last_peak;
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float lev_last_ave;
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float lev_prev_peak;
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float lev_prev_ave;
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};
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#define FSK_DEMOD_STATE_H 1
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#endif |