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+/*---------------------------------------------------------------------------*\
+
+  FILE........: fsk.h
+  AUTHOR......: Brady O'Brien
+  DATE CREATED: 6 January 2016
+
+  C Implementation of 2FSK/4FSK modulator/demodulator, based on octave/fsk_horus.m
+
+\*---------------------------------------------------------------------------*/
+
+/*
+  Copyright (C) 2016 David Rowe
+
+  All rights reserved.
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License version 2.1, as
+  published by the Free Software Foundation.  This program is
+  distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+  License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+
+#ifndef __C2FSK_H
+#define __C2FSK_H
+
+#include <stdint.h>
+#include "comp.h"
+#include "kiss_fftr.h"
+#include "modem_stats.h"
+
+#define MODE_2FSK 2
+#define MODE_4FSK 4
+
+#define MODE_M_MAX 4
+
+#define FSK_SCALE 16383
+
+/* default internal parameters */
+#define FSK_DEFAULT_P     8      /* Number of timing offsets we have to choose from, try to keep P >= 8 */
+#define FSK_DEFAULT_NSYM 50      /* See Nsym below */
+#define FSK_NONE         -1      /* unused parameter */
+
+struct FSK {
+    /*  Static parameters set up by fsk_init */
+    int Ndft;               /* freq offset est fft */
+    int Fs;                 /* sample freq */
+    int N;                  /* processing buffer size */
+    int Rs;                 /* symbol rate */
+    int Ts;                 /* samples per symbol */
+    int Nmem;               /* size of extra mem for timing adj */
+    int P;                  /* oversample rate for timing est/adj */
+    int Nsym;               /* Number of symbols processed by demodulator in each call, also the timing estimator window */
+    int Nbits;              /* Number of bits spat out in a processing frame */
+    int f1_tx;              /* f1 for modulator */
+    int tone_spacing;       /* Space between TX freqs for modulator (and option mask freq estimator) */
+    int mode;               /* 2FSK or 4FSK */
+    float tc;               /* time constant for smoothing FFTs */
+    int est_min;            /* Minimum frequency for freq. estimator */
+    int est_max;            /* Maximum frequency for freq. estimator */
+    int est_space;          /* Minimum frequency spacing for freq. estimator */
+    float* hann_table;	    /* Precomputed or runtime computed hann window table */
+    
+    /*  Parameters used by demod */
+    float* Sf;	            /* Average of magnitude spectrum */
+    COMP phi_c[MODE_M_MAX]; /* phase of each demod local oscillator */
+    COMP *f_dc;             /* down converted samples               */
+        
+    kiss_fft_cfg fft_cfg;   /* Config for KISS FFT, used in freq est */
+    float norm_rx_timing;   /* Normalized RX timing */
+            
+    /*  Parameters used by mod */
+    COMP tx_phase_c;        /* TX phase, but complex */ 
+    
+    /*  Statistics generated by demod */
+    float  EbNodB;            /* Estimated EbNo in dB */
+    float  f_est[MODE_M_MAX]; /* Estimated frequencies (peak method) */
+    float  f2_est[MODE_M_MAX];/* Estimated frequencies (mask method) */
+    int    freq_est_type;     /* which estimator to use              */
+    float  ppm;               /* Estimated PPM clock offset */
+    float  SNRest;            /* used for LLRs */
+    float  v_est;             /* used for LLRs */
+    float  rx_sig_pow;
+    float  rx_nse_pow;
+    
+    /*  Parameters used by mod/demod and driving code */
+    int nin;                /* Number of samples to feed the next demod cycle */
+    int burst_mode;         /* enables/disables 'burst' mode */
+    int lock_nin;           /* locks nin during testing */
+    
+    /*  modem statistics struct */
+    struct MODEM_STATS *stats;
+    int normalise_eye;      /* enables/disables normalisation of eye diagram */
+};
+
+/*
+ * Create a FSK modem
+ * 
+ * int Fs - Sample frequency
+ * int Rs - Symbol rate
+ * int M  - 2 for 2FSK, 4 for 4FSK
+ * int f1_tx - first tone frequency
+ * int tone_spacing - frequency spacing (for modulator and optional "mask" freq estimator)
+ */
+struct FSK * fsk_create(int Fs, int Rs, int M, int f1_tx, int tone_spacing);
+
+/*
+ * Create a FSK modem - advanced version
+ * 
+ * int Fs - Sample frequency
+ * int Rs - Symbol rate
+ * int M  - 2 for 2FSK, 4 for 4FSK
+ * int P  - number of timing offsets to choose from (suggest >= 8)
+ * int Nsym  - windows size for timing estimator
+ * int f1_tx - first tone frequency
+ * int tone_spacing - frequency spacing (for modulator and optional "mask" freq estimator)
+ */
+struct FSK * fsk_create_hbr(int Fs, int Rs, int M, int P, int Nsym, int f1_tx, int tone_spacing);
+
+/*
+ * Set the minimum and maximum frequencies at which the freq. estimator can find tones
+ */
+void fsk_set_freq_est_limits(struct FSK *fsk,int fmin, int fmax);
+
+/* 
+ * Clear the estimator states
+ */
+void fsk_clear_estimators(struct FSK *fsk);
+
+/*
+ * Fills MODEM_STATS struct with demod statistics
+ */
+void fsk_get_demod_stats(struct FSK *fsk, struct MODEM_STATS *stats);
+
+/*
+ * Destroy an FSK state struct and free it's memory
+ * 
+ * struct FSK *fsk - FSK config/state struct to be destroyed
+ */
+void fsk_destroy(struct FSK *fsk);
+
+/*
+ * Modulates Nsym bits into N samples
+ * 
+ * struct FSK *fsk   - FSK config/state struct, set up by fsk_create
+ * float fsk_out[]   - Buffer for samples of modulated FSK, fsk->Ts*(nbits/(M>>1)) in length
+ * uint8_t tx_bits[] - Buffer containing Nbits unpacked bits
+ * int     nbits     - number of bits to transmit
+ */
+void fsk_mod(struct FSK *fsk, float fsk_out[], uint8_t tx_bits[], int nbits);
+
+/*
+ * Modulates Nsym bits into N samples
+ * 
+ * struct FSK *fsk   - FSK config/state struct, set up by fsk_create
+ * float fsk_out[]   - Buffer for samples of "voltage" used to modulate an external VCO
+ *                   - fsk->Ts*(nbits/(M>>1)) in length
+ * uint8_t tx_bits[] - Buffer containing Nbits unpacked bits
+ * int     nbits     - number of bits to transmit
+ */
+void fsk_mod_ext_vco(struct FSK *fsk, float vco_out[], uint8_t tx_bits[], int nbits);
+
+/*
+ * Modulates Nsym bits into N complex samples
+ * 
+ * struct FSK *fsk   - FSK config/state struct, set up by fsk_create
+ * comp fsk_out[]    - Buffer for samples of modulated FSK, fsk->Ts*(nbits/(M>>1)) in length
+ * uint8_t tx_bits[] - Buffer containing Nbits unpacked bits
+ * int     nbits     - number of bits to transmit
+ */
+void fsk_mod_c(struct FSK *fsk, COMP fsk_out[], uint8_t tx_bits[], int nbits);
+
+/*
+ * Returns the number of samples needed for the next fsk_demod() cycle
+ *
+ * struct FSK *fsk - FSK config/state struct, set up by fsk_create
+ * returns - number of samples to be fed into fsk_demod next cycle 
+ */
+uint32_t fsk_nin(struct FSK *fsk);
+
+
+/*
+ * Demodulate some number of FSK samples. The number of samples to be 
+ *  demodulated can be found by calling fsk_nin().
+ * 
+ * struct FSK *fsk   - FSK config/state struct, set up by fsk_create
+ * uint8_t rx_bits[] - Buffer for fsk->Nbits unpacked bits to be written
+ * float fsk_in[]    - nin samples of modulated FSK
+ */
+void fsk_demod(struct FSK *fsk, uint8_t rx_bits[], COMP fsk_in[]);
+
+/*
+ * Soft decision demodulation
+ * 
+ * struct FSK *fsk - FSK config/state struct, set up by fsk_create
+ * float rx_flit[] - M x Nsym array of filtermagnitude outputs
+ * float fsk_in[]  - nin samples of modualted FSK
+ */
+void fsk_demod_sd(struct FSK *fsk, float rx_filt[], COMP fsk_in[]);
+
+/* enables/disables normalisation of eye diagram samples */
+  
+void fsk_stats_normalise_eye(struct FSK *fsk, int normalise_enable);
+
+/* Set the FSK modem into burst demod mode */
+
+void fsk_enable_burst_mode(struct FSK *fsk);
+
+/* Set freq est algorithm 0: peak 1:mask */
+void fsk_set_freq_est_alg(struct FSK *fsk, int est_type);
+
+#endif