--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.6pre17/src/fsk.c	Fri Jun 25 15:50:58 2010 +0200
@@ -0,0 +1,578 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * fsk.c - FSK modem transmit and receive parts
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2003 Steve Underwood
+ *
+ * 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 Lesser 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, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: fsk.c,v 1.60 2009/11/02 13:25:20 steveu Exp $
+ */
+
+/*! \file */
+
+#if defined(HAVE_CONFIG_H)
+#include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <inttypes.h>
+#include <string.h>
+#if defined(HAVE_TGMATH_H)
+#include <tgmath.h>
+#endif
+#if defined(HAVE_MATH_H)
+#include <math.h>
+#endif
+#include "floating_fudge.h"
+#include <assert.h>
+
+#include "spandsp/telephony.h"
+#include "spandsp/complex.h"
+#include "spandsp/dds.h"
+#include "spandsp/power_meter.h"
+#include "spandsp/async.h"
+#include "spandsp/fsk.h"
+
+#include "spandsp/private/fsk.h"
+
+const fsk_spec_t preset_fsk_specs[] =
+{
+    {
+        "V21 ch 1",
+        1080 + 100,
+        1080 - 100,
+        -14,
+        -30,
+        300*100
+    },
+    {
+        "V21 ch 2",
+        1750 + 100,
+        1750 - 100,
+        -14,
+        -30,
+        300*100
+    },
+    {
+        "V23 ch 1",
+        2100,
+        1300,
+        -14,
+        -30,
+        1200*100
+    },
+    {
+        "V23 ch 2",
+        450,
+        390,
+        -14,
+        -30,
+        75*100
+    },
+    {
+        "Bell103 ch 1",
+        2125 - 100,
+        2125 + 100,
+        -14,
+        -30,
+        300*100
+    },
+    {
+        "Bell103 ch 2",
+        1170 - 100,
+        1170 + 100,
+        -14,
+        -30,
+        300*100
+    },
+    {
+        "Bell202",
+        2200,
+        1200,
+        -14,
+        -30,
+        1200*100
+    },
+    {
+        "Weitbrecht 45.45", /* Used for TDD (Telecoms Device for the Deaf) */
+        1800,
+        1400,
+        -14,
+        -30,
+         4545
+    },
+    {
+        "Weitbrecht 50",    /* Used for TDD (Telecoms Device for the Deaf) */
+        1800,
+        1400,
+        -14,
+        -30,
+         5000
+    }
+};
+
+SPAN_DECLARE(int) fsk_tx_restart(fsk_tx_state_t *s, const fsk_spec_t *spec)
+{
+    s->baud_rate = spec->baud_rate;
+    s->phase_rates[0] = dds_phase_rate((float) spec->freq_zero);
+    s->phase_rates[1] = dds_phase_rate((float) spec->freq_one);
+    s->scaling = dds_scaling_dbm0((float) spec->tx_level);
+    /* Initialise fractional sample baud generation. */
+    s->phase_acc = 0;
+    s->baud_frac = 0;
+    s->current_phase_rate = s->phase_rates[1];
+    
+    s->shutdown = FALSE;
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(fsk_tx_state_t *) fsk_tx_init(fsk_tx_state_t *s,
+                                           const fsk_spec_t *spec,
+                                           get_bit_func_t get_bit,
+                                           void *user_data)
+{
+    if (s == NULL)
+    {
+        if ((s = (fsk_tx_state_t *) malloc(sizeof(*s))) == NULL)
+            return NULL;
+    }
+    memset(s, 0, sizeof(*s));
+
+    s->get_bit = get_bit;
+    s->get_bit_user_data = user_data;
+    fsk_tx_restart(s, spec);
+    return s;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) fsk_tx_release(fsk_tx_state_t *s)
+{
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) fsk_tx_free(fsk_tx_state_t *s)
+{
+    free(s);
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE_NONSTD(int) fsk_tx(fsk_tx_state_t *s, int16_t amp[], int len)
+{
+    int sample;
+    int bit;
+
+    if (s->shutdown)
+        return 0;
+    /* Make the transitions between 0 and 1 phase coherent, but instantaneous
+       jumps. There is currently no interpolation for bauds that end mid-sample.
+       Mainstream users will not care. Some specialist users might have a problem
+       with them, if they care about accurate transition timing. */
+    for (sample = 0;  sample < len;  sample++)
+    {
+        if ((s->baud_frac += s->baud_rate) >= SAMPLE_RATE*100)
+        {
+            s->baud_frac -= SAMPLE_RATE*100;
+            if ((bit = s->get_bit(s->get_bit_user_data)) == SIG_STATUS_END_OF_DATA)
+            {
+                if (s->status_handler)
+                    s->status_handler(s->status_user_data, SIG_STATUS_END_OF_DATA);
+                if (s->status_handler)
+                    s->status_handler(s->status_user_data, SIG_STATUS_SHUTDOWN_COMPLETE);
+                s->shutdown = TRUE;
+                break;
+            }
+            s->current_phase_rate = s->phase_rates[bit & 1];
+        }
+        amp[sample] = dds_mod(&(s->phase_acc), s->current_phase_rate, s->scaling, 0);
+    }
+    return sample;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(void) fsk_tx_power(fsk_tx_state_t *s, float power)
+{
+    s->scaling = dds_scaling_dbm0(power);
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(void) fsk_tx_set_get_bit(fsk_tx_state_t *s, get_bit_func_t get_bit, void *user_data)
+{
+    s->get_bit = get_bit;
+    s->get_bit_user_data = user_data;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(void) fsk_tx_set_modem_status_handler(fsk_tx_state_t *s, modem_tx_status_func_t handler, void *user_data)
+{
+    s->status_handler = handler;
+    s->status_user_data = user_data;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(void) fsk_rx_signal_cutoff(fsk_rx_state_t *s, float cutoff)
+{
+    /* The 6.04 allows for the gain of the DC blocker */
+    s->carrier_on_power = (int32_t) (power_meter_level_dbm0(cutoff + 2.5f - 6.04f));
+    s->carrier_off_power = (int32_t) (power_meter_level_dbm0(cutoff - 2.5f - 6.04f));
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(float) fsk_rx_signal_power(fsk_rx_state_t *s)
+{
+    return power_meter_current_dbm0(&s->power);
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(void) fsk_rx_set_put_bit(fsk_rx_state_t *s, put_bit_func_t put_bit, void *user_data)
+{
+    s->put_bit = put_bit;
+    s->put_bit_user_data = user_data;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(void) fsk_rx_set_modem_status_handler(fsk_rx_state_t *s, modem_tx_status_func_t handler, void *user_data)
+{
+    s->status_handler = handler;
+    s->status_user_data = user_data;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) fsk_rx_restart(fsk_rx_state_t *s, const fsk_spec_t *spec, int framing_mode)
+{
+    int chop;
+
+    s->baud_rate = spec->baud_rate;
+    s->framing_mode = framing_mode;
+    fsk_rx_signal_cutoff(s, (float) spec->min_level);
+
+    /* Detect by correlating against the tones we want, over a period
+       of one baud. The correlation must be quadrature. */
+    
+    /* First we need the quadrature tone generators to correlate
+       against. */
+    s->phase_rate[0] = dds_phase_rate((float) spec->freq_zero);
+    s->phase_rate[1] = dds_phase_rate((float) spec->freq_one);
+    s->phase_acc[0] = 0;
+    s->phase_acc[1] = 0;
+    s->last_sample = 0;
+
+    /* The correlation should be over one baud. */
+    s->correlation_span = SAMPLE_RATE*100/spec->baud_rate;
+    /* But limit it for very slow baud rates, so we do not overflow our
+       buffer. */
+    if (s->correlation_span > FSK_MAX_WINDOW_LEN)
+        s->correlation_span = FSK_MAX_WINDOW_LEN;
+
+    /* We need to scale, to avoid overflow in the correlation. */
+    s->scaling_shift = 0;
+    chop = s->correlation_span;
+    while (chop != 0)
+    {
+        s->scaling_shift++;
+        chop >>= 1;
+    }
+
+    /* Initialise the baud/bit rate tracking. */
+    s->baud_phase = 0;
+    s->frame_state = 0;
+    s->frame_bits = 0;
+    s->last_bit = 0;
+    
+    /* Initialise a power detector, so sense when a signal is present. */
+    power_meter_init(&(s->power), 4);
+    s->signal_present = 0;
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(fsk_rx_state_t *) fsk_rx_init(fsk_rx_state_t *s,
+                                           const fsk_spec_t *spec,
+                                           int framing_mode,
+                                           put_bit_func_t put_bit,
+                                           void *user_data)
+{
+    if (s == NULL)
+    {
+        if ((s = (fsk_rx_state_t *) malloc(sizeof(*s))) == NULL)
+            return NULL;
+    }
+    memset(s, 0, sizeof(*s));
+
+    s->put_bit = put_bit;
+    s->put_bit_user_data = user_data;
+    fsk_rx_restart(s, spec, framing_mode);
+    return s;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) fsk_rx_release(fsk_rx_state_t *s)
+{
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) fsk_rx_free(fsk_rx_state_t *s)
+{
+    free(s);
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+static void report_status_change(fsk_rx_state_t *s, int status)
+{
+    if (s->status_handler)
+        s->status_handler(s->status_user_data, status);
+    else if (s->put_bit)
+        s->put_bit(s->put_bit_user_data, status);
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE_NONSTD(int) fsk_rx(fsk_rx_state_t *s, const int16_t *amp, int len)
+{
+    int buf_ptr;
+    int baudstate;
+    int i;
+    int j;
+    int16_t x;
+    int32_t dot;
+    int32_t sum[2];
+    int32_t power;
+    complexi_t ph;
+
+    buf_ptr = s->buf_ptr;
+
+    for (i = 0;  i < len;  i++)
+    {
+        /* The *totally* asynchronous character to character behaviour of these
+           modems, when carrying async. data, seems to force a sample by sample
+           approach. */
+        for (j = 0;  j < 2;  j++)
+        {
+            s->dot[j].re -= s->window[j][buf_ptr].re;
+            s->dot[j].im -= s->window[j][buf_ptr].im;
+
+            ph = dds_complexi(&(s->phase_acc[j]), s->phase_rate[j]);
+            s->window[j][buf_ptr].re = (ph.re*amp[i]) >> s->scaling_shift;
+            s->window[j][buf_ptr].im = (ph.im*amp[i]) >> s->scaling_shift;
+
+            s->dot[j].re += s->window[j][buf_ptr].re;
+            s->dot[j].im += s->window[j][buf_ptr].im;
+
+            dot = s->dot[j].re >> 15;
+            sum[j] = dot*dot;
+            dot = s->dot[j].im >> 15;
+            sum[j] += dot*dot;
+        }
+        /* If there isn't much signal, don't demodulate - it will only produce
+           useless junk results. */
+        /* There should be no DC in the signal, but sometimes there is.
+           We need to measure the power with the DC blocked, but not using
+           a slow to respond DC blocker. Use the most elementary HPF. */
+        x = amp[i] >> 1;
+        power = power_meter_update(&(s->power), x - s->last_sample);
+        s->last_sample = x;
+        if (s->signal_present)
+        {
+            /* Look for power below turn-off threshold to turn the carrier off */
+            if (power < s->carrier_off_power)
+            {
+                if (--s->signal_present <= 0)
+                {
+                    /* Count down a short delay, to ensure we push the last
+                       few bits through the filters before stopping. */
+                    report_status_change(s, SIG_STATUS_CARRIER_DOWN);
+                    s->baud_phase = 0;
+                    continue;
+                }
+            }
+        }
+        else
+        {
+            /* Look for power exceeding turn-on threshold to turn the carrier on */
+            if (power < s->carrier_on_power)
+            {
+                s->baud_phase = 0;
+                continue;
+            }
+            if (s->baud_phase < (s->correlation_span >> 1) - 30)
+            {
+                s->baud_phase++;
+                continue;
+            }
+            s->signal_present = 1;
+            /* Initialise the baud/bit rate tracking. */
+            s->baud_phase = 0;
+            s->frame_state = 0;
+            s->frame_bits = 0;
+            s->last_bit = 0;
+            report_status_change(s, SIG_STATUS_CARRIER_UP);
+        }
+        /* Non-coherent FSK demodulation by correlation with the target tones
+           over a one baud interval. The slow V.xx specs. are too open ended
+           to allow anything fancier to be used. The dot products are calculated
+           using a sliding window approach, so the compute load is not that great. */
+
+        baudstate = (sum[0] < sum[1]);
+        switch (s->framing_mode)
+        {
+        case FSK_FRAME_MODE_SYNC:
+            /* Synchronous serial operation - e.g. for HDLC */
+            if (s->last_bit != baudstate)
+            {
+                /* On a transition we check our timing */
+                s->last_bit = baudstate;
+                /* For synchronous use (e.g. HDLC channels in FAX modems), nudge
+                   the baud phase gently, trying to keep it centred on the bauds. */
+                if (s->baud_phase < (SAMPLE_RATE*50))
+                    s->baud_phase += (s->baud_rate >> 3);
+                else
+                    s->baud_phase -= (s->baud_rate >> 3);
+            }
+            if ((s->baud_phase += s->baud_rate) >= (SAMPLE_RATE*100))
+            {
+                /* We should be in the middle of a baud now, so report the current
+                   state as the next bit */
+                s->baud_phase -= (SAMPLE_RATE*100);
+                s->put_bit(s->put_bit_user_data, baudstate);
+            }
+            break;
+        case FSK_FRAME_MODE_ASYNC:
+            /* Fully asynchronous mode */
+            if (s->last_bit != baudstate)
+            {
+                /* On a transition we check our timing */
+                s->last_bit = baudstate;
+                /* For async. operation, believe transitions completely, and
+                   sample appropriately. This allows instant start on the first
+                   transition. */
+                /* We must now be about half way to a sampling point. We do not do
+                   any fractional sample estimation of the transitions, so this is
+                   the most accurate baud alignment we can do. */
+                s->baud_phase = SAMPLE_RATE*50;
+            }
+            if ((s->baud_phase += s->baud_rate) >= (SAMPLE_RATE*100))
+            {
+                /* We should be in the middle of a baud now, so report the current
+                   state as the next bit */
+                s->baud_phase -= (SAMPLE_RATE*100);
+                s->put_bit(s->put_bit_user_data, baudstate);
+            }
+            break;
+        default:
+            /* Gather the specified number of bits, with robust checking to ensure reasonable voice immunity.
+               The first bit should be a start bit (0), and the last bit should be a stop bit (1) */
+            if (s->frame_state == 0)
+            {
+                /* Looking for the start of a zero bit, which hopefully the start of a start bit */
+                if (baudstate == 0)
+                {
+                    s->baud_phase = SAMPLE_RATE*(100 - 40)/2;
+                    s->frame_state = -1;
+                    s->frame_bits = 0;
+                    s->last_bit = -1;
+                }
+            }
+            else if (s->frame_state == -1)
+            {
+                /* Look for a continuous zero from the start of the start bit until
+                   beyond the middle */
+                if (baudstate != 0)
+                {
+                    /* If we aren't looking at a stable start bit, restart */
+                    s->frame_state = 0;
+                }
+                else
+                {
+                    s->baud_phase += s->baud_rate;
+                    if (s->baud_phase >= SAMPLE_RATE*100)
+                    {
+                        s->frame_state = 1;
+                        s->last_bit = baudstate;
+                    }
+                }
+            }
+            else
+            {
+                s->baud_phase += s->baud_rate;
+                if (s->baud_phase >= SAMPLE_RATE*(100 - 40))
+                {
+                    if (s->last_bit < 0)
+                        s->last_bit = baudstate;
+                    /* Look for the bit being consistent over the central 20% of the bit time. */
+                    if (s->last_bit != baudstate)
+                    {
+                        s->frame_state = 0;
+                    }
+                    else if (s->baud_phase >= SAMPLE_RATE*100)
+                    {
+                        /* We should be in the middle of a baud now, so report the current
+                           state as the next bit */
+                        if (s->last_bit == baudstate)
+                        {
+                            s->frame_bits |= (baudstate << s->framing_mode);
+                            s->frame_bits >>= 1;
+                            s->baud_phase -= (SAMPLE_RATE*100);
+                            if (++s->frame_state > s->framing_mode)
+                            {
+                                /* Check we have a stop bit */
+                                if (baudstate == 1)
+                                {
+                                    /* Check we have a start bit */
+                                    if ((s->frame_bits & 1) == 0)
+                                    {
+                                        /* Drop the start bit, and pass the rest back */
+                                        s->frame_bits >>= 1;
+                                        s->put_bit(s->put_bit_user_data, s->frame_bits);
+                                    }
+                                }
+                                s->frame_state = 0;
+                            }
+                        }
+                        else
+                        {
+                            s->frame_state = 0;
+                        }
+                        s->last_bit = -1;
+                    }
+                }
+            }
+            break;
+        }
+        if (++buf_ptr >= s->correlation_span)
+            buf_ptr = 0;
+    }
+    s->buf_ptr = buf_ptr;
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+SPAN_DECLARE(int) fsk_rx_fillin(fsk_rx_state_t *s, int len)
+{
+    /* The valid choice here is probably to do nothing. We don't change state
+      (i.e carrier on<->carrier off), and we'll just output less bits than we
+      should. */
+    /* TODO: Advance the symbol phase the appropriate amount */
+    return 0;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/