From f6bca05bf0ee3ec9e491a3692045b79b3a34f2d7 Mon Sep 17 00:00:00 2001
From: Joris van Rantwijk <joris@jorisvr.nl>
Date: Sun, 19 Jan 2014 12:19:19 +0100
Subject: [PATCH] Prepare pilot PLL to produce PPS events.

---
 FmDecode.cc | 35 ++++++++++++++++++++++++++++++++++-
 FmDecode.h  | 30 +++++++++++++++++++++++++++++-
 2 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/FmDecode.cc b/FmDecode.cc
index 566f9ac..9735479 100644
--- a/FmDecode.cc
+++ b/FmDecode.cc
@@ -134,6 +134,11 @@ PilotPhaseLock::PilotPhaseLock(double freq, double bandwidth, double minsignal)
     m_phasor_q1 = 0;
     m_phasor_q2 = 0;
     m_loopfilter_x1 = 0;
+
+    // Initialize PPS generator.
+    m_pilot_periods = 0;
+    m_pps_cnt       = 0;
+    m_sample_cnt    = 0;
 }
 
 
@@ -145,6 +150,9 @@ void PilotPhaseLock::process(const SampleVector& samples_in,
 
     samples_out.resize(n);
 
+    bool was_locked = (m_lock_cnt >= m_lock_delay);
+    m_pps_events.clear();
+
     if (n > 0)
         m_pilot_level = 1000.0;
 
@@ -202,8 +210,23 @@ void PilotPhaseLock::process(const SampleVector& samples_in,
 
         // Update locked phase.
         m_phase += m_freq;
-        if (m_phase > 2.0 * M_PI)
+        if (m_phase > 2.0 * M_PI) {
             m_phase -= 2.0 * M_PI;
+            m_pilot_periods++;
+
+            // Generate pulse-per-second.
+            if (m_pilot_periods == pilot_frequency) {
+                m_pilot_periods = 0;
+                if (was_locked) {
+                    struct PpsEvent ev;
+                    ev.pps_index          = m_pps_cnt;
+                    ev.abs_sample_index   = m_sample_cnt + i;
+                    ev.block_sample_index = i;
+                    m_pps_events.push_back(ev);
+                    m_pps_cnt++;
+                }
+            }
+        }
     }
 
     // Update lock status.
@@ -213,6 +236,16 @@ void PilotPhaseLock::process(const SampleVector& samples_in,
     } else {
         m_lock_cnt = 0;
     }
+
+    // Drop PPS events when pilot not locked.
+    if (m_lock_cnt < m_lock_delay) {
+        m_pilot_periods = 0;
+        m_pps_cnt = 0;
+        m_pps_events.clear();
+    }
+
+    // Update sample counter.
+    m_sample_cnt += n;
 }
 
 
diff --git a/FmDecode.h b/FmDecode.h
index 053cb1c..0f645f2 100644
--- a/FmDecode.h
+++ b/FmDecode.h
@@ -1,6 +1,9 @@
 #ifndef SOFTFM_FMDECODE_H
 #define SOFTFM_FMDECODE_H
 
+#include <cstdint>
+#include <vector>
+
 #include "SoftFM.h"
 #include "Filter.h"
 
@@ -36,7 +39,16 @@ class PilotPhaseLock
 {
 public:
 
-// TODO : pulse-per-second
+    /** Expected pilot frequency (used for PPS events). */ 
+    static constexpr int pilot_frequency = 19000;
+
+    /** Timestamp event produced once every 19000 pilot periods. */
+    struct PpsEvent
+    {
+        std::uint64_t   pps_index;
+        std::uint64_t   abs_sample_index;
+        std::uint64_t   block_sample_index;
+    };
 
     /**
      * Construct phase-locked loop.
@@ -66,6 +78,12 @@ public:
         return 2 * m_pilot_level;
     }
 
+    /** Return PPS events from the most recently processed block. */
+    std::vector<PpsEvent> get_pps_events() const
+    {
+        return m_pps_events;
+    }
+
 private:
     Sample  m_minfreq, m_maxfreq;
     Sample  m_phasor_b0, m_phasor_a1, m_phasor_a2;
@@ -77,6 +95,10 @@ private:
     Sample  m_pilot_level;
     int     m_lock_delay;
     int     m_lock_cnt;
+    int     m_pilot_periods;
+    std::uint64_t         m_pps_cnt;
+    std::uint64_t         m_sample_cnt;
+    std::vector<PpsEvent> m_pps_events;
 };
 
 
@@ -163,6 +185,12 @@ public:
         return m_pilotpll.get_pilot_level();
     }
 
+    /** Return PPS events from the most recently processed block. */
+    std::vector<PilotPhaseLock::PpsEvent> get_pps_events() const
+    {
+        return m_pilotpll.get_pps_events();
+    }
+
 private:
     /** Demodulate stereo L-R signal. */
     void demod_stereo(const SampleVector& samples_baseband,