Liquid-dsp support correction. Created SymbolSynchronzier as an interface

2026-06-05 15:34:57 -04:00 · 2018-04-03 18:23:39 +02:00
parent d26464fcd8
commit b856bc2aac
5 changed files with 125 additions and 24 deletions
@@ -0,0 +1,62 @@
+///////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2018 Edouard Griffiths, F4EXB                                   //
+//                                                                               //
+// Symbol synchronizer or symbol clock recovery mostly encapsulating             //
+// liquid-dsp's symsync "object"                                                 //
+//                                                                               //
+// This program is free software; you can redistribute it and/or modify          //
+// it under the terms of the GNU General Public License as published by          //
+// the Free Software Foundation as version 3 of the License, or                  //
+//                                                                               //
+// 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 V3 for more details.                               //
+//                                                                               //
+// You should have received a copy of the GNU General Public License             //
+// along with this program. If not, see <http://www.gnu.org/licenses/>.          //
+///////////////////////////////////////////////////////////////////////////////////
+
+#include "symsync.h"
+
+SymbolSynchronizer::SymbolSynchronizer()
+{
+    // For now use hardcoded values:
+    //   - RRC filter
+    //   - 4 samples per symbol
+    //   - 5 sybols delay filter
+    //   - 0.5 filter excess bandwidth factor
+    //   - 32 filter elements for the internal polyphase filter
+    m_sync = symsync_crcf_create_rnyquist(LIQUID_FIRFILT_RRC, 4, 5, 0.5f, 32);
+    //   - 0.02 loop filter bandwidth factor
+    symsync_crcf_set_lf_bw(m_sync, 0.02f);
+    //   - 4 samples per symbol output rate
+    symsync_crcf_set_output_rate(m_sync, 4);
+    m_syncSampleCount = 0;
+}
+
+SymbolSynchronizer::~SymbolSynchronizer()
+{
+    symsync_crcf_destroy(m_sync);
+}
+
+Real SymbolSynchronizer::run(const Sample& s)
+{
+    unsigned int nn;
+    Real v = 0.0f;
+    liquid_float_complex y = (s.m_real / SDR_RX_SCALEF) + (s.m_imag / SDR_RX_SCALEF)*I;
+    symsync_crcf_execute(m_sync, &y, 1, m_z, &nn);
+
+    for (unsigned int i = 0; i < nn; i++)
+    {
+        v = (m_syncSampleCount < 2) ? 1.0f : 0.0f; // actual sync is at 0
+
+        if (m_syncSampleCount < 4) {
+            m_syncSampleCount++;
+        } else {
+            m_syncSampleCount = 0;
+        }
+    }
+
+    return v;
+}