Rename FMDownsampler to FMDownSampler.

FMDownSampler.cpp

@@ -0,0 +1,74 @@
+/*
+ *   Copyright (C) 2020 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2020 by Geoffrey Merck F4FXL - KC3FRA
+ *
+ *   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; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   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 General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "Config.h"
+#include "FMDownSampler.h"
+
+CFMDownSampler::CFMDownSampler(uint16_t length) :
+m_ringBuffer(length),
+m_samplePack(0U),
+m_samplePackPointer(NULL),
+m_sampleIndex(0U)
+{
+  m_samplePackPointer = (uint8_t*)&m_samplePack;
+}
+
+void CFMDownSampler::addSample(q15_t sample)
+{
+  uint32_t usample = uint32_t(int32_t(sample) + 2048);
+  //only take one of three samples
+  switch(m_sampleIndex){
+    case 0:
+      m_samplePack = usample << 12;
+    break;
+    case 3:{
+      m_samplePack |= usample;
+      
+      //we did not use MSB; skip it
+      TSamplePairPack pair{m_samplePackPointer[0U], m_samplePackPointer[1U], m_samplePackPointer[2U]}; 
+
+      m_ringBuffer.put(pair);
+
+      m_samplePack = 0U;//reset the sample pack
+    }
+    break;
+    default:
+        //Just skip this sample
+    break;
+  }
+
+  m_sampleIndex++;
+  if (m_sampleIndex >= 6U)//did we pack two samples ?
+      m_sampleIndex = 0U;  
+}
+
+bool CFMDownSampler::getPackedData(TSamplePairPack& data)
+{
+  return m_ringBuffer.get(data);
+}
+
+uint16_t CFMDownSampler::getData()
+{
+  return m_ringBuffer.getData();
+}
+
+void CFMDownSampler::reset()
+{
+  m_sampleIndex = 0U;
+}