Replace the FM bandpass filter with an FIR.

FIR.cpp

@@ -0,0 +1,77 @@
+/*
+ *   Copyright (C) 2024 by Jonathan Naylor G4KLX
+ *
+ *   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 "FIR.h"
+
+#include <cassert>
+
+CFIR::CFIR(const float* taps, unsigned int count) :
+m_line(NULL),
+m_taps(NULL),
+m_count(count),
+m_index(0U)
+{
+    assert(taps != NULL);
+    assert(count > 0U);
+
+    m_line = new float[count];
+    m_taps = new float[count];
+
+    for (unsigned int i = 0U; i < count; i++) {
+        m_line[i] = 0.0F;
+        m_taps[i] = taps[i];
+    }
+}
+
+CFIR::~CFIR()
+{
+    delete[] m_line;
+    delete[] m_taps;
+}
+
+float CFIR::filter(float sample)
+{
+    m_line[m_index] = sample;
+
+    m_index++;
+    if (m_index >= m_count)
+        m_index = 0U;
+
+    float out = 0.0F;
+
+    unsigned int index = m_index;
+
+    for (unsigned int i = 0U; i < m_count; i++) {
+        if (index > 0U)
+            index--;
+        else
+            index = m_count - 1U;
+
+        out += m_taps[i] * m_line[index];
+    }
+
+    return out;
+}
+
+void CFIR::reset()
+{
+    for (unsigned int i = 0U; i < m_count; i++)
+        m_line[i] = 0.0F;
+
+    m_index = 0U;
+}