Initial firmware commit.

firmware/baseband/dsp_iir.hpp

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
+ *
+ * This file is part of PortaPack.
+ *
+ * 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, 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; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __DSP_IIR_H__
+#define __DSP_IIR_H__
+
+#include <array>
+
+#include "dsp_types.hpp"
+
+class IIRBiquadFilter {
+public:
+	// http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
+
+	// Assume all coefficients are normalized so that a0=1.0
+	constexpr IIRBiquadFilter(
+		std::array<float, 3> b,
+		std::array<float, 3> a
+	) : b(b),
+		a(a)
+	{
+	}
+
+	void execute(buffer_s16_t buffer) {
+		for(size_t i=0; i<buffer.count; i++) {
+			buffer.p[i] = execute_sample(buffer.p[i]);
+		}
+	}
+
+private:
+	const std::array<float, 3> b;
+	const std::array<float, 3> a;
+	std::array<float, 3> x { { 0.0f, 0.0f, 0.0f } };
+	std::array<float, 3> y { { 0.0f, 0.0f, 0.0f } };
+
+	float execute_sample(const float in) {
+		x[0] = x[1];
+		x[1] = x[2];
+		x[2] = in;
+
+		y[0] = y[1];
+		y[1] = y[2];
+		y[2] = b[0] * x[2] + b[1] * x[1] + b[2] * x[0]
+		                   - a[1] * y[1] - a[2] * y[0];
+
+		return y[2];
+	}
+};
+
+#endif/*__DSP_IIR_H__*/