Initial firmware commit.

firmware/baseband/clock_recovery.hpp

@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2014 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 __CLOCK_RECOVERY_H__
+#define __CLOCK_RECOVERY_H__
+
+#include <cstdint>
+
+class ClockRecovery {
+public:
+	void configure(
+		const uint32_t symbol_rate,
+		const uint32_t sampling_rate
+	);
+
+	template<typename SymbolHandler>
+	void execute(
+		const float in,
+		SymbolHandler symbol_handler
+	) {
+		const bool phase_0 = (phase_last >> 31) & (!(phase >> 31));
+		const bool phase_180 = (!(phase_last >> 31)) & (phase >> 31);
+		phase_last = phase;
+		phase += phase_increment + phase_adjustment;
+
+		if( phase_0 || phase_180 ) {
+			t2 = t1;
+			t1 = t0;
+			t0 = in;
+		}
+
+		if( phase_0 ) {
+			symbol_handler(t0);
+
+			const float error = (t0 - t2) * t1;
+			// + error == late == decrease/slow phase
+			// - error == early == increase/fast phase
+
+			error_filtered = 0.75f * error_filtered + 0.25f * error;
+
+			// Correct phase (don't change frequency!)
+			phase_adjustment = -phase_increment * error_filtered / 200.0f;
+		}
+	}
+
+private:
+	uint32_t phase { 0 };
+	uint32_t phase_last { 0 };
+	uint32_t phase_adjustment { 0 };
+	uint32_t phase_increment { 0 };
+	float t0 { 0 };
+	float t1 { 0 };
+	float t2 { 0 };
+	float error_filtered { 0 };
+
+	static constexpr float fractional_symbol_rate(
+		const uint32_t symbol_rate,
+		const uint32_t sampling_rate
+	) {
+		return float(symbol_rate) / float(sampling_rate);
+	}
+
+	static constexpr uint32_t phase_increment_u32(const float fractional_symbol_rate) {
+		return 4294967296.0f * fractional_symbol_rate;
+	}
+};
+
+#endif/*__CLOCK_RECOVERY_H__*/