OOK slicer, clock recovery classes.

firmware/baseband/phase_detector.hpp

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2016 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 __PHASE_DETECTOR_HPP__
+#define __PHASE_DETECTOR_HPP__
+
+#include <cstdint>
+#include <cstddef>
+#include <cmath>
+
+class PhaseDetectorEarlyLateGate {
+public:
+	using history_t = uint32_t;
+
+	using symbol_t = bool;
+	using error_t = int;
+
+	struct result_t {
+		symbol_t symbol;
+		error_t error;
+	};
+
+	constexpr PhaseDetectorEarlyLateGate(
+		const float samples_per_symbol
+	) : late_mask { (1U << static_cast<size_t>(std::ceil(samples_per_symbol / 2))) - 1 },
+		early_mask { late_mask << static_cast<size_t>(std::floor(samples_per_symbol / 2)) },
+		sample_bit { static_cast<size_t>(std::floor(samples_per_symbol / 2)) }
+	{
+	}
+
+	result_t operator()(const history_t symbol_history) const {
+		// history = ...0111, early
+		// history = ...1110, late
+
+		const symbol_t symbol = (symbol_history >> sample_bit) & 1;
+		const int late_side = __builtin_popcount(symbol_history & late_mask);
+		const int early_side = __builtin_popcount(symbol_history & early_mask);
+		const int lateness = late_side - early_side;
+		const int direction = lateness; //std::min(std::max(lateness, -1), 1);
+		const error_t error = direction;
+		return { symbol, error };
+	}
+
+private:
+	const history_t late_mask;
+	const history_t early_mask;
+	const size_t sample_bit;
+};
+
+#endif/*__PHASE_DETECTOR_HPP__*/