Add basic ERT (OOK) utility meter reception.

Extracted the Manchester formatting function for use in ERT, now also returns an indication of bits in error.

firmware/baseband/proc_ert.cpp

@@ -0,0 +1,117 @@
+/*
+ * 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.
+ */
+
+#include "proc_ert.hpp"
+
+#include "portapack_shared_memory.hpp"
+
+#include "i2s.hpp"
+using namespace lpc43xx;
+
+float ERTProcessor::abs(const complex8_t& v) {
+	// const int16_t r = v.real() - offset_i;
+	// const int16_t i = v.imag() - offset_q;
+	// const uint32_t r2 = r * r;
+	// const uint32_t i2 = i * i;
+	// const uint32_t r2_i2 = r2 + i2;
+	// return std::sqrt(static_cast<float>(r2_i2));
+	const float r = static_cast<float>(v.real()) - offset_i;
+	const float i = static_cast<float>(v.imag()) - offset_q;
+	const float r2 = r * r;
+	const float i2 = i * i;
+	const float r2_i2 = r2 + i2;
+	return std::sqrt(r2_i2);
+}
+
+void ERTProcessor::execute(buffer_c8_t buffer) {
+	/* 4.194304MHz, 2048 samples */
+	// auto decimator_out = decimator.execute(buffer);
+
+	const complex8_t* src = &buffer.p[0];
+	const complex8_t* const src_end = &buffer.p[buffer.count];
+
+	average_i += src->real();
+	average_q += src->imag();
+	average_count++;
+	if( average_count == 2048 ) {
+		offset_i = static_cast<float>(average_i) / 2048.0f;
+		offset_q = static_cast<float>(average_q) / 2048.0f;
+		average_i = 0;
+		average_q = 0;
+		average_count = 0;
+	}
+
+	const float gain = 128 * samples_per_symbol;
+	const float k = 1.0f / gain;
+
+	while(src < src_end) {
+		float sum = 0.0f;
+		for(size_t i=0; i<(samples_per_symbol / 2); i++) {
+			sum += abs(*(src++));
+		}
+		sum_half_period[1] = sum_half_period[0];
+		sum_half_period[0] = sum;
+
+		sum_period[2] = sum_period[1];
+		sum_period[1] = sum_period[0];
+		sum_period[0] = (sum_half_period[0] + sum_half_period[1]) * k;
+
+		manchester[2] = manchester[1];
+		manchester[1] = manchester[0];
+		manchester[0] = sum_period[2] - sum_period[0];
+
+		const auto data = manchester[0] - manchester[2];
+
+		clock_recovery(data);
+	}
+
+	i2s::i2s0::tx_mute();
+}
+
+void ERTProcessor::consume_symbol(
+	const float raw_symbol
+) {
+	const uint_fast8_t sliced_symbol = (raw_symbol >= 0.0f) ? 1 : 0;
+	scm_builder.execute(sliced_symbol);
+	idm_builder.execute(sliced_symbol);
+}
+
+void ERTProcessor::scm_handler(
+	const std::bitset<1024>& payload,
+	const size_t bits_received
+) {
+	ERTPacketMessage message;
+	message.packet.preamble = 0x1f2a60;
+	message.packet.payload = payload;
+	message.packet.bits_received = bits_received;
+	shared_memory.application_queue.push(message);
+}
+
+void ERTProcessor::idm_handler(
+	const std::bitset<1024>& payload,
+	const size_t bits_received
+) {
+	ERTPacketMessage message;
+	message.packet.preamble = 0x555516a3;
+	message.packet.payload = payload;
+	message.packet.bits_received = bits_received;
+	shared_memory.application_queue.push(message);
+}