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/Makefile

@@ -140,6 +140,7 @@ CPPSRC = main.cpp \
          proc_ais.cpp \
          proc_wideband_spectrum.cpp \
          proc_tpms.cpp \
+         proc_ert.cpp \
          dsp_squelch.cpp \
          clock_recovery.cpp \
          packet_builder.cpp \

firmware/baseband/main.cpp

@@ -58,6 +58,7 @@
 #include "proc_ais.hpp"
 #include "proc_wideband_spectrum.hpp"
 #include "proc_tpms.hpp"
+#include "proc_ert.hpp"
 
 #include "clock_recovery.hpp"
 #include "packet_builder.hpp"
@@ -370,6 +371,10 @@ int main(void) {
 					baseband_thread.baseband_processor = new TPMSProcessor();
 					break;
 
+				case 6:
+					baseband_thread.baseband_processor = new ERTProcessor();
+					break;
+
 				default:
 					break;
 				}

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);
+}

firmware/baseband/proc_ert.hpp

@@ -0,0 +1,108 @@
+/*
+ * 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 __PROC_ERT_H__
+#define __PROC_ERT_H__
+
+#include "baseband_processor.hpp"
+
+#include "channel_decimator.hpp"
+
+#include "clock_recovery.hpp"
+#include "symbol_coding.hpp"
+#include "packet_builder.hpp"
+
+#include "message.hpp"
+
+#include <cstdint>
+#include <cstddef>
+#include <bitset>
+
+// ''.join(['%d%d' % (c, 1-c) for c in map(int, bin(0x1f2a60)[2:].zfill(21))])
+constexpr uint64_t scm_preamble_and_sync_manchester { 0b101010101001011001100110010110100101010101 };
+constexpr size_t scm_preamble_and_sync_length { 42 - 10 };
+constexpr size_t scm_payload_length_max { 150 };
+
+// ''.join(['%d%d' % (c, 1-c) for c in map(int, bin(0x555516a3)[2:].zfill(32))])
+constexpr uint64_t idm_preamble_and_sync_manchester { 0b0110011001100110011001100110011001010110011010011001100101011010 };
+constexpr size_t idm_preamble_and_sync_length { 64 - 16 };
+
+// TODO: Should be 1408, but need to widen pathway to application processor...
+constexpr size_t idm_payload_length_max { 960 };
+
+class ERTProcessor : public BasebandProcessor {
+public:
+	using payload_t = std::bitset<1024>;
+
+	void execute(buffer_c8_t buffer) override;
+
+private:
+	const uint32_t baseband_sampling_rate = 4194304;
+	const size_t decimation = 1;
+	const uint32_t symbol_rate = 32768;
+
+	const uint32_t channel_sampling_rate = baseband_sampling_rate / decimation;
+	const size_t samples_per_symbol = channel_sampling_rate / symbol_rate;
+	const uint32_t clock_recovery_rate = symbol_rate * 2;
+
+	// ChannelDecimator decimator { ChannelDecimator::DecimationFactor::By2, false };
+
+	clock_recovery::ClockRecovery<clock_recovery::FixedErrorFilter> clock_recovery {
+		clock_recovery_rate, symbol_rate, { 1.0f / 18.0f },
+		[this](const float symbol) { this->consume_symbol(symbol); }
+	};
+
+	PacketBuilder<BitPattern, NeverMatch, FixedLength> scm_builder {
+		{ scm_preamble_and_sync_manchester, scm_preamble_and_sync_length, 1 },
+		{ },
+		{ scm_payload_length_max },
+		[this](const payload_t& payload, const size_t bits_received) {
+			this->scm_handler(payload, bits_received);
+		}
+	};
+
+	PacketBuilder<BitPattern, NeverMatch, FixedLength> idm_builder {
+		{ idm_preamble_and_sync_manchester, idm_preamble_and_sync_length, 1 },
+		{ },
+		{ idm_payload_length_max },
+		[this](const payload_t& payload, const size_t bits_received) {
+			this->idm_handler(payload, bits_received);
+		}
+	};
+
+	void consume_symbol(const float symbol);
+	void scm_handler(const payload_t& payload, const size_t bits_received);
+	void idm_handler(const payload_t& payload, const size_t bits_received);
+
+	float sum_half_period[2];
+	float sum_period[3];
+	float manchester[3];
+
+	int32_t average_i { 0 };
+	int32_t average_q { 0 };
+	size_t average_count { 0 };
+	float offset_i { 0.0f };
+	float offset_q { 0.0f };
+
+	float abs(const complex8_t& v);
+};
+
+#endif/*__PROC_ERT_H__*/