Add TPMS initial demodulator implementation.

Right now, 2FSK, 19200 baud, +/-38400Hz deviation. No effort is made to check CRC/checksums or decode packets.

firmware/baseband/proc_tpms.cpp

@@ -0,0 +1,73 @@
+/*
+ * 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_tpms.hpp"
+
+#include "portapack_shared_memory.hpp"
+
+#include "i2s.hpp"
+using namespace lpc43xx;
+
+void TPMSProcessor::execute(buffer_c8_t buffer) {
+	/* 2.4576MHz, 2048 samples */
+
+	auto decimator_out = decimator.execute(buffer);
+
+	/* 76.8kHz, 64 samples */
+	feed_channel_stats(decimator_out);
+	/* No spectrum display while FSK decoding.
+	feed_channel_spectrum(
+		channel,
+		decimator_out.sampling_rate * channel_filter_taps.pass_frequency_normalized,
+		decimator_out.sampling_rate * channel_filter_taps.stop_frequency_normalized
+	);
+	*/
+
+	for(size_t i=0; i<decimator_out.count; i++) {
+		// TODO: No idea why implicit cast int16_t->float is not allowed.
+		const std::complex<float> sample {
+			static_cast<float>(decimator_out.p[i].real()),
+			static_cast<float>(decimator_out.p[i].imag())
+		};
+		if( mf.execute_once(sample) ) {
+			clock_recovery(mf.get_output());
+		}
+	}
+
+	i2s::i2s0::tx_mute();
+}
+
+void TPMSProcessor::consume_symbol(
+	const float raw_symbol
+) {
+	const uint_fast8_t sliced_symbol = (raw_symbol >= 0.0f) ? 1 : 0;
+	packet_builder.execute(sliced_symbol);
+}
+
+void TPMSProcessor::payload_handler(
+	const std::bitset<1024>& payload,
+	const size_t bits_received
+) {
+	TPMSPacketMessage message;
+	message.packet.payload = payload;
+	message.packet.bits_received = bits_received;
+	shared_memory.application_queue.push(message);
+}