Added basic POCSAG receiver

Added Yes/no modal screen (for future tx warnings)
2025-07-30 10:09:25 -04:00 · 2016-08-23 08:45:33 +02:00 · 2016-08-23 08:45:33 +02:00 · 02f0271553
commit 02f0271553
parent c2fbc0c8d5
34 changed files with 944 additions and 42 deletions
--- a/firmware/baseband/proc_pocsag.cpp
+++ b/firmware/baseband/proc_pocsag.cpp
@ -0,0 +1,164 @@
+/*
+ * Copyright (C) 1996 Thomas Sailer (sailer@ife.ee.ethz.ch, hb9jnx@hb9w.che.eu)
+ * Copyright (C) 2012-2014 Elias Oenal (multimon-ng@eliasoenal.com)
+ * Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
+ * Copyright (C) 2016 Furrtek
+ *
+ * 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_pocsag.hpp"
+
+#include "event_m4.hpp"
+
+#include <cstdint>
+#include <cstddef>
+
+#define FREQ_SAMP		24000
+#define BAUD			1200
+#define SPHASEINC		(0x10000u * BAUD / FREQ_SAMP)
+
+#define POCSAG_SYNC		0x7CD215D8
+#define POCSAG_IDLE		0x7A89C197
+
+void POCSAGProcessor::execute(const buffer_c8_t& buffer) {
+	/* 1.536MHz, 2048 samples */
+	
+	if( !configured ) return;
+	
+	const auto decim_0_out = decim_0.execute(buffer, dst_buffer);
+	const auto decim_1_out = decim_1.execute(decim_0_out, dst_buffer);
+
+	auto audio = demod.execute(decim_1_out, audio_buffer);
+	
+	for (c = 0; c < 32; c++) {
+		
+		// Bit = sign
+		const int32_t sample_int = audio.p[c] * 32768.0f;
+		const int32_t audio_sample = __SSAT(sample_int, 16);
+		dcd_shreg <<= 1;
+		dcd_shreg |= (audio_sample < 0);
+
+		// Detect transitions to adjust clock
+		if ((dcd_shreg ^ (dcd_shreg >> 1)) & 1) {
+			if (sphase < (0x8000u-(SPHASEINC/2)))
+				sphase += SPHASEINC/8;
+			else
+				sphase -= SPHASEINC/8;
+		}
+		
+		sphase += SPHASEINC;
+		
+		if (sphase >= 0x10000u) {
+			sphase &= 0xffffu;
+			
+			rx_data <<= 1;
+			rx_data |= (dcd_shreg & 1);
+			
+			switch(rx_state) {
+				
+				case WAITING:
+					if (rx_data == 0xAAAAAAAA) {
+						rx_state = PREAMBLE;
+						sync_timeout = 0;
+					}
+					break;
+						
+				case PREAMBLE:
+					if (sync_timeout < 600) {
+						sync_timeout++;
+						
+						//pocsag_brute_repair(&s->l2.pocsag, &rx_data);
+
+						if (rx_data == POCSAG_SYNC) {
+							packet.clear();
+							rx_state = SYNC;
+							frame_counter = 0;
+							rx_bit = 0;
+						} else if (rx_data == POCSAG_IDLE) {
+							rx_state = WAITING;
+						}
+						
+					} else {
+						rx_state = WAITING;		// Abort
+					}
+					break;
+				
+				case SYNC:
+					rx_bit++;
+					if (rx_bit >= 32) {
+						rx_bit = 0;
+						
+						//pocsag_brute_repair(&s->l2.pocsag, &rx_data);
+						
+						packet.set(frame_counter, rx_data);
+						
+						if (rx_data == POCSAG_IDLE) {
+							rx_state = WAITING;
+							
+							packet.set_timestamp(Timestamp::now());
+							//packet.rate = pocsag::SignalRate::FSK1200;
+
+							const POCSAGPacketMessage message(packet);
+							shared_memory.application_queue.push(message);
+							
+						} else {
+							if (frame_counter < 15)
+								frame_counter++;
+							else
+								rx_state = WAITING;
+						}
+					}
+					break;
+
+				default:
+					break;
+			}
+		}
+	}
+}
+
+void POCSAGProcessor::on_message(const Message* const message) {
+	if (message->id == Message::ID::POCSAGConfigure)
+		configure(*reinterpret_cast<const POCSAGConfigureMessage*>(message));
+}
+
+void POCSAGProcessor::configure(const POCSAGConfigureMessage& message) {
+	(void)message;
+	
+	constexpr size_t decim_0_input_fs = baseband_fs;
+	constexpr size_t decim_0_output_fs = decim_0_input_fs / decim_0.decimation_factor;
+
+	constexpr size_t decim_1_input_fs = decim_0_output_fs;
+	constexpr size_t decim_1_output_fs = decim_1_input_fs / decim_1.decimation_factor;
+
+	const size_t demod_input_fs = decim_1_output_fs;
+
+	decim_0.configure(taps_11k0_decim_0.taps, 33554432);
+	decim_1.configure(taps_11k0_decim_1.taps, 131072);
+	demod.configure(demod_input_fs, 4500);
+
+	rx_state = WAITING;
+	configured = true;
+}
+
+int main() {
+	EventDispatcher event_dispatcher { std::make_unique<POCSAGProcessor>() };
+	event_dispatcher.run();
+	return 0;
+}