Testing external clock detection and auto-switch

Simplified audio spectrum computation and transfer
ACARS RX in debug mode
Disabled ABI warnings
Updated binary

firmware/baseband/proc_acars.cpp

@@ -31,6 +31,7 @@
 ACARSProcessor::ACARSProcessor() {
 	decim_0.configure(taps_11k0_decim_0.taps, 33554432);
 	decim_1.configure(taps_11k0_decim_1.taps, 131072);
+	packet.clear();
 }
 
 void ACARSProcessor::execute(const buffer_c8_t& buffer) {
@@ -54,9 +55,16 @@ void ACARSProcessor::consume_symbol(
 	const float raw_symbol
 ) {
 	const uint_fast8_t sliced_symbol = (raw_symbol >= 0.0f) ? 1 : 0;
-	const auto decoded_symbol = nrzi_decode(sliced_symbol);
+	//const auto decoded_symbol = acars_decode(sliced_symbol);
 
-	packet_builder.execute(decoded_symbol);
+	// DEBUG
+	packet.add(sliced_symbol);
+	if (packet.size() == 256) {
+		payload_handler(packet);
+		packet.clear();
+	}
+
+	//packet_builder.execute(decoded_symbol);
 }
 
 void ACARSProcessor::payload_handler(

firmware/baseband/proc_acars.hpp

@@ -28,8 +28,6 @@
 #include "rssi_thread.hpp"
 
 #include "dsp_decimate.hpp"
-#include "dsp_demodulate.hpp"
-//#include "audio_compressor.hpp"
 
 #include "spectrum_collector.hpp"
 
@@ -53,7 +51,48 @@
 #include <cstddef>
 #include <bitset>
 
-#include "ais_baseband.hpp"
+// AIS:
+// IN: 2457600/8/8 = 38400
+// Offset: 2457600/4 = 614400 (614400/8/8 = 9600)
+// Deviation: 2400
+// Symbol: 9600
+// Decimate: 2
+// 4 taps, 1 symbol, 1/4 cycle
+
+// TPMS:
+// IN: 2457600/4/2 = 307200
+// Offset: 2457600/4 = 614400 (614400/4/2 = 76800)
+// Deviation: 38400
+// Symbol: 19200
+// Decimate: 8
+// 16 taps, 1 symbol, 2 cycles
+
+// ACARS:
+// IN: 2457600/8/8 = 38400
+// Offset: 2457600/4 = 614400 (614400/8/8 = 9600)
+// Deviation: ???
+// Symbol: 2400
+// Decimate: 8
+// 16 taps, 1 symbol, 2 cycles
+
+// Number of taps: size of one symbol in samples (in/symbol)
+// Cycles: 
+
+
+// Translate+rectangular filter
+// sample=38.4k, deviation=4800, symbol=2400
+// Length: 16 taps, 1 symbol, 2 cycles of sinusoid
+// This is actually the same as rect_taps_307k2_38k4_1t_19k2_p
+constexpr std::array<std::complex<float>, 16> rect_taps_38k4_4k8_1t_2k4_p { {
+	{  6.2500000000e-02f,  0.0000000000e+00f }, {  4.4194173824e-02f,  4.4194173824e-02f },
+	{  0.0000000000e+00f,  6.2500000000e-02f }, { -4.4194173824e-02f,  4.4194173824e-02f },
+	{ -6.2500000000e-02f,  0.0000000000e+00f }, { -4.4194173824e-02f, -4.4194173824e-02f },
+	{  0.0000000000e+00f, -6.2500000000e-02f }, {  4.4194173824e-02f, -4.4194173824e-02f },
+	{  6.2500000000e-02f,  0.0000000000e+00f }, {  4.4194173824e-02f,  4.4194173824e-02f },
+	{  0.0000000000e+00f,  6.2500000000e-02f }, { -4.4194173824e-02f,  4.4194173824e-02f },
+	{ -6.2500000000e-02f,  0.0000000000e+00f }, { -4.4194173824e-02f, -4.4194173824e-02f },
+	{  0.0000000000e+00f, -6.2500000000e-02f }, {  4.4194173824e-02f, -4.4194173824e-02f },
+} };
 
 class ACARSProcessor : public BasebandProcessor {
 public:
@@ -73,23 +112,24 @@ private:
 		dst.size()
 	};
 
-	dsp::decimate::FIRC8xR16x24FS4Decim8 decim_0 { };
+	dsp::decimate::FIRC8xR16x24FS4Decim8 decim_0 { };	// Translate already done here !
 	dsp::decimate::FIRC16xR16x32Decim8 decim_1 { };
-	dsp::matched_filter::MatchedFilter mf { baseband::ais::square_taps_38k4_1t_p, 2 };
+	dsp::matched_filter::MatchedFilter mf { rect_taps_38k4_4k8_1t_2k4_p, 8 };
 
 	clock_recovery::ClockRecovery<clock_recovery::FixedErrorFilter> clock_recovery {
-		19200, 2400, { 0.0555f },
+		4800, 2400, { 0.0555f },
 		[this](const float symbol) { this->consume_symbol(symbol); }
 	};
-	symbol_coding::NRZIDecoder nrzi_decode { };
-	PacketBuilder<BitPattern, NeverMatch, BitPattern> packet_builder {
-		{ 0b1001011010010110, 16, 1 },	// SYN, SYN
+	symbol_coding::ACARSDecoder acars_decode { };
+	/*PacketBuilder<BitPattern, NeverMatch, FixedLength> packet_builder {
+		{ 0b011010000110100010000000, 24, 1 },	// SYN, SYN, SOH
 		{ },
-		{ 0b11111111, 8, 1 },
+		{ 128 },
 		[this](const baseband::Packet& packet) {
 			this->payload_handler(packet);
 		}
-	};
+	};*/
+	baseband::Packet packet { };
 
 	void consume_symbol(const float symbol);
 	void payload_handler(const baseband::Packet& packet);

firmware/baseband/proc_wfm_audio.cpp

@@ -66,47 +66,57 @@ void WidebandFMAudio::execute(const buffer_c8_t& buffer) {
 	auto audio_2fs = audio_dec_2.execute(audio_4fs, work_audio_buffer);
 	
 	// Input: 96kHz int16_t[64]
-	// audio_spectrum_decimator piles up 256 bytes before doing FFT computation
-	// This should send an AudioSpectrum every sample rate/buffer size/(256/64)/refresh scaler = 3072000/2048/4/8 = ~47 Hz
+	// audio_spectrum_decimator piles up 256 samples before doing FFT computation
+	// This sends an AudioSpectrum every: sample rate/buffer size/refresh period = 3072000/2048/50 = 30 Hz
+	// When audio_spectrum_timer expires, the audio spectrum computation is triggered
+	
 	// 0~3: feed continuous audio
 	// 4~31: ignore, wrap at 31
-	if (!(refresh_timer & 0xF8)) {
-		for (size_t i = 0; i < 64; i++) {
-			complex_audio[i] = { (int16_t)(work_audio_buffer.p[i] / 32), (int16_t)0 };
-		}
-		audio_spectrum_decimator.feed(
-			complex_audio_buffer,
-			[this](const buffer_c16_t& data) {
-				this->post_message(data);
-			}
-		);
-	} else {
-		// Spread the FFT workload in time to avoid making the audio skip
-		// "8" comes from the log2() of the size of audio_spectrum: log2(256) = 8
-		if (fft_stage && (fft_stage <= 8)) {
-			fft_c_preswapped(audio_spectrum, fft_stage - 1, fft_stage);
-			fft_stage++;
-		} else if (fft_stage > 8) {
-			AudioSpectrum spectrum;
-			const size_t spectrum_end = spectrum.db.size();
-			for(size_t i=0; i<spectrum_end; i++) {
-				//const auto corrected_sample = spectrum_window_hamming_3(audio_spectrum, i);
-				const auto corrected_sample = audio_spectrum[i];
-				const auto mag2 = magnitude_squared(corrected_sample * (1.0f / 32768.0f));
-				const float db = mag2_to_dbv_norm(mag2);
-				constexpr float mag_scale = 5.0f;
-				const unsigned int v = (db * mag_scale) + 255.0f;
-				spectrum.db[i] = std::max(0U, std::min(255U, v));
-			}
-			fifo.in(spectrum);
-			fft_stage = 0;
-		}
+	
+	audio_spectrum_timer++;
+	if (audio_spectrum_timer == 50) {
+		audio_spectrum_timer = 0;
+		audio_spectrum_state = FEED;
 	}
 	
-	if (refresh_timer == 31)
-		refresh_timer = 0;
-	else
-		refresh_timer++;
+	switch (audio_spectrum_state) {
+		case FEED:
+			// Convert audio to "complex" just so the FFT can be done :/
+			for (size_t i = 0; i < 64; i++) {
+				complex_audio[i] = { (int16_t)(work_audio_buffer.p[i] / 32), (int16_t)0 };
+			}
+			audio_spectrum_decimator.feed(
+				complex_audio_buffer,
+				[this](const buffer_c16_t& data) {
+					this->post_message(data);
+				}
+			);
+			break;
+		case FFT:
+			// Spread the FFT workload in time to avoid making the audio skip
+			// "8" comes from the log2() of the size of audio_spectrum: log2(256) = 8
+			if (fft_step < 8) {
+				fft_c_preswapped(audio_spectrum, fft_step, fft_step + 1);
+				fft_step++;
+			} else {
+				const size_t spectrum_end = spectrum.db.size();
+				for(size_t i=0; i<spectrum_end; i++) {
+					//const auto corrected_sample = spectrum_window_hamming_3(audio_spectrum, i);
+					const auto corrected_sample = audio_spectrum[i];
+					const auto mag2 = magnitude_squared(corrected_sample * (1.0f / 32768.0f));
+					const float db = mag2_to_dbv_norm(mag2);
+					constexpr float mag_scale = 5.0f;
+					const unsigned int v = (db * mag_scale) + 255.0f;
+					spectrum.db[i] = std::max(0U, std::min(255U, v));
+				}
+				AudioSpectrumMessage message { &spectrum };
+				shared_memory.application_queue.push(message);
+				audio_spectrum_state = IDLE;
+			}
+			break;
+		default:
+			break;
+	}
 	
 	/* 96kHz int16_t[64]
 	 * -> FIR filter, <15kHz (0.156fs) pass, >19kHz (0.198fs) stop, gain of 1
@@ -121,7 +131,8 @@ void WidebandFMAudio::execute(const buffer_c8_t& buffer) {
 void WidebandFMAudio::post_message(const buffer_c16_t& data) {
 	// This is called when audio_spectrum_decimator is filled up to 256 samples
 	fft_swap(data, audio_spectrum);
-	fft_stage = 1;
+	audio_spectrum_state = FFT;
+	fft_step = 0;
 }
 
 void WidebandFMAudio::on_message(const Message* const message) {
@@ -167,9 +178,6 @@ void WidebandFMAudio::configure(const WFMConfigureMessage& message) {
 	channel_spectrum.set_decimation_factor(1);
 
 	configured = true;
-	
-	AudioSpectrumConfigMessage config_message { &fifo };
-	shared_memory.application_queue.push(config_message);
 }
 
 void WidebandFMAudio::capture_config(const CaptureConfigMessage& message) {

firmware/baseband/proc_wfm_audio.hpp

@@ -53,6 +53,7 @@ private:
 		dst.data(),
 		dst.size()
 	};
+	// work_audio_buffer and dst_buffer use the same data pointer
 	const buffer_s16_t work_audio_buffer {
 		(int16_t*)dst.data(),
 		sizeof(dst) / sizeof(int16_t)
@@ -78,11 +79,16 @@ private:
 	
 	// For fs=96kHz FFT streaming
 	BlockDecimator<complex16_t, 256> audio_spectrum_decimator { 1 };
-	AudioSpectrum fifo_data[1 << AudioSpectrumConfigMessage::fifo_k] { };
-	AudioSpectrumFIFO fifo { fifo_data, AudioSpectrumConfigMessage::fifo_k };
 	std::array<std::complex<float>, 256> audio_spectrum { };
-	uint32_t refresh_timer { 0 };
-	uint32_t fft_stage { 0 };
+	uint32_t audio_spectrum_timer { 0 };
+	enum AudioSpectrumState {
+		IDLE = 0,
+		FEED,
+		FFT
+	};
+	AudioSpectrumState audio_spectrum_state { IDLE };
+	AudioSpectrum spectrum { };
+	uint32_t fft_step { 0 };
 
 	SpectrumCollector channel_spectrum { };
 	size_t spectrum_interval_samples = 0;

firmware/baseband/symbol_coding.hpp

@@ -39,6 +39,17 @@ private:
 	uint_fast8_t last { 0 };
 };
 
+class ACARSDecoder {
+public:
+	uint_fast8_t operator()(const uint_fast8_t symbol) {
+		last ^= (~symbol & 1);
+		return last;
+	}
+
+private:
+	uint_fast8_t last { 0 };
+};
+
 } /* namespace symbol_coding */
 
 #endif/*__SYMBOL_CODING_H__*/