Changed amp to integer

firmware/baseband/proc_adsbrx.cpp

@@ -32,7 +32,7 @@ using namespace adsb;
 	
 void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 	int8_t re, im;
-	float mag;
+	uint32_t mag;
 	uint32_t c;
 	uint8_t bit, byte{};
 	
@@ -45,9 +45,9 @@ void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 	for (size_t i = 0; i < buffer.count; i++) {
 		
 		// Compute sample's magnitude
-		re = buffer.p[i].real(); // make re float and scale it
-		im = buffer.p[i].imag(); // make re float and scale it
-		mag = ((re * re) + (im * im)) * (k*k); 
+		re = (int32_t)buffer.p[i].real(); // make re float and scale it
+		im = (int32_t)buffer.p[i].imag(); // make re float and scale it
+		mag = ((uint32_t)(re*re) + (uint32_t)(im*im));
 
 		if (decoding) {
 			// Decode
@@ -70,19 +70,20 @@ void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 				byte = bit | (byte << 1);
 				bit_count++;
 
-				// Only DF 17 are used so reset if anything else if found
+				// Perform checks at the end of the first byte
 				if (!(bit_count & 7)) {
 
 					// Store the byte
 					frame.push_byte(byte);
 
 					// Check at the end of the first byte of the message
-					if ( (bit_count == 8) && !(byte & (0x10<<3)) ) { 
+					uint8_t df = (byte >> 3);
+					if ( (bit_count == 8) && !(df & 0x10) ) {
 						msgLen = 56; // DFs 16 or greater are long 112. DFs 15 or less are short 56.
 					}
 
-					// Abondon all frames that arent DF17
-					if ( (bit_count == 8) && ((byte>>3) != 17) ) { 
+					// Abondon all frames that arent DF17 or DF18 extended squitters
+					if ( (bit_count == 8) && !((df == 17)||(df == 18)) ) {
 						decoding = false;
 						bit = (prev_mag > mag) ? 1 : 0;
 						frame.clear();
@@ -91,67 +92,59 @@ void ADSBRXProcessor::execute(const buffer_c8_t& buffer) {
 			} // Second sample of each bit
 			sample_count++;
 		}
-		//else
+
 		// Continue looking for preamble even if in a packet
 		// switch is new preamble id higher magnitude
+			
+		// Shift the preamble
+		for (c = 0; c < (ADSB_PREAMBLE_LENGTH ); c++) { shifter[c] = shifter[c + 1]; }
+		shifter[ADSB_PREAMBLE_LENGTH] = mag;
+			
+		// First check of relations between the first 10 samples
+		// representing a valid preamble. We don't even investigate further
+		// if this simple test is not passed
+		if (shifter[0] < shifter[1] && 
+			shifter[1] > shifter[2] &&
+			shifter[2] < shifter[3] &&
+			shifter[3] > shifter[4] &&
+			shifter[4] < shifter[1] &&
+			shifter[5] < shifter[1] &&
+			shifter[6] < shifter[1] &&
+			shifter[7] < shifter[1] &&
+			shifter[8] > shifter[9] &&
+			shifter[9] < shifter[10] &&
+			shifter[10]> shifter[11] )
 		{
-			// Look for preamble
-			
-			// Shift
-			for (c = 0; c < (ADSB_PREAMBLE_LENGTH - 1); c++)
+			// The samples between the two spikes must be < than the average
+			// of the high spikes level. We don't test bits too near to
+			// the high levels as signals can be out of phase so part of the
+			// energy can be in the near samples
+			int32_t thisAmp = (shifter[1] + shifter[3] + shifter[8] + shifter[10]);
+			int32_t high = thisAmp / 9;
+			if (
+				shifter[5] < high &&
+				shifter[6] < high &&
+				// Similarly samples in the range 11-13 must be low, as it is the
+				// space between the preamble and real data. Again we don't test
+				// bits too near to high levels, see above
+				shifter[12] < high &&
+				shifter[13] < high &&
+				shifter[14] < high )
 			{
-				shifter[c] = shifter[c + 1];
-			}
-			shifter[15] = mag;
-			
-			// First check of relations between the first 10 samples
-			// representing a valid preamble. We don't even investigate further
-			// if this simple test is not passed
-			if (shifter[0] > shifter[1] &&
-				shifter[1] < shifter[2] &&
-				shifter[2] > shifter[3] &&
-				shifter[3] < shifter[0] &&
-				shifter[4] < shifter[0] &&
-				shifter[5] < shifter[0] &&
-				shifter[6] < shifter[0] &&
-				shifter[7] > shifter[8] &&
-				shifter[8] < shifter[9] &&
-				shifter[9] > shifter[6])
-			{
-				// The samples between the two spikes must be < than the average
-				// of the high spikes level. We don't test bits too near to
-				// the high levels as signals can be out of phase so part of the
-				// energy can be in the near samples
-				float thisAmp = (shifter[0] + shifter[2] + shifter[7] + shifter[9]);
-				float high = thisAmp / 7.0f;
-				if (shifter[4] < high &&
-					shifter[5] < high)
+				if ((decoding == false) ||					   // New preamble
+					((decoding == true) && (thisAmp > amp)))   // Higher power than existing packet
 				{
+					decoding = true;
+					msgLen = 112;
+					amp = thisAmp;
+					sample_count = 0;
+					bit_count = 0;
+					frame.clear();
+				}
+			} // 4 & 5 low and 11-14 low
+		} // Check for preamble pattern
 
-					// Similarly samples in the range 11-14 must be low, as it is the
-					// space between the preamble and real data. Again we don't test
-					// bits too near to high levels, see above
-					if (shifter[11] < high &&
-						shifter[12] < high &&
-						shifter[13] < high &&
-						shifter[14] < high)
-					{
-						if ( (decoding == false) ||						// New preamble
-							 ((decoding == true)&& (thisAmp > amp)) )   // Higher power than existing packet
-						{
-							decoding = true;
-							msgLen = 112;
-							amp = thisAmp;
-							sample_count = 0;
-							bit_count = 0;
-							frame.clear();
-						}
-
-					} // 11-14 low
-				} // 4 & 5 high
-			} // Check for preamble pattern
-		}
-		
+		// Store mag for next time
 		prev_mag = mag;
 	}
 }

firmware/baseband/proc_adsbrx.hpp

@@ -40,8 +40,6 @@ public:
 	void on_message(const Message* const message) override;
 
 private:
-	static constexpr float k = 1.0f / 128.0f;
-	
 	static constexpr size_t baseband_fs = 2000000;
 	
 	BasebandThread baseband_thread { baseband_fs, this, NORMALPRIO + 20, baseband::Direction::Receive };
@@ -49,20 +47,17 @@ private:
 	
 	ADSBFrame frame { };
 	bool configured { false };
-	float prev_mag { 0 };
-	float threshold { }, threshold_low { }, threshold_high { };
-	//size_t null_count{ 0 };
+	uint32_t prev_mag { 0 };
 	size_t bit_count { 0 }, sample_count { 0 };
 	size_t msgLen{ 112 };
-	//std::pair<float, uint8_t> shifter[ADSB_PREAMBLE_LENGTH];
-	float shifter[ADSB_PREAMBLE_LENGTH];
+	uint32_t shifter[ADSB_PREAMBLE_LENGTH+1];
 	bool decoding { };
 	bool preamble { }, active { };
     uint16_t bit_pos { 0 };
     uint8_t cur_bit { 0 };
 	uint32_t sample { 0 };
-	int8_t re { }, im { };
-	float amp {0.0f};
+	int32_t re { }, im { };
+	int32_t amp {0};
 };
 
 #endif

firmware/common/message.hpp

@@ -377,7 +377,7 @@ class ADSBFrameMessage : public Message {
 public:
 	constexpr ADSBFrameMessage(
 		const adsb::ADSBFrame& frame,
-		const float amp
+		const uint32_t amp
 	) : Message { ID::ADSBFrame },
 		frame { frame },
 		amp(amp)
@@ -385,7 +385,7 @@ public:
 	}
 	
 	adsb::ADSBFrame frame;
-	float amp;
+	uint32_t amp;
 };
 
 class AFSKDataMessage : public Message {