ADS-B TX works well enough for dump1090 and gr-air-modes

Hooked ADS-B RX to baseband instead of debug IQ file, not tested

firmware/common/adsb_frame.hpp

@@ -0,0 +1,120 @@
+/*
+ * Copyright (C) 2014 Jared Boone, ShareBrained Technology, Inc.
+ * Copyright (C) 2017 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.
+ */
+ 
+#ifndef __ADSB_FRAME_H__
+#define __ADSB_FRAME_H__
+
+#include <cstring>
+#include <string>
+
+namespace adsb {
+
+alignas(4) const uint8_t adsb_preamble[16] = { 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0 };
+alignas(4) const char icao_id_lut[65] = "#ABCDEFGHIJKLMNOPQRSTUVWXYZ##### ###############0123456789######";
+
+class ADSBFrame {
+public:
+	uint8_t get_DF() {
+		return (raw_data[0] >> 3);
+	}
+
+	uint8_t get_msg_type() {
+		return (raw_data[4] >> 3);
+	}
+
+	uint32_t get_ICAO_address() {
+		return (raw_data[1] << 16) + (raw_data[2] << 8) + raw_data[3];
+	}
+
+	void clear() {
+		index = 0;
+		memset(raw_data, 0, 14);
+	}
+
+	void push_byte(uint8_t byte) {
+		if (index >= 14)
+			return;
+		
+		raw_data[index++] = byte;
+	}
+
+	uint8_t * get_raw_data() {
+		return raw_data;
+	}
+
+	std::string get_callsign() {
+		uint64_t callsign_coded = 0;
+		uint32_t c;
+		std::string callsign = "";
+		
+		// Frame bytes to long
+		for (c = 5; c < 11; c++) {
+			callsign_coded <<= 8;
+			callsign_coded |= raw_data[c];
+		}
+		
+		// Long to 6-bit characters
+		for (c = 0; c < 8; c++) {
+			callsign.append(1, icao_id_lut[(callsign_coded >> 42) & 0x3F]);
+			callsign_coded <<= 6;
+		}
+		
+		return callsign;
+	}
+	
+	void make_CRC() {
+		uint8_t adsb_crc[14];	// Temp buffer
+		uint8_t b, c, s, bitn;
+		const uint32_t crc_poly = 0x1205FFF;
+		
+		// Clear CRC
+		raw_data[11] = 0x00;
+		raw_data[12] = 0x00;
+		raw_data[13] = 0x00;
+		
+		// Compute CRC
+		memcpy(adsb_crc, raw_data, 14);
+		for (c = 0; c < 11; c++) {
+			for (b = 0; b < 8; b++) {
+				if ((adsb_crc[c] << b) & 0x80) {
+					for (s = 0; s < 25; s++) {
+						bitn = (c * 8) + b + s;
+						if ((crc_poly >> s) & 1) adsb_crc[bitn >> 3] ^= (0x80 >> (bitn & 7));
+					}
+				}
+			}
+		}
+		
+		// Insert CRC in frame
+		memcpy(&raw_data[11], &adsb_crc[11], 3);
+	}
+
+private:
+	static const uint8_t adsb_preamble[16];
+	static const char icao_id_lut[65];
+	alignas(4) uint8_t index { 0 };
+	alignas(4) uint8_t raw_data[14] { };	// 112 bits at most
+};
+
+} /* namespace adsb */
+
+#endif/*__ADSB_FRAME_H__*/