Public Access
twislaandClaude Opus 5.5
c9b1ecb772
lib/gnss: RMC, GGA, GSA and GSV into one GnssState: Fix type, position, altitude, speed, course, HDOP, UTC time (trusted only with a Fix) and the satellites in view across constellations. GSV sequences are kept per constellation and signal band and merged per satellite with the stronger SNR; GSA's system ID marks which satellites are used. 16 tests, using lines captured from the device. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT
79 lines
2.7 KiB
C++
79 lines
2.7 KiB
C++
#pragma once
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#include <cstddef>
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#include <cstdint>
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#include <map>
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#include <set>
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#include <string>
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#include <utility>
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#include <vector>
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namespace roro::gnss {
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enum class Constellation : uint8_t { Unknown, Gps, Glonass, Galileo, BeiDou, Qzss, Navic };
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const char* constellationName(Constellation c);
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enum class FixType : uint8_t { None, TwoD, ThreeD };
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struct Satellite {
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Constellation system = Constellation::Unknown;
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int prn = 0;
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int elevation = 0; // degrees above the horizon
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int azimuth = 0; // degrees from north, clockwise
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int snr = -1; // dB-Hz; -1 when not tracked
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bool used = false; // part of the current Fix
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};
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// Everything the receiver has said, as of the last sentence (see CONTEXT.md: Fix).
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struct GnssState {
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FixType fix = FixType::None;
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bool positionValid = false;
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double latitude = 0, longitude = 0; // degrees, south and west negative
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bool altitudeValid = false;
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float altitudeM = 0; // above mean sea level
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float speedKmh = 0;
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bool courseValid = false;
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float courseDeg = 0;
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int satellitesUsed = 0;
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float hdop = 99.9f;
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// UTC, trusted only with a Fix: the receiver reports a time without one, from its own clock.
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bool timeValid = false;
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int year = 0, month = 0, day = 0, hour = 0, minute = 0, second = 0;
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std::vector<Satellite> satellites; // in view, all constellations, one entry per satellite
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int64_t utcSeconds() const; // seconds since 1970-01-01 UTC; meaningful when timeValid
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};
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// NMEA 0183 (4.10 style, as the Cap's AT6668 sends it): RMC, GGA, GSA and GSV, with the
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// constellation taken from the talker ID or GSA's system ID field. Host-tested; no hardware here.
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class NmeaParser {
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public:
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// Raw bytes from the UART, in any chunks.
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void feed(const char* data, size_t len);
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// One sentence without its line end. False if malformed or its checksum is wrong.
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bool sentence(const std::string& line);
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const GnssState& state() const { return state_; }
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uint32_t goodSentences() const { return good_; }
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uint32_t badSentences() const { return bad_; }
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private:
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using Fields = std::vector<std::string>;
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void rmc(const Fields& f);
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void gga(const Fields& f);
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void gsa(const Fields& f, Constellation talker);
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void gsv(const Fields& f, Constellation talker);
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void rebuildSatellites();
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static constexpr size_t kMaxLine = 120;
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std::string line_;
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bool overflow_ = false;
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uint32_t good_ = 0, bad_ = 0;
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GnssState state_;
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// GSV sequences per (constellation, signal): pending until their last message.
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std::map<std::pair<int, int>, std::vector<Satellite>> pending_, inView_;
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std::map<int, std::set<int>> used_; // per constellation, from GSA
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};
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} // namespace roro::gnss
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