mirror of
https://github.com/dz0ny/meshcore-sar.git
synced 2026-08-11 08:20:36 +00:00
3c08e150ef
Switch the fast-GPS beacon to the firmware's canonical 16-byte wire format (magic, key6, lat/lon microdegrees, speed km/h) — no on-wire timestamp; the receiver stamps its own RX time. Drops compatibility with the older 19-byte app format. Mirror the firmware's adaptive send cadence in the app-fallback path (LocationTrackingService): anchor + dwell motion hysteresis, EMA ground speed, 9-min stationary keepalive, fix-quality (accuracy) gate, and a post-RX hold-off to avoid channel collisions. Parked nodes now beacon the stable anchor instead of GPS wander. Add the fast_gps_region config: region-scope picker in settings backed by the firmware's fast_gps_region / fast_gps_regions custom vars. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
87 lines
2.7 KiB
Dart
87 lines
2.7 KiB
Dart
import 'dart:typed_data';
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/// Fast-GPS position beacon, wire-compatible with the MeshUI firmware
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/// (`maybeSendFastGpsUpdate` in MyMesh.cpp).
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///
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/// 16-byte binary payload sent as a `DATA_TYPE_DEV` group datagram on a
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/// non-public channel:
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///
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/// ```
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/// [0] magic 0x47 ('G')
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/// [1..6] sender public-key prefix (6 bytes)
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/// [7..10] latitude in microdegrees (int32, little-endian)
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/// [11..14] longitude in microdegrees (int32, little-endian)
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/// [15] ground speed in km/h (uint8, clamped 0..255)
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/// ```
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///
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/// The beacon carries no timestamp — receivers stamp their own RX time.
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class FastGpsPacket {
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static const int magic = 0x47; // 'G'
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static const int _payloadLength = 16;
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// Store coordinates in microdegrees. This preserves sub-meter precision,
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// which comfortably satisfies the meter-accuracy requirement.
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static const double coordinateScale = 1e6;
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final String senderKey6;
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final double latitude;
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final double longitude;
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/// Ground speed in km/h (0..255), as carried in the beacon's trailing byte.
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final int speedKmh;
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const FastGpsPacket({
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required this.senderKey6,
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required this.latitude,
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required this.longitude,
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this.speedKmh = 0,
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});
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static bool isFastGpsBinary(Uint8List payload) =>
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payload.length == _payloadLength && payload[0] == magic;
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static FastGpsPacket? tryParseBinary(Uint8List payload) {
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if (!isFastGpsBinary(payload)) return null;
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final key6 = payload
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.sublist(1, 7)
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.map((b) => b.toRadixString(16).padLeft(2, '0'))
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.join();
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final data = ByteData.sublistView(payload);
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final latitude = data.getInt32(7, Endian.little) / coordinateScale;
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final longitude = data.getInt32(11, Endian.little) / coordinateScale;
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final speedKmh = data.getUint8(15);
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if (!_isValidCoordinate(latitude, longitude)) {
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return null;
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}
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return FastGpsPacket(
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senderKey6: key6,
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latitude: latitude,
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longitude: longitude,
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speedKmh: speedKmh,
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);
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}
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Uint8List encodeBinary() {
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final out = Uint8List(_payloadLength);
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final data = ByteData.sublistView(out);
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out[0] = magic;
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for (var i = 0; i < 6; i++) {
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out[1 + i] = int.parse(senderKey6.substring(i * 2, i * 2 + 2), radix: 16);
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}
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data.setInt32(7, (latitude * coordinateScale).round(), Endian.little);
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data.setInt32(11, (longitude * coordinateScale).round(), Endian.little);
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data.setUint8(15, speedKmh.clamp(0, 255));
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return out;
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}
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static bool _isValidCoordinate(double latitude, double longitude) {
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if (!latitude.isFinite || !longitude.isFinite) return false;
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return latitude >= -90.0 &&
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latitude <= 90.0 &&
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longitude >= -180.0 &&
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longitude <= 180.0;
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}
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}
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