Initial commit: FieldLogger MAUI app with Maglink BLE support

Added Maglink RTK GNSS receiver integration with correct BLE UUIDs and device name filtering (ML-* prefix).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

FieldLogger/Models/UmLogPacket.cs

@@ -0,0 +1,141 @@
+using System.Globalization;
+
+namespace FieldLogger.Models;
+
+public enum UmMode { Single = 0, Twin = 1, Null = 2, Sweep = 3, TwinSweep = 4, Omni = 5, TwinOmni = 6 }
+
+public enum UmFreqType { Active = 0, LdActive = 1, Power = 2, GroupedPower = 3, Cathodic = 4, Sonde = 5, Radio = 6, FaultFind = 7 }
+
+public enum UmUtility { None = 0, Gas = 1, Power = 2, Communications = 3, Water = 4, Sewer = 5, Fiber = 6, Other = 7 }
+
+public enum UmBatteryType { NotMeasured = 0, Alkaline = 1, AlkalineError = 2, Lithium = 3 }
+
+/// <summary>
+/// A single push-button data-log packet from the UM locating receiver
+/// (PBDL schema 1, 21 comma-delimited fields).
+/// </summary>
+public sealed class UmLogPacket
+{
+    public UmMode Mode { get; init; }
+    public int Frequency { get; init; }
+    public UmFreqType FreqType { get; init; }
+    public int Signal { get; init; }              // 0 - 99
+    public int GainDb { get; init; }              // 0 - 145 dB
+    public string DepthRaw { get; init; } = "";   // "X' Y\"" imperial, "X.Yym" metric, "- - -" no depth
+    public string CurrentRaw { get; init; } = ""; // 0 - 999mA
+    public int CompassAngle { get; init; }        // 0 - 180 degrees (direction ambiguous)
+    public int GuidanceArrows { get; init; }      // -300 to 300, negative = left
+    public int LdPhase { get; init; }
+    public bool Clipping { get; init; }
+    public int DepthCurrentSetting { get; init; } // 0 ON, 1 AUTO
+    public int LrArrowStyle { get; init; }        // 0 OFF, 1 Style 1, 2 Style 2
+    public int AudioVolume { get; init; }         // 0 - 3
+    public int AudioModulation { get; init; }     // 0 AM, 1 FM
+    public int AudioSound { get; init; }          // 0 Smooth, 1 Rough
+    public double BatteryVoltage { get; init; }
+    public UmBatteryType BatteryType { get; init; }
+    public int Backlight { get; init; }           // 0 Low, 1 Medium, 2 High
+    public UmUtility Utility { get; init; }
+    public bool MenuInUse { get; init; }
+    public string RawText { get; init; } = "";
+
+    public const int FieldCount = 21;
+
+    /// <summary>Depth converted to meters, when the raw string can be interpreted; otherwise null.</summary>
+    public double? DepthMeters => TryParseDepthMeters(DepthRaw);
+
+    /// <summary>Current in mA parsed from the raw string, when possible.</summary>
+    public double? CurrentMilliamps
+    {
+        get
+        {
+            var s = CurrentRaw.Trim().TrimEnd('A', 'a').TrimEnd('m', 'M');
+            return double.TryParse(s, NumberStyles.Float, CultureInfo.InvariantCulture, out var v) ? v : null;
+        }
+    }
+
+    public static double? TryParseDepthMeters(string raw)
+    {
+        raw = raw.Trim();
+        if (raw.Length == 0 || raw.Contains("- -"))
+            return null;
+
+        // Metric: "X.Yym" e.g. "1.23m"
+        if (raw.EndsWith("m", StringComparison.OrdinalIgnoreCase))
+        {
+            var s = raw[..^1].Trim();
+            if (double.TryParse(s, NumberStyles.Float, CultureInfo.InvariantCulture, out var meters))
+                return meters;
+            return null;
+        }
+
+        // Imperial: feet' inches"  e.g. "3' 7"" or "3' 7'"
+        if (raw.Contains('\''))
+        {
+            var parts = raw.Split('\'', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
+            if (parts.Length >= 1 &&
+                double.TryParse(parts[0], NumberStyles.Float, CultureInfo.InvariantCulture, out var feet))
+            {
+                double inches = 0;
+                if (parts.Length >= 2)
+                {
+                    var inchStr = parts[1].TrimEnd('"');
+                    double.TryParse(inchStr, NumberStyles.Float, CultureInfo.InvariantCulture, out inches);
+                }
+                return (feet + inches / 12.0) * 0.3048;
+            }
+        }
+
+        return null;
+    }
+
+    /// <summary>
+    /// Parses a 21-field PBDL schema 1 packet. Returns null if the line does not look like a data packet.
+    /// </summary>
+    public static UmLogPacket? TryParse(string line)
+    {
+        var fields = line.Trim().Split(',');
+        if (fields.Length < FieldCount)
+            return null;
+
+        // First field must be a small integer (Mode 0-6) to qualify as a data packet.
+        if (!int.TryParse(fields[0], out var mode) || mode is < 0 or > 6)
+            return null;
+
+        try
+        {
+            return new UmLogPacket
+            {
+                Mode = (UmMode)mode,
+                Frequency = ParseInt(fields[1]),
+                FreqType = (UmFreqType)ParseInt(fields[2]),
+                Signal = ParseInt(fields[3]),
+                GainDb = ParseInt(fields[4]),
+                DepthRaw = fields[5].Trim(),
+                CurrentRaw = fields[6].Trim(),
+                CompassAngle = ParseInt(fields[7]),
+                GuidanceArrows = ParseInt(fields[8]),
+                LdPhase = ParseInt(fields[9]),
+                Clipping = ParseInt(fields[10]) != 0,
+                DepthCurrentSetting = ParseInt(fields[11]),
+                LrArrowStyle = ParseInt(fields[12]),
+                AudioVolume = ParseInt(fields[13]),
+                AudioModulation = ParseInt(fields[14]),
+                AudioSound = ParseInt(fields[15]),
+                BatteryVoltage = ParseDouble(fields[16]),
+                BatteryType = (UmBatteryType)ParseInt(fields[17]),
+                Backlight = ParseInt(fields[18]),
+                Utility = (UmUtility)ParseInt(fields[19]),
+                MenuInUse = ParseInt(fields[20]) != 0,
+                RawText = line.Trim(),
+            };
+        }
+        catch (FormatException)
+        {
+            return null;
+        }
+    }
+
+    private static int ParseInt(string s) => int.Parse(s.Trim(), CultureInfo.InvariantCulture);
+    private static double ParseDouble(string s) => double.Parse(s.Trim(), NumberStyles.Float, CultureInfo.InvariantCulture);
+}