Firmware simulation, Unity project, and sim-verified robot fixes

Simulation
- sim/: the unchanged robot firmware compiled into hexapod_sim.dll
  against PC stand-ins (Arduino, Servo, Wire + register-level MPU6050,
  RF24 with matching-config radio), a kinematic body model (support
  plane + planted-foot odometry) that also drives the simulated IMU,
  and a headless smoke test (sim_smoke). build.ps1 builds and tests.
- Hexapod_Simulation_Unity/ folded in (history kept in a bundle
  outside the repo). Assets/HexapodSim loads the DLL, drives the
  existing leg rig, and offers joystick / keyboard / robot-serial
  input plus a test panel.

Robot (all found or confirmed in the simulation)
- Config.h geometry taken from the Unity model.
- IK femur elevation sign, gait stance direction, body pose
  rotation direction, yaw lever arm.
- Stance feet integrated from the current command; gait restarts at
  mid-stance; heading integrates the applied turn rate, only while
  walking.
- Leg clearance and reach checks (Limits::feetFeasible); walk command
  and body pose scaled as a whole, pose scale rate-limited, planted
  feet guarded so the body never snaps or legs collide.
- Robot-gyro self-leveling as an integrator.
- Heading mode: steering relative to the body; S walks backward.
- Standing height from the remote (STANCE_HEIGHT_RANGE_MM).

Protocol v3 (reflash both boards)
- CmdPacket gains body_height (22 bytes).

Remote
- Height slider (Nextion hHeight/nHeight, serial [ ]).
- Fixed unspecified I2C read order in RemoteIMU.

LEGACY/: owner's old Nextion HMI and remote hardware assets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2026-current/Hexapod_Simulation_Unity/Assets/Serial/Serial2.cs

@@ -0,0 +1,70 @@
+/*using System;
+using UnityEngine;
+using System.Collections;
+using System.IO.Ports;
+using System.Linq;
+
+public class Serial2 : MonoBehaviour{
+
+    public float x;
+    public float y;
+
+    public RotationControl bot;
+
+    ~Serial2() {
+        serialPort.Close();
+    }
+
+    public bool enabled = false;
+
+    SerialPort serialPort;
+
+    public void Update()
+    {
+        if (serialPort == null)
+        {
+            serialPort = new SerialPort(@"\\.\" + "COM7", 115200);
+
+            try
+            {
+                serialPort.NewLine = "\n";
+
+                serialPort.Open();
+                serialPort.DiscardOutBuffer();
+                serialPort.DiscardInBuffer();
+
+                enabled = true;
+            }
+            catch
+            {
+                enabled = false;
+            }
+        }
+
+        if (enabled)
+        {
+            if (serialPort is SerialPort)
+            {
+                string received = serialPort.ReadLine();
+                string[] data = received.Split(',');
+                x = ConvertRadiansToDegrees(float.Parse(data.First()));
+                y = ConvertRadiansToDegrees(float.Parse(data.Last()));
+
+                bot.rotation = new Quaternion(-1* limit(y, -30, 30), 0, -1* limit(x, -30, 30), 1);
+            }
+        }
+    }
+
+    public float limit(float input, float min, float max)
+    {
+        return (input < max & input > min) ? input : input < min ? min : max;
+    }
+
+    public float ConvertRadiansToDegrees(float radians)
+    {
+        float degrees = (float) ((180 / Math.PI) * radians);
+        return (degrees);
+    }
+
+}
+*/