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/Leg.cs

@@ -0,0 +1,131 @@
+using UnityEngine;
+
+public class Leg : MonoBehaviour {
+    public Transform Hip1;
+    public Transform Hip2;
+    public Transform Knie;
+
+    // rotation angles for different servos
+    public double a1 = 0;
+    public double a2 = 0;
+    public double a3 = 0;
+
+    public Vector3 point = new Vector3(10, 10, 0);
+    public Quaternion rotation = new Quaternion(0, 0, 0, 0);
+
+    public Vector3 transformationBeforeRotation = new Vector3(0, 0, 0);
+    public Vector3 transformationAfterRotation = new Vector3(0, 0, 0);
+
+    public bool invertForLeftLeg = false;
+
+    // translation to change origin to middle of body
+    public double translateX = 0;
+    public double translateY = 0;
+    public double translateZ = 0;
+
+    public GameObject pointShouldBe;
+    //public Vector3 pos = new Vector3(0, 0, 0);
+
+    public int startServo = -1;
+
+    private Foot foot = new Foot();
+
+    // Use this for initialization
+    void Start () {
+		
+	}
+
+    // Update is called once per frame
+    public void FixedUpdate()
+    {
+        foot.X = point.x;
+        foot.Y = point.y;
+        foot.Z = point.z;
+
+        foot.rotationX = rotation.x;
+        foot.rotationY = rotation.y;
+        foot.rotationZ = rotation.z;
+
+        foot.translateX = translateX;
+        foot.translateY = translateY;
+        foot.translateZ = translateZ;
+
+        // transform before rotation.
+        foot.transformation = transformationBeforeRotation;
+
+        // transform after rotation.
+        foot.transformation2 = transformationAfterRotation;
+
+        foot.invert = invertForLeftLeg;
+
+        foot.setleg();
+
+        if (!invertForLeftLeg)
+        {
+            a1 = foot.O1 - 90;
+            a2 = 90 - foot.O2;
+            a3 = foot.O3 - 90;
+        }
+        else
+        {
+            a1 = (foot.O1 - 90)*-1;
+            a2 = 90 - foot.O2;
+            a3 = foot.O3 - 90;
+        }
+
+        if (!invertForLeftLeg && startServo != -1)
+        {
+            //            Serial.Instance.send(startServo,
+            //                (int)Remap((float)a1, -90, 90, 2500, 500),
+            //                (int)Remap((float)a2, -90, 90, 2500, 500), // 0 is middel
+            //                (int)Remap((float)a3, 90, -90, 2500, 500)); // 0 is middel
+            if(false)
+            Serial.Instance.send(startServo,
+                            (int)Remap((float)a1, -90, 90, 0, 180),
+                            (int)Remap((float)a2, 90, -90, 0, 180), // 0 is middel
+                            (int)Remap((float)a3, -90, 90, 0, 180)); // 0 is middel
+        }
+        else if (invertForLeftLeg && startServo != -1)
+        {
+            double a1 = foot.O1 - 90;
+            double a2 = 90 - foot.O2;
+            double a3 = foot.O3 - 90;
+
+            //            Serial.Instance.send(startServo,
+            //                (int)Remap((float)a1, -90, 90, 500, 2500),
+            //                (int)Remap((float)a2, -90, 90, 500, 2500), // 0 is middel
+            //                (int)Remap((float)a3, 90, -90, 500, 2500)); // 0 is middel
+            if (false)
+                Serial.Instance.send(startServo,
+                (int)Remap((float)a1, 90, -90, 0, 180),
+                (int)Remap((float)a2, -90, 90, 0, 180), // 0 is middel
+                (int)Remap((float)a3, 90, -90, 0, 180)); // 0 is middel
+        }
+
+        Hip1.transform.localRotation = Quaternion.Euler(0, (float)a1, 0);
+        Hip2.transform.localRotation = Quaternion.Euler((float)a2, 0, 0);
+        Knie.transform.localRotation = Quaternion.Euler((float)a3, 0, 0);
+
+        pointShouldBe.transform.localPosition = foot.pos;
+    }
+
+    public Vector3 getLocalPos()
+    {
+        return point;
+    }
+
+    public Vector3 getWorldPos()
+    {
+        return point + new Vector3((float)translateX, (float)translateY, (float)translateZ);
+    }
+
+    public void setWorldPos(Vector3 pos)
+    {
+        this.point = pos - new Vector3((float)translateX, (float)translateY, (float)translateZ);
+    }
+
+    public static float Remap(float value, float from1, float to1, float from2, float to2)
+    {
+        return (value - from1) / (to1 - from1) * (to2 - from2) + from2;
+    }
+}