# ArduPilot + Gazebo Simulation

## Prerequisites

Before running, ensure your environment is set up:

```bash
source activate.sh
# or
source ~/.ardupilot_env && source ~/venv-ardupilot/bin/activate
```

## Quick Start (2 Terminals)

**Terminal 1 - Start Gazebo:**
```bash
./scripts/run_ardupilot_sim.sh runway
```

**Terminal 2 - Start Controller:**
```bash
./scripts/run_ardupilot_controller.sh
```

## Architecture

```
┌─────────────────┐     ┌─────────────────┐     ┌─────────────────┐
│ Gazebo          │◄───►│ ArduPilot SITL  │◄───►│ run_ardupilot.py│
│ (Physics)       │JSON │ (Flight Ctrl)   │MAV  │ (Your Logic)    │
└─────────────────┘     └─────────────────┘     └─────────────────┘
```

**Communication:**
- Gazebo ↔ SITL: JSON sensor data over UDP (port 9002)
- SITL ↔ Your Code: MAVLink over TCP (port 5760)

## World Options

```bash
./scripts/run_ardupilot_sim.sh runway     # Default (outdoor runway)
./scripts/run_ardupilot_sim.sh warehouse  # Indoor warehouse
./scripts/run_ardupilot_sim.sh gimbal     # With camera gimbal
./scripts/run_ardupilot_sim.sh zephyr     # Fixed-wing aircraft
./scripts/run_ardupilot_sim.sh custom     # Your custom world
./scripts/run_ardupilot_sim.sh my_world   # gazebo/worlds/my_world.sdf
```

## GPS-Denied Mode

The simulation runs in GPS-denied mode by default. The controller disables GPS checks and uses visual navigation.

For manual debugging with MAVProxy:
```bash
sim_vehicle.py -v ArduCopter -f gazebo-iris --model JSON --console

# In MAVProxy console:
param set ARMING_CHECK 0
mode stabilize
arm throttle force
rc 3 1500  # Throttle up
```

## Controller Options

```bash
./scripts/run_ardupilot_controller.sh                 # Auto takeoff
./scripts/run_ardupilot_controller.sh --no-takeoff    # Manual control
./scripts/run_ardupilot_controller.sh -a 10           # 10m altitude
```

## Files

| File | Purpose |
|------|---------|
| `scripts/run_ardupilot_sim.sh` | Gazebo launcher with GPU detection |
| `scripts/run_ardupilot_controller.sh` | SITL + Controller launcher |
| `scripts/run_ardupilot.py` | MAVLink interface script |
| `src/drone_controller.py` | Your landing algorithm |

## Environment Variables

The scripts automatically set these, but for manual runs:

```bash
# ArduPilot tools
export PATH=$PATH:~/ardupilot/Tools/autotest

# ArduPilot venv (has empy, pymavlink, etc.)
source ~/venv-ardupilot/bin/activate

# Gazebo plugin paths
export GZ_SIM_SYSTEM_PLUGIN_PATH=~/ardupilot_gazebo/build:$GZ_SIM_SYSTEM_PLUGIN_PATH
export GZ_SIM_RESOURCE_PATH=~/ardupilot_gazebo/models:~/ardupilot_gazebo/worlds:$GZ_SIM_RESOURCE_PATH
```

## Troubleshooting

### "No JSON sensor message" or "No heartbeat"

**Cause:** Gazebo isn't running or ArduPilot plugin isn't loaded.

**Fix:**
1. Start Gazebo first (Terminal 1)
2. Wait for world to fully load
3. Then start controller (Terminal 2)

### "sim_vehicle.py not found"

**Cause:** ArduPilot tools not in PATH.

**Fix:**
```bash
source ~/.ardupilot_env
# or
export PATH=$PATH:~/ardupilot/Tools/autotest
```

### "empy not found" during waf build

**Cause:** Wrong Python environment.

**Fix:**
```bash
source ~/venv-ardupilot/bin/activate
pip install empy==3.3.4
cd ~/ardupilot
./waf configure --board sitl
./waf copter
```

### Drone doesn't respond to commands

**Possible causes:**
1. Not in GUIDED mode - check MAVProxy: `mode`
2. Not armed - run: `arm throttle force`
3. Pre-arm checks failing - run: `param set ARMING_CHECK 0`

### Drone immediately crashes in Gazebo

**Cause:** Usually a physics/plugin issue.

**Fix:**
```bash
# Rebuild the ArduPilot Gazebo plugin
cd ~/ardupilot_gazebo/build
cmake .. -DCMAKE_BUILD_TYPE=Release
make -j4
```

### Simulation is laggy

**Cause:** Software rendering or GPU not detected.

**Check:**
```bash
glxinfo | grep "OpenGL renderer"
```

Should show your GPU name, not "llvmpipe" or "software".

**Fix for WSL:**
- Install NVIDIA drivers for WSL: https://developer.nvidia.com/cuda/wsl
- Ensure WSLg is enabled (Windows 11)

### MAVProxy console not opening

**Cause:** Missing `--console` flag or display issues.

**Fix:**
```bash
# Run directly
sim_vehicle.py -v ArduCopter -f gazebo-iris --model JSON --console --map

# If display errors:
export DISPLAY=:0  # Linux/WSL with X server
```

## Advanced: Custom Takeoff

To customize the takeoff behavior, edit `scripts/run_ardupilot.py`:

```python
# Change altitude
TAKEOFF_ALTITUDE = 15  # meters

# Change timeout
CONNECTION_TIMEOUT = 60  # seconds
```

## Logs

ArduPilot logs are saved to:
```
~/ardupilot/logs/
~/ardupilot/build/sitl/logs/
```

View with:
```bash
mavlogdump.py --types GPS,ATT ~/ardupilot/logs/LASTLOG.BIN
```