# iNAV MCP Server [](https://github.com/starlordz12/inav-mcp/actions/workflows/ci.yml) [](LICENSE) [](pyproject.toml) [](https://modelcontextprotocol.io) [](https://pypi.org/project/inav-mcp/) An [MCP](https://modelcontextprotocol.io) server that lets Claude configure, diagnose, and troubleshoot an **iNAV flight controller** over USB — built **primarily for flying wings** (elevon FPV wings like the TBS Chupito and Mojito), and also for conventional fixed-wing planes. It talks to the FC through a single serial connection, using the iNAV **CLI** for configuration writes and a small built-in **MSP** codec for live/binary reads. Every write is dry-run by default, auto-backs-up first, refuses while the board is armed, and reads back to verify.  _{Recorded against a live iNAV 6.1.0 flight controller over USB.} > ⚠️ **Safety:** Always remove props from the aircraft before any motor test. > This tool never switches the FC into MSP-RX mode and never arms the aircraft. --- ## Requirements - Python 3.10+ - An iNAV flight controller (developed against iNAV 8.x/9.x) connected over USB - The serial port the FC enumerates as (e.g. `COM3` on Windows, `/dev/ttyACM0` on Linux) ## Install **From PyPI** (once the first release is published): ```bash pip install inav-mcp ``` **From source** (for development, or to run the latest unreleased code): ```bash # from the repo root python -m venv .venv .venv/Scripts/python -m pip install -e . # Windows # source .venv/bin/activate && pip install -e . # Linux/macOS ``` For development (tests): ```bash .venv/Scripts/python -m pip install -e ".[dev]" ``` ### Try it without a flight controller You don't need any hardware to confirm the project works — the test suite runs fully offline (no FC required): ```bash .venv/Scripts/python -m pytest # Windows # .venv/bin/pytest # Linux/macOS ``` All 186 tests should pass. To actually **use** the server, though, you need a flight controller flashed with **iNAV firmware** (developed against iNAV 8.x/9.x) connected over USB — without one, the connection tools have nothing to talk to. ## Register with Claude Add the server to your Claude (Code or Desktop) MCP config (`~/.claude/settings.json` or the Claude Desktop config). **Replace the paths below with wherever you cloned this repo** — the `command` points at the Python inside your `.venv`, and `cwd` is the repo root. Windows: ```json { "mcpServers": { "inav": { "command": "C:\\path\\to\\inav-mcp\\.venv\\Scripts\\python.exe", "args": ["-m", "inav_mcp.server"], "cwd": "C:\\path\\to\\inav-mcp" } } } ``` Linux / macOS: ```json { "mcpServers": { "inav": { "command": "/path/to/inav-mcp/.venv/bin/python", "args": ["-m", "inav_mcp.server"], "cwd": "/path/to/inav-mcp" } } } ``` The server speaks MCP over **stdio**. You can also run it directly with the installed entry point `inav-mcp`. --- ## Typical workflows The server ships **prompts** that walk Claude through the common jobs — just pick one: - **`new_fixed_wing_setup`** — gather hardware details → `define_aircraft` → review → apply. - **`troubleshoot_no_arm`** — decode arming-prevention flags → guided fixes. - **`configure_modes`** — identify switches from live RC → suggest a layout → assign modes. Or drive it conversationally, e.g.: > "Connect to my FC on COM3 and tell me why it won't arm." > "Set up a 4S flying wing on DSHOT600, then show me the commands before applying." --- ## Tools (35) ### Connection & identity | Tool | What it does | |---|---| | `list_serial_ports()` | List available serial ports. | | `find_fc(baud=115200, probe_all=False)` | Auto-detect which port has an FC by probing for MSP identity — no guessing the port. | | `connect(port, baud=115200)` | Open the FC connection, return board identity. | | `disconnect()` | Close the connection. | | `board_info()` | FC variant, firmware version, target, API version, sensors. | ### Hardware setup | Tool | What it does | |---|---| | `define_aircraft(name, wing_type, esc_protocol, cells, …)` | Offline planner — stores a profile and generates the CLI config plan. | | `get_aircraft_profile()` | The current declared profile + plan. | | `apply_aircraft_setup(confirm=False)` | Apply the plan (gated: not armed, auto-backup, read-back verify). On iNAV, applying is inherently save+reboot. | | `check_config()` | `diff all` + lint against the declared profile + ARM check. | ### Flight modes & switches | Tool | What it does | |---|---| | `suggest_mode_layout(skill_level, num_switches, has_gps=False)` | Recommend a fixed-wing switch/mode layout (offline). | | `set_flight_mode(mode_name, aux_channel, range_low, range_high, confirm=False)` | Assign one mode to an aux range. | | `assign_switch(switch_channel, switch_positions, mode_per_position, confirm=False)` | Map a whole 2/3/6-pos switch in one call. | | `clear_flight_mode(mode_name, confirm=False)` | Remove a mode's switch assignments. | ### Diagnostics | Tool | What it does | |---|---| | `diagnose()` | Full sweep: arming, sensors, RC, battery, GPS → prioritized fixes. | | `why_wont_it_arm()` | Decode arming-prevention flags into plain reasons + fixes. | | `read_rc_channels()` | Live RC channel values — flip a switch, see which channel moves. | | `read_sensors()` | Live attitude, per-sensor health, battery. | | `get_status()` | MSP status + CLI `status`/`tasks`. | | `list_flight_modes()` | All modes and their current switch assignments. | | `check_failsafe()` | Read `failsafe_*` settings, explain the RC-loss procedure, flag risky setups (e.g. RTH without GPS). | ### Bench tests & calibration | Tool | What it does | |---|---| | `test_motor(motor, throttle_us=1100, duration_s=2.0, props_removed=False, confirm=False)` | Spin ONE motor briefly. Hard-gated: `props_removed=True` + `confirm=True`, refuses while armed, always auto-stops. (No `test_servo` — iNAV has no live servo override; verify surfaces with the TX sticks + `read_rc_channels()`.) | | `calibrate_accelerometer(confirm=False)` | Zero-level the accelerometer (board flat + still). Fixes most "not level" arming blocks. | | `calibrate_magnetometer(confirm=False)` | Calibrate the compass (rotate the craft ~30s). | ### Navigation & tuning | Tool | What it does | |---|---| | `read_gps()` | Live GPS fix/sats/position + nav-readiness assessment (read-only). | | `configure_gps(provider="UBLOX", sbas=None, confirm=False)` | Enable the GPS feature and set provider/SBAS. | | `set_nav(rth_altitude_m=None, rth_climb_first=None, rth_allow_landing=None, loiter_radius_m=None, confirm=False)` | Set fixed-wing RTH altitude / climb-first / landing / loiter radius. | | `read_tuning()` | Read fixed-wing PID gains, rates, and filter cutoffs. | | `set_pid(axis, p=None, i=None, d=None, ff=None, confirm=False)` | Set fixed-wing P/I/D/FF gains for one axis. | ### Config management | Tool | What it does | |---|---| | `backup_config(label=None)` | Save `diff all` to a timestamped file under `./backups/`. | | `list_backups()` | List saved backups (path, time, size, label), newest first. | | `restore_config(path, confirm=False)` | Replay a saved backup via CLI. | | `set_failsafe(procedure=None, throttle_us=None, confirm=False)` | Set the RC-loss procedure / throttle (atomic write; FC validates the procedure token). | | `cli(command, confirm_for_writes=False, props_removed=False)` | Raw CLI escape hatch (ONE command, one reboot). Writes need `confirm_for_writes`; a live `motor` test needs `props_removed=True` and is never saved. | | `cli_batch(commands, confirm_for_writes=False)` | Run MANY CLI commands in **one** session → **one** reboot. Read-only batch exits without saving; a write batch backs up + saves once (rolls back if any command is rejected). Motor/`save`/`exit` commands refused. | | `save_and_reboot(confirm=False)` | `save` to EEPROM and reboot (marks the connection stale). | ## Resources - `inav://modes-reference` — iNAV mode glossary with fixed-wing relevance. - `inav://current-profile` — the declared aircraft profile + generated plan. - `inav://last-backup` — the most recent `diff all` backup. --- ## Safety model 1. **Props-off gate** — `test_motor()` and any live `motor` command via `cli(...)` require `props_removed=True` (the generic write-confirm cannot bypass it), refuse while the board is armed, and are never saved. `test_motor()` also clamps throttle/duration and always commands the motor back to stop. 2. **Armed guard** — all writes (and motor tests / calibrations) refuse if the FC reports armed. 3. **Auto-backup** before every write; the backup path is returned. 4. **Dry-run by default** — writes return the exact commands; `confirm=True` applies. 5. **Read-back verify** — after applying, settings are re-read and mismatches flagged. 6. **`save` = reboot** — `save_and_reboot` warns and marks the connection stale. 7. **No receiver-mode changes** — the FC is never switched to MSP-RX. ## Reboot model — why batching matters On iNAV, **leaving the CLI always reboots the FC** — both `save` (persist to EEPROM) and `exit` (discard changes) trigger a reboot, after which the USB VCP re-enumerates and we reconnect (~6–8 s, surfaced as `reboot_seconds`). So **every CLI round-trip costs one reboot**, including read-only ones (`get`, `diff`, `dump`, `version`). There is no way to read over the CLI without that reboot — the only lever is to do fewer CLI sessions. What this server does to keep reboot churn down: - **Reads prefer MSP, which never reboots.** `get_status`, `read_rc_channels`, `read_sensors`, `read_gps`, `list_flight_modes`, `why_wont_it_arm`, `diagnose`, and the armed-guard all read structured data over MSP — zero reboots. Only data that's CLI-only (`diff all`, `get failsafe`, PID/rate/filter `get`s) pays a reboot. - **Writes are atomic and batch internally.** Each write tool (`apply_aircraft_setup`, `set_flight_mode`, `assign_switch`, `set_pid`, `set_failsafe`, `restore_config`, …) opens **one** CLI session: backup → apply all commands → save → reboot once. Multiple settings = one reboot. - **`cli_batch()` for ad-hoc runs.** Instead of calling `cli()` in a loop (one reboot **per** command — the cadence that can knock a board into DFU), pass a list to `cli_batch()`: one session, one reboot. Read-only batches `exit` without saving; write batches back up and `save` once (rolling back if any command is rejected). - **Resilient reconnect.** After a reboot the reconnect waits a short settle, then polls with backoff; if the original COM port doesn't return it scans for a re-enumerated one, and if the board came back in **DFU/bootloader mode** it says so and tells you to power-cycle (USB unplug/replug) rather than hanging. ## How it works - **Single serial handle** shared between MSP and CLI modes (`connection.py`), tracked by a `mode` state machine. Never two handles on one port. - **CLI-first writes** — the CLI is stable across firmware versions; MSP command IDs can drift. A thin MSP v1/v2 codec (`msp.py`) handles only the live binary reads (status, RC, attitude, analog, GPS, sensor health, mode ranges, box maps). - **Box IDs are resolved at runtime** via `MSP_BOXNAMES` + `MSP_BOXIDS` — never hardcoded. - **Arming flags** are decoded from `knowledge/arming_flags.json`, calibrated to iNAV 8.x/9.x bit positions. The table declares its calibrated major versions, and `connect()` / `board_info()` / `why_wont_it_arm()` / `diagnose()` **warn when the connected firmware is outside that range** (bit positions shift between majors, so flag *names* may be mislabelled even though the raw flag value is correct). ## Development ```bash .venv/Scripts/python -m pytest # 186 tests, all offline (no FC needed) ``` The suite covers the MSP codec round-trips, CLI response parsing, the diagnostic rule engine, offline profile/command generation, mode-range read-modify-write logic (against a mock connection), and resource/prompt registration. Project layout: ``` inav_mcp/ server.py # FastMCP app: all tools, resources, prompts connection.py # single serial handle, MSP + CLI mode switching msp.py # MSP v1/v2 codec + parsers cli.py # CLI response parsing, write-command detection modes.py # box maps, mode-range read/write, layout planner profiles.py # AircraftProfile + offline CLI command generator troubleshoot.py # diagnose() rule engine + arming-flag decode safety.py # armed guard, backup paths state.py # connection + profile singletons knowledge/ # arming_flags / modes_reference / esc_protocols / fc_targets (JSON) tests/ # offline pytest suite tools/ # gen_readme_tools.py — regenerates the tool reference below examples/ # flying_wing_quickstart.md — end-to-end walkthrough ``` Release history is in [CHANGELOG.md](CHANGELOG.md). ## Full tool reference Complete, signature-accurate list — regenerate after changing tools with `python -m tools.gen_readme_tools` (a test fails if this drifts): _35 tools — auto-generated by `tools/gen_readme_tools.py`; do not edit by hand._ | Tool | Description | |---|---| | `apply_aircraft_setup(confirm=False)` | Apply the declared aircraft profile to the FC, then save and reboot. | | `assign_switch(switch_channel, switch_positions, mode_per_position, confirm=False)` | Map a multi-position switch's detents to flight modes in one call. | | `backup_config(label=None)` | Save the current FC config to a timestamped backup file. | | `board_info()` | Read flight-controller identity over MSP. | | `calibrate_accelerometer(confirm=False)` | Calibrate the accelerometer (zero-level). Fixes most 'not level' / 'accel not | | `calibrate_magnetometer(confirm=False)` | Calibrate the compass (magnetometer). Only useful if a compass is installed. | | `check_config()` | Compare the FC's actual configuration against the declared aircraft profile. | | `check_failsafe()` | Read and explain the failsafe configuration (what happens on RC loss). | | `clear_flight_mode(mode_name, confirm=False)` | Remove all switch assignments for a flight mode (disables its slots via CLI 'aux'). | | `cli(command, confirm_for_writes=False, props_removed=False)` | Raw CLI escape hatch — run any iNAV CLI command directly. | | `cli_batch(commands, confirm_for_writes=False)` | Run MANY CLI commands in ONE CLI session — a single reboot for the whole batch. | | `configure_gps(provider='UBLOX', sbas=None, confirm=False)` | Enable the GPS feature and set the receiver provider / SBAS (atomic CLI write). | | `connect(port, baud=115200)` | Open the serial connection to the FC and return board identity. | | `define_aircraft(name, wing_type, esc_protocol, cells, fc_target=None, motor_kv=None, motor_poles=14, servo_count=None, notes=None)` | Define the aircraft hardware profile and generate a configuration plan. | | `diagnose()` | Full diagnostic sweep — the flagship troubleshooter. | | `disconnect()` | Close the serial connection to the FC. | | `find_fc(baud=115200, probe_all=False)` | Auto-detect which serial port has a flight controller, so you don't guess. | | `get_aircraft_profile()` | Return the currently declared aircraft profile. | | `get_status()` | Read FC status via both MSP and CLI. | | `list_backups()` | List saved config backups under ./backups/, newest first. No FC needed. | | `list_flight_modes()` | List all available flight modes and their current switch assignments. | | `list_serial_ports()` | List all available serial ports. | | `read_gps()` | Live GPS status: fix type, satellites, position, speed, HDOP + nav-readiness. | | `read_rc_channels()` | Read live RC channel values via MSP. | | `read_sensors()` | Read live sensor values: attitude, per-sensor health, and analog (battery). | | `read_tuning()` | Read fixed-wing PID gains, rates, and key filter cutoffs (via CLI). | | `restore_config(path, confirm=False)` | Restore FC config by replaying a backup file's CLI commands, then save+reboot. | | `save_and_reboot(confirm=False)` | Save the running config to EEPROM and reboot the FC. | | `set_failsafe(procedure=None, throttle_us=None, delay_s=None, off_delay_s=None, confirm=False)` | Set the core failsafe behaviour (atomic CLI write: backup → apply → save+reboot). | | `set_flight_mode(mode_name, aux_channel, range_low, range_high, confirm=False)` | Assign a flight mode to an aux channel range (read-modify-write via CLI 'aux'). | | `set_nav(rth_altitude_m=None, rth_climb_first=None, rth_allow_landing=None, loiter_radius_m=None, confirm=False)` | Set core fixed-wing navigation / RTH parameters (atomic CLI write). | | `set_pid(axis, p=None, i=None, d=None, ff=None, confirm=False)` | Set fixed-wing PID gains for ONE axis (atomic CLI write). | | `suggest_mode_layout(skill_level='beginner', num_switches=2, has_gps=False)` | Recommend a fixed-wing flight-mode/switch layout. Pure knowledge — no FC needed. | | `test_motor(motor, throttle_us=1100, duration_s=2.0, props_removed=False, confirm=False)` | Spin ONE motor briefly for a bench test (direction / wiring / response). | | `why_wont_it_arm()` | Decode the FC's arming-prevention flags into plain English. | ## License MIT. This project ships its own MSP codec and does **not** import GPL libraries (uNAVlib / YAMSPy) at runtime, keeping it permissively licensed.