iNAV MCP Server
An MCP 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.
<sub>Recorded against a live iNAV 6.1.0 flight controller over USB.</sub>
⚠️ 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.
COM3on Windows,/dev/ttyACM0on Linux)
Install
From PyPI (once the first release is published):
pip install inav-mcp
From source (for development, or to run the latest unreleased code):
# 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):
.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):
.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:
{
"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:
{
"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 recentdiff allbackup.
Safety model
- Props-off gate —
test_motor()and any livemotorcommand viacli(...)requireprops_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. - Armed guard — all writes (and motor tests / calibrations) refuse if the FC reports armed.
- Auto-backup before every write; the backup path is returned.
- Dry-run by default — writes return the exact commands;
confirm=Trueapplies. - Read-back verify — after applying, settings are re-read and mismatches flagged.
save= reboot —save_and_rebootwarns and marks the connection stale.- 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/filtergets) 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 callingcli()in a loop (one reboot per command — the cadence that can knock a board into DFU), pass a list tocli_batch(): one session, one reboot. Read-only batchesexitwithout saving; write batches back up andsaveonce (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 amodestate 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, andconnect()/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
.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.
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.