Lua Node Reference

Lua Node Reference

Complete catalog of all nodes available in the Lua Graph Editor, organized by category. For usage examples, see Lua Examples.

Sensors

Sensor nodes read data from the flight controller. They have no inputs and provide output values each update cycle.

Node	Outputs	Properties	ArduPilot API
GPS Position	Latitude, Longitude, Altitude (m)	--	gps:location(0)
Baro Altitude	Altitude (m)	--	baro:get_altitude()
Battery	Voltage, Current (A), Remaining %	Battery Instance (0-3)	battery
Airspeed	Airspeed (m/s)	--	ahrs:airspeed_estimate()
RC Channel	Value (us)	Channel (1-16)	rc:get_pwm(ch)
Rangefinder	Distance (m)	Instance (0-3)	rangefinder:distance_cm()
Attitude	Roll, Pitch, Yaw (deg)	--	ahrs:get_roll/pitch/yaw()
Ground Speed	Speed (m/s)	--	ahrs:groundspeed_vector()
RC Aux Switch	State (0-2), Is High, Is Mid	Aux Function (0-999)	rc:get_aux_cached()
Rangefinder (Oriented)	Distance (m)	Orientation (Forward/Down/Up)	rangefinder:distance_cm_orient()

Logic

Logic nodes handle boolean and comparison operations.

Node	Inputs	Outputs	Properties
Compare	A (number), B (number)	Result (boolean)	Operator: >, <, ==, !=, >=, <=
If / Else	Condition (boolean)	True, False	--
AND	A (boolean), B (boolean)	Result (boolean)	--
OR	A (boolean), B (boolean)	Result (boolean)	--
NOT	Input (boolean)	Result (boolean)	--
Range Check	Value (number)	In Range (boolean)	Min, Max
Switch	Value (number)	Case 0, Case 1, Case 2, Default	Case 0/1/2 Values

Math

Math nodes perform numeric calculations.

Node	Inputs	Outputs	Properties
Add	A, B	Result	--
Subtract	A, B	Result	--
Multiply	A, B	Result	--
Divide	A, B	Result (zero-safe)	--
Clamp	Value	Result	Min, Max
Map Range	Value	Result	Input Min/Max, Output Min/Max
Abs	Value	Result	--
Min	A, B	Result	--
Max	A, B	Result	--

Actions

Action nodes produce side effects. They require a boolean trigger input -- the action only fires when the trigger is true.

Node	Inputs	Properties	ArduPilot API
Send GCS Text	Trigger	Message, Severity (Emergency..Debug)	gcs:send_text()
Set Servo	Trigger, PWM (number)	Servo Number (1-16)	SRV_Channels:set_output_pwm()
Set Flight Mode	Trigger	Mode Number (0-30)	vehicle:set_mode()
Set Parameter	Trigger, Value (number)	Parameter Name	param:set()
Trigger Relay	Trigger	Relay Number (0-5), State (ON/OFF)	relay:on/off()
Log to File	Trigger, Value 1-3 (any)	File Name, Separator	io.open/write/close
Set LED	Trigger, R, G, B (numbers)	LED Instance (0-15)	serialLED:set_RGB()

Timing

Timing nodes control when and how often things happen.

Node	Inputs	Outputs	Properties
Run Every	Trigger (boolean)	Flow (boolean)	Interval (100-60000 ms)
Debounce	Input (boolean)	Output (boolean)	Delay (50-10000 ms)
On Change	Value (number)	Changed (boolean)	--
Rising Edge	Input (boolean)	Triggered (boolean)	--

Variables

Variable nodes store and retrieve values that persist across update cycles.

Node	Inputs	Outputs	Properties
Constant	--	Value (any)	Type (Number/String/Boolean), Value
Get Variable	--	Value (any)	Variable Name
Set Variable	Trigger, Value (any)	--	Variable Name

Flow

Utility nodes for organizing your graph.

Node	Purpose
Comment	A text label for documentation. No effect on compiled code

ArduPilot Lua API Reference

The graph editor generates code using these ArduPilot Lua bindings.

gcs (Ground Control Station)

gcs:send_text(severity, message)

Severity levels: 0=Emergency, 1=Alert, 2=Critical, 3=Error, 4=Warning, 5=Notice, 6=Info, 7=Debug.

vehicle

vehicle:set_mode(mode_number)
vehicle:get_mode()
vehicle:is_armed()

Mode numbers are vehicle-specific (e.g., Plane: 0=Manual, 10=Auto, 11=RTL).

ahrs (Attitude and Heading)

ahrs:get_roll()              -- radians
ahrs:get_pitch()             -- radians
ahrs:get_yaw()               -- radians
ahrs:get_home()              -- Location object
ahrs:groundspeed_vector()
ahrs:airspeed_estimate()

baro (Barometer)

baro:get_altitude()           -- meters

battery

battery:voltage(instance)
battery:current_amps(instance)
battery:capacity_remaining_pct(instance)

Instance 0 is the primary battery.

rc (Radio Control)

rc:get_pwm(channel)           -- 1-16, returns PWM in microseconds
rc:get_aux_cached(aux_fn)     -- returns switch position 0/1/2

SRV_Channels (Servo Outputs)

SRV_Channels:set_output_pwm(channel, pwm)
SRV_Channels:set_output_pwm_chan_timeout(channel, pwm, timeout_ms)

Use set_output_pwm_chan_timeout for temporary overrides.

param (Parameters)

param:get(name)               -- returns value or nil
param:set(name, value)        -- returns true on success
param:set_and_save(name, value)

rangefinder

rangefinder:distance_cm(instance)
rangefinder:distance_cm_orient(orientation)

Orientations: 0=Forward, 24=Up, 25=Down.

relay

relay:on(relay_num)
relay:off(relay_num)
relay:toggle(relay_num)

Relay numbers 0-5.

serialLED

serialLED:set_num_neopixel(instance, count)
serialLED:set_RGB(instance, led_index, r, g, b)
serialLED:send(instance)

Script Lifecycle

Every ArduPilot Lua script follows this pattern:

function update()
  -- Your logic here
  return update, interval_ms
end

return update, interval_ms

The return update, interval_ms tells ArduPilot to call update() again after interval_ms milliseconds. The graph editor handles this automatically based on the Run Interval setting.