PX4 User Guide (v1.12)

# Modules Reference: System

# battery_simulator

Source: modules/simulator/battery_simulator (opens new window)

# Description

# Usage

battery_simulator <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# battery_status

Source: modules/battery_status (opens new window)

# Description

The provided functionality includes:

  • Read the output from the ADC driver (via ioctl interface) and publish battery_status.

# Implementation

It runs in its own thread and polls on the currently selected gyro topic.

# Usage

battery_status <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# camera_feedback

Source: modules/camera_feedback (opens new window)

# Description

# Usage

camera_feedback <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# commander

Source: modules/commander (opens new window)

# Description

The commander module contains the state machine for mode switching and failsafe behavior.

# Usage

commander <command> [arguments...]
 Commands:
   start
     [-h]        Enable HIL mode
   calibrate     Run sensor calibration
     mag|accel|gyro|level|esc|airspeed Calibration type
     quick       Quick calibration (accel only, not recommended)
   check         Run preflight checks
   arm
     [-f]        Force arming (do not run preflight checks)
   disarm
   takeoff
   land
   transition    VTOL transition
   mode          Change flight mode
     manual|acro|offboard|stabilized|altctl|posctl|auto:mission|auto:loiter|auto
                 :rtl|auto:takeoff|auto:land|auto:precland Flight mode
   pair
   lockdown
     [off]       Turn lockdown off
   set_ekf_origin
     lat, lon, alt Origin Latitude, Longitude, Altitude
   lat|lon|alt   Origin latitude longitude altitude
   stop
   status        print status info

# dataman

Source: modules/dataman (opens new window)

# Description

Module to provide persistent storage for the rest of the system in form of a simple database through a C API. Multiple backends are supported:

  • a file (eg. on the SD card)
  • RAM (this is obviously not persistent)

It is used to store structured data of different types: mission waypoints, mission state and geofence polygons. Each type has a specific type and a fixed maximum amount of storage items, so that fast random access is possible.

# Implementation

Reading and writing a single item is always atomic. If multiple items need to be read/modified atomically, there is an additional lock per item type via dm_lock.

DM_KEY_FENCE_POINTS and DM_KEY_SAFE_POINTS items: the first data element is a mission_stats_entry_s struct, which stores the number of items for these types. These items are always updated atomically in one transaction (from the mavlink mission manager). During that time, navigator will try to acquire the geofence item lock, fail, and will not check for geofence violations.

# Usage

dataman <command> [arguments...]
 Commands:
   start
     [-f <val>]  Storage file
                 values: <file>
     [-r]        Use RAM backend (NOT persistent)
 The options -f and -r are mutually exclusive. If nothing is specified, a file
 'dataman' is used
   poweronrestart Restart dataman (on power on)
   inflightrestart Restart dataman (in flight)
   stop
   status        print status info

# dmesg

Source: systemcmds/dmesg (opens new window)

# Description

Command-line tool to show bootup console messages. Note that output from NuttX's work queues and syslog are not captured.

# Examples

Keep printing all messages in the background:

dmesg -f &

# Usage

dmesg <command> [arguments...]
 Commands:
     [-f]        Follow: wait for new messages

# esc_battery

Source: modules/esc_battery (opens new window)

# Description

This implements using information from the ESC status and publish it as battery status.

# Usage

esc_battery <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# gyro_calibration

Source: modules/gyro_calibration (opens new window)

# Description

Simple online gyroscope calibration.

# Usage

gyro_calibration <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# gyro_fft

Source: modules/gyro_fft (opens new window)

# Description

# Usage

gyro_fft <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# heater

Source: drivers/heater (opens new window)

# Description

Background process running periodically on the LP work queue to regulate IMU temperature at a setpoint.

This task can be started at boot from the startup scripts by setting SENS_EN_THERMAL or via CLI.

# Usage

heater <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# land_detector

Source: modules/land_detector (opens new window)

# Description

Module to detect the freefall and landed state of the vehicle, and publishing the vehicle_land_detected topic. Each vehicle type (multirotor, fixedwing, vtol, ...) provides its own algorithm, taking into account various states, such as commanded thrust, arming state and vehicle motion.

# Implementation

Every type is implemented in its own class with a common base class. The base class maintains a state (landed, maybe_landed, ground_contact). Each possible state is implemented in the derived classes. A hysteresis and a fixed priority of each internal state determines the actual land_detector state.

# Multicopter Land Detector

ground_contact: thrust setpoint and velocity in z-direction must be below a defined threshold for time GROUND_CONTACT_TRIGGER_TIME_US. When ground_contact is detected, the position controller turns off the thrust setpoint in body x and y.

maybe_landed: it requires ground_contact together with a tighter thrust setpoint threshold and no velocity in the horizontal direction. The trigger time is defined by MAYBE_LAND_TRIGGER_TIME. When maybe_landed is detected, the position controller sets the thrust setpoint to zero.

landed: it requires maybe_landed to be true for time LAND_DETECTOR_TRIGGER_TIME_US.

The module runs periodically on the HP work queue.

# Usage

land_detector <command> [arguments...]
 Commands:
   start         Start the background task
     fixedwing|multicopter|vtol|rover|airship Select vehicle type
   stop
   status        print status info

# load_mon

Source: modules/load_mon (opens new window)

# Description

Background process running periodically on the low priority work queue to calculate the CPU load and RAM usage and publish the cpuload topic.

On NuttX it also checks the stack usage of each process and if it falls below 300 bytes, a warning is output, which will also appear in the log file.

# Usage

load_mon <command> [arguments...]
 Commands:
   start         Start the background task
   stop
   status        print status info

# logger

Source: modules/logger (opens new window)

# Description

System logger which logs a configurable set of uORB topics and system printf messages (PX4_WARN and PX4_ERR) to ULog files. These can be used for system and flight performance evaluation, tuning, replay and crash analysis.

It supports 2 backends:

  • Files: write ULog files to the file system (SD card)
  • MAVLink: stream ULog data via MAVLink to a client (the client must support this)

Both backends can be enabled and used at the same time.

The file backend supports 2 types of log files: full (the normal log) and a mission log. The mission log is a reduced ulog file and can be used for example for geotagging or vehicle management. It can be enabled and configured via SDLOG_MISSION parameter. The normal log is always a superset of the mission log.

# Implementation

The implementation uses two threads:

  • The main thread, running at a fixed rate (or polling on a topic if started with -p) and checking for data updates
  • The writer thread, writing data to the file

In between there is a write buffer with configurable size (and another fixed-size buffer for the mission log). It should be large to avoid dropouts.

# Examples

Typical usage to start logging immediately:

logger start -e -t

Or if already running:

logger on

# Usage

logger <command> [arguments...]
 Commands:
   start
     [-m <val>]  Backend mode
                 values: file|mavlink|all, default: all
     [-x]        Enable/disable logging via Aux1 RC channel
     [-e]        Enable logging right after start until disarm (otherwise only
                 when armed)
     [-f]        Log until shutdown (implies -e)
     [-t]        Use date/time for naming log directories and files
     [-r <val>]  Log rate in Hz, 0 means unlimited rate
                 default: 280
     [-b <val>]  Log buffer size in KiB
                 default: 12
     [-p <val>]  Poll on a topic instead of running with fixed rate (Log rate
                 and topic intervals are ignored if this is set)
                 values: <topic_name>
   on            start logging now, override arming (logger must be running)
   off           stop logging now, override arming (logger must be running)
   stop
   status        print status info

# netman

Source: systemcmds/netman (opens new window)

# Description

Network configuration manager saves the network settings in non-volatile memory. On boot the update option will be run. If a network configuration does not exist. The default setting will be saved in non-volatile and the system rebooted. On Subsequent boots, the update option will check for the existence of net.cfg in the root of the SD Card. It will saves the network settings from net.cfg in non-volatile memory, delete the file and reboot the system.

The save option will net.cfg on the SD Card. Use this to edit the settings. The show option will display the network settings to the console.

# Examples

$ netman save # Save the parameters to the SD card. $ netman show # display current settings. $ netman update -i eth0 # do an update

# Usage

netman <command> [arguments...]
 Commands:
   show          Display the current persistent network settings to the console.
   update        Check SD card for net.cfg and update network persistent network
                 settings.
   save          Save the current network parameters to the SD card.
     [-i <val>]  Set the interface name
                 default: eth0

# pwm_input

Source: drivers/pwm_input (opens new window)

# Description

Measures the PWM input on AUX5 (or MAIN5) via a timer capture ISR and publishes via the uORB 'pwm_input` message.

# Usage

pwm_input <command> [arguments...]
 Commands:
   start
   test          prints PWM capture info.
   stop
   status        print status info

# rc_update

Source: modules/rc_update (opens new window)

# Description

The rc_update module handles RC channel mapping: read the raw input channels (input_rc), then apply the calibration, map the RC channels to the configured channels & mode switches and then publish as rc_channels and manual_control_setpoint.

# Implementation

To reduce control latency, the module is scheduled on input_rc publications.

# Usage

rc_update <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

# replay

Source: modules/replay (opens new window)

# Description

This module is used to replay ULog files.

There are 2 environment variables used for configuration: replay, which must be set to an ULog file name - it's the log file to be replayed. The second is the mode, specified via replay_mode:

  • replay_mode=ekf2: specific EKF2 replay mode. It can only be used with the ekf2 module, but allows the replay to run as fast as possible.
  • Generic otherwise: this can be used to replay any module(s), but the replay will be done with the same speed as the log was recorded.

The module is typically used together with uORB publisher rules, to specify which messages should be replayed. The replay module will just publish all messages that are found in the log. It also applies the parameters from the log.

The replay procedure is documented on the System-wide Replay (opens new window) page.

# Usage

replay <command> [arguments...]
 Commands:
   start         Start replay, using log file from ENV variable 'replay'
   trystart      Same as 'start', but silently exit if no log file given
   tryapplyparams Try to apply the parameters from the log file
   stop
   status        print status info

# send_event

Source: modules/events (opens new window)

# Description

Background process running periodically on the LP work queue to perform housekeeping tasks. It is currently only responsible for tone alarm on RC Loss.

The tasks can be started via CLI or uORB topics (vehicle_command from MAVLink, etc.).

# Usage

send_event <command> [arguments...]
 Commands:
   start         Start the background task
   stop
   status        print status info

# sensors

Source: modules/sensors (opens new window)

# Description

The sensors module is central to the whole system. It takes low-level output from drivers, turns it into a more usable form, and publishes it for the rest of the system.

The provided functionality includes:

  • Read the output from the sensor drivers (sensor_gyro, etc.). If there are multiple of the same type, do voting and failover handling. Then apply the board rotation and temperature calibration (if enabled). And finally publish the data; one of the topics is sensor_combined, used by many parts of the system.
  • Make sure the sensor drivers get the updated calibration parameters (scale & offset) when the parameters change or on startup. The sensor drivers use the ioctl interface for parameter updates. For this to work properly, the sensor drivers must already be running when sensors is started.
  • Do sensor consistency checks and publish the sensors_status_imu topic.

# Implementation

It runs in its own thread and polls on the currently selected gyro topic.

# Usage

sensors <command> [arguments...]
 Commands:
   start
     [-h]        Start in HIL mode
   stop
   status        print status info

# temperature_compensation

Source: modules/temperature_compensation (opens new window)

# Description

The temperature compensation module allows all of the gyro(s), accel(s), and baro(s) in the system to be temperature compensated. The module monitors the data coming from the sensors and updates the associated sensor_correction topic whenever a change in temperature is detected. The module can also be configured to perform the coeffecient calculation routine at next boot, which allows the thermal calibration coeffecients to be calculated while the vehicle undergoes a temperature cycle.

# Usage

temperature_compensation <command> [arguments...]
 Commands:
   start         Start the module, which monitors the sensors and updates the
                 sensor_correction topic
   calibrate     Run temperature calibration process
     [-g]        calibrate the gyro
     [-a]        calibrate the accel
     [-b]        calibrate the baro (if none of these is given, all will be
                 calibrated)
   stop
   status        print status info

# tune_control

Source: systemcmds/tune_control (opens new window)

# Description

Command-line tool to control & test the (external) tunes.

Tunes are used to provide audible notification and warnings (e.g. when the system arms, gets position lock, etc.). The tool requires that a driver is running that can handle the tune_control uorb topic.

Information about the tune format and predefined system tunes can be found here: https://github.com/PX4/Firmware/blob/master/src/lib/tunes/tune_definition.desc

# Examples

Play system tune #2:

tune_control play -t 2

# Usage

tune_control <command> [arguments...]
 Commands:
   play          Play system tune or single note.
     error       Play error tune
     [-t <val>]  Play predefined system tune
                 default: 1
     [-f <val>]  Frequency of note in Hz (0-22kHz)
     [-d <val>]  Duration of note in us
     [-s <val>]  Volume level (loudness) of the note (0-100)
                 default: 40
     [-m <val>]  Melody in string form
                 values: <string> - e.g. "MFT200e8a8a"
   libtest       Test library
   stop          Stop playback (use for repeated tunes)

# work_queue

Source: systemcmds/work_queue (opens new window)

# Description

Command-line tool to show work queue status.

# Usage

work_queue <command> [arguments...]
 Commands:
   start
   stop
   status        print status info

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