The information on this page refers to firmware v2.65a and higher.

In addition to the serial commands, the STorM32 controller also understands MAVLink messages, as defined in the MAVLink standard. The STorM32 controller supports a rich set of MAVLink messages and features, the MAVLink 2 protocol, the MAVLink Camera Protocol, and the MAVLink FTP microservice.

The STorM32 controller in fact integrates two MAVLink components, which are referred to as the MAVLink Gimbal and MAVLink Camera components:

MAVLink Gimbal: This component deals with the gimbal operation. It is the part which you know from older firmware versions, but with massively extended functionality.
MAVLink Camera: This component is coupled with the NT Camera and provides a complete MAVLink Camera Protocol microservice server. It allows you to control the camera through MAVLink in unprecedented useful ways.

The MAVLink Gimbal and MAVLink Camera components share some parameters, but function-wise they are independent of each other. That is, both can be used simultaneously, the MAVLink Gimbal component can be used alone without the MAVLink Camera component, and vice versa.

Comment: In case you find it confusing what "two MAVLink components" is supposed to mean, then just connect the STorM32 controller (with both components enabled) to MissionPlanner: You will find that it will show you two components, one named GIMBAL and the other named CAMERA :).

Parameters

The STorM32's MAVLink parameters are located in the [GUI:Interfaces Tool] window, which is accessible via the [GUI:Experts Only] menu.

It has the following parameters:

Mavlink Gimbal: Enables the MAVLink Gimbal component and sets its component ID and gimbal device ID.
Mavlink Gimbal Stream: Activates emission of the selected message by the gimbal component. Also determines if the STorM32 controller is in gimbal manager mode.
Mavlink ComPort: Selects the serial com port which is used for the MAVLink communication. Applies to both the MAVLink Gimbal and MAVLink Camera components.
Mavlink System ID: Sets the system ID of the STorM32 controller (default = “0”). Applies to both the MAVLink Gimbal and MAVLink Camera components. If it is set to “0”, then the system ID is autodetected, i.e., the STorM32 waits for incoming heartbeat messages from an autopilot and then uses its system ID.
Mavlink Camera: Enables the MAVLink Camera component and sets its component ID.

The STorM32 system ID should match the system ID of the autopilot, or autodetection should be enabled with Mavlink System ID = “0” (which is the default).

The baudrate of the serial port selected with Mavlink ComPort is determined by the respective baudrate parameter in the [GUI:Interfaces Tool] window. Per default it is 115200 bps. It is recommended to use a baudrate of 230400 bps, if possible.

Comment: In the [GUI:Dashboard] Info Center, the MAVLINK field shows MAVLINK is PRESENT when the STorM32 controller is receiving valid MAVLink messages, implying a MAVLink connection is established. This can be handy for diagnosis.

Comment: If Mavlink Gimbal or Mavlink Camera is set, then the serial port selected in Mavlink ComPort is exclusive to the MAVLink communication. That is, incoming MAVLink messages on this port are accepted and served, but serial commands are rejected, while on all other ports serial messages are accepted but MAVLink messages are rejected. If both parameters are off, then the STorM32 controller will, in addition to the serial commands, also accept MAVLink messages on any of its serial ports, but it will not emit any MAVLink messages such as heartbeats.

Comment: Implication of the previous comment: If the USB port is selected in Mavlink ComPort one cannot connect to the GUI via the STorM32's USB port anymore.

Comment: For v1.3x boards: If the UART port is selected for MAVLink, then the BT module and the serial MAVLink connection cannot be used at the same time.

MAVLink Protocol Version

STorM32 uses the MAVLink v2 protocol version.

It also supports the MAVLink v1 protocol insofar as it properly reads and handles incoming MAVLink v1 packets, but it does not send out v1 packets, i.e., all MAVLink messages emitted by the STorM32 controller are in the MAVLink v2 protocol format.

Comment: In older STorM32 firmware versions it was possible to choose between MAVLink v1 and v2 formats. This option has been removed, there really should be no reason nowadays anymore to not use MAVLink v2.

Gimbal Protocol V2

The STorM32 controller supports the gimbal device messages of the MAVLink Gimbal Protocol V2 standard; it does not support the v2 gimbal manager messages.

In detail: The messages GIMBAL_DEVICE_INFORMATION, GIMBAL_DEVICE_ATTITUDE_STATUS, GIMBAL_DEVICE_SET_ATTITUDE, and AUTOPILOT_STATE_FOR_GIMBAL_DEVICE are fully supported. Note: This does not imply that all possible functionality is supported, e.g., currently YAW_IN_EARTH_FRAME is not supported.

In addition, the STorM32 controller implements its own MAVLink dialect (storm32.xml). A main part of it is the STorM32 Gimbal Protocol, which defines the STorM32's versions of the gimbal manager messages (identifiable by the 'STORM32' label in the names). They may look somewhat similar to the standard messages, and they can indeed adopt the same behavior and functionality as the standard, but the underlying concept is different and provides a much richer and more mature concept for gimbal operation than the standard. For details please consult the article STorM32 Gimbal Protocol.

In order to identify a STorM32 gimbal, and hence if the STorM32's extensions are available, request the GIMBAL_DEVICE_INFORMATION message. The vendor name and model name fields are populated with "olliw.eu" and "STorM32", respectively, which should allow unambiguous identification.

Virtual Channels

The STorM32 controller listens to the RC_CHANNELS MAVLink message, and can be configured to use its channel values as virtual input (for configuration see e.g. the manuals for using STorM32 with BetaPilot or ArduPilot).

In this configuration, all STorM32 functions can be invoked by selecting any of the “Virtual-1” - “Virtual-16” input channels, exactly as one would do it if the STorM32 controller would be directly connected to a receiver by traditional means (PWM, PPM, sbus, and so on), except that the ppm values for the virtual input channels are read off the RC_CHANNELS MAVLink message. This allows us to do many useful things, such as activating a script or triggering video on/off from the transmitter.

Comment: The STorM32 controller is not requesting the RC_CHANNELS MAVLink message by itself. This must be achieved by the user, and the how to do it depends on specifics such as flight controller, flight controller firmware, system setup, and so on. Usually, the flight controller has an option which makes it streaming this message. In case of BetaPilot, this message is streamed by default.

STorM32-Link

The STorM32 controller listens to the AUTOPILOT_STATE_FOR_GIMBAL_DEVICE MAVLink message, and can be configured to use its data for the STorM32-Link.

For details on the configuration, please read the manual Using STorM32 with BetaPilot.

Pass-Through

It is possible to connect the STorM32 GUI to any routing component in a MAVLink system, such as an autopilot or on-board companion computer, and to communicate directly with the STorM32 gimbal via MAVLink tunnel messages.

This is extremely convenient when the STorM32 gimbal is permanently installed in a vehicle, as it allows us to configure the gimbal without having to have physical access to the STorM32's USB or UART ports. The pass-through also works with wireless telemetry links, which opens up options such as tuning the gimbal during flight, and other unheard-of possibilities for in-flight control of the gimbal.

The pass-through mode of operation is enabled by checking in the GUI the [MAVLink] checkbox, which is located next to the [Port] combobox. The GUI then effectively operates like a mini MAVLink ground control station (the system ID is determined from the attached components, its component ID is MAV_COMP_ID_TUNNEL_NODE = 242 per default).

Comment: The pass-through communication is based on standard MAVLink, and thus should work for any MAVLink standard compliant autopilot. The bottom line is that it may not work on systems which do not fully support the MAVLink standard.

Comment: Pass-through works for both the MAVLink Gimbal and MAVLink Camera components. The GUI chooses the MAVLink Gimbal if enabled, otherwise the MAVLink Camera for communication.

Comment: GUI features which need physical access to a USB/UART port on the STorM32 controller do not work in pass-through mode. For instance, upgrading firmware won't work.

This preliminary demo video demonstrates the pass-through feature:

MAVLink Parameters

All STorM32 parameters are exposed to the MAVLink parameter interface, i.e., the STorM32 controller can equally be configured also via MAVLink.

The MAVLink parameter names are slightly different to the names in the GUI, but the differences are small enough to allow unique identification. Both the normal parameter protocol as well as the extended parameter protocol are supported. The parameter values are byte-wise encoded (the MAV_PROTOCOL_CAPABILITY_PARAM_ENCODE_BYTEWISE bit is set in the capabilities field of the AUTOPILOT_VERSION message).

MAVLink FTP

The MAVLink Gimbal and MAVLink Camera components support the MAVLink FTP micro service, which allows us to download various gimbal and camera definition files stored in the STorM32 controller.

Supported OpCodes/Commands

These opcodes/commands are support (unsupported commands will be NACKed with error code Fail):

MAVFTP_OPCODE_None
MAVFTP_OPCODE_TerminateSession
MAVFTP_OPCODE_ResetSessions
MAVFTP_OPCODE_ListDirectory
MAVFTP_OPCODE_OpenFileRO
MAVFTP_OPCODE_ReadFile
MAVFTP_OPCODE_CalcFileCRC32
MAVFTP_OPCODE_BurstReadFile

MAVLink Events

The MAVLink Gimbal component makes use of the MAVLink event micro service. It is currently used to report prearm status flags. The event definition json file can be found here.

Divergent from the protocol, the REQUEST_EVENT message is not served by sending a stream of reponses for each requested event, but by (re)sending only the last event.

The prearm checks need to be enabled, by setting the parameter Prearm Checks to a non-zero value.

Testing the Connection

The serial MAVLink connection can be tested in several ways. Suggestions are given in Using STorM32 with BetaPilot: Testing the Connection.

MAVLink Gimbal

Setting the Mavlink Gimbal parameter enables the MAVLink Gimbal component, and also determines its component ID: “Gimbal1” corresponds to MAV_COMP_ID_GIMBAL (= 154), “Gimbal2” to MAV_COMP_ID_GIMBAL2 (= 171), “Gimbal3” to MAV_COMP_ID_GIMBAL3 (= 172), and so on.

Mavlink Gimbal = “Gimbal1” or higher
Mavlink Gimbal Stream: Activates the emission of the selected message with a frequency of 4 Hz. Also determines if the STorM32 controller is in gimbal manager mode.

The system ID can be adjusted via the Mavlink System ID parameter, which usually can be left at its default value (0).

The gimbal device ID, which is relevant for the Gimbal Protocol V2 and STorM32 Gimbal Protocol extensions, is always set to be identical to the component ID.

The STorM32 controller becomes a gimbal manager when Mavlink Gimbal Stream = “manager status” is set. Otherwise it behaves as a gimbal device.

A common setting for Mavlink Gimbal Stream is “device status”, when newer autopilot setups are used. For older autopilot setups, one typically would select “mountstatus”.

The MAVLink Gimbal component supports the File Transfer Protocol micro service, which allows us to download e.g. component metadata .json files directly from the STorM32 gimbal controller.

Messages

The following MAVLink messages are supported:

MAVLINK_MSG_ID_HEARTBEAT (#0, 0x00) (out)

See HEARTBEAT.

The emission of the heartbeat needs to be activated in the GUI via the Mavlink Gimbal parameter. The heartbeat is emitted at 1 Hz, with the following values:

type: MAV_TYPE_GIMBAL (= 26)
autopilot: MAV_AUTOPILOT_INVALID (= 8)
base_mode: in NORMAL mode MAV_MODE_FLAG_STABILIZE_ENABLED (= 0x10) and MAV_MODE_FLAG_SAFETY_ARMED (= 0x80) are set, MAV_MODE_FLAG_CUSTOM_MODE_ENABLED (= 0x01) is always set
custom_mode: lowest byte (0x000000FF) = STATE value; highest bit (0x80000000) is set if prearm checks are not passed
system_status: either MAV_STATE_BOOT (= 1), MAV_STATE_STANDBY (= 3), MAV_STATE_ACTIVE (= 4) or MAV_STATE_EMERGENCY (= 6)

The prearm check flag in the custom_mode field allows GCSes and autopilots to determine the STorM32's prearm check condition, and to act accordingly.

MAVLINK_MSG_ID_SYSTEM_TIME (#2, 0x02) (in)

See SYSTEM_TIME.

The UNIX epoch time in this message is logged by the NT Logger (if time_unix_usec is > 0). The SYSTEM_TIME message is usually emitted by the autopilot, and the UNIX epoch time becomes > 0 when e.g. a 3D GPS fix has been obtained. The UNIX epoch time facilitates synchronizing the autopilot data logs and the NT Logger data logs.

The parameter Virtual Channel Configuration needs to be set to “serial” for the values received by this message to become available for inputs as “Virtual-1” to “Virtual-16”.

MAVLINK_MSG_ID_COMMAND_INT (#75, 0x4B) (in)

See COMMAND_INT.

Same as for MAVLINK_MSG_ID_COMMAND_LONG, see next.

MAVLINK_MSG_ID_COMMAND_LONG (#76, 0x4C) (in)

See COMMAND_LONG.

Each command is acknowledged with a COMMAND_ACK message (with result MAV_RESULT_ACCEPTED or MAV_RESULT_DENIED for supported commands, and MAV_RESULT_UNSUPPORTED otherwise). The following commands are supported (parameter fields not mentioned are ignored):

MAV_CMD_DO_SET_PARAMETER (#180, 0xB4)
* param1 = parameter index
* param2 = parameter value

MAV_CMD_DO_SET_SERVO (#183, 0xB7)
* param1 = instance (must be 0, else denied)
* param2 = pwm value (only 700...2300 accepted, else denied)

MAV_CMD_DO_DIGICAM_CONFIGURE (#202, 0xCA)
* param1 = mode 
     0: CAMERA_MODE_PHOTO
     1: CAMERA_MODE_VIDEO
* param6 = command identity 
     0: command accepted by all cameras
     1-6: command accepted only if camera is CAMERA1-CAMERA6

MAV_CMD_DO_DIGICAM_CONTROL (#203, 0xCB)
* param5 = shot
     if CAMERA_MODE_PHOTO: 
         0: off
         1: SHUTTER
     if CAMERA_MODE_VIDEO
         0: VIDEOOFF
         1: VIDEOON
* param6 = command identity 
     0: command accepted by all cameras
     1-6: command accepted only if camera is CAMERA1-CAMERA6

MAV_CMD_DO_MOUNT_CONFIGURE (#204, 0xCC)
* param1 = mount_mode (0 = MAV_MOUNT_MODE_RETRACT and 1 = MAV_MOUNT_MODE_NEUTRAL recenters the camera)
 
The command is denied in gimbal manager mode.

MAV_CMD_DO_MOUNT_CONTROL (#205, 0xCD)
* param1 = pitch, angle in degree (COMMENT: the sign is opposite to convention!)
* param2 = roll, angle in degree
* param3 = yaw, angle in degree (COMMENT: the sign is opposite to convention!)
* param7 = mount_mode (0 = MAV_MOUNT_MODE_RETRACT and 1 = MAV_MOUNT_MODE_NEUTRAL recenters the camera)
 
The command is denied in gimbal manager mode.

MAV_CMD_DO_SET_CAM_TRIGG_DIST (#206, 0xCE)
* param1 = distance (must be 0, else denied)
* param3 = trigger camera once immediately 
     0: off
     1: SHUTTER

MAV_CMD_PREFLIGHT_STORAGE (#245, 0xF5)
* param1 = parameter storage
     0: restore parameter values from EEPROM
     1: store parameter values in EEPROM
     2: ignored, as it maybe harmful

MAV_CMD_PREFLIGHT_REBOOT_SHUTDOWN (#246, 0xF6)
* param3
     0: do nothing
     1: restart with full reset
     2: shut down motors
* param4 = component ID, must be 0 or match gimbal ID

MAV_CMD_GET_MESSAGE_INTERVAL (#510, 0x01FE)
* param1 =  MAVLink message ID

MAV_CMD_SET_MESSAGE_INTERVAL (#511, 0x01FF)
* param1 =  message ID of the message to stream
     158: stream MOUNT_STATUS message (target is set according to param7, for details see message description)
     285: stream GIMBAL_DEVICE_ATTITUDE_STATUS message (target is set according to param7, see message description)
     60011: stream STORM32_GIMBAL_MANAGER_STATUS message (only if in gimbal manager mode)
* param2 = interval between two messages, in microseconds; set to -1 to disable
* param7 = request target
 
Stream rates of up to 100 Hz are supported. Note however that this can take a significant toll and may strain the STorM32's microcontroller capabilities. Please resort to common sense. The resulting stream rate is in multiples of 1.5 ms.

MAV_CMD_REQUEST_MESSAGE (#512, 0x0200)
* param1 = message ID of the requested message
     148: send AUTOPILOT_VERSION message
     158: send MOUNT_STATUS message (target is set according to param7, default is requester IDs)
     253: send STATUSTEXT message with firmware and board type information
     283: send GIMBAL_DEVICE_INFORMATION message
     285: send GIMBAL_DEVICE_ATTITUDE_STATUS message (target is set according to param7, default is requester IDs)
     300: send PROTOCOL_VERSION message
     397: send COMPONENT_METADATA message
     60010: send STORM32_GIMBAL_MANAGER_INFORMATION message (only if in gimbal manager mode)
     60011: send STORM32_GIMBAL_MANAGER_STATUS message (only if in gimbal manager mode)
* param7 = response target

MAV_CMD_REQUEST_PROTOCOL_VERSION (#519, 0x0207)
  send PROTOCOL_VERSION message (supported, but is deprecated, use MAV_CMD_REQUEST_MESSAGE instead)

MAV_CMD_REQUEST_AUTOPILOT_CAPABILITIES (#520, 0x0208)
  send AUTOPILOT_VERSION message (supported, but is deprecated, use MAV_CMD_REQUEST_MESSAGE instead)

MAV_CMD_DO_SEND_BANNER (#42428, 0xA5BC)
  send STATUSTEXT messages with banner

MAV_CMD_STORM32_DO_GIMBAL_MANAGER_CONTROL_PITCHYAW (#60002, 0xEA62)
  This command is handled in gimbal manager mode. The gimbal device ID (param7) must match the STorM32's gimbal component ID.

MAV_CMD_STORM32_DO_GIMBAL_MANAGER_SETUP (#60010, 0xEA6A)
  This command is handled in gimbal manager mode. The gimbal device ID (param7) must match the STorM32's gimbal component ID.

MAVLINK_MSG_ID_COMMAND_ACK (#77, 0x4D) (out)

See COMMAND_ACK.

MAVLINK_MSG_ID_FILE_TRANSFER_PROTOCOL (#110, 0x6E) (in/out)

See FILE_TRANSFER_PROTOCOL.

MAVLINK_MSG_ID_AUTOPILOT_VERSION (#148, 0x94) (out)

See AUTOPILOT_VERSION.

The flight_sw_version and board_version fields are set to the firmware version and board revision (firmware version: e.g. 262 for version v2.62x, board revision: e.g. 33 for v3.3 boards). VID and PID are set to 0x16D0 and 0x0FCB, respectively. UID is set to the STM32 UUID.

MAVLINK_MSG_ID_MOUNT_STATUS (#158, 0x9E) (out)

ArduPilot specific message. See MOUNT_STATUS.

Emission of this message with 4 Hz can be activated in the GUI with the Mavlink Gimbal Stream parameter. It also can be emitted with a user defined rate by requesting a data stream with the MAV_CMD_SET_MESSAGE_INTERVAL command, or by requesting a single-shot emission with the MAV_CMD_REQUEST_MESSAGE command. The yaw angle is relative to the forward direction (vehicle frame).

The 4 Hz message stream activated with Mavlink Gimbal Stream is always broadcast. The messages emitted as result of MAV_CMD_SET_MESSAGE_INTERVAL or MAV_CMD_REQUEST_MESSAGE commands can be broadcast or targeted, as specified by param7 in the command. When requested with MAV_CMD_SET_MESSAGE_INTERVAL it holds: If a stream of targeted messages is requested, then the emission is in addition to the broadcast 4 Hz stream (if activated). If a broadcast stream is requested, it overrules the broadcast 4 Hz stream.

This allows for two streams, one broadcast stream at a low rate, e.g. to inform a GCS, and one targeted stream at a high rate, e.g. to inform an on-board companion computer.

Consider to use the GIMBAL_DEVICE_ATTITUDE_STATUS message instead, e.g., set Mavlink Gimbal Stream = “device status” for enabling a 4 Hz stream.

MAVLINK_MSG_ID_AUTOPILOT_VERSION_REQUEST (#183, 0xB7) (in)

ArduPilot specific message. See AUTOPILOT_VERSION_REQUEST.

Is supported, but is deprecated, use MAV_CMD_REQUEST_MESSAGE instead.

MAVLINK_MSG_ID_MESSAGE_INTERVAL (#244, 0xF4) (out)

See MESSAGE_INTERVAL.

MAVLINK_MSG_ID_STATUSTEXT (#253, 0xFD) (out)

See STATUSTEXT.

This message is sent out after a PARAM_REQUEST_LIST has been served, and provides firmware and board type information. It also can be requested with the MAV_CMD_REQUEST_MESSAGE or MAV_CMD_DO_SEND_BANNER commands.

Emission of this message with a user-supplied text can also be triggered through a script using the SENDMAVTEXT script command.

MAVLINK_MSG_ID_GIMBAL_DEVICE_INFORMATION (#283, 0x11B) (out)

See GIMBAL_DEVICE_INFORMATION.

The min/max values reported in this message are the RC Input Min/Max values for each axis, if the axis is enabled (for disabled axes NAN is reported).

MAVLINK_MSG_ID_GIMBAL_DEVICE_SET_ATTITUDE (#284, 0x11C) (in)

See GIMBAL_DEVICE_SET_ATTITUDE.

Only handled if not in gimbal manager mode. Current limitations: Yaw in earth frame is not supported, even when the STorM32-Link is enabled and available. The velocity fields are not supported and ignored.

The message is rejected when not either the YAW_IN_VEHICLE_FRAME or the YAW_IN_EARTH_FRAME flag is set (that is, the legacy usage of this message is not supported).

MAVLINK_MSG_ID_GIMBAL_DEVICE_ATTITUDE_STATUS (#285, 0x11D) (out)

See GIMBAL_DEVICE_ATTITUDE_STATUS.

Emission of this message with 4 Hz can be activated in the GUI with the Mavlink Gimbal Stream parameter. It also can be emitted with a user defined rate by requesting a data stream with the MAV_CMD_SET_MESSAGE_INTERVAL command, or by requesting a single-shot emission with the MAV_CMD_REQUEST_MESSAGE command. The yaw angle is relative to the forward direction (vehicle frame).

The 4 Hz message stream activated with Mavlink Gimbal Stream is always broadcast. The messages emitted as result of MAV_CMD_SET_MESSAGE_INTERVAL or MAV_CMD_REQUEST_MESSAGE commands can be broadcast or targeted, as specified by param7 in the command. When requested with MAV_CMD_SET_MESSAGE_INTERVAL it holds: If a stream of targeted messages is requested, then the emission is in addition to the broadcast 4 Hz stream (if activated). If a broadcast stream is requested, it overrules the broadcast 4 Hz stream.

This allows for two streams, one broadcast stream at a low rate, e.g. to inform a GCS, and one targeted stream at a high rate, e.g. to inform an on-board companion computer.

MAVLINK_MSG_ID_AUTOPILOT_STATE_FOR_GIMBAL_DEVICE (#286, 0x11E) (in)

See AUTOPILOT_STATE_FOR_GIMBAL_DEVICE.

This message can be send to the STorM32 controller and is then used for STorM32-Link.

MAVLINK_MSG_ID_PROTOCOL_VERSION (#300, 0x12C) (out)

See PROTOCOL_VERSION.

MAVLINK_MSG_ID_TUNNEL (#385, 0x181) (in/out)

See TUNNEL.

The STorM32 controller occupies the block of payload_type values from 200 - 209 (see MAV_TUNNEL_PAYLOAD_TYPE). The payload types 200 and 201 are used for communicating with the GUI. Payload types 202 and 203 are for communicating with a flight controller, but can also be used otherwise.

MAVLINK_MSG_ID_COMPONENT_METADATA (#397, 0x18D) (out)

See COMPONENT_METADATA.

MAVLINK_MSG_ID_EVENT (#410, 0x19A) (out)

See EVENT.

Is emitted at intervals of 0.2 Hz, or immediately if the event status has changed. Is used to report the prearm status. Only emitted if prearm checks are enabled (Prearm Checks = non-zero value).

MAVLINK_MSG_ID_CURRENT_EVENT_SEQUENCE (#411, 0x19B) (out)

See CURRENT_EVENT_SEQUENCE.

Is emitted at intervals of 0.2 Hz. Only emitted if prearm checks are enabled (Prearm Checks = non-zero value).