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116 lines
7.1 KiB
Markdown
116 lines
7.1 KiB
Markdown
# Simple MAVLink Cameras (Camera Protcol v1)
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This topic explains how to use PX4 with a MAVLink [camera](../camera/index.md) that implements the [Camera Protocol v1 (Simple Trigger Protocol)](https://mavlink.io/en/services/camera_v1.html) with PX4 and a Ground Station.
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:::warning
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[MAVLink cameras](../camera/mavlink_v2_camera.md) that use the [MAVLink Camera Protocol v2](https://mavlink.io/en/services/camera.html) should be used instead when possible!
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This approach is retained for use with older MAVLink cameras.
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:::
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## 개요
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[Camera Protocol v1](https://mavlink.io/en/services/camera_v1.html) defines a small set of commands that allow triggering of a camera for:
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- still image capture at a frequency based on either time or distance
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- video capture
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- limited camera configuration
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PX4 supports this command set for triggering cameras with native support for the protocol (as described in this topic), and also for [cameras attached to flight controller outputs](../camera/fc_connected_camera.md).
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Ground stations and MAVLink SDKs generally address camera commands to the autopilot, which then forwards them to a connected MAVLink channel of type `onboard`.
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PX4 also re-emits any camera mission items it encouters in a mission as camera commands: commands that aren't accepted are logged.
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In all cases the commands are sent with the system id of the autopilot and the component ID of 0 (i.e. addressed to all components, including cameras).
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PX4 will also emit a [CAMERA_TRIGGER](https://mavlink.io/en/messages/common.html#CAMERA_TRIGGER) whenever an image capture is triggered (the camera itself may also emit this message on triggering).
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## Controlling the Camera
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### MAVLink Commands & Messages
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The [Camera Protocol v1 (Simple Trigger Protocol)](https://mavlink.io/en/services/camera_v1.html) defines the following commands:
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- [MAV_CMD_DO_TRIGGER_CONTROL](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_TRIGGER_CONTROL)
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- [MAV_CMD_NAV_CMD_DO_DIGICAM_CONTROL](https://mavlink.io/en/messages/common.html#MAV_CMD_NAV_CMD_DO_DIGICAM_CONTROL)
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- [MAV_CMD_DO_SET_CAM_TRIGG_DIST](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_SET_CAM_TRIGG_DIST)
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- [MAV_CMD_DO_SET_CAM_TRIGG_INTERVAL](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_SET_CAM_TRIGG_INTERVAL)
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- [MAV_CMD_OBLIQUE_SURVEY](https://mavlink.io/en/messages/common.html#MAV_CMD_OBLIQUE_SURVEY)
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- [MAV_CMD_DO_CONTROL_VIDEO](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_CONTROL_VIDEO)
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A MAVLink camera will support some subset of these commands.
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As the protocol has no feature discovery process, the only way to know is by inspecting the [COMMAND_ACK](https://mavlink.io/en/messages/common.html#COMMAND_ACK) returned in response.
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Cameras should also emit [CAMERA_TRIGGER](https://mavlink.io/en/messages/common.html#CAMERA_TRIGGER) each time an image is captured.
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[Camera Protocol v1](https://mavlink.io/en/services/camera_v1.html) describes the protocol in more detail.
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### Ground Stations
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Ground stations can use any commands in the [Camera Protocol v1 (Simple Trigger Protocol)](https://mavlink.io/en/services/camera_v1.html) and should address them to the autopilot component id.
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If the commands are not supported by the camera, it will return a [COMMAND_ACK](https://mavlink.io/en/messages/common.html#COMMAND_ACK) with an error result.
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Generally the commands are addressed to the autopilot, because this works whether the camera is connected via MAVLink or directly to the flight controller.
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If addressed to the autopilot PX4 will emit [CAMERA_TRIGGER](https://mavlink.io/en/messages/common.html#CAMERA_TRIGGER) each time an image is captured, and may log the camera capture event.
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<!-- "May" because the camera feedback module is "supposed" to log just camera capture from a capture pin connected to camera hotshoe, but currently logs all camera trigger events from the camera trigger driver https://github.com/PX4/PX4-Autopilot/pull/23103 -->
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In theory you might also address commands to the camera directly.
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### Camera Commands in Missions
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The following [Camera Protocol v1 (Simple Trigger Protocol)](https://mavlink.io/en/services/camera_v1.html) commands can be used in missions (this is the same list as above).
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- [MAV_CMD_DO_TRIGGER_CONTROL](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_TRIGGER_CONTROL)
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- [MAV_CMD_NAV_CMD_DO_DIGICAM_CONTROL](https://mavlink.io/en/messages/common.html#MAV_CMD_NAV_CMD_DO_DIGICAM_CONTROL)
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- [MAV_CMD_DO_SET_CAM_TRIGG_DIST](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_SET_CAM_TRIGG_DIST)
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- [MAV_CMD_DO_SET_CAM_TRIGG_INTERVAL](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_SET_CAM_TRIGG_INTERVAL)
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- [MAV_CMD_OBLIQUE_SURVEY](https://mavlink.io/en/messages/common.html#MAV_CMD_OBLIQUE_SURVEY)
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- [MAV_CMD_DO_CONTROL_VIDEO](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_CONTROL_VIDEO)
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PX4 re-emits them with the same system ID as the autopilot and component ID of [MAV_COMP_ID_ALL](https://mavlink.io/en/messages/common.html#MAV_COMP_ID_ALL):
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<!-- See camera_architecture.md topic for detail on how this is implemented -->
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### Manual Control
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Manual triggering using these cameras is not supported (for either Joystick or RC Controllers).
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## PX4 설정
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<!-- set up the mode and triggering -->
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### MAVLink Port & Forwarding Configuration
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Connect PX4 to your MAVLink camera by attaching it to an unused serial port on your flight controller, such as `TELEM2`.
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You can then configure the port as a [MAVLink Peripheral](../peripherals/mavlink_peripherals.md).
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The document explains how, but in summary:
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1. Modify an unused `MAV_n_CONFIG` parameter, such as [MAV_2_CONFIG](../advanced_config/parameter_reference.md#MAV_2_CONFIG), so that it is assigned to port to which your camera is connected.
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2. Set the corresponding [MAV_2_MODE](../advanced_config/parameter_reference.md#MAV_2_MODE) to `2` (Onboard).
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This ensures that the right set of MAVLink messages are emitted and forwarded.
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3. You may need to set some of the other parameters, depending on your connection - such as the baud rate.
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Then connect and configure the camera as recommended in its user guide.
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<!-- Removed this because I am pretty sure forwarding happens automatically for this set. Keeping it simple.
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1. Set [MAV_2_FORWARD](../advanced_config/parameter_reference.md#MAV_2_FORWARD) if you want to enable forwarding of MAVLink messages to other ports, such as the one that is connected to the ground station.
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-->
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### Camera Mode & Triggering
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Configure the PX4 camera driver to enable the MAVLink camera backend, and set the triggering mode to capture on command in survey missions.
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Using _QGroundControl_:
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- Open [Vehicle Setup > Camera](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/setup_view/camera.html#px4-camera-setup).
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- Set the values as shown:
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:::info
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You can also [set the parameters directly](../advanced_config/parameters.md):
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- [TRIG_MODE](../advanced_config/parameter_reference.md#TRIG_MODE) — `4`: Distance based, on command (Survey mode)
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- [TRIG_INTERFACE](../advanced_config/parameter_reference.md#TRIG_INTERFACE) — `3`: MAVLink
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:::
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