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92 lines
4.2 KiB
92 lines
4.2 KiB
2 months ago
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See the [list of topics used](../include/realdds/topics/) for a general overview of the topic structure.
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# The DDS Device
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A DDS device is a collection of topics on which information flows.
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Specifically:
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* `<topic-root>/`
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* `notification` — [server notifications, responses, etc.](notifications.md)
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* `control` — [client requests to server](control.md)
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* `metadata` — [optional stream information](metadata.md)
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* `rt/<topic-root>_` — ROS2-compatible [streams](streaming.md)
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* `<stream-name>` — [Image](https://github.com/ros2/common_interfaces/blob/rolling/sensor_msgs/msg/Image.msg)/[Imu](https://github.com/ros2/common_interfaces/blob/rolling/sensor_msgs/msg/Imu.msg) streams
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## The Topic Root
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Note that topics are all using the same `<topic-root>` that is specified in the [`device-info`](discovery.md). I.e., if the topic-root is known, all other topics can be found.
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As long as the `<topic-root>` is a valid topic path, it can be anything and is entirely determined by [Discovery](discovery.md).
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Currently, the topic root as used by `rs-dds-adapter` is built as:
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> realsense/ `<device-model>` _ `<serial-number>`
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## Settings
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On the client, device behavior with librealsense can be fine-tuned with JSON settings passed through the participant (and therefore from the librealsense context's `dds` settings), inside a `device` object:
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```JSON
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{
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"dds": {
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"device": {
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"control": { "reply-timeout-ms": 2000 },
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"metadata": { "reliability": "reliable" }
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}
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}
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}
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```
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The above overrides the default reply timeout to 2 seconds and makes the metadata topic use reliable QoS rather than the default `best-effort`.
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#### Standard topic QoS settings
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`control`, `notification`, and `metadata` topics all can have their own objects to override default QoS and other settings. See the above for an example. They all share common settings:
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* `reliability` can be a string denoting the `kind`, or an object:
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* `kind` is `best-effort` or `reliable`
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* `durability` can be a string denoting the `kind`, or an object:
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* `kind` is `volatile`, `transient-local`, `transient`, or `persistent`
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* `history` can be a number denoting the `depth`, or an object:
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* `kind` is `keep-last` or `keep-all`
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* `depth` is the number of samples to manage with `keep-last`
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* `data-sharing` is a boolean: `true` to automatically enable if needed; `false` to turn off
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* `endpoint` is an object:
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* `history-memory-policy` is `preallocated`, `preallocated-with-realloc`, `dynamic-reserve`, or `dynamic-reusable`
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Note that these settings are **overrides**. The default values may be different depending on the topic for which they're intended (for example, `metadata` uses `best-effort` by default while `control` and `notification` use `reliable`).
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#### Other Settings
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| Field | Default | Type | Description |
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|--------------------------|--------:|---------|--------------------|
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| `control`/
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| `reply-timeout-ms` | 2000 | size_t | Reply timeout, in milliseconds
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#### Device Options
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To use device-level options, the control-reply needs to be used.
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The server publishes device options as part of the initialization sequence, in the `device-options` message.
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If available, the [`query-option` and `set-option` controls](control.md#query-option--set-option) can be used (no `stream-name`) to retrieve or update the values. **Setting these options will not take effect until the device is reset.**
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The following device options may be available:
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| Setting | Default | Type | `option-name` | Description |
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|----------------|--------:|------------------|-----------------|---------------|
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| Domain ID | 0 | int, 0-232 | `domain-id` | The DDS domain number to use to segment communications on the network
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| IP address | empty | string "#.#.#.#" | `ip-address` | The static IP that the server uses for itself (empty=DHCP on)
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| Multicast IP | - | string "#.#.#.#" | `multicast-ip` | The IP address to use for multicasting (empty to disable)
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## Continue with:
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* [Notifications](notifications.md)
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* [Initialization](initialization.md)
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* [Control](control.md)
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* [Streaming](streaming.md)
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* [Metadata](metadata.md)
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* [Stream Configurations](stream-configurations.md)
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