feat(rtps, cdr): Add cdr and rtps components

[finger563]

Description

This PR adds the initial cdr and rtps components and wires them into the repo, examples, docs, CI, and host-side test tooling.

Highlights:

• add a standalone cdr component for reusable CDR / PL_CDR payload handling
• add an rtps component built on socket / task with:
  • RTPS message/header/submessage helpers
  • SPDP participant discovery
  • SEDP publication/subscription discovery
  • temporary UInt32 user-data publish/receive support
• update rtps to use the shared cdr component for parameter-body and payload CDR handling
• add ESP-IDF examples for both cdr and rtps
• update the RTPS example to support real two-node Wi-Fi testing with initiator / responder roles via menuconfig
• add a pure-stdlib host RTPS harness in python/rtps_host.py
• update the Python RTPS harness defaults so it works out of the box with the default ESP RTPS example
• add / expand docs for cdr, rtps, and rtsp, including protocol explanations, Mermaid diagrams, compatibility/status tables, and spec references
• wire the new components into Doxygen, Sphinx docs, CI build matrices, and component upload workflow

Motivation and Context

This change starts the DDS / ROS 2 interoperability foundation in ESPP by introducing:

1. a reusable CDR serialization layer that can stand alone from DDS/RTPS, and
2. an RTPS transport/discovery layer that is cross-platform because it is built on the existing socket component.

The immediate goal is to support standards-shaped RTPS discovery and a simple host/device validation path while keeping the architecture manageable:

• cdr owns byte layout, encapsulation, alignment, strings, arrays, and sequences
• rtps owns discovery, transport, GUIDs, locators, and temporary user-data exchange
• future DDS matching / higher-level type support can build on top of these layers

This PR also improves the docs/test story so the new components are understandable and usable from both ESP targets and a PC host.

How has this been tested?

• Built the new CDR example:
  • source ~/esp/esp-idf/export.sh && cd components/cdr/example && idf.py build
• Built the RTPS example:
  • source ~/esp/esp-idf/export.sh && cd components/rtps/example && rm -f sdkconfig && idf.py build
• Verified rtps builds after being updated to depend on and use cdr
• Verified cdr and rtps public header documentation changes still compile cleanly via the example builds
• Ran Python syntax validation:
  • python3 -m py_compile python/rtps_host.py
• Ran a host-side RTPS loopback smoke test with two rtps_host.py processes:
  • one default responder instance
  • one initiator instance publishing espp/rtps_example/request
  • confirmed discovery plus echoed espp/rtps_example/response samples
• Previously validated the docs pipeline updates on this branch with the repo docs build flow, including the RTPS / RTSP / CDR pages

Screenshots (if appropriate, e.g. schematic, board, console logs, lab pictures):

Showing

• one example initiator on qtpy esp32s3
• one example responder on qtpy esp32s3
• python test script

Responder:

Initiator:

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update
• Hardware (schematic, board, system design) change
• Software change

Checklist:

• My change requires a change to the documentation.
• I have added / updated the documentation related to this change via either README or WIKI

Software

• I have added tests to cover my changes.
• I have updated the .github/workflows/build.yml file to add my new test to the automated cloud build github action.
• All new and existing tests passed.
• My code follows the code style of this project.

[github-actions]

✅Static analysis result - no issues found! ✅

[Copilot]

Pull request overview

This PR introduces two new ESPP components—cdr (Common Data Representation helpers) and rtps (an RTPS discovery + temporary UInt32 data scaffold)—and wires them into documentation and CI, including a pure-stdlib Python host harness for discovery and smoke testing.

Changes:

• Add components/cdr with CDR/PL_CDR reader/writer utilities plus an example and docs pages.
• Add components/rtps with SPDP/SEDP discovery framing, participant/endpoint tracking, and a temporary UInt32 user-data path, plus an ESP example and docs pages.
• Extend documentation tooling (Mermaid support) and CI matrices to build/upload the new components.

Reviewed changes

Copilot reviewed 36 out of 36 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
python/rtps_host.py	New pure-stdlib RTPS discovery + temporary UInt32 host harness.
python/README.md	Document the new RTPS host harness and example invocations.
docker_build_docs.sh	Install doc Python requirements inside the docs build container before building.
doc/requirements.txt	Add sphinxcontrib-mermaid for Mermaid diagram support.
doc/en/rtsp.rst	Add “How RTSP Works” explanation and Mermaid diagrams/spec links.
doc/en/rtps.rst	New RTPS component documentation page (scope, flow, specs, example link).
doc/en/rtps_example.md	Include RTPS example README into docs.
doc/en/index.rst	Add cdr and rtps pages to the docs toctree.
doc/en/cdr.rst	New CDR component documentation page.
doc/en/cdr_example.md	Include CDR example README into docs.
doc/Doxyfile	Add CDR/RTPS headers + examples to Doxygen inputs/example paths.
doc/conf_common.py	Enable Mermaid Sphinx extension and set Mermaid configuration.
components/rtps/src/rtps.cpp	Implement RTPS message framing/parsing, discovery, and temporary UInt32 data path.
components/rtps/README.md	RTPS component overview, expected compatibility, and feature status.
components/rtps/include/rtps.hpp	Public RTPS API: types, config, discovery, and temp UInt32 helpers.
components/rtps/idf_component.yml	RTPS component manager manifest + dependencies.
components/rtps/example/sdkconfig.defaults	RTPS example default config (partition table, task stacks).
components/rtps/example/README.md	RTPS two-board initiator/responder smoke-test instructions.
components/rtps/example/partitions.csv	Custom partition table for RTPS example.
components/rtps/example/main/rtps_example.cpp	RTPS example app: Wi-Fi STA + discovery + request/response loop.
components/rtps/example/main/Kconfig.projbuild	Menuconfig options for role/domain/participant/topics/Wi-Fi.
components/rtps/example/main/CMakeLists.txt	Example main component registration + dependencies.
components/rtps/example/CMakeLists.txt	RTPS example project setup and component list.
components/rtps/CMakeLists.txt	RTPS component build registration and requirements.
components/cdr/src/cdr.cpp	CDR translation unit (header-only-ish implementation anchor).
components/cdr/README.md	CDR component overview and example description.
components/cdr/include/cdr.hpp	CDR/PL_CDR encapsulation + reader/writer APIs and helpers.
components/cdr/idf_component.yml	CDR component manager manifest.
components/cdr/example/sdkconfig.defaults	Minimal defaults for the CDR example.
components/cdr/example/README.md	CDR example usage and expected output.
components/cdr/example/main/CMakeLists.txt	CDR example main component registration.
components/cdr/example/main/cdr_example.cpp	CDR example app: serialize/deserialize primitives, strings, sequences.
components/cdr/example/CMakeLists.txt	CDR example project setup and component list.
components/cdr/CMakeLists.txt	CDR component build registration.
.github/workflows/upload_components.yml	Add cdr and rtps to the upload list.
.github/workflows/build.yml	Add CI builds for cdr/example and rtps/example.

[Copilot]

Pull request overview

Copilot reviewed 37 out of 37 changed files in this pull request and generated 6 comments.

[Copilot]

Pull request overview

Copilot reviewed 37 out of 37 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

python/rtps_host.py:1

• RTPS submessages can legally use a length of 0 to mean “extends to end of message”. With the current loop, length == 0 causes offset not to advance (after the header), leading to an infinite loop. Additionally, the code unconditionally interprets the length as little-endian without checking the submessage endianness flag. Fix by treating length == 0 as len(packet) - offset (after reading the submessage header), and either reject non-little-endian submessages or decode fields according to the endianness bit.