Merge pull request #4 from microROS/embedded_ROS2_on-going_works

Documented prior/on-going works

articles/embedded.md

@@ -31,7 +31,7 @@ A number of things that would be great to have, lets call it a wishlist... Feel
 | W-PORTABILITY | **Portability of ROS 2-based software** | The embedded ROS 2 stack shall resemble or directly use the ROS 2 API -- more precisely the rclcpp API -- to facilitate porting standard ROS 2 nodes to MCUs. |
 | W-DEVICES | **Support of a broad spectrum of device classes** | The embedded ROS 2 stack shall support a broad range of MCU device classes, starting from a few tens kilobyte of RAM. |
 | W-RTOS | **Support of a broad spectrum of RTOS(s)** | The stack shall be adaptable to different RTOS (e.g., NuttX, FreeRTOS, Zephyr) and provide abstractions with regard to the application software to facilitate porting application components to between RTOSs.|
-| W-MW | **Support of prevalent communication technologies** | To cover the broad range of use-cases for MCUs in robotics, the embedded ROS 2 stack shall be usable with the default ROS 2 middleware standard DDS, simple (custom) serial communication protocols just as common wireless technologies like Bluetooth Low Energy |
+| W-COMM | **Support of prevalent communication technologies** | To cover the broad range of use-cases for MCUs in robotics, the embedded ROS 2 stack shall be usable with the default ROS 2 middleware standard DDS, simple (custom) serial communication protocols just as common wireless technologies like Bluetooth Low Energy |
 | W-MODULARITY | **High Modularity** | The embedded ROS 2 stack shall be highly modular, not only to allow for adaptation to specific hardware features and different RTOS, but also to allow the integration with existing frameworks and to be able to create customized sub-stacks. For example, it shall be usable in the style of rosserial, thus bringing basically the message serialization to the MCU only. Similarly, it should be possible to derive a sub-stack that provides node graph features and publish/subscribe but no parameters and services, and so on. |
 | W-CONTROL | **Support control-oriented applications**  | MCUs are great for control, and micro-ROS should be as well. This usually means hard real-time performance with low jitter and small response times. |
 | W-POWER | **Make low-power modes possible** | MCUs are often used in battery-powered applications, and/or in applications with a large amount of standby time. Therefore, the stack should make it easily possible to save power. |
@@ -51,48 +51,48 @@ To determine how feasible that is, and to come up with the actual requirements a
 | Q-LANG | W-PORTABILITY | Which language should be used, and at what spec level? |
 | Q-API | W-PORTABILITY, W-MODULARITY, W-STATIC, W-POWER | How should the API look in general?|
 | Q-PERF | W-PORTABILITY, W-DEVICES, W-CONTROL, W-STATIC | What are the performance implications of the API?|
-| Q-MIDDLEWARE | W-MW | Which communication/middleware technology is used?|
+| Q-COMM | W-COMM | Which communication/middleware technology is used?|
 
-## Actions
+## Analyses and Experiments
 
-> *TODO: Maybe don't call this action, but "fact finding" or the like?*
-
-To answer these questions, both the OFERA EU project as well as several others have already undertaken or are planning exploratory work.
+To answer these questions, the OFERA EU project as well as several others have already undertaken or are planning exploratory work.
 
 *Meta-Note*: Please only add a short description here, linking to more detailed pages if necessary.
 
-| Key | Related Question | Action | Description | Links |
-|-----|------------------|--------|-------------|-------|
-| A-RTOS | Q-RTOS | RTOS Proof-of-Concept | Provide a proof-of-concept RTOS. In the OFERA project, we chose NuttX, because it is largely POSIX compatible and thus eases porting. There are also experiments based on RIOT and FreeRTOS | TODO |
-| A-BUILD-META | Q-BUILD | Meta-Build | Explores a meta-build approach to transform ROS 2 CMakeLists.txt to RTOS-specific build instructions. | TODO |
-| A-BUILD-NUTTX | Q-BUILD | NuttX-specific build | OFERA has integrated (parts of) micro-ROS directly as an app in the NuttX build. |TODO |
-| A-BUILD-ARDUINO | Q-BUILD | Arduino Build | Robotis has explored building all the libraries using the Arduino IDE. This required some manual changes and thus does not scale, but can get you off the ground. | TODO |
-| A-NUTTX-LIBCXX | Q-LANG | C++11/higher support for NuttX | Build libxx from the LLVM project on NuttX, as a pre-requisite to building rclcpp. | TODO |
-| A-PERF-RCLCPP-RESOURCE | Q-PERF | Determine resource use of rclcpp | |  TODO |
+| Key | Related Question | Action | Description |
+|-----|------------------|--------|-------------|
+| A-RTOS | Q-RTOS | RTOS Proof-of-Concept | Provide a proof-of-concept RTOS. In the OFERA project, we chose [NuttX](http://nuttx.org/), because it is largely POSIX compatible and thus eases porting. There are also experiments based on [RIOT](https://www.riot-os.org/) (cf. [github.com/astralien3000/riot-ros2](https://github.com/astralien3000/riot-ros2)) and FreeRTOS (cf. [github.com/ros2/ros2_embedded_freertos](https://github.com/ros2/ros2_embedded_freertos)) |
+| A-BUILD-META | Q-BUILD | Meta-Build | Explores a meta-build approach to transform ROS 2 CMakeLists.txt to RTOS-specific build instructions. |
+| A-BUILD-NUTTX | Q-BUILD | NuttX-specific build | OFERA has integrated (parts of) micro-ROS directly as an app in the [NuttX build](https://github.com/ROBOTIS-GIT/OpenCR/tree/feature-ROS2-micrortps/arduino/opencr_arduino/opencr/libraries/ROS2). |
+| A-BUILD-ARDUINO | Q-BUILD | Arduino Build | ROBOTIS has explored building all the libraries using the Arduino IDE, cf. [github.com/ROBOTIS-GIT/OpenCR](https://github.com/ROBOTIS-GIT/OpenCR/tree/feature-ros2-micrortps). This required some manual changes and thus does not scale, but can get you off the ground. |
+| A-NUTTX-LIBCXX | Q-LANG | C++11/higher support for NuttX | Build libxx from the LLVM project on NuttX, as a pre-requisite to building rclcpp. |
+| A-PERF-RCLCPP-RESOURCE | Q-PERF | Determine resource use of rclcpp | |
 
 
 ## Prior and on-going works
 
 ### ROS2-based approaches
-*   [EU project OFERA](http://ofera.eu/): The EU project OFERA (Open Framework for Embedded Robot Applications) aims at a ROS 2-compatible stack for MCUs in the range of STM32F4 or STM32L1, i.e. with possibly less than 100kB RAM. The project partners currently investigate of using the ROS 2 rmw, rcl and rclcpp layers as-is on the micro-XRCE-DDS implementation of the upcoming XRCE-DDS standard. In parallel, a more modular approach in the style of rosserial is investigated. In the project's use-cases, NuttX is considered as primary choice for the RTOS. Beyond the project page, additional details of the project results can be found at [http://micro-ros.com](http://micro-ros.com).
+*   [**EU project OFERA**](http://ofera.eu/): The EU project OFERA (Open Framework for Embedded Robot Applications) aims at a ROS 2-compatible stack for MCUs in the range of STM32F4 or STM32L1, i.e. with possibly less than 100kB RAM. The project partners currently investigate of using the ROS 2 rmw, rcl and rclcpp layers as-is on the Micro XRCE-DDS implementation of the upcoming XRCE-DDS standard. In parallel, a more modular approach in the style of rosserial is investigated. In the project's use-cases, NuttX is considered as primary choice for the RTOS. Beyond the project page, additional details of the project results can be found at [microros.github.io/micro-ROS/](https://microros.github.io/micro-ROS/).
+
+*   [**ROS 2 library for OpenCR by ROBOTIS**](https://github.com/ROBOTIS-GIT/OpenCR/tree/feature-ros2-micrortps/arduino/opencr_arduino/opencr/libraries/ROS2): Tailored and optimized implementation of the ROS 2 publish/subscribe and clock API for the Micro XRCE-DDS (formerly micro-RTPS) implementation of the upcoming XRCE-DDS middleware standard running on an STM32F7.
 
-*   [ROS 2 library for OpenCR by ROBOTIS](https://github.com/ROBOTIS-GIT/OpenCR/tree/feature-ROS2-micrortps/arduino/opencr_arduino/opencr/libraries/ROS2)
+*   [**freeRTPS**](https://github.com/ros2/freertps): A free, portable, minimalist implementation of the RTPS protocol for microcontrollers such as the STM32F7 developed at the OSRF. FreeRTPS shall allow to run ROS 2 with standard DDS as-is on stronger MCUs. This project has been discontinued in 2016.
 
+*   [**ros2_embedded_nuttx**](https://github.com/ros2/ros2_embedded_nuttx): Early port (in 2014) of ROS 2 alpha for the STM32F4Discovery board and the STM3240G eval board running the RTOS NuttX developed by Víctor Mayoral Vilches and Esteve Fernandez at the OSRF.
 
 ### ROS1-based approaches
 
-*   [rosserial](http://wiki.ros.org/rosserial) -- well-known and widely used in the ROS community ...
+*   [**rosserial**](http://wiki.ros.org/rosserial): Well-known and widely used in the ROS community.
 
-*   [mROS](https://github.com/tlk-emb/mROS/) -- a new work on bringing ROS1 concepts (including nodes and the ROS1 middleware) on stronger MCUs, cf. also
+*   [**mROS**](https://github.com/tlk-emb/mROS/): A new work on bringing ROS1 concepts (including nodes and the ROS1 middleware) on stronger MCUs, cf.
     *Hideki Takase, Tomoya Mori, Kazuyoshi Takagi and Naofumi Takagi: 'Work-in-Progress: Design Concept of a Lightweight Runtime Environment for Robot Software Components onto Embedded Devices' in Proc. of ESWEEK, Torino, Italy, September 2018.*
-*   [freeRTPS](TODO): TODO
 
-*   [ros2_embedded_nuttx](TODO): TODO
+## Design Discussion
 
-## First Design Ideas
+The following figure may serve as a starting point for the design discussion. It depicts the major layers from the real-time operating system to the application, in the style the ROS 2 standard stack.
 
-* This is our proposed architecture:
+![micro-ROS](/img/embedded/features_with_dependencies.png)
 
-![micro-ROS](/img/embedded/micro-ROS_proposed_architecture.png)
+At the same time, the diagram illustrates the possible feature set of the client library -- ideally in a modular fashion so that different profiles can be derived from it. The vertical bar at each feature gives an indication of the dependencies with lower layers and thus on the portability to different RTOS and middlewares.
 
-... *possibly also the diagram with the API features and the vertical bars indicating the depth of implementation* ...
+In the OFERA project, a more detailed diagram has been developed, which can be found at [microros.github.io/micro-ROS/](https://microros.github.io/micro-ROS/).