Micro-ROS brings ROS 2 to microcontrollers. Here, we perform an analysis of the related approaches and eventually show a comparison table.

ROSSerial is a protocol for wrapping standard ROS serialized messages and multiplexing multiple topics and services over a device such as a serial port or network socket. In addition to a protocol definition, there are three types of packages found in this suite:

- Client Libraries: Client libraries allow users to easily get ROS nodes up and running on various systems. These clients are ports of the general ANSI C++ rosserial_client library.

- ROS-side Interfaces: These packages provide a node for the host machine to bridge the connection from the rosserial protocol to the more general ROS network.

- Examples and Use Cases.

It is worth saying that this option cannot be fully compared with micro-ROS because this approach is meant to work with ROS 1, instead of micro-ROS which is focused on ROS 2.

Reference: [ROSserial Wiki](http://wiki.ros.org/rosserial)

RIOT-ROS2 is a modification of the main ROS 2 stack, to make it able to run on microcontrollers thanks to the RIOT Operating System.

ROS 2 is composed of several layers. Some have been modified to be able to run on the microcontroller, this is a list of the available layers for RIOS-ROS2 project:

- ROS Client Library bindings: RCLC

- ROS Client Library: RCL

- ROS MiddleWare: rmw_ndn

- ROS IDL Generators: generator_c

- ROS IDL Type Support: CBOR

- ROS IDL Interfaces:

- common_interfaces

- rcl_interfaces

As a final data, it looks like the development is frozen. This consideration is due to the fact that the last commit goes back to [July 2018](https://github.com/astralien3000/riot-ros2/commits/master).

Reference:[RIOT-ROS2](https://github.com/astralien3000/riot-ros2/wiki)

| | rosserial | RIOT-ROS2 | micro-ROS |

|-------|-----------|-----------|-----------|

| OS | bare-metal | RIOT | NuttX, FreeRTOS and Zephyr |

| Communications architecture | Bridged | N/A| Bridged |

| Message format | ROS1 | N/A |CDR (from DDS) |

| Communication links | UART | UART | UART, SPI, IP (UDP), 6LowPAN, ... |

| Communication protocol | Custom | NDN | XRCE-DDS (or any rmw implementation) |

| Code Base | Independent implementation | Standard ROS 2 stack up to RCL | Standard ROS 2 stack up to RCL (RCLCPP coming) |

| Node API | Custom rosserial API | RCL,RCLC | RCL (soon RCLCPP) |

| Callback execution | Sequential, in order of messages | N/A | Choice of ROS 2 executors or MCU optimized executors |

| Timers | Not included | Not included | Normal ROS 2 timers |

| Time sync to host | Custom | N/A | NTP/PTP |

| Lifecycle | Not supported | Partial | Partial, full coming |