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Exceeding the 64 kB XRCE size limit in micro-ROS

With a strong focus on improving the throughput and the usability, we have optimized micro-ROS by including the off-standard 64 kB limit tweak.

eProsima’s Micro XRCE-DDS, the micro-ROS middleware implementation, follows the DDS-XRCE standard, which sets a threshold of 64 kB of maximum topic size when publishing and subscribing (page 52 OMG DDS-XRCE standard).

The DDS-XRCE specification by the OMG Consortium, is focused on communicating eXtremely Resource Constrained Environments with the DDS world.

It defines a wire protocol between a resource constrained, low-powered device (client) and an Agent (the server). The embedded nature of this protocol sets a small overhead and the mentioned 64 kB message size limit.

This great achievement in conjunction with the continuous transfer mode allows to transmit huge amounts of data directly from the sensors to the ROS 2 dataspace without buffering them into the MCU memory. Making micro-ROS a suitable platform for interfacing with ROS 2 from the embedded world.

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