xicro: Interface any-bit Microcontroller with ROS2

Rationale behind “xicro”:

The Robot Operating System (ROS) is a popular open-source framework for developing robotic systems. ROS2, the latest version of the framework, is designed to support real-time, distributed systems, and has become a popular choice for robotics researchers and developers. However, one limitation of ROS2 is that it is designed to run on high-performance computers, which can be expensive and impractical for many robotics applications.

To address this limitation, several middleware solutions have been developed to allow ROS2 to run on microcontrollers with limited resources. One such solution is MicroROS, a middleware that provides a communication layer between microcontrollers and ROS2. However, MicroROS is limited to microcontrollers with 32-bit architecture, and cannot be used with lower-bit architecture such as AVR. This limitation poses a challenge for developers who want to use ROS2 with low-cost, low-power microcontrollers that are widely available in the market.

To overcome this limitation, a software library is needed that allows any-bit architecture microcontroller to connect with ROS2 using UART or UDP. This library should provide a lightweight and efficient communication protocol that is optimized for microcontrollers with limited resources. By enabling low-cost microcontrollers to connect with ROS2, this library can help democratize access to ROS2 and make it more accessible to developers working on low-cost robotics projects.

General features of “xicro”:

• xicro auto-generates a library for a microcontroller (.h file)
• xicro auto-generates a node that communicates with UART
• xicro (should) supports all Arduino, ESP32, ESP8266 and STM32 families.

“xicro” is a part of an ongoing project of CoXsys Robotics under GPL license.

Installation

Xicro requires metapackage

• install metapackage

  xxx_ws is your workspace

    cd ~/xxx_ws/src      #cd to your workspace
    mkdir Xicro          #create metapackage
    cd Xicro             #cd to metapackage
    git clone https://github.com/imchin/Xicro .
    cd ~/xxx_ws
    colcon build
    source ~/xxx_ws/install/setup.bash
  

• install python library

    pip3 uninstall serial
    pip3 install pyserial
    pip3 install numpy
    

Setup parameter in yaml

cd ~/xxx_ws/src/Xicro/xicro_pkg/config      
code setup_xicro.yaml

setup_xicro.yaml is contain

• microcontroller

  • 1. idmcu : It sets the ID of the MCU for the system Xicro.

    The mcu Id may range from 0 to 15.

  • 2. namespace : This is the name of the file that will be created.

  • 3. generate_library_Path : Is the path for creating .h and .cpp files.

    Xicro will create a folder with files at the path.

    Path reference from ~/

  • 4. connection

    • 1. type : Support 2 mode 1.Serial UART 2.Wifi UDP (Only arduino and esp32)

    • 2. serial_port : Name open port of MCU

    • 3. baudrate : Can config baudrate Baudrate affects the data transmission rate. Can use <=2000000

      **Recommended at 115200.

    • 4. ip_address_mcu : Ip address of mcu in WLAN

    • 5. udp_port_mcu : port of connection UDP mode

• ros : setup ros is reference from microcontroller

  example publisher is mean microcontroller publish to ros network

  • 1. publisher : Configuration for publishing topic from MCU to ROS2.

    In format : [ [ID_topic,Name_topic,Interface],[ID_topic_2,Name_topic_2,Interface_2],…….]

    • 1. ID_topic : It sets the ID of the topic_publish for the system Xicro. The ID_topic Id may range from 0 to 255.
    • 2. Name_topic : Specify the topic name you want MCU to publish to ROS2.
    • 3. Interface : variable interfacefile configuration for use in the topic  Is contain 2 part in format

    “(The name of the package that contains the interface file)/(Name_of_fileinterface).msg”

  • 2. subscriber : Configuration for subscribe topic from ROS2 to MCU.

    In format : [ [ID_topic,Name_topic,Interface],[ID_topic_2,Name_topic_2,Interface_2],…….]

    • 1. ID_topic : It sets the ID of the topic_subscribe for the system Xicro.

      The ID_topic Id may range from 0 to 255.

    • 2. Name_topic : Specify the topic name you want MCU subscribe from ROS2.
    • 3. Interface : variable interfacefile configuration for use in the topic  Is contain 2 part in format

    “(The name of the package that contains the interface file)/(Name_of_fileinterface).msg”

  • 3. srv_client : Configuration for service client.

    In format : [ [ID_service,Name_service,Interface,time_out],[ID_service_2,Name_service_2,Interface_2,time_out_2],…….]

    • 1. ID_service : It sets the ID of the service_client for the system Xicro.

      The ID_service Id may range from 0 to 255.

    • 2. Name_service : Specify the servive name you want MCU service call to ROS2.

    • 3. Interface : variable interfacefile configuration for use in the service Is contain 2 part in format

      “(The name of the package that contains the interface file)/(Name_of_fileinterface).srv”

    • 4. time_out : Limit the maximum service usage time. (In type float)

  • 4. srv_server : Configuration for service server. In format : [ [ID_service,Name_service,Interface,time_out],[ID_service_2,Name_service_2,Interface_2,time_out_2],…….]

    • 1. ID_service : It sets the ID of the service_server for the system Xicro.

      The ID_service Id may range from 0 to 255.

    • 2. Name_service : Specify the servive name you want ROS2 service call to MCU.

    • 3. Interface : variable interfacefile configuration for use in the service Is contain 2 part in format

      “(The name of the package that contains the interface file)/(Name_of_fileinterface).srv”

    • 4. time_out : Limit the maximum service usage time. (In type float)

  • 5. action_client : Configuration for action client. In format : [ [ID_action,Name_action,Interface,time_out],[ID_action_2,Name_action_2,Interface_2,time_out_2],…….]

    • 1. ID_action : It sets the ID of the action_client for the system Xicro

      The ID_action Id may range from 0 to 255.

    • 2. Name_action : Specify the action name you want MCU action send_goal to ROS2.

    • 3. Interface : variable interfacefile configuration for use in the action Is contain 2 part in format

      “(The name of the package that contains the interface file)/(Name_of_fileinterface).action”

    • 4. time_out : Limit the maximum action usage time. (In type float)

  • 6. action_server : Configuration for action server. In format : [ [ID_action,Name_action,Interface,time_out],[ID_action_2,Name_action_2,Interface_2,time_out_2],…….]

    • 1. ID_action : It sets the ID of the action_server for the system Xicro

      The ID_action Id may range from 0 to 255.

    • 2. Name_action : Specify the action name you want ROS2 action send_goal to MCU.
    • 3. Interface : variable interfacefile configuration for use in the action Is contain 2 part in format

    “(The name of the package that contains the interface file)/(Name_of_fileinterface).action”

    • 4. time_out : Limit the maximum action usage time. (In type float)

Create xicro library

The library will be generated based on setup_xicro.yaml

  cd ~/xxx_ws/src      #cd to your workspace
  colcon build
  ros2 run xicro_pkg generate_library.py -mcu_type -module_name // Xicro library .h , .cpp will be created at $generate_library_Path in setup_xicro.yaml

-mcu_type (require) : This is the mcu family that you want to use.

• Canbe [arduino , esp , stm32]

-module_name : HAL library

• Ignore it if you don’t use the stm32 family. 

  Example

  In case use arduino family.

        ros2 run xicro_pkg generate_library.py -mcu_type arduino  // Exmaple generate for arduino family.
    

In case use esp family.

        ros2 run xicro_pkg generate_library.py -mcu_type esp  // Exmaple generate for esp family.
    

In case use STM32F411RE

        ros2 run xicro_pkg generate_library.py -mcu_type stm32 -module_name "stm32f4xx_hal.h"  // Exmaple generate for stm32F4xx
    

Create xicro node

The node will be generated based on setup_xicro.yaml

    ros2 run xicro_pkg generate_xicro_node.py -mcu_type // Xicro node will be created at path ~xxx_ws/scr/Xicro/xicro_pkg/scripts

-mcu_type (require) : This is the mcu family that you want to use, Can be

• canbe [arduino , esp , stm32]

The entry point is add auto by command.

Step to use

• Create xicro library

• Create xicro node

• Upload code contain xicro_library to MCU

• Connect MCU to computer

• check permission port open

• run xicro node