Eclipse Zenoh

The Eclipse Zenoh: Zero Overhead Pub/sub, Store/Query and Compute.

Zenoh (pronounce /zeno/) unifies data in motion, data at rest, and computations. It carefully blends traditional pub/sub with geo-distributed storages, queries and computations, while retaining a level of time and space efficiency that is well beyond any of the mainstream stacks.

Check the website zenoh.io and the roadmap for more detailed information.

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Zenoh-Pico: native C library for constrained devices

zenoh-pico is the Eclipse zenoh implementation that targets constrained devices, offering a native C API. It is fully compatible with its main Rust Zenoh implementation, providing a lightweight implementation of most functionalities.

Currently, zenoh-pico provides support for the following (RT)OSs and protocols:

(RT)OS	Transport Layer	Network Layer	Data Link Layer
Unix	UDP (unicast and multicast), TCP	IPv4, IPv6, 6LoWPAN	WiFi, Ethernet, Thread
Windows	UDP (unicast and multicast), TCP	IPv4, IPv6	WiFi, Ethernet
Zephyr	UDP (unicast and multicast), TCP	IPv4, IPv6, 6LoWPAN	WiFi, Ethernet, Thread, Serial
Arduino	UDP (unicast and multicast), TCP	IPv4, IPv6	WiFi, Ethernet, Bluetooth (Serial profile), Serial
ESP-IDF	UDP (unicast and multicast), TCP	IPv4, IPv6	WiFi, Ethernet, Serial
MbedOS	UDP (unicast and multicast), TCP	IPv4, IPv6	WiFi, Ethernet, Serial
OpenCR	UDP (unicast and multicast), TCP	IPv4	WiFi
Emscripten	Websocket	IPv4, IPv6	WiFi, Ethernet
FreeRTOS-Plus-TCP	UDP (unicast), TCP	IPv4	Ethernet
Raspberry Pi Pico	UDP (unicast and multicast), TCP	IPv4	WiFi (for "W" version), Serial, USB (CDC)

Check the website zenoh.io and the roadmap for more detailed information.

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1. How to install it

The Eclipse zenoh-pico library is available as Debian, RPM, and tgz packages in the Eclipse zenoh-pico download area. Those packages are built using manylinux2010 x86-32 and x86-64 for compatibility with most Linux platforms. There are two kind of packages:

• libzenohpico: only contains the library file (.so)
• libzenohpico-dev: contains the zenoh-pico header files for development and depends on the libzenohpico package

For other platforms - like RTOS for embedded systems / microcontrollers -, you will need to clone and build the sources. Check [below](#2. how-to-build-it) for more details.

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2. How to build it

⚠️ WARNING ⚠️ : Zenoh and its ecosystem are under active development. When you build from git, make sure you also build from git any other Zenoh repository you plan to use (e.g. binding, plugin, backend, etc.). It may happen that some changes in git are not compatible with the most recent packaged Zenoh release (e.g. deb, docker, pip). We put particular effort in mantaining compatibility between the various git repositories in the Zenoh project.

2.1 Unix Environments

To build the zenoh-pico library, you need to ensure that cmake is available on your platform -- if not please install it.

Once the cmake dependency is satisfied, just do the following for CMake version 3 and higher:

-- CMake version 3 and higher --

cd /path/to/zenoh-pico
make
make install # on Linux use **sudo**

If you want to build with debug symbols, set the BUILD_TYPE=Debugenvironment variable before to run make:

cd /path/to/zenoh-pico
BUILD_TYPE=Debug make
make install # on Linux use **sudo**

For those that still have CMake version 2.8, do the following commands:

cd /path/to/zenoh-pico
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release ../cmake-2.8
make
make install # on Linux use **sudo**

2.2. Real Time Operating System (RTOS) for Embedded Systems and Microcontrollers

In order to manage and ease the process of building and deploying into a a variety of platforms and frameworks for embedded systems and microcontrollers, PlatformIO can be used as a supporting platform.

Once the PlatformIO dependency is satisfied, follow the steps below for the tested micro controllers.

2.2.1. Zephyr

Note: tested with reel_board, nucleo-f767zi, nucleo-f420zi, and nRF52840 boards.

A typical PlatformIO project for Zephyr framework must have the following structure:

project_dir
├── include
├── lib
├── src
│    └── main.c
├── zephyr
│    ├── prj.conf
│    └── CMakeLists.txt
└── platformio.ini

To initialize this project structure, execute the following commands:

mkdir -p /path/to/project_dir
cd /path/to/project_dir
platformio init -b reel_board
platformio run

Include the CMakelist.txt and prj.conf in the project_dir/zephyr folder as shown in the structure above,

cp /path/to/zenoh-pico/docs/zephyr/reel_board/CMakelists.txt /path/to/project_dir/zephyr/
cp /path/to/zenoh-pico/docs/zephyr/reel_board/prj.conf /path/to/project_dir/zephyr/

and add zenoh-pico as a library by doing:

ln -s /path/to/zenoh-pico /path/to/project_dir/lib/zenoh-pico

or just include the following line in platformio.ini:

lib_deps = https://github.com/eclipse-zenoh/zenoh-pico

Finally, your code should go into project_dir/src/main.c. Check the examples provided in examples directory.

To build and upload the code into the board, run the following command:

platformio run
platformio run -t upload

2.2.2. Arduino

Note: tested with az-delivery-devkit-v4 ESP32 board

A typical PlatformIO project for Arduino framework must have the following structure:

project_dir
├── include
├── lib
├── src
│    └── main.ino
└── platformio.ini

To initialize this project structure, execute the following commands:

mkdir -p /path/to/project_dir
cd /path/to/project_dir
platformio init -b az-delivery-devkit-v4
platformio run

Add zenoh-pico as a library by doing:

ln -s /path/to/zenoh-pico /path/to/project_dir/lib/zenoh-pico

or just include the following line in platformio.ini:

lib_deps = https://github.com/eclipse-zenoh/zenoh-pico

Finally, your code should go into project_dir/src/main.ino. Check the examples provided in examples directory.

To build and upload the code into the board, run the following command:

platformio run
platformio run -t upload

2.2.3. ESP-IDF

Note: tested with az-delivery-devkit-v4 ESP32 board

A typical PlatformIO project for ESP-IDF framework must have the following structure:

project_dir
├── include
├── lib
├── src
|    ├── CMakeLists.txt
│    └── main.c
├── CMakeLists.txt
└── platformio.ini

To initialize this project structure, execute the following commands:

mkdir -p /path/to/project_dir
cd /path/to/project_dir
platformio init -b az-delivery-devkit-v4
platformio run

Add zenoh-pico as a library by doing:

ln -s /path/to/zenoh-pico /path/to/project_dir/lib/zenoh-pico

or just include the following line in platformio.ini:

lib_deps = https://github.com/eclipse-zenoh/zenoh-pico

Finally, your code should go into project_dir/src/main.ino. Check the examples provided in examples directory.

To build and upload the code into the board, run the following command:

platformio run
platformio run -t upload

2.2.4. MbedOS

Note: tested with nucleo-f747zi and nucleo-f429zi boards

A typical PlatformIO project for MbedOS framework must have the following structure:

project_dir
├── include
├── src
│    └── main.ino
└── platformio.ini

To initialize this project structure, execute the following commands:

mkdir -p /path/to/project_dir
cd /path/to/project_dir
platformio init -b az-delivery-devkit-v4
platformio run

Add zenoh-pico as a library by doing:

ln -s /path/to/zenoh-pico /path/to/project_dir/lib/zenoh-pico

or just include the following line in platformio.ini:

lib_deps = https://github.com/eclipse-zenoh/zenoh-pico

Finally, your code should go into project_dir/src/main.ino. Check the examples provided in examples directory.

To build and upload the code into the board, run the following command:

platformio run
platformio run -t upload

2.2.5. OpenCR

Note: tested with ROBOTIS OpenCR 1.0 board

A typical PlatformIO project for OpenCR framework must have the following structure:

project_dir
├── include
├── lib
├── src
│    └── main.ino
└── platformio.ini

Note: to add support for OpenCR in PlatformIO, follow the steps presented in our blog.

To initialize this project structure, execute the following commands:

mkdir -p /path/to/project_dir
cd /path/to/project_dir
platformio init -b opencr
platformio run

Add zenoh-pico as a library by doing:

ln -s /path/to/zenoh-pico /path/to/project_dir/lib/zenoh-pico

or just include the following line in platformio.ini:

lib_deps = https://github.com/eclipse-zenoh/zenoh-pico

Finally, your code should go into project_dir/src/main.ino. Check the examples provided in examples directory.

To build and upload the code into the board, run the following command:

platformio run
platformio run -t upload

2.2.6. Raspberry Pi Pico

Note: tested with Raspberry Pi Pico W and Raspberry Pi Pico 2 W boards

Ensure your system has the necessary tools and libraries installed. Run the following commands:

sudo apt update
sudo apt install -y cmake gcc-arm-none-eabi libnewlib-arm-none-eabi build-essential g++ libstdc++-arm-none-eabi-newlib

Set up the Raspberry Pi Pico SDK by cloning the repository:

export PICO_SDK_PATH=$HOME/src/pico-sdk
mkdir -p $PICO_SDK_PATH
cd $PICO_SDK_PATH
git clone https://github.com/raspberrypi/pico-sdk.git .
git submodule update --init

Clone the FreeRTOS Kernel repository for the project:

export FREERTOS_KERNEL_PATH=$HOME/src/FreeRTOS-Kernel/
mkdir -p $FREERTOS_KERNEL_PATH
cd $FREERTOS_KERNEL_PATH
git clone https://github.com/FreeRTOS/FreeRTOS-Kernel.git .
git submodule update --init

Setup and build the examples:

• PICO_BOARD - Pico board type: pico, pico_w, pico2, pico2_w (default: pico_w)
• WIFI_SSID - Wi-Fi network SSID
• WIFI_PASSWORD - Wi-Fi password
• ZENOH_CONFIG_MODE - client or peer mode (default: client)
• ZENOH_CONFIG_CONNECT - connect endpoint (only for client mode, optional)
• ZENOH_CONFIG_LISTEN - listen endpoint (only for peer mode, optional)

cd examples/rpi_pico
cmake -Bbuild -DPICO_BOARD="pico" -DWIFI_SSID=wifi_network_ssid -DWIFI_PASSWORD=wifi_network_password -DZENOH_CONFIG_MODE=[client|peer] -DZENOH_CONFIG_CONNECT=connect -DZENOH_CONFIG_LISTEN=listen
cmake --build ./build

To flash the Raspberry Pi Pico board, connect it in bootloader mode (it will appear as a removable drive) and copy the generated .uf2 file onto it.

Serial connection:

To connect via UART specify pins or predefined device name and baud rate:

e.g.

-DZENOH_CONFIG_CONNECT="serial/0.1#baudrate=38400"
-DZENOH_CONFIG_CONNECT="serial/uart1_0#baudrate=38400"

Valid PIN combinations and associated device names:

PINS	Device name
0.1	uart0_0
4.5	uart1_0
8.9	uart1_1
12.13	uart0_1
16.17	uart0_2

USB Serial connection (experemental):

To enable this feature, zenoh-pico should be compiled with Z_FEATURE_LINK_SERIAL_USB and Z_FEATURE_UNSTABLE_API enabled.

To connect via USB CDC, specify usb device:

e.g.

-DZENOH_CONFIG_CONNECT="serial/usb#baudrate=112500"

On the host Zenoh, specify the USB CDC device:

e.g.

zenohd -l serial//dev/ttyACM1#baudrate=112500

3. Running the Examples

The simplest way to run some of the example is to get a Docker image of the zenoh router (see http://zenoh.io/docs/getting-started/quick-test/) and then to run the examples on your machine.

3.1. Starting the Zenoh Router

Assuming you've pulled the Docker image of the zenoh router on a Linux host (to leverage UDP multicast scouting as explained here, then simply do:

docker run --init --net host eclipse/zenoh:main

To see the zenoh manual page, simply do:

docker run --init --net host eclipse/zenoh:main --help

⚠️ Please notice that the --net host option in Docker is restricted to Linux only. The cause is that Docker doesn't support UDP multicast between a container and its host (see cases moby/moby#23659, moby/libnetwork#2397 or moby/libnetwork#552). The only known way to make it work is to use the --net host option that is only supported on Linux hosts.

3.2. Basic Pub/Sub Example

Assuming that (1) you are running the zenoh router, and (2) you are under the build directory, do:

./z_sub

And on another shell, do:

./z_pub

3.3. Basic Queryable/Get Example

Assuming you are running the zenoh router, do:

./z_queryable

And on another shell, do:

./z_get

3.4. Basic Pub/Sub Example - P2P over UDP multicast

Zenoh-Pico can also work in P2P mode over UDP multicast. This allows a Zenoh-Pico application to communicate directly with another Zenoh-Pico application without requiring a Zenoh Router.

Assuming that (1) you are under the build directory, do:

./z_sub -m peer -l udp/224.0.0.123:7447#iface=lo0

And on another shell, do:

./z_pub -m peer -l udp/224.0.0.123:7447#iface=lo0

where lo0 is the network interface you want to use for multicast communication.

Warning

Multicast communication does not perform any negotiation upon group joining. Because of that, it is important that all transport parameters are the same to make sure all your nodes in the system can communicate. One common parameter to configure is the batch size since its default value depends on the actual platform when operating on multicast:

• with zenoh-pico you can configure it via the BATCH_MULTICAST_SIZE build option (see below)
• with other Zenoh APIs, set the "transport/link/tx/batch_size" value in configuration file

E.g., the batch size on Linux and Windows is 65535 bytes, on Mac OS X is 9216, anything else is 8192.

3.4. Basic Pub/Sub Example - Mixing Client and P2P communication

To allow Zenoh-Pico unicast clients to talk to Zenoh-Pico multicast peers, as well as with any other Zenoh client/peer, you need to start a Zenoh Router that listens on both multicast and unicast:

docker run --init --net host eclipse/zenoh:main -l udp/224.0.0.123:7447#iface=lo0 -l tcp/127.0.0.1:7447

Assuming that (1) you are running the zenoh router as indicated above, and (2) you are under the build directory, do:

./z_sub -m client -e tcp/127.0.0.1:7447 

A subscriber will connect in client mode to the zenoh router over TCP unicast.

And on another shell, do:

./z_pub -m peer -l udp/224.0.0.123:7447#iface=lo0

A publisher will start publishing over UDP multicast and the zenoh router will take care of forwarding data from the Zenoh-Pico publisher to the Zenoh-Pico subscriber.

Troubleshooting

Activate debug logs

By default debug logs are deactivated but if you're encountering issues they can help you finding the cause. To activate them you need to pass the build flag value: -DZENOH_DEBUG=3

Error when opening a session on a microcontroller

If you get an error when opening the session even though everything is setup correctly, it might be because the default buffer sizes are too large for the limited memory available on your system.

The first thing to try is to reduce the values of the following configuration options (found in CMakeLists.txt):

• BATCH_UNICAST_SIZE: The maximum size of a packet in client mode.
• BATCH_MULTICAST_SIZE: The maximum size of a packet in peer mode.
• FRAG_MAX_SIZE: The maximum size of a message that can be fragmented into multiple packets.

Until you find values that suits both your app requirements and your system memory constraints.

These values can also be passed directly as cmake args. For example, in a platformio.ini you might write:

board_build.cmake_extra_args=
  -DBATCH_UNICAST_SIZE=1024
  -DFRAG_MAX_SIZE=2048