Mesh Network Protocol for embedded devices

This is the low speed mesh network protocol. It allows to turn almost any kind of MCU device + Radio module device into a mesh node. It is designed to be lightweight, easy to use and portable to many plaftorms. The protocol uses serial port of your MCU in order to communicate with radio modulee connected to it.

The network extends and heals itself automatically by communicating with other nodes, which have same protocol version installed. Most versions of this protocol are compatible, but for the best performance it is recommended to use the latest version.

The protocol has been tested with radio modules JDY-40 during the development, and potentially can use radio modules with similar UART interface, which might be:

• JDY-41
• SV-610
• HC-11
• HC-12
• LC12S
• GT-38
• LoRa modules

MCU - stands for Microcontroller Computer Unit. (Arduino, Raspberry Pi, PC, etc.)

Node architecture:

 (Library code runs here which turns MCU into a mesh node)
        |                                          
        |                                          
        V                                          
+----------------+              +-----------------+
|                |     USART    |                 |
|      MCU       |<------------>|   Radio module  |
|                |              |                 |
+----------------+              +-----------------+

Network possible architecture:

+----------------+               +-----------------+                 +----------------+ 
|                |               |                 |                 |                | 
|      Node      |  (( Ether ))  |      Node       |   (( Ether ))   |      Node      |  
|   Address: 1   |               |   Address: 2    |                 |    Address: 3  | 
|                |               |                 |                 |                | 
+----------------+  <--------->  +-----------------+  <----------->  +----------------+ 
                  ^               ^                                                    
                   \             /                                                     
                    \           /                                                      
       (( Ether ))   \         /   (( Ether ))                                                    
                      \       /                                                        
                       \     /                                                         
                        v   v                                                           
              +----------------+                                                       
              |                |                                                       
              |      Node      |                                                       
              |   Address: 4   |                                                       
              |                |                                                       
              +----------------+                                                       

Quick links to usage examples:

• arduino-nano
• linux
• linux-cli-tool

Goal:

The goal of this project is to provide ability to build easy to use, mesh - architecture, data transferring network out of cheap, low memory, components. This protocol can be used for:

• Home automation
• Remote control
• Remote monitoring (telemetry)
• Decentralized messaging
• etc.

Support project:

If you earn money with using that code - Please donate to bitcoin address: bc1qc50tm0ppj3hh7fecd6d0rv8tdygy8uhe2cemzt to support the project. Or you can buy me a coffee:

Working principle:

The way, how the protocol spreads the data:

The protocol routes the packets in the most dumb way. It spereads the packet in the way, similar to the spread of the atenuating wave in the pool. It means, that all near devices, that can catch the packet - cathes it. Then the device's router - determines if the packet is reached it's destination or has to be transitted further with decrease of lifetime value of the packet. Once lifetime value is reached zero during routing - the packet gets destroyed by the exact device which currently routes it.

The packets, that were just sent by user by send_to_exact, broadcast, send_ping_pong or send_with_transaction method in the device, which performs the operation - that packets bypasses routing and are sent directly into sending queue, and then into the ether. It means that lifetime of the packet is not decreased by the router of the device. So the message can be sent even with lifetime set to 0, anyway it will be transmitted in the ether for the first time. Sending of packets from the queues happends during call of update method.

It means, that the user can send the message with:

• Set the lifetime to 0, and the packet will be transmitted into the ether, nearest device will receive it, check if the destination is reached. If the destination is reached - catch the data. Otherwise - try to transmit further with decrease of lifetime value which will lead to packet destruction due to the end of packet's lifetime.

• Also set the lifetime to 1, and the packet will be transmitted into the ether, nearest device will receive it, check if the destination is reached, If the destination is reached - catch the data. Otherwise - try to transmit further with decrease of lifetime value which will lead to packet destruction due to the same reason.

• Set the lifetime to 2 and the packet will be transmitted into the ether, nearest device will receive it, check if the destination is reached, If the destination is reached - catch the data. Otherwise - try to transmit further with decrease of lifetime value which will lead packet transition back into the ether, but with less lifetime value.

• And so on..

Every node have 2 internal queues, they are not exposed to user:

• send - for sending packets
• transit - for packets, that are sent to the other devices. Sizes of those queues are configurable. And their both configuration of size is made by PACKET_QUEUE_SIZE constant in ./src/mesh_lib/node/constants.rs.

How the protocol avoid packet duplication:

During sending of the packet - it is offered to set filter_out_duplication parameter to true to prevent network from being jammed by duplicated packets. It works in the next way: Once intermediate node receives the packet with ignore_duplication flag set to true,

• it remembers the sender_device_identifier of the packet and id of the packet for the RECEIVER_FILTER_DUPLICATE_IGNORE_PERIOD. - This period is configurable. if the same packet with same sender_device_identifier and with same id is sent again - it will be ignored by the node. It leads protocol to spread one exact packet trough the network only once.

Special purpose packets as Ping-Pong or Transaction packets are always with filter_out_duplication flag set to true by default.

Status:

The version is: 1.1.0: Every planned functionality is working. It is:

• Send data.
• Receive data.
• Send data with ignorance of duplicated packets.
• Send data with limited of number of hops.
• Broadcast data to all nodes.
• Message transition by the intermediate nodes.
• Send data with ping flag, and receive answer with pong flag set.
• Send data via Transaction and receive packet about transaction being finished.
• Full backward compatible with version 1.0.5. (but anyway it is better to be in sync :) )

Cross-platform compatibility

For now the protocol is ported to:

• Arduino nano
• Linux (Raspberry PI, Desktop)

Potentially can be ported to:

• Windows
• Mac
• STM32
• ESP8266
• Raspberry PI pico

Porting to other platforms

While initially designed to be able to run at least on Atmega328p chips - it can be ported to huge variety of other platforms. Protocol is using embedded-hal, so platforms shall be supported by embedded-hal.

Also this protocol is welcomed to be ported on other platforms. In order to simplify process of porting of this protocol to the new platforms - the common behaviour is moved out of implementation to make it interchangable with implementations of PlatformMillis and PlatformSerial traits for each other platform.

To be able to run protocol on new platforms, it is needed to have implemented PlatformMillis and PlatformSerial traits for this specific platform.

• PlatformSerial - trait to communicate with radio module over USART.
• PlatformMillis - trait to track of time since program start.

In case - if you have implemented PlatformSerial and PlatformMillis trait for your platform, you can contact developers of this library to include links for your implementations in this README. Contacs are:

• Telegram channel: https://t.me/embedded_nano_mesh
• Github: https://github.com/boshtannik This will help this project grow.

Usage steps:

In case, if implementations are already present for platform, you need - just follow three steps to use it: (Examples are for arduino nano) 1 - Include implementations of platform-serial and platform-millis for your platform into your project. Cargo.toml:

embedded-nano-mesh = "1.1.4"
platform-millis-arduino-nano = { git = "https://github.com/boshtannik/platform-millis-arduino-nano.git" }
platform-serial-arduino-nano = { git = "https://github.com/boshtannik/platform-serial-arduino-nano.git" }

2 - Include implementation of platform-serial and platform-millis in your project, and of course the library embedded-nano-mesh itself. src/main.rs:

use embedded_nano_mesh::*;

use platform_millis_arduino_nano::{init_timer, ms, Atmega328pMillis};
use platform_serial_arduino_nano::{init_serial, ArduinoNanoSerial};

3 - Use PlatformSerial and PlatformMillis implementations during use of dependent methods on this traits: src/main.rs:

/// Send ping-pong example:
match mesh_node.send_ping_pong::<Atmega328pMillis, ArduinoNanoSerial>( ... ) { ... }

/// Send with transaction example:
match mesh_node.send_with_transaction::<Atmega328pMillis, ArduinoNanoSerial>( ... ) { ... }

/// Update example.
loop {
  let _ = mesh_node.update::<Atmega328pMillis, ArduinoNanoSerial>();
}

Note that send_to_exact and broadcast do not require PlatformSerial and PlatformMillis generics being provided. Full examples are available below.

Arduino nano port.

The implementation of PlatformSerial for Arduino nano board is done by:

• platform-serial-arduino-nano

The implementation of PlatformMillis for Arduino nano board is done by:

• platform-millis-arduino-nano

Usage examples can be found here:

• arduino-nano

Sometimes code binary might not fit onto your arduino board memory, in order to reduce the size of final binary - it is recommended to compile it with --release flag - it increases optimisation level tlat leads to smaller binary.

Linux port.

The implementation of PlatformSerial for Linux is done by:

• platform-serial-linux

The implementation of PlatformMillis for Linux is done by:

• platform-millis-linux

Usage examples can be found here:

• linux

Short usage description

1 - Instantiate Node structure. 2 - Constantly call update method of Node in a loop. 3 - Call any method of Node structure that you need, such as:

• send_to_exact
• broadcast
• receive
• send_ping_pong
• send_with_transaction

Methods description

The central component of this protocol is the Node structure, which offers interface for actions like send_to_exact, broadcast, receive, send_ping_pong, and send_with_transaction. The Node should be constantly updated by call its update method, during call of update method - it does all internal work:

• routes packets trough the network, transits packets that were sent to other devices, handles lifetime of packets.
• handles special packets like ping and pong, or any kind of transaction one.
• saves received packets that wil lbe available trough receive method.
• sends packets, that are in the send queue.

As the protocol relies on physical environment - it is crucial to provide ability to the library to rely on time counting and on USART interface, as it is described above by PlatformSerial and PlatformMillis implementations.

During the use of methods, that relies on PlatformMillis trait and PlatformSerial trait - it is needed to provide those implementations during the method call. Those methods are:

• update
• send_ping_pong
• send_with_transaction

You can regulate the distance that the packet will be able to make - by configuring the lifetime during making the send of the message. For example:

• setting lifetime to 1 will limit the message's reach to the nearest devices in the network.
• setting lifetime to 10 will make the packet able to pass 10 nodes before being destroyed.

New Method

To initialize a Node, you need to provide NodeConfig with values:

• ExactAddressType: Sets the device's identification address in the node pool. It is ok to have multiple deivces sharing same address in the same network.
• listen_period: Sets period in milliseconds that determines how long the device will wait before transmitting on the network. It prevents network congestion.

main.rs:

let mut mesh_node = Node::new(NodeConfig {
    device_address: ExactAddressType::new(1).unwrap(),
    listen_period: 150 as ms,
});

Broadcast Method

To send the message to all nodes in the network, you can send it with standard broadcast method, It sends packet with destination address set as GeneralAddressType::BROADCAST. Every device will treat GeneralAddressType::Broadcast as it's own address, will keep the message as received and will transit copy of that message further. main.rs:

mesh_node.broadcast(
    NodeString::from("Hello, world!").into_bytes(),
    3.into(),
);

Send to exact Method

Sends the message to device with exact address in the network. The send_to_exact method requires the following arguments:

The term "echoed message" refers to a duplicated message that has been re-transmitted into the ether by an intermediate device.

• data: A PacketDataBytes instance to hold the message bytes.
• destination_device_identifier: A ExactAddressType instance indicating exact target device.
• lifetime: A LifeTimeType instance to control for how far the message can travel.
• filter_out_duplication: A boolean flag to filter out echoed messages from the network.

main.rs:

mesh_node.send_to_exact(
    NodeString::from("Hello, world!").into_bytes(),
    ExactAddressType::new(3).unwrap(),
    3.into(),
    true,
);

Receive Method

The receive method optionally returns received data in a PacketDataBytes instance in case if that packet was previously received by this exact device. It does not matter if that data was sent via broadcast, send_to_exact, ping_pong or send_with_transaction method because anyway it will be available via receive method. The way that packet was sent to this device can be checked in special_state field of returned value. Field shall contain PacketState enum instance.

main.rs:

match mesh_node.receive() {
    Some(packet) => ...,
    Node => ....,
}

Send Ping-Pong Method

The send_ping_pong method sends a message with a "ping" flag to the destination node and waits for the same message with a "pong" flag which tells that the device have received the message at least once. It returns an error if the ping-pong exchange fails. The following arguments are required:

• data: A PacketDataBytes instance.
• destination_device_identifier: A ExactAddressType instance, that indicates exact target device address.
• lifetime: A LifeTimeType instance.
• timeout: An ms instance specifying how long to wait for a response.

main.rs:

   match mesh_node.send_ping_pong::<Atmega328pMillis, ArduinoNanoSerial>(
        NodeString::from("This is the message to be sent").into_bytes(),
        ExactAddressType::new(2).unwrap(),
        10 as LifeTimeType,
        3000 as ms,
    ) {
        Ok(()) => ..., // Means that receiving device got the message exaclty once.
        Err(SpecialSendError::SendingQueueIsFull) => ..., // Message wasnt even sent.
        Err(SpecialSendError::Timeout) => ..., // No response from the receiving device.
    }

Send with Transaction Method

The send_with_transaction method sends a message and handles all further work to ensure the target device have received it only once and correctly. It returns an error if the transaction failed. The required arguments are:

• data: A PacketDataBytes instance.
• destination_device_identifier: A ExactAddressType instance, that indicates exact target device address.
• lifetime: A LifeTimeType instance.
• timeout: An ms instance to specify the response wait time.

main.rs:

    match mesh_node.send_with_transaction::<Atmega328pMillis, ArduinoNanoSerial>(
        NodeString::from("This is the message to be sent").into_bytes(),
        ExactAddressType::new(2).unwrap(),
        10 as LifeTimeType,
        3000 as ms,
    ) {
        Ok(()) => ..., // Means that receiving device got the message exaclty once.
        Err(SpecialSendError::SendingQueueIsFull) => ..., // Message wasnt even sent.
        Err(SpecialSendError::Timeout) => ..., // No response from the receiving device.
    }

Update Method

The update method is used to perform all internal operation of the Node. It shall be called in a loop with providing PlatformMillis and PlatformSerial instances

• it allows Node to interact with MCU peripherals, such as time counting and USART. With out call this method in a loop - the node will stop working.

main.rs:

  loop {
    let _ = mesh_node.update::<Atmega328pMillis, ArduinoNanoSerial>();
  }

Reduce packet collisions

It is recommended to set listen_period value on multiple devices different from each other, like:

• device 1 - 230 ms,
• device 2 - 240 ms,
• device 3 - 250 ms, this will reduce chance of the network to sychronize, and shall make less packet collisions. You can play with this values in order to reduce the chance of packet collisions.

Note: The higher count of nodes in the network leads to the more network stability. In the stable networks - there is less need to use transaction or ping_pong sending, unless, you send something very important.

Warning

This protocol does not provide data encryption. To secure your data from being stolen, you should implement (de/en)cryption mechanisms independently.

All nodes must have the same version of the protocol installed to communicate. Different implementations of the Packet structure, or serialization or deserealization methods will lead to communication issues.

Note

Under the hood, data is packed into a Packet instance. If you need customize packets for your needs - you need configure the Packet ./src/mesh_lib/node/packet/mod.rs and ./src/mesh_lib/node/packet/types.rs Also serialization and deserealization part shall be changed too.

License

This project is licensed under:

• GNU General Public License, Version 3.0 (LICENSE-GPL or GPL License)
• Apache License, Version 2.0 (LICENSE-APACHE or Apache License 2.0)
• MIT License (LICENSE-MIT or MIT License)

You can choose the license that best suits your preferences.

Contribution

You can contribute to this project by make fork of 'main' branch and then creating pyull request to this repository. Pull request shall be created with next data mentioned.

• Name of the issue the the pull request solves.
• Link to the issue in the pull request description.
• Abstract description of the cause of problem and the way it was solved.
• Optionally notes or wishes for further maintainance or improvement.
• Before pushing the pull request - merge it with main branch again to void all possible conflicts.
• Push the pull request.