Optimized RF24Network Layer v2.0.1
2024 - Optimized RF24 Network Layer for NRF24L01 & NRF52x radios
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Network Layer for RF24 Radios

This class implements an OSI Network Layer using nRF24L01(+) radios driven by the newly optimized RF24 library fork or using nRF52x radios with the newly created nrf_to_nrf library.

See also
RF24 Library docs for general RF24 configuration and setup.

Purpose/Goal

Original: Create an alternative to ZigBee radios for Arduino communication.

New: Enhance the current functionality for maximum efficiency, reliability, and speed

Xbees are excellent little radios, backed up by a mature and robust standard protocol stack. They are also expensive.

For many Arduino uses, they seem like overkill. So I am working to improve the current standard for nRF24L01 radios. The best RF24 modules are available for less than $6 from many sources. With the RF24Network layer, I hope to cover many common communication scenarios.

Please see TMRh20's blog post for a comparison against the ZigBee protocols

News - 2023 API Changes

Introducing RF24Network & RF24Mesh v2.0 with some significant API changes, adding the use of C++ Templates in order to support a range of ESB enabled radios, most recently NRF52x radios.

Important Notes:

  • Any network layer that uses v2 needs to have RF24Network/RF24Mesh dependencies of v2 or newer. RF24 v1.x is an exception here.
  • General usage should remain backward compatible, see the included examples of the related libraries for more info
  • Any third party libs that extend the network/mesh layer may also need to be updated to incorporate the new templated class prototypes:
    template<class radio_t>
    class ESBNetwork;
    template<class network_t, class radio_t>
    class ESBMesh;
    Definition RF24Network.h:384
  • Third party libs should also be able to use the backward-compatible typedef in their template:
    • ESBGateway.h:
      template<typename network_t, typename mesh_t>
      class ESBGateway
      and inform the compiler what types they intend to support:
    • ESBGateway.cpp:
      template class ESBGateway<RF24Network, RF24Mesh>;
  • The auto installers do not perform a version check like package managers, so having the correct versions of the software is important.
  • We will be maintaining the v1.x versions with bugfixes etc for those who cannot or do not wish to migrate to the newer template approach.

Please see the recent changes listed in the github releases page

Features

The layer provides

  • Network ACKs: Efficient acknowledgement of network-wide transmissions, via dynamic radio acks and network protocol acks.
  • Updated addressing standard for optimal radio transmission.
  • Extended timeouts and staggered timeout intervals. The new txTimeout variable allows fully automated extended timeout periods via auto-retry/auto-reUse of payloads.
  • Optimization to the core library provides improvements to reliability, speed and efficiency. See RF24 library documentation for more info.
  • Built in sleep mode using interrupts. (Still under development – enable via RF24Network_config.h)
  • Host Addressing. Each node has a logical address on the local network.
  • Message Forwarding. Messages can be sent from one node to any other, and this layer will get them there no matter how many hops it takes.
  • Ad-hoc Joining. A node can join a network without any changes to any existing nodes.

The layer does not provide

How to learn more

Additional Information & Add-ons

Topology for Mesh Networks using nRF24L01(+)

This network layer takes advantage of the fundamental capability of the nRF24L01(+) radio to listen actively to up to 6 other radios at once. The network is arranged in a Tree Topology, where one node is the base, and all other nodes are children either of that node, or of another. Unlike a true mesh network, multiple nodes are not connected together, so there is only one path to any given node.

Octal Addressing and Topology

Each node must be assigned an 15-bit address by the administrator. This address exactly describes the position of the node within the tree. The address is an octal number. Each digit in the address represents a position in the tree further from the base.

  • Node 00 is the base node.
  • Nodes 01-05 are nodes whose parent is the base.
  • Node 021 is the second child of node 01.
  • Node 0321 is the third child of node 021, an so on.
  • The largest node address is 05555, so up to 781 nodes are allowed on a single channel. An example topology is shown below, with 5 nodes in direct communication with the master node, and multiple leaf nodes spread out at a distance, using intermediate nodes to reach other nodes.

How routing is handled

When sending a message using ESBNetwork::write(), you fill in the header with the logical node address. The network layer figures out the right path to find that node, and sends it through the system until it gets to the right place. This works even if the two nodes are far separated, as it will send the message down to the base node, and then back out to the final destination.

All of this work is handled by the ESBNetwork::update() method, so be sure to call it regularly or your network will miss packets.

Starting up a node

When a node starts up, it only has to contact its parent to establish communication. No direct connection to the Base node is needed. This is useful in situations where relay nodes are being used to bridge the distance to the base, so leaf nodes are out of range of the base.

Directionality

By default all nodes are always listening, so messages will quickly reach their destination.

You may choose to sleep any nodes on the network if using interrupts. This is useful in a case where the nodes are operating on batteries and need to sleep. This greatly decreases the power requirements for a sensor network. The leaf nodes can sleep most of the time, and wake every few minutes to send in a reading. Routing nodes can be triggered to wake up whenever a payload is received See ESBNetwork::sleepNode() in the class documentation, and RF24Network_config.h to enable sleep mode.