The RF24 Wireless Communication Stack: Communication, Consistency & Exploits
Using RF24Ethernet & RF24Gateway for an IoT Network
RF24Ethernet & RF24Gateway are two complimentary software libraries for Arduino that allow users to quickly design, develop & implement IoT networks that utilize TCP/IP for general communication. They use the Arduino Ethernet client/server APIs, so anyone with minimal programming experience can construct and deploy an IoT network in short order.
Recently, we discovered a buffer overflow in RF24Network that affected nearly the entire communication stack on Arduino devices. This buffer overflow was "externally triggered", meaning that an external user or system would need to send a certain packet type to a device to trigger the buffer overflow. It doesn't occur under "normal" operation of the system.
The interesting thing about this, is that my devices have been susceptible to this overflow for a long time, and there has been near-daily attempts to disrupt my network. It seems that somebody nearby has a LOT of time on their hands, and a penchant for causing problems.
The good part of this is RF24Mesh, the part of the RF24 Comm Stack that keeps things working, almost no matter what. RF24Mesh is a wireless-mesh system for the comm stack that provides addressing, DHCP type protocols, and self-healing/management of the network. With RF24Mesh involved, the network typically remains stable, despite the constant attacks.
The exploit in RF24Network has now been patched, so users are encouraged to update as soon as possible.
As far as the rest of the stack goes, everything is coming together with support for nRF52 and nRF54 radios, which now work with the comm stack. I have a little bit of work remaining in this regard, but basic support for these radios has been incorporated throughout the stack in the latest releases.
A chart of ping response times for one node on the network using NodeRed
There are a lot of different uses for this system, from monitoring, to managing and collecting data from sensors, to remotely controlling devices, etc. and it is very flexible and standardized. I've been using the NodeRed system with MQTT mainly for my devices. MQTT is a standard protocol for messaging and IoT systems, so it is well suited to this type of thing.
For anyone interested in wireless IoT systems, I would highly recommend checking out RF24Ethernet/RF24Gateway. You can be up and running in minutes, with a closed system using just two Arduino devices & RF24Ethernet, or a fully fledged IoT setup, using a Raspberry Pi/Linux for a gateway and a number of Arduino nodes running RF24Ethernet.
Setting up direct TCP/IP connectivity between Arduinos using a nRF24 or nRF52 radio link w/RF24Ethernet
Utilizing the new functionality of the RF24Ethernet library
With some recent experimentation and prototyping involving the lwIP IP Stack, I was able to modify the RF24Ethenet library to function standalone, without the need for a Linux/Raspberry Pi device running RF24Gateway. This allows users to directly connect multiple Arduino devices using the RF24Ethernet library, utilizing TCP or UDP protocols to communicate between devices.
The RF24Ethernet library API is based on the official Arduino Ethernet API, so users utilize the same coding style to communicate over nRF24 or nRF52 radio links.
Setting things up:
1. The first thing to do is verify you have working radios. With nRF52 devices, they are built-in so, there is not much to worry about, but with nRF24 radios, users need to keep in mind power supply and wiring issues, so testing using the official gettingStarted sketch included with the RF24 library is recommended before attempting this.
2. Install RF24Mesh and its dependencies from Arduino Library Manager
3. Install the RF24Ethernet library from ZIP from https://github.com/nRF24/RF24Ethernet/tree/lwIP Note: Once deployed, the updated library will be available from the Arduino Library Manager. Users may need to uninstall/reinstall to get the latest updates at that time.
4. Install the Arduino lwIP library using the Arduino Library Manager as required for non-ESP32 & non-ESP8266 devices which already include lwIP.
5. Run the included examples from the Headless directory in the RF24Ethernet examples on two devices. I've tested so far on Arduino Due, ESP8266, ESP32 and nRF52 based devices. The RPi Pico still utilizes the uIP stack due to technical issues using lwIP with the Arduino MBED based core.
What to expect:
The main server example sets up a RF24Mesh 'Master Node' which handles addressing and address look-ups for all other nodes. Nodes not in range of the Master Node will attempt to connect automatically via routing traffic through other connected nodes.
The client examples simply connect to the Master Node and request an HTML based web-page.
In a real life deployment this activity may be reversed. With the Master Node running a modified Client example, and sensor or other nodes running modified Server examples, the Master Node could then connect to each device in turn and retrieve data as required.
To designate a master node, simply call the following before calling mesh.begin()
mesh.setNodeID(0);
then from the main loop()
mesh.DHCP();
Things to Note:
RF24Ethernet makes use of two separate IP Stacks, the older, unmaintained uIP Stack works on smaller devices like Uno, Nano, Mega, etc, while the newer, lwIP stack is used automatically for devices >50MHz CPU speed, including the Arduino Due, ESP32, ESP8266, and nRF52 based devices using the nrf_to_nrf radio library.
To ensure you are using the lwIP stack, users can #define USE_LWIP 1 & #define RF24ETHERNET_USE_UDP 1 in the RF24Ethernet.h file or prior to compilation.
The nrf_to_nrf Radio Library for nRF52x Devices and nRF24L01 Compatible Communication.
A brief tutorial on payload sizes & handling
Max Payload Sizes: The nrf_to_nrf Core Library
The nrf_to_nrf library allows many configuration options, but here I want to talk about payload sizes and communication using the core nrf_to_nrf library, as well as that in combination with RF24Network and higher libraries.
The max payload size of the nRF52840s is 127 bytes. This is with CRC disabled and static payload sizes. The radios support 0, 8, 16 or 24-bit CRC, so that extra data takes up 0, 1, 2 or 3 bytes depending on your chosen options. nRF24 devices only support 0, 8 or 16-bit CRC, so users are limited in their selection when communicating with nRF24 devices.
Similarly, the nRF24 will only handle 32-bytes maximum payload size, with any CRC value and either static or dynamic payloads. The nRF52x devices are slightly different, so one needs to be aware how changing these options affect the max payload size.
The above is with the core nrf_to_nrf driver. Once we get into libraries like the RF24Network library, another 8-bytes of data are required for the network header, which contains information like the destination address, sender address, and a counter.
This means that when communicating solely between nRF52 devices, we almost always want to configure the max payload size to 123, since RF24Network will figure out the max payload size based on this information, and fragment payloads accordingly. By default RF24Network is nRF24 compatible, so only is configured to handle 32-byte payloads.
To configure RF24Network, before calling network.begin(); we want to call radio.begin(); followed by radio.enableDynamicPayloads(123); This will allow maximum payload sizes prior to fragmentation.
The same is true when using the RF24Mesh library, call radio.begin(); followed by radio.enableDynamicPayloads(123); prior to calling mesh.begin();
If using encryption, the RF24Network layer will take this into account, so the max payload sizes with RF24Network are as follows:
Max Payload Sizes in RF24Network:
1. RF24Network, default: 24 bytes before fragmentation, 144 bytes with fragmentation
2. RF24Network, w/enableDynamicPayloads(123): 115 bytes before fragmentation, 144 bytes with fragmentation
3. RF24Network, w/enableDynamicPayloads(123) + enableEncryption = true: 103 bytes before fragmentation, 144 bytes with fragmentation
So we've been putting in a bunch of work lately on the RF24/NRF52x communication stack for Arduino, and surprisingly, given the age of the libraries, we were able to make a number of changes that significantly impact the performance of the network and mesh.
RF24Mesh:
1. Utilize all poll requests.
The prior behavior of the mesh was to send out a poll request via multicast and gather the responses. Then the mesh layer would attempt to request an address via one of the nodes that responded to the poll. If this failed however, the node would continue on and send out another poll. The current behavior now utilizes up to 4 received poll responses and loops through them all until either failure or a successful address request is made before moving to the next multicast level and sending out another poll request.
2. Enhance the ability to verify connectivity
The prior behavior of the mesh was to call `getAddress(_nodeID);` and verify its own address with the master node. The call would fail if anything but a successful address response was received. Now there is some logic added to return immediately if the address is not found in the master list or is default. It will also return immediately if the nodes address has been zeroed out. Retries will take place if the request failed or timed out. Finally, the node actually verifies that the received address matches its own address.
Update: I am currently testing a new method of connection checking, where each node only contacts their parent node instead of the master node. This appears to reduce traffic, increase connection times, and improve the overall stability of the mesh.
It may not seem like much, but the changes should tend to reduce network traffic, while providing more seamless mesh operation.
RF24Network:
1. Fix error sending data
Per the RF24 documentation and behavior, when using some of the advanced write functions, there is a need to call `radio.txStandby()` if a write fails, otherwise the radio will essentially hang and all subsequent writes will fail. This was partially missed in RF24Network, so a call has been added when an auto-ack payload fails. This should improve reliability and consistency in sending data.
RF24:
1. Interrupt enhancements.
The use of interrupts on Linux platforms like the Raspberry Pi has been greatly improved and no longer requires root access to operate. Unlike the RF24 library, the interrupt functionality uses GPIO pin numbers instead of BCM pin numbers. ie: Use GPIO 24 instead of pin 18.
RF24Ethernet
1. Fix re-transmit mechanism
The associated UIP IP stack incorporated with RF24Ethernet uses a retransmit mechanism when acks are not received etc, but it was not working. This is now fixed and results in much more reliable, longer connectivity with MQTT, HTTP and other protocols & applications that transmit data.
All in all its been a good year for the RF24/NRF52x communication stack, with support also recently added for Nordics NRF52x SOCs, there are so many potential ways these libraries can be configured! Encryption and authentication features are also available with the newer radio modules, which will easily handle audio streaming and more advanced functionality.
Comes with preconfigured devices, just plug and play!
I've finally decided to put together some electronics kits with preconfigured devices, using the RF24 communication stack. As the system is now very stable and reliable, I think it is about time I started putting devices together and selling them to support future development and designs.
The current kit will come with a RPi4B and all the attachments like HDMI cable, a case, and power supply along with 3 Arduino Uno R3, 2 temperature & humidity sensors and 1 RBG LED ring, plus of course the RF24 radios. I've also designed some custom PCB shields for everything to just plug into, with power for the radios and extra capacitors, so its super simple to put it all together.
The setup uses Node-Red and RF24Gateway to provide a mesh network that seamlessly links all your devices together, and allows you to add custom devices to the network and/or expand the network by purchasing more devices or setting them up yourself with the Arduino platform.
If they sell, I intend to design more devices to go with the currently available products.
What are the different layers and which one do I use?
Over the past number of years, I've been developing a communication stack for nrf24l01+ radios, generally to be used with Arduino and Raspberry Pi devices. The comm. stack is organized into separate layers, per the OSI model, which allows users to establish communication between any number of devices depending on their needs.
1.The RF24 layer: This layer is generally used for simple device-to-device communication, where speed and simplicity are key. One example is for radio control of a single device, where a stream of small data packets are communicated from one device directly to another in rapid succession. Streaming of audio in real-time is another example where the RF24 layer would be used directly. Using the RF24 layer can be a bit complex, and some knowledge of radio communication is beneficial.
2. The RF24Network layer: This layer expands on the RF24 layer by providing a number of features, both to enhance radio communication and provide users with the features of an OSI layer 3 (network) layer. RF24Network nodes are arranged in a static tree topology, and this layer provides all the features to manage them. RF24Network handles routing, fragmentation/reassembly of large packets, and communication to any other device is straight-forward. Users don't require knowledge of the RF24 layer to operate a network of nodes at the RF24Network layer, and it can be much simpler than using the RF24 layer directly. Recommended when not able to use the RF24Mesh library, when there is a need for static nodes, or to simplify one-to-one communication.
3. The RF24Mesh layer: This layer expands on all underlying layers by providing an automated, self-healing network that allows nodes to move around and or re-establish connectivity as required. This layer is generally recommended when creating a network of devices, as it automates addressing for RF24Network, and provides a more seamless interaction. Users generally communicate using the RF24Network API, with RF24Mesh providing address lookups and automation for the network.
4. The RF24Ethernet/RF24Gateway layer: This layer allows communication using standard networking protocols, such as TCP, UDP, ICMP. It is generally recommended to run RF24Gateway on a Raspberry Pi as the master node, with smaller devices running RF24Ethernet. Allows very simple or very complex communication scenarios, with users requiring little to no knowledge of radio or RF24 programming APIs.
The RF24Ethernet API is very similar to the Arduino Ethernet API, and RF24Gateway allows users to use standard networking tools to communicate with devices running RF24Ethernet. Recommended for communication scenarios where speed is not essential, but reliability and consistency is, such as a home automation system using MQTT and Node-Red and/or a sensor network reporting data. Users can run a wireless, Arduino based webserver, or interact with nodes using their mobile device over MQTT, HTTP, etc.
As can be demonstrated, each layer has its place, providing communication capabilities for a very wide range of scenarios, and allowing users to benefit from the built-in features or to dig right in and customize things to the nth degree. Generally, the higher you go up in the stack, the simpler the interaction, with complex underlying code providing the simplest and most advanced user interaction.
RF24Mesh - Dynamic Mesh Networking for NRF24L01+ Radio Modules
An Overview of Progress so Far
Overview:
RF24Mesh is a C++/Arduino/Linux/Raspberry Pi library allowing many devices to simultaneously connect wirelessly and remain connected in a mesh style network using nrf24l01+ radio modules. Nodes can communicate with any other node on the network, including a master node that acts as a gateway for the mesh, providing addressing and lookups.
Once assigned a unique ID, everything is automated, and nodes can move around and rejoin the mesh at any point where another node is in range. RF24Mesh supports some of the smallest and most power efficient devices available.
The RF24 Communication Stack is based on the OSI model, and RF24Mesh makes use of the features of the lower layers (RF24 (Layer 2) , RF24Network (Layer 3), and the overall capabilities can be extended via RF24Ethernet (Layers 4&5 TCP/IP)
Setting it Up:
The main thing when setting up a mesh network is to configure and test your devices accordingly, to make sure they are in a fully operational state. Most if not all of the available radio chips being sold are clones, so I've found it necessary to modify the radio devices slightly in some cases. In many cases, a capacitor (10-100uF) is added directly to the VCC/GND of the module itself to help with common power supply issues.
In the case of these modules, I've found that scraping down the last bit of the antenna, and soldering on a small 3-4" piece of wire greatly improves their performance:
In the case of the high powered PA + LNA modules, I've found it necessary to add shielding as in the post found here. Placing them close to a ground plane seems to help as well. Operating them at a lower power level may be required if the power supply is not adequate.
The modules that are low powered with an antenna generally work out of the box.
I generally recommend using an adapter, to provide a stable power source, even for the low powered modules. I've been using them with many of my modules.
From there it is a matter of installing the Arduino libraries etc. which is covered in the documentation and in earlier blog posts and the official documentation below.
How it works:
RF24Mesh leverages the features provided in the supporting libraries, RF24 and RF24Network to provide connectivity between many devices, even if they are far away from the central node or moving around. Each node is assigned a unique identifier (1-255) and uses that high level-address to request a dynamic address at the network layer, according to the structure of the mesh and proximity to other devices in the mesh. Nodes typically communicate using the RF24Network API, with RF24Mesh working at a higher layer to provide address lookups, dynamic addressing and connectivity.
Nodes arrange themselves using a tree topology around the master node, which provides address lookups etc. for the mesh. At any given time, each node has a path of communication through the network, and can re-establish and verify a new link if the current path fails. In each network there is the master node (the base node), children of the master node (relay nodes) with children nodes themselves, and leaf nodes, (children of the master or its children) with no child nodes attached.
The protocol is fairly simple for each node. On power up or reset, nodes attempt to find a connection by using multicast. Multicasting is arranged into 5 levels, so the master node is contacted first, then its direct children, then their direct children and so on, making the way nodes attach themselves to the network tend towards close proximity to the master node in a tree-like structure. Once contact is made the node requests an address from the master node, either directly or through other nodes. Once an address has been assigned and verified, the node is considered connected to the mesh and can then communicate with all other nodes in the mesh, and beyond to other systems etc.
Nodes have the option of managing their connection however desired, and quite often, a simple timer is suitable to verify connectivity after a set period of time. Transmitting nodes can also detect when communication is failing and re-establish their connectivity to the mesh as required. That is, at any given time, nodes will have a single path to communicate over the network, but if that link fails, they can re-establish their communication path through the network.
The communication layers are interoperable, meaning a network can combine devices running RF24Network and RF24Mesh libraries together, with static nodes running RF24Network, and dynamic nodes running RF24Mesh. Devices running RF24Ethernet (TCP/IP) can also communicate using the other layers of the libraries, interacting directly with RF24Mesh and/or RF24Network nodes. This allows an array of devices to operate on the same wireless mesh network, from ATTiny all the way to the more powerful devices like ESP32 and Raspberry Pi, using the RF24Network, RF24Mesh APIs and/or standard networking tools and protocols. (ICMP/TCP/UDP, etc.)
Current status, testing etc.
RF24Mesh is now past the development/beta testing stage and considered (by me) to be stable and well tested. The mesh can handle a large number of nodes, theoretically up to 255, but in practice, more like 15-25 nodes sending or receiving data every few seconds is a reasonable bet. It generally depends on the type of traffic and frequency with which it is generated, as a much larger number of nodes reporting data every minute presents only a small load for the network.
The progress made with RF24Mesh is very encouraging, supporting simple communication scenarios, small household sensor networks, home automation systems, and larger expanded networks stretching over relatively long distances with the more powerful RF24 modules.
The RF24 communication stack is generally complete, with bug reports and issues dropping off quite nicely, but development is still ongoing. As always, please report any potential bugs or issues using the GitHub link below.
Or see the following for a video based description:
This is a quick tutorial on how to wirelessly control or monitor Arduino devices using nothing more than NRF24L01+ radio modules, a Raspberry Pi and a mobile device. I have found MQTT to be one of the best methods of controlling these devices wirelessly, in the case of simple input/output scenarios like monitoring sensor values or sending RGB values to wireless lighting systems.
This assumes users are familiar with the core RF24 library as well as installing libraries from the Arduino IDE, and building and running programs on the RPi.
Requirements:
Raspberry Pi with NRF24l01+ device attached
One or more Arduino devices with NRF24L01+ device attached
The RPi should be connected to the same network as your mobile device
Pre-configuration:
Ensure all devices are functional with RF24 core examples before attempting.
Install RF24 libraries on RPi from your home directory:
4. Follow the command prompts and install the RF24, RF24Network, RF24Mesh, and RF24Gateway libraries
Install RF24 libraries on Arduino:
1. From Arduino IDE select Sketch > Include Libraries > Library Manager
2. Install the RF24, RF24Network, RF24Mesh and RF24Ethernet libraries
RPi Setup:
Now that the correct libraries are installed, we need to install an MQTT broker on the Raspberry Pi. Setup is as easy as running the following command:
sudo apt-get install mosquitto
Note: As of mosquitto 2.0 you need to add listener 1883 andallow_anonymous true in mosquitto.conf.
Then we need to start the Gateway on the RPi, so it will pass traffic from the connected sensor nodes etc, to the MQTT server.
The RF24Gateway library is installed in ~/rf24libs/RF24Gateway/
In this example, we will use the ncurses example, located at ~/rf24libs/RF24Gateway/examples/ncurses
Edit the file RF24Gateway_ncurses.cpp and modify the radio constructor to suit your pin connections: RF24 radio(22,0); is the default, then type 'make -B' to build the example.
To run the example, type ' sudo ./RF24Gateway_ncurses ', and it should pop up asking for an IP and subnet mask to use. This is mainly arbitrary, and any suitable private IP/Mask can be selected.
Once the gateway is running, we can switch our attention to the Arduino.
Arduino Setup:
1. Open the MQTT example: File > Examples > RF24Ethernet > MQTT > mqtt_basic
2. Edit the radio constructor to suit your chosen CE/CS pins: RF24 radio(7,8); is default.
3. Edit the IP address of the device to match the range chosen when configuring the RPi.
4. Edit the IP of the gateway to match exactly the IP of the RPi
5. Edit the IP of the server to match exactly the IP of the RPI
6. Upload the sketch to the Arduino.
Note: If using an external MQTT server, the RPI must be configured to forward packets and perform NAT, see the forwarding and routing section here.
You should see serial output like the following:
Attempting MQTT connection...connected
If not, something has gone wrong. Ensure your device is connecting to the mesh and showing up in the address list. If not, troubleshoot using examples from RF24 or RF24Mesh to diagnose the connectivity issues.
Nodes running the MQTT example will publish their NodeID every second to the MQTT server, at outTopic and will receive all messages published to the inTopic.
Setup on iPhone etc:
On my iPhone, I chose to use the program MQTTTerminal (MQTTool is also good with no ads). Setup is easy, just input the external IP address of the MQTT server (the ip of your RPi) and the port (1883). Then set the Publish Topic to inTopic and the Subscribe Topic to outTopic.
You should see messages incoming from the device(s) and can send data to the devices from the app.
From here it is a simple matter of customizing the topics and messages to suit your needs, whether controlling a simple LED on the Arduino, or reporting temperature and humidity from sensors.
This can be expanded using programs like Node Red to create an open-source home automation system. See my more recent blog post.
RF24Ethernet - For DIY Internet of Things and Home Sensor Networks
Adding internet connectivity to RF24Networks using nrf24l01+ modules as ethernet cards
RF24Ethernet, What is it and how does it work?
For anybody not familiar with my blog, I have done a lot of recent work in improving the radio driver and related network library for NRF24L01+ radio modules, using Arduino and Raspberry Pi or using two or more Arduinos. These very inexpensive and feature-rich devices can be used to create your own home sensor network, with very little cost when compared to most available solutions.
RF24Ethernet will allow you to use a Raspberry Pi or Arduino as the 'gateway' machine to your network, and lets you connect to your sensors directly, using any device that has a web-browser, whether it is an iPod, PC, etc. or your sensors can connect out to the internet for information.
Current Libraries:
RF24 - OSI Layer 2 radio driver for nrf24l01+ modules
RF24Network - OSI Layer 3 network driver for RF24
RF24Ethernet - OSI Layer 4 Protocol (TCP/IP) driver for RF24Network
RF24Mesh - Mesh networking layer for RF24Network (Dynamic config and topology)
How it works: (Updated)
The RF24Ethernet library is currently in the testing phase, and uses the UIP TCP/IP stack.
The library has been modelled after the Arduino Ethernet library, allowing users to create web enabled, wireless devices, without having to learn the RF24 or RF24Network APIs. The addition of a real protocol (TCP) on top of RF24Network provides a level of simplicity, consistency and reliability beyond what was previously possible.
The IP address of each node needs to be statically assigned. Translation between RF24/RF24Network (MAC) addresses and IP addresses is handled in one of two ways, depending on the configuration. The default configuration uses ARP requests to find the correct node when TCP data is incoming, and users can optionally utilize RF24Mesh to provide MAC/IP translation and/or dynamic address assignment at the network layer.
Configuration/Testing: (Updated)
Configuration is now integrated directly into RF24Ethernet, with the RF24Network address specified as the MAC address, and this can be further automated by utilizing the RF24Mesh layer along with RF24Ethernet. Users have the option of creating a static network, or utilizing RF24Mesh to create a dynamic network with nodes capable of moving around physically or utilizing fail-over nodes. The RF24toTUN application running on a Raspberry Pi automatically performs discovery and routing for incoming TCP/IP data, so users only have to configure static IP addresses, and a unique identifier for each node when used with RF24Mesh.
Setup (Arduino & RPi):
RPi:
Install RF24, RF24Network, RF24Mesh & RF24toTUN libraries Note: RF24toTUN requires the boost libraries. Run sudo apt-get install libboost1.50-all a: wget http://tmrh20.github.io/RF24Installer/RPi/install.sh
b: chmod +x install.sh
c: ./install.sh (Note: This should be run without sudo or all your base files will belong to root) Arduino:
c: Install RF24Ethernet library
d: If using with a RPi, run any of the Getting_Started examples. You should be able to ping and connect to the remote Arduino.
e: If using with a SLIP interface (non-RPi) :
1. Run the SLIP_Gateway.ino example on the Arduino connected to the PC/MAC etc
2. Run the SLIP_InteractiveServer.ino example on another Arduino.
3. Once the SLIP interface is configured as per the examples, you should be able to ping and connect to the remote Arduino.
RF24Ethernet - Setup, config and demo
The initial proof of concept interface borrowed directly from the SerialIP library, using the uIP TCP/IP stack and uIP proto-sockets/proto-threads. Since testing was very succesful, the library has been developed to provide a simpler user interface, very similar to the Arduino Ethernet library. In its current form, a node running RF24Ethernet can act as a standard TCP server, and can function as a telnet or web server, by modifying the included example.
How can this be used?
The possibilities from here are virtually endless, with very inexpensive sensor networks being provided with direct TCP/IP connectivity. One of the more obvious applications involves simple retrieval of information from network or internet sources, such as the time or the current weather. Controlling a connected LED or other attached device can be as simple as opening a bookmark in your browser.
To take things a whole lot further, this could even allow RF24Network to be utilized as a bridge betwen LANs, using sensor networks for emergency commuinications etc, when main connections are down. Testing shows that speeds across the network are slightly better than or equivalent to a dial-up connection, so it seems to provide a practical solution for low-speed data transfers like sensor data, text-based email or chat.
Results of Testing:
The above picture presents an idea of the latency, etc when sending ping requests of varying sizes from the RPi master node to a connected sensor node.
Working with UIP TCP/IP stack has been a bit of a challenge to say the least, but things seem to be coming along nicely. The RF24toTUN library has been updated to route payloads according to the radio MAC address, so integration with RF24Network is coming along nicely. Support for the RPi to send fragmented multicast payloads has been added, so ARP requests are working nicely within RF24Network. This will allow full integration with RF24Mesh, to create a dynamic TCP/IP mesh sensor network if desired, with very little to no configuration needed by the user. I've commited the current code to a new branch (master_dev) to hold the new code until it is cleaned up and more functionality is added. Currently, it only supports incoming data connections as a simple server, and ICMP packets.
Update Nov30:
The Server and Client API to match the official Ethernet library is now in place and working for the most part. DHCP, DNS lookups and UDP in generall is not developed yet. There are still some bugs and oddities to work out, but overall, the TCP server and client seem to perform fairly well given the circumstances. Web client and server examples have been included.
Update Dec 7:
The library seems to be working very well now, and the API is about 95% complete. Most bugs have been addressed, with only a few minor issues left, generally surrounding timeouts during very large data transfers. The existing examples have been updated, and some new examples have been added, demonstrating a simple web server and interaction with a sensor node via a web browser.Some documentation has also been created and is linked below.
Update Dec9:
RF24Mesh has been integrated with RF24toTUN, to provide automated addressing and mesh support for RF24Ethernet. When building RF24toTUN, use 'sudo make install MESH=1' to compile with RF24Mesh support. If using with RF24Ethernet, see the new SimpleServer_Mesh.ino example for usage. An install script has also been created for RPi, to simplify installation of the various libraries.
Update Dec 14:
Updated RF24Ethernet to support SLIP or TUN devices as well. This requires RF24Mesh to perform MAC/IP translation. Two new examples have been added, SLIP_Gateway.ino demonstrates how an Arduino can act as a simple USB interface to any device that supports SLIP. SLIP_InteractiveServer demonstrates how to use RF24Ethernet and RF24Mesh with a SLIP or TUN interface.
Update Dec 28:
Modified the MAC address format due to issues with standards when using it on RPi/Linux. Modified the timing of uip restarts. Updated RF24toTUN to provide cmd line configuration for all major options including node addressing. Fixes and updates to RF24Network and RF24toTUN seem to have addressed some buggy behaviour.
Update Dec 30:
Todays latest updates should be applied along with the latest updates to RF24toTUN and RF24Network. The main change fixes corrupt client requests, which would have been noticed when establishing outgoing connections. The remaining changes revolve around reliability, the order of operations, and the timing of things, and seem to really bring RF24Ethernet closer to a stable, reliable library. Update Jan 2, 2015
This round of updates comes after a very long round of testing and coding. The RF24 library has been updated to provide even better timing, reliability and throughput. Changes to RF24Network improve fragmentation/reassembly. RF24toTUN has been updated to fully support all 3 datarates, and throughput has been improved for all speeds. RF24Ethernet has been updated to provide a timeout for connections, part of better handling for TCP window reopening and failures, and allows users to configure the periodic timer via uip-conf.h to provide faster transfers. These changes bring RF24Ethernet a lot closer to a stable release. Testing shows that these updates provide easily noticeable increases in reliability and speed at all levels, and updating all the mentioned libraries is recommended.
Update Jan 4, 2015
Added connection timeouts to recover from hangs during failed client donwloads, which adds improved reliability to the library. Added better TCP window management to prevent those hangs during client downloads, along with configuration options. Documentation updated to include new features and options.
Update Jan 16, 2015
Updated to v1.2b - Adds UDP and DNS support along with a pile of fixes and updates. Users should update RF24Network and RF24toTUN along with RF24Ethernet. This will be the final update to this blog post. See the documenation below or check back here at tmrh20.blogspot.com for additional posts.
