Raspberry Pi/Linux with the nrf24l01+ & RF24Gateway

 A guide/example of advanced RF24/nrf24l01+ usage and monitoring on Linux devices

Overview:

There are many examples of basic RF24 usage, but not so many demonstrating complex communication scenarios and networking. The RF24 communication stack is free, with all development information, examples, code and documentation available on GitHub, designed with Arduino and RaspberryPi/Linux devices in mind.

The RF24 stack generally follows the OSI model, and provides a separate library for each layer, with efforts toward proper documentation for each layer. This allows any type of data/communication to pass over the radios, including TCP, UDP or any other protocol, and users can write their own code to link devices together using any layer(s).

So, what can we really do with these little radios?

The nature and low-cost of the system allows literally anybody with interest in wireless communication to setup, deploy, and experiment with small scale, self-healing wireless networks, or start writing their own code with the core RF24 driver, in a very short period of time.

The stack currently does not include sensor specific code or functionality, it is simply a communication stack which enables all kinds of different functionality.


Requirements, Hardware Setup & Installation:

1. A Raspberry Pi or Linux device a compatible radio device connected
    RPi Install Script

2. An Arduino device with a compatible radio device connected
    Arduino Install (Select RF24, RF24Network, RF24Mesh, RF24Ethernet libraries)

See the RF24 docs for hardware setup info & installation
Note: Please report any issues at https://github.com/TMRh20/RF24/issues

Demonstration and Information:

The video below demonstrates how to use RF24Gateway in general - Setting up nodes and communicating over RF24 using RF24Network, RF24Mesh, and standard protocols (ICMP, HTTP, SSH), along with monitoring

1. Config on RPi & Arduino devices
2. Complex mesh networks: How the different layers (RF24Network,RF24Mesh & RF24Ethernet) can be used with RF24Gateway
3. RF24Ethernet: Simple TCP/IP communication and web server running on Arduino over RF24
4. RF24Mesh: Node config & interaction with RF24Gateway
5. RF24Network: Node config & interaction with RF24Gateway
6. How to use WireShark to monitor user payloads with RF24Gateway and LUA Wireshark dissector script (using laptop w/SSH & X11 forwarding in this example)
7. How to configure Raspberry Pi as a standard node in an existing RF24Mesh
8. How to sniff RF24Network, RF24Mesh, and RF24Ethernet traffic using RF24Gateway & Wireshark(optional)
9. Tacos... oops they were already eaten, maybe next time

As shown in the video, any nodes running RF24Ethernet, RF24Mesh or RF24Network can be used with a master node running RF24Gateway, allowing users to try out or utilize the different layers quite easily.

RF24Ethernet: Provides TCP/IP communication. Very simple and reliable way to control on/off devices via a web browser or scripting. Has all functionality of lower layers.

RF24Mesh: Provides automatic (mesh) networking for RF24Network. RF24Mesh networks are self-healing and dynamic in nature.

RF24Network: Provides addressing, routing, fragmentation/reassembly of payloads via manual/statically defined wireless networks.

See the detailed overview and related pages at http://nrf24.github.io/RF24Ethernet

A Smaller Custom Arduino Quadcopter

The new 13.5" (34cm) custom quad             

  I've enjoyed building and flying my first custom Quadcopter based on an Arduino and FreeIMU, so decided to build another smaller version. The original really needs some wide open spaces to open up and fly, and I wanted something I could fly in more confined areas. This one is quite a bit smaller, measuring in at 13.5" compared to 21" and is much lighter. It is very similar to the first electronically, but uses a GY-86 module and Arduino Nano for the FC board. The IMU module has a gyro, barometer, compass, and accelerometer. It uses the same APC220 transceiver for control, but a standard RC unit is recommended in most cases.

Video from one of the initial test flights 

  As seen in the pics, the FC board is very simple, and I used the complex design method of 'connect the dots'. Just below the orange transceiver, jumpers can be seen which are used to disconnect it from the hardware serial port when connecting to USB for programming. The other pins shown just beside the Arduino are for connecting the ESCs, one of which powers the board. The Nano is mounted on header pins, so can be easily removed. This one was modelled somewhat after the first, but uses 10mm square carbon fiber booms and no aluminium mounts. The setup in MultiWii is pretty much the same, but with the GY-86 chosen under sensor definitions.

  The 1.5mm sheet was cut into two squares measuring 1.75" x 5" for the main body, and holes were drilled through the booms to bolt them directly between the sheets. Drilling through the booms may not provide the most strength, but with a small well balanced quad, I'm hoping it will hold up. The motor mounts required both a top and bottom plate as well due to the thin layer of carbon fiber in the centre of the boom. Drilling through the carbon fiber sheets completely dulled a standard drill bit as well.

  The two quads side-by-side

  A quick test flight with a 3S 1000maH battery and 3-blade 5045 props provided about 6 minutes of casual flight time, but it should be better with a 2S battery and 6" props according to eCalc. The tool also says the props will stall, but it hovers and moves nicely so not sure about that. The FC board is attached directly to the frame using some nylon standoffs, but vibration is minimal after balancing.

  I had a lot of difficulty trying to balance such small props individually, so admitted defeat and went directly to dynamic balancing. I came across laser balancing in this video and I always keep some spare lasers around (who doesn't?) so I tried it, and the balance was the best I've achieved. I balanced the motors before adding the props/adaptors and re-balancing.

 

  I had a few issues with these motors, since the mounts are a bit flimsy, and will break if there is excessive vibration. I've since attached the motors using hard rubber between the metal mounts and the carbon fiber to provide some give, and it seems to be working ok so far. Something also seems to have gotten into one of them, tearing apart the wiring, but it was easy to rewind with new magnet wire. Luckily, I bought 5 motors, but I may need to purchase a different type of motor if troubles keep popping up.

Main Parts List:

Quad:

4X HobbyKing Donkey ST2004-1550kv Brushless Motor

4X Propeller Adaptor (Colet Type) 3MM

2X Counter Rotating Three Blade 5x4.5 Propeller

2X Counter Rotating Three Blade 6x4.5 Propeller

4X Turnigy Multistar 10 Amp Multi-rotor Brushless ESC

2X 1000mAh 3S 25C Lipo Pack

2X 1000mAh 2S 25C Lipo Pack

1X 10mm Carbon Fiber Square Tube - 750mm

1X Woven Carbon Fiber Sheet 300x100 (1.5MM Thick)

FC Board:

1X Arduino Nano

1X GY-86 10DOF IMU Module: MS5611 HMC5883L MPU6050

1X APC220 Wireless Serial Data Module

FC Board PinOut:
pin3: front motor
pin9: rear motor
pin10: right motor
pin11: left motor
A4: GY-86 SDA
A5: GY-86 SCL
TX: APC220 RX
RX: APC220 TX