The Nordic nRF24 is a family of silicon integrated radio transceivers operating in the 2.4GHz band, the most popular one being the nRF24L01. This is the core element of some extremely cheap module boards available in online stores like eBay, Aliexpress and Banggood.
These boards do not provide WiFi (801.11) or Bluetooth connectivity (both in the 2.5GHz band), but they can be used to establish custom wireless networks between small electronic devices, including Arduino, RaspberryPi and Particle (formerly known as Spark).
Whenever we talk about networks you must take in account a few key aspects of networking, one of the most important being the network topology.
During this series we will aim to establish a star network between a series of Arduino based peripheral nodes and a central hub node, being either a RaspberryPi or a Particle Core/Photon: this represents a basic but invaluable configuration allowing for complex elaborations on remotely collected information, either on premise (RPi) or in the cloud (Particle).
If this series gets enough attention I might invest some more time and extend it to cover more complex topologies like tree and mesh, with the latter being my favorite and, IMHO, most valuable for inexpensive IoT projects.
To keep things simple our peripheral nodes will be only collecting button presses, communicating to the central hub whenever a button gets pressed: the central hub will periodically (once every
30 seconds) print out the amount of button clicks it has received with a breakdown for each node; something like:
Received 14 clicks in the past 1 minute(s) * 5 click(s) from node A * 2 click(s) from node B * 7 click(s) from node F
This will obviously represent just an example of what you will be able to do from the hub node; nothing prevents you, as an example, from pushing data into a database and generating graphs. You could aggregate the data differently or, more likely, collect other types of data from your sensor nodes: I’m not here to place constraints to your imagination!
Keep in mind though, the little radio transceivers we are using have a few limitations that are commonly misunderstood, which will be analyzed when we get there during the project.
This walk through will be split into the following posts: