Our project Tiles, little BLE-connected platforms for customer interaction tracking, is entering a project phase which allows me to blog and inform you a bit more. Since yesterday night, the Raspberry PI and Arduino in the hub uses one power source. This makes the overall design easier. We also have been working on a Raspberry PI B+ hat, using Eagle, to further optimize our design.
One visible change is also that it now blinks :-) The hub rotates an LED light to signal the BLE scanning process. It flashes once you liftup the product, well, the apple in this case.
We’ve now also locked down the architecture and below is a rough sketch that should help understand it. Again, a quick summary below.
- “Tiles” are the wirelessly connected platforms. We use Punchthrough’s LightBlue Bean and remove the battery holder to make the platforms 8mm high. We still use CR2032 batteries, which gives us about 1 week battery life right now. We would get more, but I send our a MetaEvent every 10sec which is hard on the battery.
- The “Hub” collects all data. It scans for tiles, continuously, and connects. The hub runs on the raspberry pi, uses a BLE dongle (choice is key here) and uses node.js for all programming. It sends on data to the server with CoAP – a UDP-based IoT protocol.
- The “Server” collects all data for all hubs (yep, there can be many) and provides the necessary APIs for managing the User/Tile association, authentication and authorization (Oauth2 used here), etc.
One more thing – I’ve connected the server to Xively, a data logging platform. We collect mainly the battery rundown to estimate battery life and also the temperature values from the lightblue beans. At this point I just want to share some nice graphs to show you how much sense it makes to track that data. It will definitely help us to optimize the design / battery consumption further. Right now we stay optimized for demo purposes, but we can later reduce the events sent for example to get a better battery life.