Lab setup of the Largest sensor system by Defsystem.

After our smallest system in the previous article, it is time to show our largest system so far. Sadly, we are not allowed to show the final image of the full system. So a picture of a lab setup has to suffice. Also, the contracts prevents us of giving more detailed information on the sensors used.

But let us at least give an abstract description of it. (There is also a tabular list of the following at the end of the article.) This is a sensor device for an automated IoT device consisting of ten environmental sensors and four controllable power sockets to activate environmental control measures. It is provisioned via Bluetooth (BLE) and communicates with a REST backend over Wi‑Fi via HTTPs and schema-based JSON (based on RelaxNG/json-rnc) to report sensor readings and to retrieve commands from a controlling smartphone application (developed by a different party) to control the actors and to calibrate the more complicated sensors.

Fault tolerance and gracefull degredation

The system is designed and tested to be fail-safe. It degrades gracefully. That is, if any component is compromised, disconnected or otherwise not working, the rest of the sensors and actors are still used and the rest of the system continues to work as good as possible with the remaining components.

Break down of the properties in tabular list

• ten environmental sensors
• four controllable power sockets to activate environmental control measures
• network access via Wi‑Fi
• Wi‑Fi provisioned via Bluetooth (BLE)
• communication with a REST backend over Wi‑Fi via JSON and HTTPs
• JSON protocol based on RelaxNG schemas (json-rnc)
• sends sensor readings to backend
• retrieves commands from a controlling smartphone application (from a different party) to control the actors and to calibrate the more complicated sensors
• some sensors connected via one wire bus
• most sensors and actors connected via I2C bus with libraries completely written in uLisp®

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