Sense Beacon

A low-powered environmental sensing device, which combines LoRaWAN™ for long range data transmission and Bluetooth LE for presence announcement, and device maintenance.

The Sense Beacon is designed to utilise a NRF52 micro-processor with my ‘Xbee Format’ LoRaWAN™ module (based on the RN2483). This provides a platform that, not only, can communicate over long distances, but also communicate locally. The purpose of the BLE communication (provided by the NRF52) is to provide a short-ranged beaconing service based on Eddystone. Two Eddystone frame types are used, the TLM frame provides telemetry data (voltage/time alive/soc temperature) and the UID frame is registered with the Google Beacon Platform to provide proximity based information.

The Sense Beacon uses an RTOS to periodically take environmental readings from I2C sensors and, once a number of samples have been taken, transmit these over LoRaWAN™; the RTOS also maintains the Eddystone beaconing. The code can identify and appropriately handle a variety of network issues, has exponential back off with jittering when attempting to resend messages and takes precautions for thread safety.

Upon power-on the beacon briefly enters a period whereby a user can reconfigure many of the settings of the sense device; if a user is connected to the sense device it will remain in this state until configuration is complete - after this the battery must be removed and re-inserted to re-enable device configuration.

The power efficiency of the device allows it to run from a single coin cell battery, but external pin-outs are provided in case a larger battery is required for current-hungry sensors. Whilst I intend the Sense Device to use LoRaWAN™, the Xbee header does provide the ability to swap this device out for Zigbee / other XBEE format daughterboard.

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