Data loggers are used to record data about the environment, for example, temperature or ground movement. However, to retrieve data from the data loggers, users have to physically retrieve the data logger. We thus proposed to build data loggers capable of wirelessly transmitting information to a collector.

When selecting a protocol, we considered both range and throughput. Although LoRa is one obvious choice due to the long range it supports, the maximum throughput is also less than 100kbps. As such, it would take an unreasonably long time to transfer large amounts of data. We thus used ESP-NOW for data transmission, a proprietary connectionless protocol by Espressif making use of 802.11 vendor-specific action frames. Empirically, we have achieved speeds of up to approximately 400kbps in ideal conditions (with the nodes next to each other), and approximately 200-300kbps when mounted on a UAV and flying over the ground nodes.

Future Improvements

At the moment, the nodes are not optimised for power at all. The GPS module and 2.4GHz radio is always on, drawing significant power. The ESP32 can be put into light sleep between samples to further reduce power consumption.