IoT – exploration of LoRa – part 1

This series documents a set of experiments to explore LoRa for a telemetry application. Note this is simple multipoint to point LoRa, it does not use LoRaWAN.

The block diagram above shows the information flow between the main elements.

Above is the sensor client end of the system. The prototype sensor is a BME280 digital temperature, humidity and pressure sensor connected by I2C to a 3.3V 8MHz Arduino Pro Mini which drives a inair9b SX1276 based LoRa wireless module. The payload is binary coded for efficiency of the radio link.

The LoRa – RESTful gateway above is implemented using a Wemos D1 mini ESP8266 module (on the underside of the stack) and a Hallard RF95 LoRa shield to suit. The ESP8266 connects to the Internet by WiFi and submits sensor data by REST to Thingspeak.


Above is a screenshot of the three measurement channels from Thingspeak.

Neither of the LoRa modules used TCXOs, so their frequency stability was not good enough for evaluation of low rate / long distance modulation types. A couple of RF95TW modules with better stability are on a slow boat from China.