This is a demo Dragino LoRa Mini Dev featuring LoRa® technology client (based on one of the examples from Arduino-LoRa) that uploads telemetry data to my AdaFruit.IO and Azure IoT Hubs Windows 10 IoT Core on Raspberry PI proof of concept (PoC) field gateways.

Bill of materials (Prices Sep 2018)

• Draguino LoRa MiniDev USD23
• Seeedstudio Temperature&Humidity Sensor USD11.50 NZD20
• 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

The code is pretty basic, it shows how to pack the payload and set the necessary RFM9X/SX127X LoRa module configuration, has no power conservation, advanced wireless configuration etc.

The Grove 4 pin Male Jumper to Grove 4 pin Conversion Cable was a quick & convenient way to get the I2C Grove temperature and humidity sensor connected up.

/*
  Adapted from LoRa Duplex communication with Sync Word

  Sends temperature & humidity data from Seeedstudio 

  https://www.seeedstudio.com/Grove-Temperature-Humidity-Sensor-High-Accuracy-Min-p-1921.html

  To my Windows 10 IoT Core RFM 9X library

  https://blog.devmobile.co.nz/2018/09/03/rfm9x-iotcore-payload-addressing/

*/
#include
#include
#include
const int csPin = 10;          // LoRa radio chip select
const int resetPin = 9;       // LoRa radio reset
const int irqPin = 2;         // change for your board; must be a hardware interrupt pin

// Field gateway configuration
const byte FieldGatewayAddress[] = "LoRaIoT1";
const float FieldGatewayFrequency =  915000000.0;
//const float FieldGatewayFrequency =  433000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int PayloadSizeMaximum = 64 ;
char payload[PayloadSizeMaximum] = "";
const byte SensorReadingSeperator = ',' ;

// Manual serial number configuration
char DeviceId[] = {"LoRaMiniDev5"};

const int LoopSleepDelaySeconds = 10 ;

void setup() {
  Serial.begin(9600);
  while (!Serial);

  Serial.print("LoRa Setup-");
  Serial.println( DeviceId ) ;

  // override the default CS, reset, and IRQ pins (optional)
  LoRa.setPins(csPin, resetPin, irqPin);// set CS, reset, IRQ pin

  if (!LoRa.begin(FieldGatewayFrequency))
  {
    Serial.println("LoRa init failed. Check your connections.");
    while (true);
  }

  // Need to do this so field gateways pays attention to messsages from this device
  LoRa.enableCrc();
  LoRa.setSyncWord(FieldGatewaySyncWord);  

  //LoRa.dumpRegisters(Serial);
  Serial.println("LoRa Setup done.");

  // Configure the Seeedstudio TH02 temperature & humidity sensor
  Serial.println("TH02 setup");
  TH02.begin();
  delay(100);
  Serial.println("TH02 Setup done");  

  Serial.println("Setup done");
}

void loop()
{
  int payloadLength = 0 ;
  float temperature ;
  float humidity ;

  Serial.println("Loop called");
  memset(payload, 0, sizeof(payload));

  // prepare the payload header with "To" Address length (top nibble) and "From" address length (bottom nibble)
  payload[0] = (strlen(FieldGatewayAddress)<<4) | strlen( DeviceId ) ;
  payloadLength += 1;

  // Copy the "To" address into payload
  memcpy(&payload[payloadLength], FieldGatewayAddress, strlen(FieldGatewayAddress));
  payloadLength += strlen(FieldGatewayAddress) ;

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], DeviceId, strlen(DeviceId));
  payloadLength += strlen(DeviceId) ;

  // Read the temperature and humidity values then display nicely
  temperature = TH02.ReadTemperature();
  humidity = TH02.ReadHumidity();

  Serial.print("T:");
  Serial.print( temperature, 1 ) ;
  Serial.print( "C" ) ;

  Serial.print(" H:");
  Serial.print( humidity, 0 ) ;
  Serial.println( "%" ) ;

  // Copy the temperature into the payload
  payload[ payloadLength] = 't';
  payloadLength += 1 ;
  payload[ payloadLength] = ' ';
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(temperature, -1, 1, &payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += sizeof(SensorReadingSeperator) ;

  // Copy the humidity into the payload
  payload[ payloadLength] = 'h';
  payloadLength += 1 ;
  payload[ payloadLength] = ' ';
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(humidity, -1, 0, &payload[payloadLength]));  

  // display info about payload then send it (No ACK) with LoRa unlike nRF24L01
  Serial.print( "RFM9X/SX127X Payload length:");
  Serial.print( payloadLength );
  Serial.println( " bytes" );

  LoRa.beginPacket();
  LoRa.write( payload, payloadLength );
  LoRa.endPacket();      

  Serial.println("Loop done");

  delay(LoopSleepDelaySeconds * 1000l);
}

In the debug output window the messages from the device looked like this

09:53:05-RX From LoRaMiniDev5 PacketSnr 9.3 Packet RSSI -65dBm RSSI -109dBm = 11 byte message "t 16.8,h 98"
 Sensor LoRaMiniDev5t Value 16.8
 Sensor LoRaMiniDev5h Value 98
 AzureIoTHubClient SendEventAsync start
 AzureIoTHubClient SendEventAsync finish
The thread 0xba0 has exited with code 0 (0x0).
The thread 0xb24 has exited with code 0 (0x0).
09:53:15-RX From LoRaMiniDev5 PacketSnr 9.3 Packet RSSI -65dBm RSSI -108dBm = 11 byte message "t 16.7,h 98"
 Sensor LoRaMiniDev5t Value 16.7
 Sensor LoRaMiniDev5h Value 98
 AzureIoTHubClient SendEventAsync start
 AzureIoTHubClient SendEventAsync finish
The thread 0x76c has exited with code 0 (0x0).
The thread 0x91c has exited with code 0 (0x0).

Then in my Azure IoT Hub monitoring software

The dragino LoRa Mini Dev with an external antenna connector would be a good indoor data acquisition node for student project when powered by a 2nd hand cellphone charger.