SparkFun Pro RF – LoRa, 915MHz Payload Addressing Client

Last week a package arrived from NiceGear with a SparkFun Pro RF – LoRa, 915MHz and some cables. With this gear I have built yet another client for my Azure IoT Hub and AdaFruit.IOLoRa Field Gateways.

Now that the device is running well, I’ll look at reducing power consumption and splitting the the payload packing code into a library. Also noticed an extra “,” on the end of a message so need to come up with a better way of doing the payload packing.

/*
  Copyright ® 2018 December devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>

#include <LoRa.h>
#include <avr/dtostrf.h>
#include "DHT.h"

#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const char DeviceAddress[] = {"SparkFunX1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int InterruptPin = 12;
const int ChipSelectPin = 6;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 10 ;

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;

#define DHTPIN 4     // what digital pin we're connected to

// Uncomment whatever type you're using!
//#define DHTTYPE DHT11   // DHT 11
#define DHTTYPE DHT22   // DHT 22  (AM2302), AM2321
//#define DHTTYPE DHT21   // DHT 21 (AM2301)

DHT dht(DHTPIN, DHTTYPE);


void setup()
{
  SerialUSB.begin(9600);
#ifdef DEBUG
  while (!SerialUSB);
#endif
  SerialUSB.println("Setup called");

  SerialUSB.println("LoRa setup start");
  
  // override the default chip select and reset pins
  LoRa.setPins(InterruptPin, ChipSelectPin); 
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    SerialUSB.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

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

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(SerialUSB);
#endif
  SerialUSB.println("LoRa Setup done.");

  // Configure the Seeedstudio TH02 temperature & humidity sensor
  SerialUSB.println("DHT setup start");
  dht.begin();
  delay(100);
  SerialUSB.println("DHT setup done");

  PayloadHeader((byte*)FieldGatewayAddress,strlen(FieldGatewayAddress), (byte*)DeviceAddress, strlen(DeviceAddress));

  SerialUSB.println("Setup done");
  SerialUSB.println();
}


void loop()
{
  float temperature = 17.2;
  float humidity = 75.0;

  SerialUSB.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity & battery voltage values then display nicely
  temperature = dht.readTemperature();
  humidity = dht.readHumidity();
  if (isnan(humidity) || isnan(temperature)) 
  {
    SerialUSB.println("Failed to read from DHT sensor!");
    return;
  } 
   
  SerialUSB.print("T:");
  SerialUSB.print( temperature, 1 ) ;
  SerialUSB.println( "C " ) ;
  PayloadAdd( "T", temperature, 1);

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

#ifdef DEBUG_TELEMETRY
  SerialUSB.println();
  SerialUSB.print( "RFM9X/SX127X Payload length:");
  SerialUSB.print( payloadLength );
  SerialUSB.println( " bytes" );
#endif

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

  SerialUSB.println("Loop done");
  SerialUSB.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader( byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadHeader- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif

  payloadLength = 0 ;

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

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

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-float ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value, decimalPlaces );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( char *sensorId, int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-unsigned int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = addressesLength + 1;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadReset- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif
}
  • SparkFun Pro RF – LoRa, 915MHz USD29.95 NZD49
  • Grove – Temperature & Humidity Sensor Pro (AM2302) USD9.90
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Moteino M0 Payload Addressing client

Last week a package arrived from LowPowerLab with some Moteino0 devices and accessories . With this gear I have built yet another client for my Azure IoT Hub and AdaFruit.IOLoRa Field Gateways.

It took me a while longer that usual to get the Motenio working as the sketch setup call appeared to hang in DEBUG builds.

After staring at the code for a while I noticed that I hadn’t changed LoRa.dumpRegisters method parameter from Serial to SerialUSB. A couple of hours lost due to a dumb typo by me.

Now that the device is running well, I’ll look at reducing power consumption and splitting the the payload packing code into a library.

/*
  Copyright ® 2018 November devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>
#include <avr/dtostrf.h>
#include <LoRa.h>
#include <TH02_dev.h>

//#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const char DeviceAddress[] = {"Moteino01"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = A2;
const int InterruptPin = 9;
const int ResetPin = -1;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 10 ;

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;


void setup()
{
  SerialUSB.begin(9600);
#ifdef DEBUG
  while (!SerialUSB);
#endif
  SerialUSB.println("Setup called");

  SerialUSB.println("LoRa setup start");
  
  // override the default chip select and reset pins
  LoRa.setPins( ChipSelectPin, ResetPin, InterruptPin ); 
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    SerialUSB.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

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

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(USBSerial);
#endif
  SerialUSB.println("LoRa Setup done.");

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

  PayloadHeader((byte*)FieldGatewayAddress,strlen(FieldGatewayAddress), (byte*)DeviceAddress, strlen(DeviceAddress));

  SerialUSB.println("Setup done");
  SerialUSB.println();
}


void loop()
{
  float temperature ;
  float humidity ;

  SerialUSB.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity & battery voltage values then display nicely
  temperature = TH02.ReadTemperature();
  SerialUSB.print("T:");
  SerialUSB.print( temperature, 1 ) ;
  SerialUSB.println( "C " ) ;

  PayloadAdd( "T", temperature, 1);

  humidity = TH02.ReadHumidity();
  SerialUSB.print("H:");
  SerialUSB.print( humidity, 0 ) ;
  SerialUSB.println( "% " ) ;

  PayloadAdd( "H", humidity, 0) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println();
  SerialUSB.print( "RFM9X/SX127X Payload length:");
  SerialUSB.print( payloadLength );
  SerialUSB.println( " bytes" );
#endif

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

  SerialUSB.println("Loop done");
  SerialUSB.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader( byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadHeader- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif

  payloadLength = 0 ;

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

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

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( const char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-float ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value, decimalPlaces );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( const char *sensorId, int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadAdd( const char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadAdd-unsigned int ");
  SerialUSB.print( "SensorId:");
  SerialUSB.print( sensorId );
  SerialUSB.print( " sensorIdLen:");
  SerialUSB.print( sensorIdLength );
  SerialUSB.print( " Value:");
  SerialUSB.print( value );
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  SerialUSB.print( " payloadLength:");
  SerialUSB.print( payloadLength);
  SerialUSB.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = addressesLength + 1;

#ifdef DEBUG_TELEMETRY
  SerialUSB.println("PayloadReset- ");
  SerialUSB.print( "To Address len:");
  SerialUSB.print( toAddressLength );
  SerialUSB.print( " From Address len:");
  SerialUSB.print( fromAddressLength );
  SerialUSB.print( " Addresses length:");
  SerialUSB.print( addressesLength );
  SerialUSB.println( );
#endif
}
Azure IoT Central

Bill of materials (prices as at November 2018)

  • Moteino M0 USD34.95
  • Seeedstudio Temperature and Humidity Sensor Pro USD11.50
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Arduino MKR1300 WAN Payload Addressing client

Last week a package arrived from SeeedStudio with some Arduino devices and Grove shields. With this gear I have built yet another client for my Azure IoT Hub and AdaFruit.IO  LoRa Field Gateways.

For my application I directly access the on-board Semtech SX127X chip by passing the Murata CMWX1ZZABZ functionality. To do this I (November 2018) I had to upgrade the device firmware using the Arduino updater.

Arduino MKR1300 WAN device with Grove Shield & patch antenna

The application is a modified version of my Arduino code with additional debugging support and payload formatting functionality.

/*
  Copyright ® 2018 November devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>
#include <avr/dtostrf.h>
#include <LoRa.h>
#include <TH02_dev.h>

#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const char DeviceAddress[] = {"MKR1300LoRa1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int InterruptPin = LORA_IRQ_DUMB;
const int ChipSelectPin = 6;
const int ResetPin = 1;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 60 ;

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;


void setup()
{
  Serial.begin(9600);
#ifdef DEBUG
  while (!Serial);
#endif
  Serial.println("Setup called");

  Serial.println("LoRa setup start");
  
  // override the default chip select and reset pins
  LoRa.setPins(InterruptPin, ChipSelectPin, ResetPin); 
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    Serial.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

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

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(Serial);
#endif
  Serial.println("LoRa Setup done.");

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

  PayloadHeader((byte*)FieldGatewayAddress,strlen(FieldGatewayAddress), (byte*)DeviceAddress, strlen(DeviceAddress));

  Serial.println("Setup done");
  Serial.println();
}


void loop()
{
  float temperature ;
  float humidity ;

  Serial.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity & battery voltage values then display nicely
  temperature = TH02.ReadTemperature();
  Serial.print("T:");
  Serial.print( temperature, 1 ) ;
  Serial.println( "C " ) ;

  PayloadAdd( "T", temperature, 1);

  humidity = TH02.ReadHumidity();
  Serial.print("H:");
  Serial.print( humidity, 0 ) ;
  Serial.println( "% " ) ;

  PayloadAdd( "H", humidity, 0) ;

#ifdef DEBUG_TELEMETRY
  Serial.println();
  Serial.print( "RFM9X/SX127X Payload length:");
  Serial.print( payloadLength );
  Serial.println( " bytes" );
#endif

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

  Serial.println("Loop done");
  Serial.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader( byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

#ifdef DEBUG_TELEMETRY
  Serial.println("PayloadHeader- ");
  Serial.print( "To Address len:");
  Serial.print( toAddressLength );
  Serial.print( " From Address len:");
  Serial.print( fromAddressLength );
  Serial.print( " Addresses length:");
  Serial.print( addressesLength );
  Serial.println( );
#endif

  payloadLength = 0 ;

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

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

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  Serial.println("PayloadAdd-float ");
  Serial.print( "SensorId:");
  Serial.print( sensorId );
  Serial.print( " sensorIdLen:");
  Serial.print( sensorIdLength );
  Serial.print( " Value:");
  Serial.print( value, decimalPlaces );
  Serial.print( " payloadLength:");
  Serial.print( payloadLength);
#endif

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  Serial.print( " payloadLength:");
  Serial.print( payloadLength);
  Serial.println( );
#endif
}


void PayloadAdd( char *sensorId, int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  Serial.println("PayloadAdd-int ");
  Serial.print( "SensorId:");
  Serial.print( sensorId );
  Serial.print( " sensorIdLen:");
  Serial.print( sensorIdLength );
  Serial.print( " Value:");
  Serial.print( value );
  Serial.print( " payloadLength:");
  Serial.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  Serial.print( " payloadLength:");
  Serial.print( payloadLength);
  Serial.println( );
#endif
}


void PayloadAdd( char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen( sensorId ) ;

#ifdef DEBUG_TELEMETRY
  Serial.println("PayloadAdd-unsigned int ");
  Serial.print( "SensorId:");
  Serial.print( sensorId );
  Serial.print( " sensorIdLen:");
  Serial.print( sensorIdLength );
  Serial.print( " Value:");
  Serial.print( value );
  Serial.print( " payloadLength:");
  Serial.print( payloadLength);
#endif  

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  Serial.print( " payloadLength:");
  Serial.print( payloadLength);
  Serial.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = addressesLength + 1;

#ifdef DEBUG_TELEMETRY
  Serial.println("PayloadReset- ");
  Serial.print( "To Address len:");
  Serial.print( toAddressLength );
  Serial.print( " From Address len:");
  Serial.print( fromAddressLength );
  Serial.print( " Addresses length:");
  Serial.print( addressesLength );
  Serial.println( );
#endif
}

After updating the firmware configuring the data to display in Azure IoT Central (or AdaFruit.IO) took minimal time.

Arduino MKR 1300 Data in Azure IoT Central

Bill of materials (Prices as at Nov 2018)

  • Arduino MKR WAN 1300 USD39.80
  • Arduino MKR Connection Carrier (Grove Compatible) USD22.80
  • Grove Temperature & Humidity Sensor USD11.50

So far the battery life is looking pretty good considering all I have done is used Delay to stop the loop method for 60 seconds.

Next steps are to see if I can retrieve a unique identifier from the Murata firmware and improve battery life by hibernating the processor etc.

Azure IoT Hubs LoRa Field Gateway BCD Addressing

After some testing with more client devices, especially the Easy Sensors Arduino Nano radio shield RFM69/95 or NRF24L01+ I have decided to move to non text addresses for devices and the LoRa field gateway.

THIS IS A BREAKING CHANGE

The unique identifier provided by the SHA204A crypto and authentication chip on the EasySensors shield highlighted this issue. The Binary Coded Decimal(BCD) version of the 72 bit identifier was too long to fit in the from address.

My Arduino MKR1300 sample code has some helper functions to populate the message header, add values, and prepare the message payload for reuse.

On the server side I have added code to log the build version and Raspbery PI shield type

// Log the Application build, shield information etc.
LoggingFields appllicationBuildInformation = new LoggingFields();

#if DRAGINO
   appllicationBuildInformation.AddString("Shield", "DraginoLoRaGPSHat");
#endif

...

#if UPUTRONICS_RPIPLUS_CS1
   appllicationBuildInformation.AddString("Shield", "UputronicsPiPlusLoRaExpansionBoardCS1");
#endif
appllicationBuildInformation.AddString("Timezone", TimeZoneSettings.CurrentTimeZoneDisplayName);
appllicationBuildInformation.AddString("OSVersion", Environment.OSVersion.VersionString);
appllicationBuildInformation.AddString("MachineName", Environment.MachineName);

// This is from the application manifest 
Package package = Package.Current;
PackageId packageId = package.Id;
PackageVersion version = packageId.Version;

appllicationBuildInformation.AddString("ApplicationVersion", string.Format($"{version.Major}.{version.Minor}.{version.Build}.{version.Revision}"));
this.logging.LogEvent("Application starting", appllicationBuildInformation, LoggingLevel.Information);

Then when the message payload is populated the from address byte array is converted to BCD

private async void Rfm9XDevice_OnReceive(object sender, Rfm9XDevice.OnDataReceivedEventArgs e)
{
   string addressBcdText;
   string messageBcdText;
   string messageText = "";
   char[] sensorReadingSeparators = new char[] { ',' };
   char[] sensorIdAndValueSeparators = new char[] { ' ' };

   addressBcdText = BitConverter.ToString(e.Address);
   messageBcdText = BitConverter.ToString(e.Data);
   try
   {
      messageText = UTF8Encoding.UTF8.GetString(e.Data);
   }
   catch (Exception)
   {
      this.logging.LogMessage("Failure converting payload to text", 
   LoggingLevel.Error);
      return;
   }


#if DEBUG
   Debug.WriteLine(@"{0:HH:mm:ss}-RX From {1} PacketSnr {2:0.0} Packet 
   RSSI {3}dBm RSSI {4}dBm = {5} byte message ""{6}""", DateTime.Now, 
   messageBcdText, e.PacketSnr, e.PacketRssi, e.Rssi, e.Data.Length, 
   messageText);
#endif
   LoggingFields messagePayload = new LoggingFields();
   messagePayload.AddInt32("AddressLength", e.Address.Length);
   messagePayload.AddString("Address-BCD", addressBcdText);
   messagePayload.AddInt32("Message-Length", e.Data.Length);
   messagePayload.AddString("Message-BCD", messageBcdText);
   messagePayload.AddString("Message-Unicode", messageText);
   messagePayload.AddDouble("Packet SNR", e.PacketSnr);
   messagePayload.AddInt32("Packet RSSI", e.PacketRssi);
   messagePayload.AddInt32("RSSI", e.Rssi);
   this.logging.LogEvent("Message Data", messagePayload, LoggingLevel.Verbose);

//...

   JObject telemetryDataPoint = new JObject(); // This could be simplified but for field gateway will use this style
   LoggingFields sensorData = new LoggingFields();

   telemetryDataPoint.Add("DeviceID", addressBcdText);
   sensorData.AddString("DeviceID", addressBcdText);
   telemetryDataPoint.Add("PacketSNR", e.PacketSnr.ToString("F1"));
   sensorData.AddString("PacketSNR", e.PacketSnr.ToString("F1"));
   telemetryDataPoint.Add("PacketRSSI", e.PacketRssi);
   sensorData.AddInt32("PacketRSSI", e.PacketRssi);
   telemetryDataPoint.Add("RSSI", e.Rssi);
   sensorData.AddInt32("RSSI", e.Rssi);

   //Chop up each sensor read into an ID & value
   foreach (string sensorReading in sensorReadings)
   {
      string[] sensorIdAndValue = sensorReading.Split(sensorIdAndValueSeparators, StringSplitOptions.RemoveEmptyEntries);

      // Check that there is an id & value
      if (sensorIdAndValue.Length != 2)
      {
         this.logging.LogMessage("Sensor reading invalid format", LoggingLevel.Warning);
         return;
      }

      string sensorId = sensorIdAndValue[0];
      string value = sensorIdAndValue[1];

      try
      {
         if (this.applicationSettings.SensorIDIsDeviceIDSensorID)
         {
            // Construct the sensor ID from SensordeviceID & Value ID
            telemetryDataPoint.Add(string.Format("{0}{1}", addressBcdText, sensorId), value);

            sensorData.AddString(string.Format("{0}{1}", addressBcdText, sensorId), value);
            Debug.WriteLine(" Sensor {0}{1} Value {2}", addressBcdText, sensorId, value);
         }
         else
         {
            telemetryDataPoint.Add(sensorId, value);
            sensorData.AddString(sensorId, value);
            Debug.WriteLine(" Device {0} Sensor {1} Value {2}", addressBcdText, sensorId, value);
         }
      }
      catch (Exception ex)
      {
         this.logging.LogMessage("Sensor reading invalid JSON format " + ex.Message, LoggingLevel.Warning);
         return;
      }
   }

  this.logging.LogEvent("Sensor readings", sensorData, LoggingLevel.Information);

   try
   {
      using (Message message = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(telemetryDataPoint))))
      {
         Debug.WriteLine(" AzureIoTHubClient SendEventAsync start");
         await this.azureIoTHubClient.SendEventAsync(message);
         Debug.WriteLine(" AzureIoTHubClient SendEventAsync finish");
      }
   }
   catch (Exception ex)
   {
      this.logging.LogMessage("AzureIoTHubClient SendEventAsync failed " + ex.Message, LoggingLevel.Error);
   }
}

This does mean longer field names but I usually copy n paste them from the Arduino serial monitor of the Event Tracing For Windows (ETW) logging.

Azure IoT Hub LoRa Field Gateway ETW Logging

Easy Sensors Arduino Nano Radio Shield RFM69/95 Payload Addressing client

After not much project work for a while some new RFM9X devices arrived from EasySensors in Belarus.

This sample client built with an Arduino Nano clone and an Arduino Nano radio shield RFM69/95 or NRF24L01+.

I used the shield’s onboard SHA204A crypto and authentication chip, a Seeedstudio Temperature & Humidity sensor and uploaded the data to Azure IoT Central (Will also work with my AdaFruit.IO LoRa field gateway).

/*
  Copyright ® 2018 November devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>
#include <LoRa.h>
#include <sha204_library.h>
#include <TH02_dev.h>

//#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 60 ;

// ATSHA204 secure authentication, validation with crypto and hashing (currently only using for unique serial number)
const byte Atsha204Port = A3;
atsha204Class sha204(Atsha204Port);
const byte DeviceSerialNumberLength = 9 ;
byte deviceSerialNumber[DeviceSerialNumberLength] = {""};

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;


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

#if DEBUG
  while (!Serial);
#endif
 
  Serial.println("Setup called");

  Serial.print("Field gateway:");
  Serial.print( FieldGatewayAddress ) ;
  Serial.print(" Frequency:");
  Serial.print( FieldGatewayFrequency,0 ) ;
  Serial.print("MHz SyncWord:");
  Serial.print( FieldGatewaySyncWord ) ;
  Serial.println();
  
   // Retrieve the serial number then display it nicely
  if(sha204.getSerialNumber(deviceSerialNumber))
  {
    Serial.println("sha204.getSerialNumber failed");
    while (true); // Drop into endless loop requiring restart
  }

  Serial.print("SNo:");
  for (int i = 0; i < sizeof( deviceSerialNumber) ; i++)
  {
    // Add a leading zero
    if ( deviceSerialNumber[i] < 16)
    {
      Serial.print("0");
    }
    Serial.print(deviceSerialNumber[i], HEX);
    Serial.print(" ");
  }
  Serial.println();

  Serial.println("LoRa setup start");

  // override the default chip select and reset pins
  LoRa.setPins(ChipSelectPin, ResetPin);
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    Serial.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

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

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(Serial);
#endif
  Serial.println("LoRa Setup done.");

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

  PayloadHeader(FieldGatewayAddress,strlen(FieldGatewayAddress), deviceSerialNumber, DeviceSerialNumberLength);

  Serial.println("Setup done");
  Serial.println();
}


void loop()
{
  float temperature ;
  float humidity ;

  Serial.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity values then display nicely
  temperature = TH02.ReadTemperature();
  Serial.print("T:");
  Serial.print(temperature, 1) ;
  Serial.println("C ") ;

  PayloadAdd( "T", temperature, 1);

  humidity = TH02.ReadHumidity();
  Serial.print("H:" );
  Serial.print(humidity, 0) ;
  Serial.println("% ") ;

  PayloadAdd( "H", humidity, 0) ;

#ifdef DEBUG_TELEMETRY
  Serial.println();
  Serial.print("RFM9X/SX127X Payload length:");
  Serial.print(payloadLength);
  Serial.println(" bytes");
#endif

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

  Serial.println("Loop done");
  Serial.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader(byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = 0 ;

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

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

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  Serial.print("PayloadAdd float-payloadLength:");
  Serial.print( payloadLength);
  Serial.println( );
#endif
}


void PayloadAdd( char *sensorId, int value )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  Serial.print("PayloadAdd int-payloadLength:" );
  Serial.print(payloadLength);
  Serial.println( );
#endif
}


void PayloadAdd( char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  Serial.print("PayloadAdd uint-payloadLength:");
  Serial.print(payloadLength);
  Serial.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  
  payloadLength = toAddressLength + fromAddressLength + 1;
}

Arduino monitor output

ArduinoNanoEasySensorsRF95ShieldArduinoLogging

Prototype hardware

ArduinoNanoEasySensorsRF95ShieldHardware

Bill of materials (prices as at November 2018)

  • Arduino Nano clone USD4.70
  • Easy Sensors Arduino Nano Radio Shield for RFM95 USD16
  • Seeedstudio Temperature and Humidity Sensor Pro USD11.50
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Azure IoT Central temperature and humidity display.

ArduinoNanoEasySensorsRF95ShieldAzureIoTCentral

Azure IoT Hubs LoRa Windows 10 IoT Core Field Gateway

This project is now live on github.com, sample Arduino with Dragino LoRa Shield for Arduino, MakerFabs Maduino, Dragino LoRa Mini Dev, M2M Low power Node and Netduino with Elecrow LoRa RFM95 Shield clients uploaded in the next couple of days.

AzureIOTHubExplorerScreenGrab20180912

The bare minimum configuration is

{
  "AzureIoTHubDeviceConnectionString": "HostName=qwertyuiop.azure-devices.net;DeviceId=LoRaGateway;SharedAccessKey=1234567890qwertyuiop987654321qwertyuiop1234g=",
  "AzureIoTHubTransportType": "Amqp",
  "SensorIDIsDeviceIDSensorID": true,
  "Address": "LoRaIoT1",
  "Frequency": 915000000.0
}

So far battery life and wireless communications range for the Arduino clients is looking pretty good. CRC presence checking and validation is turned so have a look at one of the sample clients.

ArduinoUnoR3DraginoLoRa
It took a bit longer than expected as upgrading to the latest version (v1.18.0 as at 12 Sep 2018) of Microsoft.Azure.Devices.Client (from 1.6.3) broke my field gateway with timeouts and exceptions.

I’ll be doing some more testing over the next couple of weeks so it is a work in progress.

ASP MVC Core V2.1 and Cross-Origin Resource Sharing

I’m working on an project for a customer which implements a number of application programming Interfaces(API) for a Single Page Application(SPA) and other clients. We are using entity tags (ETags) for versioning and the front end developers found the couldn’t access them from javascipt running in mainstream browser clients (June 2018).

The problems was understanding how Cross-Origin Resource Sharing (CORS) worked and how it interacted with our security model (API key and OAuth2.0 depending on the client)

In our scenario we first found the pre-flight check wasn’t working because in the HyperText Transfer Protocol (HTTP) OPTIONS method our X-API-KEY check was failing

OPTIONS http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
Access-Control-Request-Headers: x-api-key
Access-Control-Request-Method: GET
Accept-Encoding: gzip, deflate
Content-Length: 0
Host: xyz.azurewebsites.net
Connection: Keep-Alive
Pragma: no-cache

HTTP/1.1 400 Bad Request
Transfer-Encoding: chunked
Server: Kestrel
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 05:48:30 GMT

13
API Key is invalid.
0

So I disabled X-API-KEY validation in startup.cs

public async Task Invoke(HttpContext context)
{
   if (context.Request.Method == "OPTIONS")
   {
      await this.next.Invoke(context);
      return;
   }

   var claims = new List();
…

OPTIONS then worked

OPTIONS http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
Access-Control-Request-Headers: x-api-key
Access-Control-Request-Method: GET
Accept-Encoding: gzip, deflate
Content-Length: 0
Host: xyz.azurewebsites.net
Connection: Keep-Alive
Pragma: no-cache

HTTP/1.1 404 Not Found
Server: Kestrel
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 05:52:20 GMT
Content-Length: 0

I then turned on CORS allowing pretty much anything

public void ConfigureServices(IServiceCollection services)
{
   services.AddCors(options =>
   {
      options.AddPolicy("CorsPolicy",
      builder => builder.AllowAnyOrigin()
         .AllowAnyMethod()
         .AllowAnyHeader()
         .AllowCredentials());
   });
   services.AddMvc();
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
   if (env.IsDevelopment())
   {
      app.UseDeveloperExceptionPage();
   }

   TelemetryConfiguration.Active.InstrumentationKey = this.configuration.GetSection("ApplicationInsights").GetSection("InstrumentationKey").Value;

   loggerFactory.AddLog4Net();
   this.log.Info("Startup.Configure called");

   app.ApplyUserKeyValidation();
   app.UseCors("CorsPolicy");
   app.UseMvc();
   }
}

OPTIONS then worked

OPTIONS http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
Access-Control-Request-Headers: x-api-key
Access-Control-Request-Method: GET
Accept-Encoding: gzip, deflate
Content-Length: 0
Host: xyz.azurewebsites.net
Connection: Keep-Alive
Pragma: no-cache

HTTP/1.1 204 No Content
Vary: Origin
Server: Kestrel
Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: x-api-key
Access-Control-Allow-Origin: file://
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 05:57:33 GMT

GET then worked

GET http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
X-API-KEY: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Accept-Language: en-NZ
Accept-Encoding: gzip, deflate
If-None-Match: 00-00-00-00-00-00-00-76
Host: xyz.azurewebsites.net
Connection: Keep-Alive

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
ETag: 00-00-00-00-00-00-00-76
Vary: Origin,Accept-Encoding
Server: Kestrel
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: file://
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 05:57:34 GMT
Content-Length: 2216

[{"...."}}

But HEAD didn’t work

HEAD http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
X-API-KEY: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Accept-Language: en-NZ
Accept-Encoding: gzip, deflate
If-None-Match: 00-00-00-00-00-00-00-76
Host: xyz.azurewebsites.net
Connection: Keep-Alive

HTTP/1.1 400 Bad Request
Content-Length: 0
Vary: Origin
Server: Kestrel
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: file://
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 05:59:55 GMT

From the Application Insights logging and RestTest client (which I ran locally and remotely) I could see that the client side code couldn’t access the value of our eTag.  It had to be “exposed”

public void ConfigureServices(IServiceCollection services)
{
   services.AddCors(options =>
   {
      options.AddPolicy("CorsPolicy",
            builder => builder.AllowAnyOrigin()
            .AllowAnyMethod()
            .AllowAnyHeader()
            .WithExposedHeaders("etag")
            .AllowCredentials()
         );
      });
      services.AddMvc();
   }
...

GET then worked

GET http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
X-API-KEY: ABCDEFGHIJKLMNOPQRSTUVWXYZ
ETag: 00-00-00-00-00-00-00-76
Accept-Language: en-NZ
Accept-Encoding: gzip, deflate
If-None-Match: 00-00-00-00-00-00-00-76
Host: xyz.azurewebsites.net
Connection: Keep-Alive

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Content-Type: application/json; charset=utf-8
Content-Encoding: gzip
ETag: 00-00-00-00-00-00-00-76
Vary: Origin,Accept-Encoding
Server: Kestrel
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: file://
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 07:53:41 GMT

[{"...."}}

HEAD then worked

OPTIONS http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
Access-Control-Request-Headers: x-api-key,etag
Access-Control-Request-Method: HEAD
Accept-Encoding: gzip, deflate
Content-Length: 0
Host: xyz.azurewebsites.net
Connection: Keep-Alive
Pragma: no-cache

HTTP/1.1 204 No Content
Vary: Origin
Server: Kestrel
Access-Control-Allow-Credentials: true
Access-Control-Allow-Headers: x-api-key,etag
Access-Control-Allow-Origin: file://
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 07:57:31 GMT

HEAD http://xyz.azurewebsites.net/api/portfolio HTTP/1.1
...
X-API-KEY: ABCDEFGHIJKLMNOPQRSTUVWXYZ
ETag: 00-00-00-00-00-00-00-76
Accept-Language: en-NZ
Accept-Encoding: gzip, deflate
Host: xyz.azurewebsites.net
Connection: Keep-Alive
Pragma: no-cache

HTTP/1.1 304 Not Modified
Vary: Origin
Server: Kestrel
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: file://
X-Powered-By: ASP.NET
...
Date: Sun, 24 Jun 2018 07:57:31 GMT

I had some oddness with releasing code updates which I think was down to caching of pre-flight request responses.
Next steps tidy up the headers etc. and lock the CORS configuration down to expose the minimum necessary required for the application to work.