The Things Network HTTP Azure IoT Central Integration

This post is an overview of the Azure IoT Central configuration required to process The Things Network(TTN) HTTP integration uplink messages. I have assumed that the reader is already reasonably familiar with these products. There is an overview of configuring TTN HTTP integration in my “Simplicating and securing the HTTP handler” post.

The first step is to copy the IDScope from the Device connection blade.

Device connection blade

Then copy one of the primary or secondary keys

For more complex deployment the ApplicationEnrollmentGroupMapping configuration enables The Things Network(TTN) devices to be provisioned using different GroupEnrollment keys based on the applicationid in the Uplink message which initiates their provisoning.

"DeviceProvisioningService": {
      "GlobalDeviceEndpoint": "global.azure-devices-provisioning.net",
      "IDScope": "",
      "EnrollmentGroupSymmetricKeyDefault": "TopSecretKey",
      "DeviceProvisioningPollingDelay": 500,
      "ApplicationEnrollmentGroupMapping": {
         "Application1": "TopSecretKey1",
         "Application2": "TopSecretKey2"
      }
   }

Shortly after the first uplink message from a TTN device is processed, it will listed in the “Unassociated devices” blade with the DevEUI as the Device ID.

Unassociated devices blade

The device can then be associated with an Azure IoT Central Device Template.

Unassociated devices blade showing recently associated device

The device template provides for the mapping of uplink message payload_fields to measurements. In this example the payload field has been generated by the TTN HTTP integration Cayenne Low Power Protocol(LPP) decoder. Many LoRaWAN devices use LPP to minimise the size of the network payload.

Azure IoT Central Device template blade

Once the device has been associated with a template a user friendly device name etc. can be configured.

Azure IoT Central Device properties blade

In the telemetry event payload sent to Azure IoT Central there are some extra fields to help with debugging and tracing.

// Assemble the JSON payload to send to Azure IoT Hub/Central.
log.LogInformation($"{messagePrefix} Payload assembly start");
JObject telemetryEvent = new JObject();
try
{
   JObject payloadFields = (JObject)payloadObect.payload_fields;
   telemetryEvent.Add("HardwareSerial", payloadObect.hardware_serial);
   telemetryEvent.Add("Retry", payloadObect.is_retry);
   telemetryEvent.Add("Counter", payloadObect.counter);
   telemetryEvent.Add("DeviceID", payloadObect.dev_id);
   telemetryEvent.Add("ApplicationID", payloadObect.app_id);
   telemetryEvent.Add("Port", payloadObect.port);
   telemetryEvent.Add("PayloadRaw", payloadObect.payload_raw);
   telemetryEvent.Add("ReceivedAtUTC", payloadObect.metadata.time);

   // If the payload has been unpacked in TTN backend add fields to telemetry event payload
   if (payloadFields != null)
   {
      foreach (JProperty child in payloadFields.Children())
      {
         EnumerateChildren(telemetryEvent, child);
      }
   }
}
catch (Exception ex)
{
   log.LogError(ex, $"{messagePrefix} Payload processing or Telemetry event assembly failed");
   throw;
}

Azure IoT Central has mapping functionality which can be used to display the location of a device.

Azure Device

The format of the location payload generated by the TTN LPP decoder is different to the one required by Azure IoT Central. I have added temporary code (“a cost effective modification to expedite deployment” aka. a hack) to format the TelemetryEvent payload so it can be processed.

if (token.First is JValue)
{
   // Temporary dirty hack for Azure IoT Central compatibility
   if (token.Parent is JObject possibleGpsProperty)
   {
      if (possibleGpsProperty.Path.StartsWith("GPS", StringComparison.OrdinalIgnoreCase))
      {
         if (string.Compare(property.Name, "Latitude", true) == 0)
         {
            jobject.Add("lat", property.Value);
         }
         if (string.Compare(property.Name, "Longitude", true) == 0)
         {
            jobject.Add("lon", property.Value);
         }
         if (string.Compare(property.Name, "Altitude", true) == 0)
         {
            jobject.Add("alt", property.Value);
         }
      }
   }
   jobject.Add(property.Name, property.Value);
}

I need review the IoT Plug and Play specification documentation to see what other payload transformations maybe required.

I did observe that if a device had not reported its position the default location was zero degrees latitude and zero degrees longitude which is about 610 KM south of Ghana and 1080 KM west of Gabon in the Atlantic Ocean.

Azure IoT Central mapping default position

After configuring a device template, associating my devices with the template, and modifying each device’s properties I could create a dashboard to view the temperature and humidity information returned by my Seeeduino LoRaWAN devices.

Azure IoT Central dashboard

The Things Network HTTP Integration Part6

Provisioning Devices on demand.

For development and testing being able to provision an individual device is really useful, though for Azure IoT Central it is not easy (especially with the deprecation of DPS-KeyGen). With an Azure IoT Hub device connection strings are available in the portal which is convenient but not terribly scalable.

Azure IoT Hub is integrated with, and Azure IoT Central forces the use of the Device Provisioning Service(DPS) which is designed to support the management of 1000’s of devices.

My HTTP Integration for The Things Network(TTN) is intended to support many devices and integrate with Azure IoT Central so I built yet another “nasty” console application to explore how the DPS works. The DPS also supports device attestation with a Trusted Platform Module(TPM) but this approach was not suitable for my application.

My command-line application supports individual and group enrollments with Symmetric Key Attestation and it can also generate group enrollment device keys.

class Program
{
   private const string GlobalDeviceEndpoint = "global.azure-devices-provisioning.net";

   static async Task Main(string[] args)
   {
      string registrationId;
...   
      registrationId = args[1];

      switch (args[0])
      {
         case "e":
         case "E":
            string scopeId = args[2];
            string symmetricKey = args[3];

            Console.WriteLine($"Enrolllment RegistrationID:{ registrationId} ScopeID:{scopeId}");
            await Enrollement(registrationId, scopeId, symmetricKey);
            break;
         case "k":
         case "K":
            string primaryKey = args[2];
            string secondaryKey = args[3];

            Console.WriteLine($"Enrollment Keys RegistrationID:{ registrationId}");
            GroupEnrollementKeys(registrationId, primaryKey, secondaryKey);
            break;
         default:
            Console.WriteLine("Unknown option");
            break;
      }
      Console.WriteLine("Press <enter> to exit");
      Console.ReadLine();
   }

   static async Task Enrollement(string registrationId, string scopeId, string symetricKey)
   {
      try
      {
         using (var securityProvider = new SecurityProviderSymmetricKey(registrationId, symetricKey, null))
         {
            using (var transport = new ProvisioningTransportHandlerAmqp(TransportFallbackType.TcpOnly))
            {
               ProvisioningDeviceClient provClient = ProvisioningDeviceClient.Create(GlobalDeviceEndpoint, scopeId, securityProvider, transport);

               DeviceRegistrationResult result = await provClient.RegisterAsync();

               Console.WriteLine($"Hub:{result.AssignedHub} DeviceID:{result.DeviceId} RegistrationID:{result.RegistrationId} Status:{result.Status}");
               if (result.Status != ProvisioningRegistrationStatusType.Assigned)
               {
                  Console.WriteLine($"DeviceID{ result.Status} already assigned");
               }

               IAuthenticationMethod authentication = new DeviceAuthenticationWithRegistrySymmetricKey(result.DeviceId, (securityProvider as SecurityProviderSymmetricKey).GetPrimaryKey());

               using (DeviceClient iotClient = DeviceClient.Create(result.AssignedHub, authentication, TransportType.Amqp))
               {
                  Console.WriteLine("DeviceClient OpenAsync.");
                  await iotClient.OpenAsync().ConfigureAwait(false);
                  Console.WriteLine("DeviceClient SendEventAsync.");
                  await iotClient.SendEventAsync(new Message(Encoding.UTF8.GetBytes("TestMessage"))).ConfigureAwait(false);
                  Console.WriteLine("DeviceClient CloseAsync.");
                  await iotClient.CloseAsync().ConfigureAwait(false);
               }
            }
         }
      }
      catch (Exception ex)
      {
         Console.WriteLine(ex.Message);
      }
   }

   static void GroupEnrollementKeys(string registrationId, string primaryKey, string secondaryKey)
   {
      string primaryDeviceKey = ComputeDerivedSymmetricKey(Convert.FromBase64String(primaryKey), registrationId);
      string secondaryDeviceKey = ComputeDerivedSymmetricKey(Convert.FromBase64String(secondaryKey), registrationId);

      Console.WriteLine($"RegistrationID:{registrationId}");
      Console.WriteLine($" PrimaryDeviceKey:{primaryDeviceKey}");
      Console.WriteLine($" SecondaryDeviceKey:{secondaryDeviceKey}");
   }

   public static string ComputeDerivedSymmetricKey(byte[] masterKey, string registrationId)
   {
      using (var hmac = new HMACSHA256(masterKey))
      {
         return Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(registrationId)));
      }
   }
}

I have five seeeduino LoRaWAN and a single Seeeduino LoRaWAN W/GPS device leftover from another project so I created a SeeeduinoLoRaWAN enrollment group.

DPS Enrollment Group configuration

Initially the enrollment group had no registration records so I ran my command-line application to generate group enrollment keys for one of my devices.

Device registration before running my command line application

Then I ran the command-line application with my scopeID, registrationID (LoRaWAN deviceEUI) and the device group enrollment key I had generated in the previous step.

Registering a device and sending a message to the my Azure IoT Hub

After running the command line application the device was visible in the enrollment group registration records.

Device registration after running my command line application

Provisioning a device with an individual enrollment has a different workflow. I had to run my command-line application with the RegistrationID, ScopeID, and one of the symmetric keys from the DPS individual enrollment device configuration.

DPS Individual enrollment configuration

A major downside to an individual enrollment is either the primary or the secondary symmetric key for the device has to be deployed on the device which could be problematic if the device has no secure storage.

With a group enrollment only the registration ID and the derived symmetric key have to be deployed on the device which is more secure.

Registering a device and sending a message to the my Azure IoT Hub

In Azure IoT Explorer I could see messages from both my group and individually enrolled devices arriving at my Azure IoT hub

After some initial issues I found DPS was quite reliable and surprisingly easy to configure. I did find the DPS ProvisioningDeviceClient.RegisterAsync method sometimes took several seconds to execute which may have some ramifications when my application is doing this on demand.

Wilderness Labs nRF24L01 Wireless field gateway Meadow client

After a longish pause in development work on my nrf24L01 AdaFruit.IO and Azure IOT Hub field gateways I figured a client based on my port of the techfooninja nRF24 library to Wilderness Labs Meadow would be a good test.

This sample client is an Wilderness Labs Meadow with a Sensiron SHT31 Temperature & humidity sensor (supported by meadow foundation), and a generic nRF24L01 device connected with jumper cables.

Bill of materials (prices as at March 2020)

  • Wilderness Labs Meadow 7F Micro device USD50
  • Seeedstudio Temperature and Humidity Sensor(SHT31) USD11.90
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90
  • 2.4G Wireless Module nRF24L01+PA USD9.90

The initial version of the code was pretty basic with limited error handling and no power conservation support.

namespace devMobile.IoT.FieldGateway.Client
{
   using System;
   using System.Text;
   using System.Threading;

   using Radios.RF24;

   using Meadow;
   using Meadow.Devices;
   using Meadow.Foundation.Leds;
   using Meadow.Foundation.Sensors.Atmospheric;
   using Meadow.Hardware;
   using Meadow.Peripherals.Leds;

   public class MeadowClient : App<F7Micro, MeadowClient>
   {
      private const string BaseStationAddress = "Base1";
      private const string DeviceAddress = "WLAB1";
      private const byte nRF24Channel = 15;
      private RF24 Radio = new RF24();
      private readonly TimeSpan periodTime = new TimeSpan(0, 0, 60);
      private readonly Sht31D sensor;
      private readonly ILed Led;

      public MeadowClient()
      {
         Led = new Led(Device, Device.Pins.OnboardLedGreen);

         try
         {
            sensor = new Sht31D(Device.CreateI2cBus());

            var config = new Meadow.Hardware.SpiClockConfiguration(
                           2000,
                           SpiClockConfiguration.Mode.Mode0);

            ISpiBus spiBus = Device.CreateSpiBus(
               Device.Pins.SCK,
               Device.Pins.MOSI,
               Device.Pins.MISO, config);

            Radio.OnDataReceived += Radio_OnDataReceived;
            Radio.OnTransmitFailed += Radio_OnTransmitFailed;
            Radio.OnTransmitSuccess += Radio_OnTransmitSuccess;

            Radio.Initialize(Device, spiBus, Device.Pins.D09, Device.Pins.D10, Device.Pins.D11);
            //Radio.Address = Encoding.UTF8.GetBytes(Environment.MachineName);
            Radio.Address = Encoding.UTF8.GetBytes(DeviceAddress);

            Radio.Channel = nRF24Channel;
            Radio.PowerLevel = PowerLevel.Low;
            Radio.DataRate = DataRate.DR250Kbps;
            Radio.IsEnabled = true;

            Radio.IsAutoAcknowledge = true;
            Radio.IsDyanmicAcknowledge = false;
            Radio.IsDynamicPayload = true;

            Console.WriteLine($"Address: {Encoding.UTF8.GetString(Radio.Address)}");
            Console.WriteLine($"PowerLevel: {Radio.PowerLevel}");
            Console.WriteLine($"IsAutoAcknowledge: {Radio.IsAutoAcknowledge}");
            Console.WriteLine($"Channel: {Radio.Channel}");
            Console.WriteLine($"DataRate: {Radio.DataRate}");
            Console.WriteLine($"IsDynamicAcknowledge: {Radio.IsDyanmicAcknowledge}");
            Console.WriteLine($"IsDynamicPayload: {Radio.IsDynamicPayload}");
            Console.WriteLine($"IsEnabled: {Radio.IsEnabled}");
            Console.WriteLine($"Frequency: {Radio.Frequency}");
            Console.WriteLine($"IsInitialized: {Radio.IsInitialized}");
            Console.WriteLine($"IsPowered: {Radio.IsPowered}");
         }
         catch (Exception ex)
         {
            Console.WriteLine(ex.Message);
         }

         while (true)
         {
            sensor.Update();

            Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-TX T:{sensor.Temperature:0.0}C H:{sensor.Humidity:0}%");

            Led.IsOn = true;

            string values = "T " + sensor.Temperature.ToString("F1") + ",H " + sensor.Humidity.ToString("F0");

            // Stuff the 2 byte header ( payload type & deviceIdentifierLength ) + deviceIdentifier into payload
            byte[] payload = new byte[1 + Radio.Address.Length + values.Length];
            payload[0] = (byte)((1 << 4) | Radio.Address.Length);
            Array.Copy(Radio.Address, 0, payload, 1, Radio.Address.Length);
            Encoding.UTF8.GetBytes(values, 0, values.Length, payload, Radio.Address.Length + 1);

            Radio.SendTo(Encoding.UTF8.GetBytes(BaseStationAddress), payload);

            Thread.Sleep(periodTime);
         }
      }

      private void Radio_OnDataReceived(byte[] data)
      {
         // Display as Unicode
         string unicodeText = Encoding.UTF8.GetString(data);
         Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-RX Unicode Length {0} Unicode Length {1} Unicode text {2}", data.Length, unicodeText.Length, unicodeText);

         // display as hex
         Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-RX Hex Length {data.Length} Payload {BitConverter.ToString(data)}");
      }

      private void Radio_OnTransmitSuccess()
      {
         Led.IsOn = false;

         Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-TX Succeeded!");
      }

      private void Radio_OnTransmitFailed()
      {
         Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-TX failed!");
      }
   }
}

After sorting out power to the SHT31 (I had to push the jumper cable further into the back of the jumper cable plug). I could see temperature and humidity values getting uploaded to Adafruit.IO.

Visual Studio 2019 debug output

Adafruit.IO “automagically” provisions new feeds which is helpful when building a proof of concept (PoC)

Adafruit.IO feed with default feed IDs

I then modified the feed configuration to give it a user friendly name.

Feed Configuration

All up configuration took about 10 minutes.

Meadow device temperature and humidity

Meadow LoRa Radio 915 MHz Payload Addressing client

This is a demo Wilderness Labs Meadow client that uploads temperature and humidity data to my Azure IoT Hubs/Central, AdaFruit.IO or MQTT on Raspberry PI field gateways.

Bill of materials (Prices Jan 2020).

//---------------------------------------------------------------------------------
// Copyright (c) January 2020, devMobile Software
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//---------------------------------------------------------------------------------
namespace devMobile.IoT.FieldGateway.Client
{
   using System;
   using System.Text;
   using System.Threading;

   using devMobile.IoT.Rfm9x;

   using Meadow;
   using Meadow.Devices;
   using Meadow.Foundation.Leds;
   using Meadow.Foundation.Sensors.Atmospheric;
   using Meadow.Hardware;
   using Meadow.Peripherals.Leds;

   public class MeadowClient : App<F7Micro, MeadowClient>
   {
      private const double Frequency = 915000000.0;
      private readonly byte[] fieldGatewayAddress = Encoding.UTF8.GetBytes("LoRaIoT1");
      private readonly byte[] deviceAddress = Encoding.UTF8.GetBytes("Meadow");
      private readonly Rfm9XDevice rfm9XDevice;
      private readonly TimeSpan periodTime = new TimeSpan(0, 0, 60);
      private readonly Sht31D sensor;
      private readonly ILed Led;

      public MeadowClient()
      {
         Led = new Led(Device, Device.Pins.OnboardLedGreen);

         try
         {
            sensor = new Sht31D(Device.CreateI2cBus());

            ISpiBus spiBus = Device.CreateSpiBus(500);

            rfm9XDevice = new Rfm9XDevice(Device, spiBus, Device.Pins.D09, Device.Pins.D10, Device.Pins.D12);

            rfm9XDevice.Initialise(Frequency, paBoost: true, rxPayloadCrcOn: true);
#if DEBUG
            rfm9XDevice.RegisterDump();
#endif
            rfm9XDevice.OnReceive += Rfm9XDevice_OnReceive;
            rfm9XDevice.Receive(deviceAddress);
            rfm9XDevice.OnTransmit += Rfm9XDevice_OnTransmit;
         }
         catch (Exception ex)
         {
            Console.WriteLine(ex.Message);
         }

         while (true)
         {
            sensor.Update();

            Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-TX T:{sensor.Temperature:0.0}C H:{sensor.Humidity:0}%");

            string payload = $"t {sensor.Temperature:0.0},h {sensor.Humidity:0}";

            Led.IsOn = true;

            rfm9XDevice.Send(fieldGatewayAddress, Encoding.UTF8.GetBytes(payload));

            Thread.Sleep(periodTime);
         }
      }

      private void Rfm9XDevice_OnReceive(object sender, Rfm9XDevice.OnDataReceivedEventArgs e)
      {
         try
         {
            string addressText = UTF8Encoding.UTF8.GetString(e.Address);
            string addressHex = BitConverter.ToString(e.Address);
            string messageText = UTF8Encoding.UTF8.GetString(e.Data);

            Console.WriteLine($"{DateTime.UtcNow:HH:mm:ss}-RX PacketSnr {e.PacketSnr:0.0} Packet RSSI {e.PacketRssi}dBm RSSI {e.Rssi}dBm = {e.Data.Length} byte message {messageText}");
         }
         catch (Exception ex)
         {
            Console.WriteLine(ex.Message);
         }
      }

      private void Rfm9XDevice_OnTransmit(object sender, Rfm9XDevice.OnDataTransmitedEventArgs e)
      {
         Led.IsOn = false;

         Console.WriteLine("{0:HH:mm:ss}-TX Done", DateTime.Now);
      }
   }
}

The Meadow platform is a work in progress (Jan 2020) so I haven’t put any effort into minimising power consumption but will revisit this in a future post.

Meadow device with Seeedstudio SHT31 temperature & humidity sensor
Meadow sensor data in Field Gateway ETW logging
Meadow Sensor data in Azure IoT Central

Armtronix IA005 SX1276 loRa node

A month ago I ordered a pair of IA005: SX1276 Lora node STM32F103 devices from the Armtronix shop on Tindie for evaluation. At USD18 each these devices were competitively priced and I was interested in trialling another maple like device.

Bill of materials (Prices as at December 2019)

  • IA005 SX1276 loRa node USD36 (USD18 each)
  • Grove – Temperature&Humidity Sensor USD11.5
  • Grove – 4 pin Female Jumper to Grove 4 pin Conversion Cable USD3.90
Armtronix device with Seeedstudio temperature & humidity sensor

I used a modified version of my Arduino client code which worked after I got the pins sorted and the female jumper sockets in the right order.

/*
  Copyright ® 2019 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 <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[] = {"ArmTronix01"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = PA4;
const int InterruptPin = PA11;
const int ResetPin = PC13;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 30 ;

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(ChipSelectPin, ResetPin, InterruptPin); 
  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.print( "RFM9X/SX127X Payload len:");
  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.print("PayloadHeader- ");
  Serial.print( "To len:");
  Serial.print( toAddressLength );
  Serial.print( " From len:");
  Serial.print( fromAddressLength );
  Serial.print( " Header len:");
  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( const char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

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


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

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


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

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


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

  payloadLength = addressesLength + 1;

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

To get the application to download I had to configure the board in the Arduino IDE

Then change the jumpers

Initially I had some problems deploying my software because I hadn’t followed the instructions (the wiki everyone referred to appeared to be offline) and run the installation batch file (New dev machine since my previous maple based project).

15:40:56.207 -> LoRa Setup done.
15:40:56.207 -> TH02 setup start
15:40:56.307 -> TH02 setup done
15:40:56.307 -> PayloadHeader- To len:8 From len:11 Header len:19
15:40:56.354 -> Setup done
15:40:56.354 -> 
15:40:56.354 -> Loop called
15:40:56.354 -> PayloadReset- To len:8 From len:11 Header len:19
15:40:56.408 -> T:23.9C 
15:40:56.408 -> PayloadAdd-float SensorId:T Len:1 Value:23.9 payloadLen:20 payloadLen:27
15:40:56.508 -> H:70% 
15:40:56.508 -> PayloadAdd-float SensorId:H Len:1 Value:70 payloadLen:27 payloadLen:32
15:40:56.608 -> RFM9X/SX127X Payload len:32 bytes
15:40:56.655 -> Loop done
15:40:56.655 -> 
15:41:26.647 -> Loop called
15:41:26.647 -> PayloadReset- To len:8 From len:11 Header len:19
15:41:26.684 -> T:24.0C 
15:41:26.730 -> PayloadAdd-float SensorId:T Len:1 Value:24.0 payloadLen:20 payloadLen:27
15:41:26.784 -> H:69% 
15:41:26.784 -> PayloadAdd-float SensorId:H Len:1 Value:69 payloadLen:27 payloadLen:32
15:41:26.884 -> RFM9X/SX127X Payload len:32 bytes
15:41:26.931 -> Loop done
15:41:26.931 -> 
15:41:56.904 -> Loop called
15:41:56.904 -> PayloadReset- To len:8 From len:11 Header len:19
15:41:56.948 -> T:24.1C 
15:41:56.982 -> PayloadAdd-float SensorId:T Len:1 Value:24.1 payloadLen:20 payloadLen:27
15:41:57.054 -> H:69% 
15:41:57.054 -> PayloadAdd-float SensorId:H Len:1 Value:69 payloadLen:27 payloadLen:32
15:41:57.157 -> RFM9X/SX127X Payload len:32 bytes
15:41:57.191 -> Loop done
15:41:57.191 -> 
15:42:27.211 -> Loop called
15:42:27.211 -> PayloadReset- To len:8 From len:11 Header len:19
15:42:27.258 -> T:24.1C 
15:42:27.258 -> PayloadAdd-float SensorId:T Len:1 Value:24.1 payloadLen:20 payloadLen:27
15:42:27.343 -> H:69% 
15:42:27.343 -> PayloadAdd-float SensorId:H Len:1 Value:69 payloadLen:27 payloadLen:32
15:42:27.427 -> RFM9X/SX127X Payload len:32 bytes
15:42:27.481 -> Loop done
15:42:27.481 -> 
15:42:57.504 -> Loop called
15:42:57.504 -> PayloadReset- To len:8 From len:11 Header len:19
15:42:57.504 -> T:24.1C 
15:42:57.550 -> PayloadAdd-float SensorId:T Len:1 Value:24.1 payloadLen:20 payloadLen:27
15:42:57.604 -> H:68% 
15:42:57.604 -> PayloadAdd-float SensorId:H Len:1 Value:68 payloadLen:27 payloadLen:32
15:42:57.704 -> RFM9X/SX127X Payload len:32 bytes
15:42:57.755 -> Loop done
15:42:57.755 -> 

I configured the device to upload to my Azure IoT Hub/Azure IoT Central gateway and it has been running reliably for a couple of days.

Azure IoT Central temperature and humidity values

Initially I had some configuration problems but I contacted Armtronix support and they promptly provided a couple of updated links for product and device documentation.

Grove-VOC and eCO2 Gas Sensor (SGP30)

In preparation for a project to monitor the fumes (initially Volatile Organic Compounds) levels around the 3D Printers and Laser Cutters in a school makerspace I purchased a Grove -VOC and eCO2 Gas Sensor (SGP30) for evaluation.

Seeeduino Nano easySensors shield and Grove VOC & eCO2 Sensor

Seeeduino Nano devices have a single on-board I2C socket which meant I didn’t need a Grove Shield for Arduino Nano which reduced the size and cost of the sensor node.

I downloaded the sample code from the Seeedstudio wiki and modified my Easy Sensors Arduino Nano Radio Shield RFM69/95 Payload Addressing client to use the sensor.

My first attempt failed with an issues accessing an Analog port to read the serial number from the Microchip ATSHA204 security chip. After looking at the Seeed SGP30 library source code (based on Sensiron samples) I think the my Nano device was running out of memory. I then searched for other Arduino compatible SGP30 libraries and rebuilt he application with the one from Sparkfun,

/*
  Copyright ® 2019 August 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

  Seeedstudio Grove - VOC and eCO2 Gas Sensor (SGP30)
  https://www.seeedstudio.com/Grove-VOC-and-eCO2-Gas-Sensor-SGP30-p-3071.html

  Seeeduino Nano 
  https://www.seeedstudio.com/Seeeduino-Nano-p-4111.html
  
  Polycarbonate enclosure approx 3.5" x 4.5"
    2 x Cable glands
    1 x Grommet to seal SMA antenna connector
    3M command adhesive strips to hold battery & device in place
   
*/
#include <stdlib.h>
#include "SparkFun_SGP30_Arduino_Library.h" 
#include <LoRa.h>
#include <sha204_library.h>

//#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA
#define DEBUG_VOC_AND_CO2

#define UNITS_VOC "ppb"
#define UNITS_CO2 "ppm"

// LoRa field gateway configuration (these settings must match your field gateway)
const byte DeviceAddressMaximumLength = 15 ;
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;
const int InterruptPin = 2;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const unsigned long SensorUploadDelay = 60000;

// 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] = {""};

SGP30 mySensor; //create an object of the SGP30 class

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.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:");
  DisplayHex( deviceSerialNumber, DeviceSerialNumberLength);
  Serial.println();

  Serial.println("LoRa setup start");

  // override the default chip select and reset pins
  LoRa.setPins(ChipSelectPin, ResetPin, InterruptPin);
  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 DF Robot SHT20, temperature & humidity sensor
  Serial.println("SGP30 setup start");  
  Wire.begin();
  if(mySensor.begin() == false)
  {
    Serial.println("SQP-30 initialisation failed");
    while (true); // Drop into endless loop requiring restart
  }
  mySensor.initAirQuality();
  delay(1000);  
  Serial.println("SGP30 setup done");

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

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


void loop()
{
  unsigned long currentMilliseconds = millis();  

  Serial.println("Loop called");

  mySensor.measureAirQuality();

  PayloadReset();  

  PayloadAdd( "v", mySensor.TVOC, false);
     
  PayloadAdd( "c", mySensor.CO2, false);
  
  #ifdef DEBUG_VOC_AND_CO2  
    Serial.print("VoC:");
    Serial.print( mySensor.TVOC ) ;
    Serial.print( UNITS_VOC ) ;
    Serial.print(" Co2:");
    Serial.print( mySensor.CO2 ) ;
    Serial.println( UNITS_CO2 ) ;
  #endif

  #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(SensorUploadDelay - (millis() - currentMilliseconds ));
}


void PayloadHeader( const byte *to, byte toAddressLength, const 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( const char *sensorId, float value, byte decimalPlaces, bool last)
{
  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]));
  if (!last)
  {
    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, bool last )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(itoa( value,(char *)&payload[payloadLength],10));
  if (!last)
  {
    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, bool last )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(utoa( value,(char *)&payload[payloadLength],10));
  if (!last)
  {
    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;
}


void DisplayHex( byte *byteArray, byte length) 
{
  for (int i = 0; i < length ; i++)
  {
    // Add a leading zero
    if ( byteArray[i] < 16)
    {
      Serial.print("0");
    }
    Serial.print(byteArray[i], HEX);
    if ( i < (length-1)) // Don't put a - after last digit
    {
      Serial.print("-");
    }
  }
}    

The code is available on GitHub.

11:32:52.947 -> Setup called
11:32:52.947 -> Field gateway:LoRaIoT1 Frequency:915000000MHz SyncWord:18
11:32:53.085 -> SNo:01-23-21-61-D6-D1-F5-86-EE
11:32:53.118 -> LoRa setup start
11:32:53.118 -> LoRa Setup done.
11:32:53.153 -> SGP30 setup start
11:32:54.083 -> SGP30 setup done
11:32:54.117 -> Setup done
11:32:54.117 -> 
11:32:54.117 -> Loop called
11:32:54.152 -> VoC:0ppb Co2:400ppm
11:32:54.187 -> Loop done
11:32:54.187 -> 
11:33:54.092 -> Loop called
11:33:54.127 -> VoC:0ppb Co2:400ppm
11:33:54.195 -> Loop done
11:33:54.195 -> 
11:34:54.098 -> Loop called
11:34:54.133 -> VoC:17ppb Co2:425ppm
11:34:54.201 -> Loop done
11:34:54.201 -> 
11:35:54.109 -> Loop called
11:35:54.142 -> VoC:11ppb Co2:421ppm
11:35:54.210 -> Loop done
11:35:54.210 -> 
11:36:54.109 -> Loop called
11:36:54.143 -> VoC:3ppb Co2:409ppm
11:36:54.212 -> Loop done
11:36:54.212 -> 
11:37:54.135 -> Loop called
11:37:54.135 -> VoC:12ppb Co2:400ppm
11:37:54.204 -> Loop done
11:37:54.204 -> 
11:38:54.126 -> Loop called
11:38:54.161 -> VoC:11ppb Co2:439ppm
11:38:54.231 -> Loop done

To configure the device in Azure IoT Central (similar process for Adafruit.IO, working on support for losant, ubidots and MyDevices) I copied the SNo: from the Arduino development tool logging window and appended c for the CO2 parts per million (ppm), v for VOC parts per billion (ppb) unique serial number from the ATSHA204A chip. (N.B. pay attention to the case of the field names they are case sensitive)

Azure IoT Central configuration

Overall the performance of the VoC sensor data is looking pretty positive, the eCO2 readings need some further investigation as they track the VOC levels. The large spike in the graph below is me putting an open vivid marker on my desk near the sensor.

eCO2 and VOC levels in my office for a day

Bill of materials (prices as at August 2019)

  • Seeeduino Nano USD6.90
  • Grove – VOC and eCO2 Gas Sensor (SGP30) USD15.90
  • EasySensors Arduino Nano radio shield RFM95 USD15.00

DF Robot Temperature & Humidity Sensor(SHT20) trial

In preparation for a project to build weather stations to place at a couple of local schools I purchased a DF Robot SHT20 Temperature & Humidity Sensor for evaluation.

Seeeduino Nano, EasySensors Shield & DF Robot Sensor test rig

The Seeeduino Nano devices I’m testing have a single on-board I2C socket which meant I didn’t need a Grove Shield for Arduino Nano which reduced the size and cost of the sensor node.

To test my setup I installed the DFRobot Arduino SHT20 library and downloaded a demo application to my device.

I started with my Easy Sensors Arduino Nano Radio Shield RFM69/95 Payload Addressing client and modified it to use the SHT20 sensor.

/*
  Copyright ® 2019 August 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

  DF Robot SHT20 Temperature & Humidity sensor   https://www.dfrobot.com/wiki/index.php/SHT20_I2C_Temperature_%26_Humidity_Sensor_(Waterproof_Probe)_SKU:_SEN0227  

  Seeeduino Nano 
  https://www.seeedstudio.com/Seeeduino-Nano-p-4111.html
  
  Polycarbonate enclosure approx 3.5" x 4.5"
    2 x Cable glands
    1 x ufl to SMA connector
    3M command adhesive strips to hold battery & device in place
   
*/
#include <stdlib.h>
#include <DFRobot_SHT20.h>
#include <LoRa.h>
#include <sha204_library.h>

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

#define UNITS_HUMIDITY "%"
#define UNITS_TEMPERATURE "°c"

// LoRa field gateway configuration (these settings must match your field gateway)
const byte DeviceAddressMaximumLength = 15 ;
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;
const int InterruptPin = 2;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const unsigned long SensorUploadDelay = 60000;

// 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] = {""};

// SHT20 Air temperature and humidity sensor
DFRobot_SHT20 sht20;

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.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:");
  DisplayHex( deviceSerialNumber, DeviceSerialNumberLength);
  Serial.println();

  Serial.println("LoRa setup start");

  // override the default chip select and reset pins
  LoRa.setPins(ChipSelectPin, ResetPin, InterruptPin);
  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 DF Robot SHT20, temperature & humidity sensor
  Serial.println("SHT20 setup start");  
  sht20.initSHT20();
  delay(100);
  sht20.checkSHT20();    
  Serial.println("SHT20 setup done");

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

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


void loop()
{
  unsigned long currentMilliseconds = millis();  
  float temperature ;
  float humidity ;

  Serial.println("Loop called");

  PayloadReset();  

  humidity = sht20.readHumidity();          
  PayloadAdd( "h", humidity, 0, false);

  temperature = sht20.readTemperature();               
  PayloadAdd( "t", temperature, 1, false);
  
  #ifdef DEBUG_TEMPERATURE_AND_HUMIDITY  
    Serial.print("H:");
    Serial.print( humidity, 0 ) ;
    Serial.print( UNITS_HUMIDITY ) ;
    Serial.print("T:");
    Serial.print( temperature, 1 ) ;
    Serial.println( UNITS_TEMPERATURE ) ;
  #endif

  #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(SensorUploadDelay - (millis() - currentMilliseconds ));
}


void PayloadHeader( const byte *to, byte toAddressLength, const 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( const char *sensorId, float value, byte decimalPlaces, bool last)
{
  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]));
  if (!last)
  {
    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, bool last )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(itoa( value,(char *)&payload[payloadLength],10));
  if (!last)
  {
    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, bool last )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(utoa( value,(char *)&payload[payloadLength],10));
  if (!last)
  {
    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;
}


void DisplayHex( byte *byteArray, byte length) 
{
  for (int i = 0; i < length ; i++)
  {
    // Add a leading zero
    if ( byteArray[i] < 16)
    {
      Serial.print("0");
    }
    Serial.print(byteArray[i], HEX);
    if ( i < (length-1)) // Don't put a - after last digit
    {
      Serial.print("-");
    }
  }
}    

The code is available on GitHub.

20:52:09.656 -> Setup called
20:52:09.690 -> Field gateway:LoRaIoT1 Frequency:915000000MHz SyncWord:18
20:52:09.794 -> SNo:01-23-21-61-D6-D1-F5-86-EE
20:52:09.828 -> LoRa setup start
20:52:09.828 -> LoRa Setup done.
20:52:09.862 -> SHT20 setup start
20:52:09.932 -> End of battery: no
20:52:09.932 -> Heater enabled: no
20:52:09.965 -> Disable OTP reload: yes
20:52:09.999 -> SHT20 setup done
20:52:09.999 -> Setup done
20:52:09.999 -> 
20:52:09.999 -> Loop called
20:52:10.067 -> H:60%T:20.0°c
20:52:10.136 -> Loop done
20:52:10.136 -> 
20:53:09.915 -> Loop called
20:53:10.019 -> H:61%T:20.5°c
20:53:10.088 -> Loop done
20:53:10.088 -> 

To configure the device in Azure IoT Central (similar process for Adafruit.IO, working on support for losant, ubidots and MyDevices) I copied the SNo: from the Arduino development tool logging window and appended p10 for PM 1 value, p25 for PM2.5 value and p100 for PM10 value to the unique serial number from the ATSHA204A chip. (N.B. pay attention to the case of the field names they are case sensitive)

When I moved the sensor indoors it appeared to take a while to warm up and after a while the metal body still felt cold. The sensor element is surrounded by quite a bit of protective packaging for outdoors use and I that would have a bit more thermal inertia the than the lightweight indoor enclosure.

It would be good to run the sensor alongside a calibrated temperature & humidity sensor to see how accurate and responsive it is.

Bill of materials (prices as at August 2019)

  • Seeeduino Nano USD6.90
  • Grove Screw Terminal USD2.90
  • DF Robot SHT20 I2C Temperature & Humidity Sensor USD22.50
  • EasySensors Arduino Nano radio shield RFM95 USD15.00

Grove – Laser PM2.5 Sensor(HM3301) trial

In preparation for a project to monitor the particulates levels around the 3D Printers and Laser Cutters in a school makerspace I purchased a Grove -Laser PM2.5 Sensor (HM3301) for evaluation.

Seeeduino, Grove HM3301 and easysensors shield

The Seeeduino Nano devices I’m testing have a single on-board I2C socket which meant I didn’t need a Grove Shield for Arduino Nano which reduced the size and cost of the sensor node.

To test my setup I installed the Seeed PM2.5 Sensor HM3301 Software Library and downloaded the demo application to my device.

I started with my Easy Sensors Arduino Nano Radio Shield RFM69/95 Payload Addressing client and modified it to use the HM3301 sensor.

After looking at the demo application I stripped out the checksum code and threw the rest away. In my test harness I have extracted only the PM1.0/PM2.5/PM10.0 (concentration CF=1, Standard particulate) in μg/ m3 values from the sensor response payload.

/*
  Copyright ® 2019 August 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 "Seeed_HM330X.h"

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

const byte SensorPayloadLength = 28 ;
const byte SensorPayloadBufferSize  = 29 ;
const byte SensorPayloadPM1_0Position = 4;
const byte SensorPayloadPM2_5Position = 6;
const byte SensorPayloadPM10_0Position = 8;

HM330X sensor;
byte SensorPayload[SensorPayloadBufferSize];
  
// LoRa field gateway configuration (these settings must match your field gateway)
const byte DeviceAddressMaximumLength = 15 ;
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;
const int InterruptPin = 2;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const unsigned long SensorUploadDelay = 60000;

// 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);

#ifdef 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:");
  DisplayHex( deviceSerialNumber, DeviceSerialNumberLength);
  Serial.println();

  Serial.println("LoRa setup start");

  // override the default chip select and reset pins
  LoRa.setPins(ChipSelectPin, ResetPin, InterruptPin);
  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 CO2, temperature & humidity sensor
  Serial.println("HM3301 setup start");
  if(sensor.init())
  {
    Serial.println("HM3301 init failed");
    while (true); // Drop into endless loop requiring restart
  
  }
  delay(100);
  Serial.println("HM3301 setup done");

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

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

void loop()
{
  unsigned long currentMilliseconds = millis();  
  byte sum=0;
  short pm1_0 ;
  short pm2_5 ;
  short pm10_0 ;

  Serial.println("Loop called");

  if(sensor.read_sensor_value(SensorPayload,SensorPayloadBufferSize) == NO_ERROR)
  {
    // Calculate then validate the payload "checksum"
    for(int i=0;i<SensorPayloadLength;i++)
    {
        sum+=SensorPayload[i];
    }
    if(sum!=SensorPayload[SensorPayloadLength])
    {
        Serial.println("Invalid checksum");
        return;
    }    

    PayloadReset();
    
    pm1_0 = (u16)SensorPayload[SensorPayloadPM1_0Position]<<8|SensorPayload[SensorPayloadPM1_0Position+1];
    Serial.print("PM1.5: ");
    Serial.print(pm1_0);
    Serial.println("ug/m3 ") ;

    PayloadAdd( "P10", pm1_0, false);
    
    pm2_5 = (u16)SensorPayload[SensorPayloadPM2_5Position]<<8|SensorPayload[SensorPayloadPM2_5Position+1];
    Serial.print("PM2.5: ");
    Serial.print(pm2_5);
    Serial.println("ug/m3 ") ;

    PayloadAdd( "P25", pm2_5, 1, false);

    pm10_0 = (u16)SensorPayload[SensorPayloadPM10_0Position]<<8|SensorPayload[SensorPayloadPM10_0Position+1];
    Serial.print("PM10.0: ");
    Serial.print(pm10_0);
    Serial.println("ug/m3 ");

    PayloadAdd( "P100", pm10_0, 0, true) ;

    #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(SensorUploadDelay - (millis() - currentMilliseconds ));
}

void PayloadHeader( const byte *to, byte toAddressLength, const 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( const char *sensorId, float value, byte decimalPlaces, bool last)
{
  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]));
  if (!last)
  {
    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, bool last )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(itoa( value,(char *)&payload[payloadLength],10));
  if (!last)
  {
    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, bool last )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(utoa( value,(char *)&payload[payloadLength],10));
  if (!last)
  {
    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;
}

void DisplayHex( byte *byteArray, byte length) 
{
  for (int i = 0; i < length ; i++)
  {
    // Add a leading zero
    if ( byteArray[i] < 16)
    {
      Serial.print("0");
    }
    Serial.print(byteArray[i], HEX);
    if ( i < (length-1)) // Don't put a - after last digit
    {
      Serial.print("-");
    }
  }
}    

The code is available on GitHub.

20:45:38.021 -> Setup called
20:45:38.054 -> Field gateway:LoRaIoT1 Frequency:915000000MHz SyncWord:18
20:45:38.156 -> SNo:01-23-8C-48-D6-D1-F5-86-EE
20:45:38.190 -> LoRa setup start
20:45:38.190 -> LoRa Setup done.
20:45:38.224 -> HM3301 setup start
20:45:38.292 -> HM3301 setup done
20:45:38.292 -> Setup done
20:45:38.292 -> 
20:45:38.325 -> Loop called
20:45:38.325 -> PM1.5: 10ug/m3 
20:45:38.359 -> PM2.5: 14ug/m3 
20:45:38.359 -> PM10.0: 19ug/m3 
20:45:38.393 -> Loop done
20:45:38.393 -> 
20:46:38.220 -> Loop called
20:46:38.220 -> PM1.5: 10ug/m3 
20:46:38.255 -> PM2.5: 15ug/m3 
20:46:38.255 -> PM10.0: 20ug/m3 
20:46:38.325 -> Loop done
20:46:38.325 -> 
20:47:38.181 -> Loop called
20:47:38.181 -> PM1.5: 10ug/m3 
20:47:38.181 -> PM2.5: 14ug/m3 
20:47:38.216 -> PM10.0: 19ug/m3 
20:47:38.250 -> Loop done
20:47:38.284 -> 
20:48:38.123 -> Loop called
20:48:38.123 -> PM1.5: 10ug/m3 
20:48:38.158 -> PM2.5: 14ug/m3 
20:48:38.158 -> PM10.0: 19ug/m3 
20:48:38.193 -> Loop done
20:48:38.227 -> 
20:49:38.048 -> Loop called
20:49:38.082 -> PM1.5: 10ug/m3 
20:49:38.082 -> PM2.5: 14ug/m3 
20:49:38.117 -> PM10.0: 19ug/m3 
20:49:38.151 -> Loop done
20:49:38.151 -> 
20:50:38.010 -> Loop called
20:50:38.010 -> PM1.5: 9ug/m3 
20:50:38.010 -> PM2.5: 13ug/m3 
20:50:38.045 -> PM10.0: 18ug/m3 
20:50:38.079 -> Loop done
20:50:38.079 -> 

To configure the device in Azure IoT Central (similar process for Adafruit.IO, working on support for losant, ubidots and MyDevices) I copied the SNo: from the Arduino development tool logging window and appended p10 for PM 1 value, p25 for PM2.5 value and p100 for PM10 value to the unique serial number from the ATSHA204A chip. (N.B. pay attention to the case of the field names they are case sensitive)

Azure IoT Central telemetry configuration

The rapidly settled into a narrow range of readings, but spiked when I took left it outside (winter in New Zealand) and the values spiked when food was being cooked in the kitchen which is next door to my office.

It would be good to run the sensor alongside a professional particulates monitor so the values could be compared and used to adjust the readings of the Grove sensor if necessary.

Hour of PM1, PM2.5 & PM10 readings in my office early evening
CO2 and particulates values while outside on my deck from 10:30pm to 11:30pm

Bill of materials (prices as at August 2019)

  • Seeeduino Nano USD6.90
  • Grove – Laser PM2.5 Sensor (HM3301) USD29.90
  • EasySensors Arduino Nano radio shield RFM95 USD15.00

Grove – Carbon Dioxide Sensor(SCD30) trial

In preparation for another student project to monitor the temperature, humidity and CO2 levels in a number of classrooms I purchased a couple of Grove – CO2, Temperature & Humidity Sensors (SCD30) for evaluation.

Seeeduino, Grove SCD30 and easysensors shield

Seeeduino Nano devices have a single on-board I2C socket which meant I didn’t need a Grove Shield for Arduino Nano which reduced the size and cost of the sensor node.

I downloaded the seeedstudio wiki example calibration code, compiled and uploaded it to one of my Seeeduino Nano devices. When activated for the first time a period of minimum 7 days is needed so that the sensor algorithm can find its initial parameter set. During this period the sensor has to be exposed to fresh air for at least 1 hour every day.

During the calibration process I put the device in my garage and left the big door open for at least an hour every day. Once the sensor was calibrated I bought it inside at put it on the bookcase in my office.

I modified my Easy Sensors Arduino Nano Radio Shield RFM69/95 Payload Addressing client to use the sensor.

/*
  Copyright ® 2019 August 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 "SCD30.h"

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

// LoRa field gateway configuration (these settings must match your field gateway)
const byte DeviceAddressMaximumLength = 15 ;
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;
const int InterruptPin = 2;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const unsigned long SensorUploadDelay = 300000;

// 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);

#ifdef 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:");
  DisplayHex( deviceSerialNumber, DeviceSerialNumberLength);
  Serial.println();

  Serial.println("LoRa setup start");

  // override the default chip select and reset pins
  LoRa.setPins(ChipSelectPin, ResetPin, InterruptPin);
  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 CO2, temperature & humidity sensor
  Serial.println("SCD30 setup start");
  Wire.begin();
  scd30.initialize();  
  delay(100);
  Serial.println("SCD30 setup done");

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

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

void loop()
{
  unsigned long currentMilliseconds = millis();  
  float temperature ;
  float humidity ;
  float co2;

  Serial.println("Loop called");

  if(scd30.isAvailable())
  {
    float result[3] = {0};
    PayloadReset();

    // Read the CO2, temperature & humidity values then display nicely
    scd30.getCarbonDioxideConcentration(result);

    co2 = result[0];
    Serial.print("C:");
    Serial.print(co2, 1) ;
    Serial.println("ppm ") ;

    PayloadAdd( "C", co2, 1, false);
    
    temperature = result[1];
    Serial.print("T:");
    Serial.print(temperature, 1) ;
    Serial.println("C ") ;

    PayloadAdd( "T", temperature, 1, false);

    humidity = result[2];
    Serial.print("H:" );
    Serial.print(humidity, 0) ;
    Serial.println("% ") ;

    PayloadAdd( "H", humidity, 0, true) ;

    #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(SensorUploadDelay - (millis() - currentMilliseconds ));
}
...
}    

The code is available on GitHub.

20:38:56.746 -> Setup called
20:38:56.746 -> Field gateway: Frequency:915000000MHz SyncWord:18
20:38:56.849 -> SNo:01-23-39-BD-D6-D1-F5-86-EE
20:38:56.884 -> LoRa setup start
20:38:56.919 -> LoRa Setup done.
20:38:56.919 -> SCD30 setup start
20:38:56.986 -> SCD30 setup done
20:38:56.986 -> Setup done
20:38:57.020 -> 
20:39:06.966 -> Received packet
20:39:06.966 -> Packet size:18
20:39:06.999 -> To len:9
20:39:06.999 -> From len:8
20:39:06.999 -> To:01-23-39-BD-D6-D1-F5-86-EE
20:39:07.034 -> From:4C-6F-52-61-49-6F-54-31
20:39:07.069 -> FieldGateway:4C-6F-52-61-49-6F-54-31
20:39:07.104 -> RSSI -55
20:39:07.139 -> Loop called
20:39:07.139 -> C:730.8ppm 
20:39:07.139 -> T:23.1C 
20:39:07.173 -> H:46% 
20:39:07.173 -> Loop done
20:39:07.208 -> 
20:39:37.123 -> Loop called
20:39:37.158 -> C:529.9ppm 
20:39:37.158 -> T:23.2C 
20:39:37.158 -> H:48% 
20:39:37.228 -> Loop done
20:39:37.228 -> 

To configure the device in Azure IoT Central (similar process for Adafruit.IO, working on support for losant, ubidots and MyDevices) I copied the SNo: from the Arduino development tool logging window and appended c for the CO2 parts per million (ppm), h for the humidity % and t for the temperature °C to the unique serial number from the ATSHA204A chip. (N.B. pay attention to the case of the field names they are case sensitive)

Azure IoT Central telemetry configuration

Overall the performance of the sensor is looking pretty positive, the CO2 levels fluctuate in a acceptable range (based on office occupancy), and the temperature + humidity readings track quite closely to the other two sensor nodes in my office. The only issue so far is my lack of USB-C cables to power the devices in the field

CO2, Humidity and Temperature in my office for a day

Bill of materials (prices as at August 2019)

  • Seeeduino Nano USD6.90
  • Grove – CO2, Humidity & Temperature Sensor(SCD30) USD59.95
  • EasySensors Arduino Nano radio shield RFM95 USD15.00

STM32 Blue Pill LoRaWAN node

A few weeks ago I ordered an STM32 Blue Pill LoRaWAN node from the M2M Shop on Tindie for evaluation. I have bought a few M2M client devices including a Low power LoRaWan Node Model A328, and Low power LoRaWan Node Model B1284 for projects and they have worked well. This one looked interesting as I had never used a maple like device before.

Bill of materials (Prices as at July 2019)

  • STM32 Blue Pill LoRaWAN node USD21
  • Grove – Temperature&Humidity Sensor USD11.5
  • Grove – 4 pin Female Jumper to Grove 4 pin Conversion Cable USD3.90

The two sockets on the main board aren’t Grove compatible so I used the 4 pin female to Grove 4 pin conversion cable to connect the temperature and humidity sensor.

STM32 Blue Pill LoRaWAN node test rig

I used a modified version of my Arduino client code which worked after I got the pin reset pin sorted and the female sockets in the right order.

/*
  Copyright ® 2019 July 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.
  
  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 <itoa.h>     
#include <SPI.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 DeviceAddress[] = {"BLUEPILL"};

// Azure IoT Hub FieldGateway
const char FieldGatewayAddress[] = {"LoRaIoT1"}; 
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Bluepill hardware configuration
const int ChipSelectPin = PA4;
const int InterruptPin = PA0;
const int ResetPin = -1;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;

const int LoopDelaySeconds = 300 ;

// Sensor configuration
const char SensorIdTemperature[] = {"t"};
const char SensorIdHumidity[] = {"h"};


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(ChipSelectPin, ResetPin, InterruptPin);
  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.");

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

 // 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() {
  // read the value from the sensor:
  double temperature = TH02.ReadTemperature();
  double humidity = TH02.ReadHumidity();

  Serial.print("Humidity: ");
  Serial.print(humidity, 0);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(temperature, 1);
  Serial.println(" *C");

  PayloadReset();

  PayloadAdd(SensorIdHumidity, humidity, 0) ;
  PayloadAdd(SensorIdTemperature, temperature, 1) ;

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

  Serial.println("Loop done");

  delay(LoopDelaySeconds * 1000);
}


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( const 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( const 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( const 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
}

To get the application to compile I also had to include itoa.h rather than stdlib.h.

maple_loader v0.1
Resetting to bootloader via DTR pulse
[Reset via USB Serial Failed! Did you select the right serial port?]
Searching for DFU device [1EAF:0003]...
Assuming the board is in perpetual bootloader mode and continuing to attempt dfu programming...

dfu-util - (C) 2007-2008 by OpenMoko Inc.

Initially I had some problems deploying my software because I hadn’t followed the instructions and run the installation batch file.

14:03:56.946 -> Setup called
14:03:56.946 -> LoRa setup start
14:03:56.946 -> LoRa setup done.
14:03:56.946 -> TH02 setup
14:03:57.046 -> TH02 Setup done
14:03:57.046 -> Setup done
14:03:57.115 -> Humidity: 76 %	Temperature: 18.9 *C
14:03:57.182 -> Loop done
14:08:57.226 -> Humidity: 74 %	Temperature: 18.7 *C
14:08:57.295 -> Loop done
14:13:57.360 -> Humidity: 76 %	Temperature: 18.3 *C
14:13:57.430 -> Loop done
14:18:57.475 -> Humidity: 74 %	Temperature: 18.2 *C
14:18:57.544 -> Loop done
14:23:57.593 -> Humidity: 70 %	Temperature: 17.8 *C
14:23:57.662 -> Loop done
14:28:57.733 -> Humidity: 71 %	Temperature: 17.8 *C
14:28:57.802 -> Loop done
14:33:57.883 -> Humidity: 73 %	Temperature: 17.9 *C
14:33:57.952 -> Loop done
14:38:57.997 -> Humidity: 73 %	Temperature: 18.0 *C
14:38:58.066 -> Loop done
14:43:58.138 -> Humidity: 73 %	Temperature: 18.1 *C
14:43:58.208 -> Loop done
14:48:58.262 -> Humidity: 73 %	Temperature: 18.3 *C
14:48:58.331 -> Loop done
14:53:58.374 -> Humidity: 73 %	Temperature: 18.2 *C
14:53:58.444 -> Loop done
14:58:58.509 -> Humidity: 73 %	Temperature: 18.3 *C
14:58:58.578 -> Loop done
15:03:58.624 -> Humidity: 65 %	Temperature: 16.5 *C
15:03:58.694 -> Loop done
15:08:58.766 -> Humidity: 71 %	Temperature: 18.8 *C
15:08:58.836 -> Loop done
15:13:58.893 -> Humidity: 75 %	Temperature: 19.1 *C
15:13:58.963 -> Loop done

I configured the device to upload to my Azure IoT Hub/Azure IoT Central gateway and after getting the device name configuration right it has been running reliably for a couple of days

Azure IoT Central Temperature and humidity

The device was sitting outside on the deck and rapid increase in temperature is me bringing it inside.