nRF24L01 Raspberry PI Gateway Hardware

For those who came to my MS Ignite AU Intelligent Cloud booth session

Building Wireless Field Gateways

Connecting wireless sensor nodes to the cloud is not the mission it used to be, because the Azure team (and many OS projects) have developed tooling which can help hobbyist and professional developers build solutions. How could you build a home scale robust, reliable and secure solution with off the shelf kit without blowing the budget?

Sparkfun nRF24L01 module &Adafruit perma proto hat

NRF24L01 Raspberry PI DIY Gateway Hardware

BoM (all prices as at Feb 2016)

You will also need some short lengths of wire and a soldering iron.

For those who want an “off the shelf” solution (still requires a minor modification for interrupt support) I have used the Raspberry Pi to NRF24l01+ Shield USD9.90

2015-09-25t072754-447z-20150925_091942-855x570_q85_pad_rcrop

Instructions for modifications and software to follow.

Mikrobus.Net Quail, Weather & nRF-C clicks and xively

My next proof of concept uses a Weather click and nRF C click to upload temperature and humidity data to a Xively gateway running on a spare Netduino 2 Plus. I have a couple of Azure Event hub gateways (direct & queued) which require a Netduino 3 Wifi (for TLS/AMQPS support) and I’ll build a client for them in a coming post.

I initially purchased an nRF T click but something wasn’t quite right with its interrupt output. The interrupt line wasn’t getting pulled low at all so there were no send success/failure events. If I disabled the pull up resistor and strobed the interrupt pin on start-up the device would work for a while.


using (OutputPort Int = new OutputPort(socket.Int, true))
{
 Int.Write(true);
};

...

_irqPin = new InterruptPort(socket.Int, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);

The code sends a reading every 10 seconds and has been running for a couple of days. It strobes Led1 for each successful send and turns on Led2 when a send fails.

private static readonly byte[] deviceAddress = Encoding.UTF8.GetBytes("Quail");
private static readonly byte[] gatewayAddress = Encoding.UTF8.GetBytes("12345");
private const byte gatewayChannel = 10;
private const NRFC.DataRate gatewayDataRate = NRFC.DataRate.DR1Mbps;
private const int XivelyUpdateDelay = 10000;
private const char XivelyGatewayChannelIdTemperature = 'J';
private const char XivelyGatewayChannelIdHumidity = 'K';

public static void Main()
{
   NRFC nRF24Click = new NRFC(Hardware.SocketFour);
   nRF24Click.Configure(deviceAddress, gatewayChannel, gatewayDataRate);
   nRF24Click.OnTransmitFailed += nRF24Click_OnTransmitFailed;
   nRF24Click.OnTransmitSuccess += nRF24Click_OnTransmitSuccess;
   nRF24Click.Enable();

   // Configure the weather click
   WeatherClick weatherClick = new WeatherClick(Hardware.SocketOne, WeatherClick.I2CAddresses.Address0);
   weatherClick.SetRecommendedMode(WeatherClick.RecommendedModes.WeatherMonitoring);

   Thread.Sleep(XivelyUpdateDelay);

   while (true)
   {
      string temperatureMessage = XivelyGatewayChannelIdTemperature + weatherClick.ReadTemperature().ToString("F1");
      Debug.Print(temperatureMessage);
      MBN.Hardware.Led1.Write(true);
      nRF24Click.SendTo(gatewayAddress, Encoding.UTF8.GetBytes(temperatureMessage));

      Thread.Sleep(XivelyUpdateDelay);

      string humidityMessage = XivelyGatewayChannelIdHumidity + weatherClick.ReadHumidity().ToString("F1");
      Debug.Print(humidityMessage);
      MBN.Hardware.Led1.Write(true);
      nRF24Click.SendTo(gatewayAddress, Encoding.UTF8.GetBytes(humidityMessage));

      Thread.Sleep(XivelyUpdateDelay);
   }
}

static void nRF24Click_OnTransmitSuccess()
{
   MBN.Hardware.Led1.Write(false);
   if (MBN.Hardware.Led2.Read())
   {
      MBN.Hardware.Led2.Write(false);
   }

   Debug.Print("nRF24Click_OnTransmitSuccess");
}

static void nRF24Click_OnTransmitFailed()
{
   MBN.Hardware.Led2.Write(true);

   Debug.Print("nRF24Click_OnTransmitFailed");
}

I need to have a look at interfacing some more sensors and soak testing the solution.

The MikroBus.Net team have done a great job with the number & quality of the drivers they have available.

Mikrobus.Net Quail, EthClick and xively

My second proof of concept application for the Mikrobus.Net Quail and EthClick uploads temperature and humidity data to Xively every 30 seconds for display and analysis.

Temperature and humidity Xively data stream

Temperature and humidity Xively data stream

The Xively REST API uses an HTTP PUT which initially didn’t work because the payload was not getting attached.

I patched the AssembleRequest method in the EtherClick driver to fix this issue.

private byte[] AssembleRequest()
{
   var a = RequestType;
   a += " " + Path + " " + Protocol + "\r\nHost: ";
   a += Host + "\r\n";

   foreach (object aHeader in Headers.Keys)
      a += (string)aHeader + ": " + (string)Headers[aHeader] + "\r\n";

   a += "\r\n"; // Cache-Control: no-cache\r\n  //Accept-Charset: utf-8;\r\n

   if (Content != null && Content != string.Empty && (RequestType == "POST" || RequestType == "PUT")) a += Content;

   return Encoding.UTF8.GetBytes(a);
}

The code reads the WeatherClick temperature and humidity values then assembles a CSV payload which it uploads with an HTTP PUT

</pre>
public class Program
{
   private const string xivelyHost = @"api.xively.com";
   private const string xivelyApiKey = @"YourAPIKey";
   private const string xivelyFeedId = @"YourFeedID";

   public static void Main()
   {
      WeatherClick weatherClick = new WeatherClick(Hardware.SocketOne, WeatherClick.I2CAddresses.Address0);
      weatherClick.SetRecommendedMode(WeatherClick.RecommendedModes.WeatherMonitoring);

      EthClick ethClick = new EthClick(Hardware.SocketTwo);
      ethClick.Start(ethClick.GenerateUniqueMacAddress("devMobileSoftware"), "QuailDevice");

      // Wait for an internet connection
      while (true)
      {
         if (ethClick.ConnectedToInternet)
         {
            Debug.Print("Connected to Internet");
            break;
         }
         Debug.Print("Waiting on Internet connection");
      }

      while (true)
      {
         Debug.Print("T " + weatherClick.ReadTemperature().ToString("F1") + " H " + weatherClick.ReadHumidity().ToString("F1") + " P " + weatherClick.ReadPressure(PressureCompensationModes.Uncompensated).ToString("F1"));

         HttpRequest request = new HttpRequest(@"http://" + xivelyHost + @"/v2/feeds/" + xivelyFeedId + @".csv");
         request.Host = xivelyHost;
         request.RequestType = "PUT";
         request.Headers.Add("Content-Type", "text/csv");
         request.Headers.Add("X-ApiKey", xivelyApiKey );

         request.Content = "OfficeT," + weatherClick.ReadTemperature().ToString("F1") + "\r\n" + "OfficeH," + weatherClick.ReadHumidity().ToString("F1") ;
         request.Headers.Add("Content-Length", request.Content.Length.ToString());

         var response = request.Send();
         if (response != null)
         {
            Debug.Print("Response: " + response.Message);
         }
         else
         {
            Debug.Print("No response");
         }
      Thread.Sleep(30000);
      }
   }
}
MikrobustNet Quail with Eth and Weather Clicks

MikrobustNet Quail with Eth and Weather Clicks

This proof of concept code appears to be reliable and has run for days at a time. The IP stack looks like it needs a bit more work.

Netduino 3 Wifi Queued Azure Event Hub Field Gateway V1.0

My ADSL connection had been a bit flaky which had meant I had lost some sensor data with my initial Azure Event Hub gateway. In attempt make the solution more robust this version of the gateway queues unsent messages using the on-board MicroSD card support.

The code assumes that a file move is an “atomic operation”, so it streams the events received from the devices into a temporary directory (configurable) then moves them to the upload directory (configurable).

This code is proof of concept and needs to be soak tested, improved error handling and some additional multi threading locking added plus the magic constants refactored.

This code is called in the nRF24 receive messages handler

private void OnReceive(byte[] data)
{
   activityLed.Write(!activityLed.Read());

   // Ensure that we have a payload
   if (data.Length < 1 )
   {
      Debug.Print( "ERROR - Message has no payload" ) ;
      return ;
   }

   string message = new String(Encoding.UTF8.GetChars(data));
   Debug.Print("+" + DateTime.UtcNow.ToString("HH:mm:ss") + " L=" + data.Length + " M=" + message);

   string filename = DateTime.UtcNow.ToString("yyyyMMddhhmmssff") + ".txt";

   string tempDirectory = Path.Combine("\\sd", "temp");
   string tempFilePath = Path.Combine(tempDirectory, filename);

   string queueDirectory = Path.Combine("\\sd", "data");
   string queueFilePath = Path.Combine(queueDirectory, filename);

   File.WriteAllBytes(tempFilePath, data);

   File.Move(tempFilePath, queueFilePath);

   new Microsoft.SPOT.IO.VolumeInfo("\\sd").FlushAll();
}

A timer initiates the upload process which uses the AMQPNetlite library

bool UploadInProgress = false;

      
void uploaderCallback(object state)
{
   Debug.Print("uploaderCallback - start");

   if (UploadInProgress)
   {
      return;
   }
   UploadInProgress = true;

   string[] eventFilesToSend = Directory.GetFiles(Path.Combine("\\sd", "data")) ;

   if ( eventFilesToSend.Length == 0 )
   {
      Debug.Print("uploaderCallback - no files");
      UploadInProgress = false;
      return ;
   }

   try
   {
      Debug.Print("uploaderCallback - Connect");
      Connection connection = new Connection(new Address(serviceBusHost, serviceBusPort, serviceBusSasKeyName, serviceBusSasKey));

      Session session = new Session(connection);

      SenderLink sender = new SenderLink(session, "send-link", eventHubName);

      for (int index = 0; index < System.Math.Min(eventUploadBatchSizeMaximum, eventFilesToSend.Length); index++)
      {
         string eventFile = eventFilesToSend[ index ] ;

         Debug.Print("-" + DateTime.UtcNow.ToString("HH:mm:ss") + " " + eventFile ); ;

         Message message = new Message()
         {
            BodySection = new Data()
            {
               Binary = File.ReadAllBytes(eventFile),
            },
         ApplicationProperties = new Amqp.Framing.ApplicationProperties(),
         };

         FileInfo fileInfo = new FileInfo(eventFile);

         message.ApplicationProperties["AcquiredAtUtc"] = fileInfo.CreationTimeUtc;
         message.ApplicationProperties["UploadedAtUtc"] = DateTime.UtcNow;
         message.ApplicationProperties["GatewayId"] = gatewayId;
         message.ApplicationProperties["DeviceId"] = deviceId;
         message.ApplicationProperties["EventId"] = Guid.NewGuid();

         sender.Send(message);

         File.Delete(eventFile);

         new Microsoft.SPOT.IO.VolumeInfo("\\sd").FlushAll();
      }

      sender.Close();
      session.Close();
      connection.Close();
   }
   catch (Exception ex)
   {
      Debug.Print("ERROR: Upload failed with error: " + ex.Message);
   }
   finally
   {
      Debug.Print("uploaderCallback - finally");
      UploadInProgress = false;
   }
}

The timer period and number of files uploaded in each batch is configurable. I need to test the application to see how it handles power outages and MicroSD card corruption. The source is Netduino NRF24L01 AMQPNetLite Queued Azure EventHub Gatewaywith all the usual caveats.

This project wouldn’t have been possible without

Netduino 3 Wifi pollution Sensor Part 2

In a previous post I had started building a driver for the Seeedstudio Grove Dust Sensor. It was a proof of concept and it didn’t handle some edge cases well.

While building the pollution monitor with a student we started by simulating the negative occupancy of the Shinyei PPD42NJ Particle sensor with the Netduino’s on-board button. This worked and reduced initial complexity. But it also made it harder to simulate the button being pressed as the program launches (the on-board button is also the reset button), or simulate if the button was pressed at the start or end of the period.

Dust sensor simulation with button

Netduino 3 Wifi Test Harness

The first sample code processes button press interrupts and displays the values of the data1 & data2 parameters

public class Program
{
   public static void Main()
   {
      InterruptPort button = new InterruptPort(Pins.GPIO_PIN_D5, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
      button.OnInterrupt += button_OnInterrupt;

      Thread.Sleep(Timeout.Infinite);
   }

   static void button_OnInterrupt(uint data1, uint data2, DateTime time)
   {
      Debug.Print(time.ToString("hh:mm:ss.fff") + " data1 =" + data1.ToString() + " data2 = " + data2.ToString());
   }
}

Using the debugging output from this application we worked out that data1 was the Microcontroller Pin number and data2 was the button state.

12:00:14.389 data1 =24 data2 = 0
12:00:14.389 data1 =24 data2 = 1
12:00:14.389 data1 =24 data2 = 0
12:00:15.851 data1 =24 data2 = 1
12:00:16.078 data1 =24 data2 = 0

We then extended the code to record the duration of each button press.

public class Program
{
   static DateTime buttonLastPressedAtUtc = DateTime.UtcNow;

   public static void Main()
   {
      InterruptPort button = new InterruptPort(Pins.ONBOARD_BTN, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
      button.OnInterrupt += button_OnInterrupt;

      Thread.Sleep(Timeout.Infinite);
   }

   static void button_OnInterrupt(uint data1, uint data2, DateTime time)
   {
      if (data2 == 0)
      {
         TimeSpan duration = time - buttonLastPressedAtUtc;

         Debug.Print(duration.ToString());
      }
      else
      {
         buttonLastPressedAtUtc = time;
      }
   }
}

The thread ” (0x4) has exited with code 0 (0x0).
00:00:00.2031790
00:00:00.1954150
00:00:00.1962350

The next step was to keep track of the total duration of the button presses since the program started executing.

public class Program
{
   static DateTime buttonLastPressedAtUtc = DateTime.UtcNow;
   static TimeSpan buttonPressedDurationTotal;

   public static void Main()
   {
      InterruptPort button = new InterruptPort(Pins.ONBOARD_BTN, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
      button.OnInterrupt += button_OnInterrupt;

      Thread.Sleep(Timeout.Infinite);
   }

   static void button_OnInterrupt(uint data1, uint data2, DateTime time)
   {
      if (data2 == 0)
      {
         TimeSpan duration = time - buttonLastPressedAtUtc;

         buttonPressedDurationTotal += duration;
          Debug.Print(duration.ToString() + " " + buttonPressedDurationTotal.ToString());
      }
      else
      {
         buttonLastPressedAtUtc = time;
      }
   }
}

The thread ” (0x4) has exited with code 0 (0x0).
00:00:00.2476460 00:00:00.2476460
00:00:00.2193600 00:00:00.4670060
00:00:00.2631400 00:00:00.7301460
00:00:00.0001870 00:00:00.7303330

We then added a timer to display the amount of time the button was pressed in the configured period.

public class Program
{
   static TimeSpan measurementDueTime = new TimeSpan(0, 0, 30);
   static TimeSpan measurementperiodTime = new TimeSpan(0, 0, 30);
   static DateTime buttonLastPressedAtUtc = DateTime.UtcNow;
   static TimeSpan buttonPressedDurationTotal;


   public static void Main()
   {
      InterruptPort button = new InterruptPort(Pins.GPIO_PIN_D5, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
      button.OnInterrupt += button_OnInterrupt;

      Timer periodTimer = new Timer(periodTimerProc, button, measurementDueTime, measurementperiodTime);

      Thread.Sleep(Timeout.Infinite);
   }

   static void periodTimerProc(object status)
   {
      InterruptPort button = (InterruptPort)status;

      if (button.Read())
      {
         TimeSpan duration = DateTime.UtcNow - buttonLastPressedAtUtc;

         buttonPressedDurationTotal += duration; 
      }

      Debug.Print(buttonPressedDurationTotal.ToString());

      buttonPressedDurationTotal = new TimeSpan(0, 0, 0);
      buttonLastPressedAtUtc = DateTime.UtcNow;
   }

   static void button_OnInterrupt(uint data1, uint data2, DateTime time)
   {
      if (data2 == 0)
      {
         TimeSpan duration = time - buttonLastPressedAtUtc;

         buttonPressedDurationTotal += duration;

         Debug.Print(duration.ToString() + " " + buttonPressedDurationTotal.ToString());
      }
      else
      {
         buttonLastPressedAtUtc = time;
      }
   }
}

The thread ” (0x4) has exited with code 0 (0x0).
00:00:00
00:00:00
00:00:00.2299050 00:00:00.2299050
00:00:00.1956980 00:00:00.4256030
00:00:00.1693190 00:00:00.5949220
00:00:00.5949220

After some testing we identified that the handling of button presses at the period boundaries was problematic and revised the code some more. We added a timer for the startup period to simplify the interrupt handling code.

public class Program
{
   static TimeSpan measurementDueTime = new TimeSpan(0, 0, 60);
   static TimeSpan measurementperiodTime = new TimeSpan(0, 0, 30);
   static DateTime buttonLastPressedAtUtc = DateTime.UtcNow;
   static TimeSpan buttonPressedDurationTotal;

   public static void Main()
   {
      InterruptPort button = new InterruptPort(Pins.GPIO_PIN_D5, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
      button.OnInterrupt += button_OnInterrupt;

      Timer periodTimer = new Timer(periodTimerProc, button, Timeout.Infinite, Timeout.Infinite);

      Timer startUpTImer = new Timer(startUpTimerProc, periodTimer, measurementDueTime.Milliseconds, Timeout.Infinite);

      Thread.Sleep(Timeout.Infinite);
   }

   static void startUpTimerProc(object status)
   {
      Timer periodTimer = (Timer)status;

      Debug.Print( DateTime.UtcNow.ToString("hh:mm:ss") + " -Startup complete");

      buttonLastPressedAtUtc = DateTime.UtcNow;
      periodTimer.Change(measurementDueTime, measurementperiodTime);
   }

   static void periodTimerProc(object status)
   {
      InterruptPort button = (InterruptPort)status;
      Debug.Print(DateTime.UtcNow.ToString("hh:mm:ss") + " -Period timer");

      if (button.Read())
      {
         TimeSpan duration = DateTime.UtcNow - buttonLastPressedAtUtc;

         buttonPressedDurationTotal += duration;
      }

      Debug.Print(buttonPressedDurationTotal.ToString());

      buttonPressedDurationTotal = new TimeSpan(0, 0, 0);
      buttonLastPressedAtUtc = DateTime.UtcNow;
   }

   static void button_OnInterrupt(uint data1, uint data2, DateTime time)
   {
      Debug.Print(DateTime.UtcNow.ToString("hh:mm:ss") + " -OnInterrupt");

      if (data2 == 0)
      {
         TimeSpan duration = time - buttonLastPressedAtUtc;

         buttonPressedDurationTotal += duration;

         Debug.Print(duration.ToString() + " " + buttonPressedDurationTotal.ToString());
      }
      else
      {
         buttonLastPressedAtUtc = time;
      }
   }
}

The debugging output looked positive, but more testing is required.

The thread ” (0x2) has exited with code 0 (0x0).
12:00:13 -Startup complete
12:01:13 -Period timer
00:00:00
12:01:43 -Period timer
00:00:00
12:01:46 -OnInterrupt
12:01:48 -OnInterrupt
00:00:01.2132510 00:00:01.2132510
12:01:49 -OnInterrupt
12:01:50 -OnInterrupt
00:00:01.3001240 00:00:02.5133750
12:01:53 -OnInterrupt
12:01:54 -OnInterrupt
00:00:01.1216510 00:00:03.6350260
12:02:13 -Period timer
00:00:03.6350260

Next steps – multi threading, extract code into a device driver and extend to support sensors like the SeeedStudio Smart dust Sensor which has two digital outputs, one for small particles (e.g. smoke) the other for larger particles (e.g. dust).

Netduino 3 Wifi pollution Sensor Part 1

I am working on a Netduino 3 Wifi based version for my original concept as a STEM project for high school students. I wanted to be able to upload data to a Microsoft Azure Eventhub or other HTTPS secured RESTful endpoint (e.g. xivelyIOT) to show how to build a securable solution. This meant a Netduino 3 Wifi device with the TI C3100 which does all the crypto processing was necessary.

The aim was to (over a number of blog posts) build a plug ‘n play box that initially was for measuring airborne particulates and then overtime add more sensors e.g. atmospheric gas concentrations, (Grove multichannel gas sensor), an accelerometer for earthquake early warning/monitoring (Grove 3-Axis Digital Accelerometer) etc.

Netduino 3 Wifi based pollution sensor

Bill of materials for prototype as at (October 2015)

  • Netduino 3 Wifi USD69.95
  • Seeedstudio Grove base shield V2 USD8.90
  • Seeedstudio Grove smart dust sensor USD16.95
  • Seeedstudio Grove Temperature & Humidity Sensor pro USD14.90
  • Seeedstudio ABS outdoor waterproof case USD1.65
  • Seeedstudio Grove 4 pin female to Grove 4 pin conversion cable USD3.90
  • Seeedstudio Grove 4 pin buckled 5CM cabed USD1.90

After the first assembly I have realised the box is a bit small. There is not a lot of clearance around the Netduino board (largely due to the go!bus connectors on the end making it a bit larger than a standard *duino board) and the space for additional sensors is limited so I will need to source a larger enclosure.

The dust sensor doesn’t come with a cable so I used the conversion cable instead. NOTE – The pins on the sensor are numbered right->Left rather than left->right.

The first step is to get the temperature and humidity sensor working with my driver code, then adapt the Seeedstudio Grove-Dust sensor code for the dual outputs of the SM-PWM-01 device.

According to the SM-PWM-01A device datasheet The P1 output is for small particles < 1uM (smoke) and P2 output is for large particles > 2uM (dust). The temperature & humidity sensor is included in the first iteration as other researchers have indicated that humidity levels can impact on the accuracy of optical particle counters.

Then, once the sensors are working as expected I will integrate a cut back version of the AMQPNetLite code and configuration storage code I wrote for my Netduino 3 wifi Azure EventHub Field Gateway.

Netduino 3 Wifi Azure Event Hub Field Gateway V2.0

After some testing I have improved the error handling and robustness of my Netduino 3 wifi based Azure Eventhub field gateway.

private void OnReceive(byte[] data)
{
   activityLed.Write(!activityLed.Read());

   // Ensure that we have a payload
   if (data.Length < 1 ) { Debug.Print( "ERROR - Message has no payload" ) ; return ; } string message = new String(Encoding.UTF8.GetChars(data)); Debug.Print(DateTime.UtcNow.ToString("HH:mm:ss") + " L=" + data.Length + " M=" + message); Thread thread = new Thread(() => EventHubSendMessage( data));
   thread.Start();
}

private void EventHubSendMessage( byte[] messageBody)
{
   #region Diagnostic assertions
   Debug.Assert(eventHubName != null);
   Debug.Assert(deviceId != null);
   Debug.Assert(gatewayId != null);
   Debug.Assert(messageBody != null);
   Debug.Assert(messageBody.Length > 0);
   #endregion

   if ((connection == null) || (session == null ) || (senderLink == null ))
   {
      lock (lockThis)
      {
         if (connection == null)
         {
            Debug.Print("AMQP Establish connection");
            try
            {
               connection = new Connection(new Address(serviceBusHost, serviceBusPort, serviceBusSasKeyName, serviceBusSasKey));

               connection.Closed = ConnectionClosedCallback;

               Debug.Print("AMQP Establish connection done");
            }
            catch (Exception ex)
            {
               Debug.Print("ERROR: AMQP Establish connection: " + ex.Message);
            }
         }

         if (connection == null)
         {
            return;
         }

         if (session == null)
         {
            Debug.Print("AMQP Establish session");
            try
            {
               session = new Session(connection);

               session.Closed = SessionClosedCallback;

               Debug.Print("AMQP Establish session done");
            }
            catch (Exception ex)
            {
               Debug.Print("ERROR: AMQP Establish session: " + ex.Message);
            }
         }

         if (session == null)
         {
            return;
         }

         if (senderLink == null)
         {
            Debug.Print("AMQP Establish SenderLink");
            try
            {
               senderLink = new SenderLink(session, "send-link", eventHubName);

               senderLink.Closed = SenderLinkClosedCallback;

               Debug.Print("AMQP Establish SenderLink done");
            }
            catch (Exception ex)
            {
               Debug.Print("ERROR: AMQP Establish SenderLink: " + ex.Message);
            }
         }

         if (senderLink == null)
         {
            return;
         }
      }
   }

         
   try
   {
      Debug.Print("AMQP Send start");
      DateTime startAtUtc = DateTime.UtcNow;

      Message message = new Message()
      {
         BodySection = new Data()
         {
            Binary = messageBody
         },
         ApplicationProperties = new Amqp.Framing.ApplicationProperties(),
      };

      message.ApplicationProperties["UploadedAtUtc"] = DateTime.UtcNow;
      message.ApplicationProperties["GatewayId"] = gatewayId;
      message.ApplicationProperties["DeviceId"] = deviceId;
      message.ApplicationProperties["EventId"] = Guid.NewGuid();

      senderLink.Send(message);
      DateTime finishAtUtc = DateTime.UtcNow;
      TimeSpan duration = finishAtUtc - startAtUtc;
      Debug.Print("AMQP Send done duration " + duration.ToString());
   }
   catch (Exception ex)
   {
      Debug.Print("ERROR: Publish failed with error: " + ex.Message);
   }
}

The software is quite reliable, when my internet connection fails it recovers gracefully and resumes uploading events when connectivity is restored.

The only issue is when the wireless access point is restarted, when the device reconnects it locks up and doesn’t recover. I have posted in the Netduino forums and logged at issue at the Github Netduino wifi repository.

I have been exploring rebooting the device in the NetworkChange_NetworkAvailabilityChanged handler when connectivity is restored.

Based on my logging the sending of events is pretty quick and the threads are interleaved

03:20:59 L=25 M={“D”:2,”H”:63.0,”T”:18.8}
AMQP Send start
03:20:59 L=25 M={“D”:1,”H”:54.5,”T”:18.7}
AMQP Send start
03:20:59 L=17 M={“D”:10,”P”:27.9}
AMQP Send start
AMQP Send done duration 00:00:00.2738220
AMQP Send done duration 00:00:00.4709960
AMQP Send done duration 00:00:01.0813910
03:21:01 L=17 M={“D”:10,”P”:27.4}
AMQP Send start
AMQP Send done duration 00:00:00.2820090
03:21:03 L=17 M={“D”:10,”P”:26.9}

Here is the code with usual caveats.

Next steps queuing messages in memory and then on the MicroSD card.