Mikrobus.Net Quail and Weather Click

In my second batch of MikroElektronika Mikrobus sensors I had purchased a Weather click because I was interested to see how the temperature and humidity values it returned compared with the Silicon labs Si7005 devices I use with my Arduino and Netduino devices. (I was a bit suspicious of the Si7005 humidity values)

I downloaded the Mikrobus.Net driver for the BME280 and created a simple console application to see how well the sensor and driver worked

public class Program
{
   public static void Main()
   {
      WeatherClick weatherClick = new WeatherClick(Hardware.SocketOne, WeatherClick.I2CAddresses.Address0);

      weatherClick.SetRecommendedMode(WeatherClick.RecommendedModes.WeatherMonitoring);

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

         Thread.Sleep(30000);
      }
   }
}

The temperature values looked pretty good but the humidity values were rough half of what I was getting from the SI7005 connected to a devDuino V2 on the desk next to my Quail board

The thread ‘<No Name>’ (0x2) has exited with code 0 (0x0).
T 24.9 H 49.3 P 1014.8
T 25.0 H 49.4 P 1014.9
T 25.0 H 49.1 P 1014.8
T 25.0 H 49.9 P 1014.8
T 24.9 H 49.1 P 1014.9
T 25.0 H 50.8 P 1014.9
T 25.0 H 49.2 P 1015.0

The code for doing the conversions looked pretty complex so I modified a Netduino BME280 driver (uses a different approach for conversions) I have used on another projects to work on the Quail/Mikrobus architecture.

The modified driver returned roughly the same values so it looks like the problem is most probably with the SI7005 code.(or my understand of the humidity values it returns)

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 Silicon Labs Si7005 Device Driver

A while back I wrote a post about some problems I was having with a Silicon Labs Si7005 device and now I have had some time to package up the code.

My code strobes the I2C SDA line and then initiates a request that will always fail, from there on everything works as expected.

public SiliconLabsSI7005(byte deviceId = DeviceIdDefault, int clockRateKHz = ClockRateKHzDefault, int transactionTimeoutmSec = TransactionTimeoutmSecDefault)
{
   this.deviceId = deviceId;
   this.clockRateKHz = clockRateKHz;
   this.transactionTimeoutmSec = transactionTimeoutmSec;

   using (OutputPort i2cPort = new OutputPort(Pins.GPIO_PIN_SDA, true))
   {
      i2cPort.Write(false);
      Thread.Sleep(250);
   }

   using (I2CDevice device = new I2CDevice(new I2CDevice.Configuration(deviceId, clockRateKHz)))
   {
      byte[] writeBuffer = { RegisterIdDeviceId };
      byte[] readBuffer = new byte[1];

      // The first request always fails
      I2CDevice.I2CTransaction[] action = new I2CDevice.I2CTransaction[] 
      { 
         I2CDevice.CreateWriteTransaction(writeBuffer),
         I2CDevice.CreateReadTransaction(readBuffer)
      };

      if( device.Execute(action, transactionTimeoutmSec) == 0 )
      {
         //   throw new ApplicationException("Unable to send get device id command");
      }
   }
}

This is how the driver should be used in an application

public static void Main()
{
   SiliconLabsSI7005 sensor = new SiliconLabsSI7005();

   while (true)
   {
      double temperature = sensor.Temperature();

      double humidity = sensor.Humidity();

      Debug.Print("T:" + temperature.ToString("F1") + " H:" + humidity.ToString("F1"));

      Thread.Sleep(5000);
      }
   }

I have added code to catch failures and there is a sample application in the project. For a project I’m working on I will modify the code to use one of the I2C sharing libraries so I can have a number of devices on the bus

Netduino 3 Wifi xively nRF24L01 Gateway

The first version of this code acquired data from a number of *duino devices and uploaded it to xively for a week without any problems(bar my ADSL modem dropping out every so often which it recovered from without human intervention). The data streams are the temperature and humidity for the three bedrooms in my house (the most reliable stream is Bedroom 1). Next version will use the new Netduino.IP stack and run on a Netduino 2 Plus

Netduino 3 Wifi with nRF24L01 shield

Netduino 3 Wifi + nRF24L01 shield

To make the software easy to setup all the gateway configuration is stored on a MicroSD and can be modified with a text editor. When the application starts it looks for a file in the root directory of the MicroSD card called app.config. If the file does not exist an empty template is created.

httprequestreadwritetimeoutmsec=2500
httprequesttimeoutmsec=2500
webproxyaddress=
webproxyport=
xivelyapibaseurl=http://api.xively.com/v2/feeds/
xivelyapikey=XivelyAPIKeyGoesHere
xivelyapifeedid=XivelyFeedIDGoesHere
xivelyapicontenttype=text/csv
xivelyapiendpoint=.csv
nrf2l01address=AddressGoesHere
nrf2l01channel=ChannelGoesHere
nrf2l01datarate=0
channel1=Sensor1
channel2=Sensor2
channel3=Sensor3
channel4=Sensor4
channel5=Sensor5
...
...

The first byte of each (upto 32 byte) nRF24L01 message is used to determine the Xively channel.

For testing I used a simple *duino program which uploads temperature and humidity readings every 5 seconds. It’s not terribly efficient or elegant and is just to illustrate how to package up the data.

#include <RF24_config>
#include <nRF24L01.h>
#include <SPI.h>
#include <RF24.h>
#include "Wire.h"
#include <TH02_dev.h>

//UNO R3 with embedded coolness board
//RF24 radio(3, 7);
//devDuino  with onboard
RF24 radio(8, 7);

char payload[32] = "";
const uint64_t pipe = 0x3165736142LL; // Base1 pay attention to byte ordering and address length

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

  radio.begin();
  radio.setPALevel(RF24_PA_MAX);
  radio.setChannel(10);
  radio.enableDynamicPayloads();
  radio.openWritingPipe(pipe);

  radio.printDetails();

  /* Power up,delay 150ms,until voltage is stable */
  delay(150);

  TH02.begin();

  delay(1000);
}

void loop()
{
  float temperature = TH02.ReadTemperature();
  float humidity = TH02.ReadHumidity();

  radio.powerUp();

  payload[0] = 'A';
  dtostrf(temperature, 5, 1, &payload[1]);
  Serial.println(payload);
  boolean result = radio.write(payload, strlen(payload));
  if (result)
    Serial.println("T Ok...");
  else
    Serial.println("T failed.");

  payload[0] = 'B';
  dtostrf(humidity, 5, 1, &payload[1]);
  Serial.println(payload);
  result = radio.write(payload, strlen(payload));
  if (result)
    Serial.println("H Ok...");
  else
    Serial.println("H failed.");

  radio.powerDown();

  delay(5000);
}

The gateway code creates a thread for each call to the Xively REST API. (In future the code may need to limit the number of concurrent requests)

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

   // Ensure that we have a valid payload
   if ( data.Length == 0 )
   {
      Debug.Print( "ERROR - Message has no payload" ) ;
      return ;
   }

   // Extract the device id
   string deviceId = xivelyApiChannleIDPrefix + data[0].ToString();
   string message = new String(Encoding.UTF8.GetChars(data, 1, data.Length - 1));

   string xivelyApiChannel = appSettings.GetString( deviceId, string.Empty ) ;
   if ( xivelyApiChannel.Length == 0 )
   {
      Debug.Print("ERROR - Inbound message has unknown channel " + deviceId);
      return ;
   }
   Debug.Print(DateTime.Now.ToString("HH:mm:ss") + " " + xivelyApiChannel + " " + message); ;

   Thread thread = new Thread(() =&gt; xivelyFeedUpdate(xivelyApiChannel, message ));
   thread.Start();
   }

private void xivelyFeedUpdate( string channel, string value)
{
   #region Assertions
   Debug.Assert(channel != null);
   Debug.Assert(channel != string.Empty );
   Debug.Assert(value != null);
   #endregion

   try
   {
      WebProxy webProxy = null;

      if (webProxyAddress.Length &gt; 1)
      {
         webProxy = new WebProxy(webProxyAddress, webProxyPort);
      }

      using (HttpWebRequest request = (HttpWebRequest)WebRequest.Create(xivelyApiBaseUrl + xivelyApiFeedID + xivelyApiEndpoint))
      {
         byte[] buffer = Encoding.UTF8.GetBytes(channel + "," + value);

         DateTime httpRequestedStartedAtUtc = DateTime.UtcNow;

         if (webProxy != null)
         {
            request.Proxy = webProxy;
         }
         request.Method = "PUT";
         request.ContentLength = buffer.Length;
         request.ContentType = xivelyApiContentType;
         request.Headers.Add("X-ApiKey", xivelyApiKey);
         request.KeepAlive = false;
         request.Timeout = httpRequestTimeoutmSec;
         request.ReadWriteTimeout = httpRequestReadWriteTimeoutmSec;

         // request body
         Debug.Print("HTTP request");
         using (Stream stream = request.GetRequestStream())
         {
            stream.Write(buffer, 0, buffer.Length);
         }

         using (var response = (HttpWebResponse)request.GetResponse())
         {
            Debug.Print(" Status: " + response.StatusCode + " : " + response.StatusDescription);
         }

         TimeSpan duration = DateTime.UtcNow - httpRequestedStartedAtUtc;
         Debug.Print(" Duration: " + duration.ToString());
      }
   }
   catch (Exception ex)
   {
      Debug.Print(ex.Message);
   }
}

To use this code download the Nordic nRF24L01 library from Codeplex then include that plus my Netduino NRF24L01 Xively Gateway in a new solution and it should just work.

Deploy the application to a Netduino 2 Plus or Netduino 3 Wifi device and run it to create the app.config file, then use a text editor to update the file with your Xively & device settings.

I’ll upload this and a couple of other projects to GitHub shortly.

Bill of materials (prices as at July 2015)

Silicon Labs Si7005 Device Driver oddness

I have been working on a Netduino I2C driver for the Silicon Labs Si7005 Digital I2C Humidity & Temperature Sensor for weather station and building monitoring applications as it looks like a reasonably priced device which is not to complex to interface with.I’m using a SeeedStudio Grove – Temperature&Humidity Sensor (High-Accuracy & Mini) for development.

The first time I try and read anything from the device it fails. Otherwise my driver works as expected.

Netduino 2 Plus & Silicon Labs Si7005

Bill of materials (prices as at April 2015)

  • Netduino Plus 2 USD60 NZD108
  • Grove – Temperature&Humidity Sensor (High-Accuracy & Mini) USD11.50
  • Grove – Base Shield USD8.90

This code just shows the flow, I’ll package into a driver shortly

I strobe the I2C line which seems to help

using (OutputPort i2cPort = new OutputPort(Pins.GPIO_PIN_SDA, true))
{
   i2cPort.Write(false);
   Thread.Sleep(1000);
}

I then try and read the Device ID (0x50) from register 0X11 but this (and any other read fails)

byte[] writeBuffer = { RegisterIdDeviceId };
byte[] readBuffer = new byte[1];

I2CDevice.I2CTransaction[] action = new I2CDevice.I2CTransaction[] 
{ 
   I2CDevice.CreateWriteTransaction(writeBuffer),
   I2CDevice.CreateReadTransaction(readBuffer)
};

int length = device.Execute(action, TransactionTimeoutMilliseconds);
Debug.Print(&quot;Byte count &quot; + length.ToString());
foreach (byte Byte in readBuffer)
{
   Debug.Print(Byte.ToString(&quot;X2&quot;));
}

I can read the temperature and humidity by writing to the command register

byte[] writeBuffer = { RegisterIdConiguration, CMD_MEASURE_TEMP };

I2CDevice.I2CTransaction[] action = new I2CDevice.I2CTransaction[] 
{ 
   I2CDevice.CreateWriteTransaction(writeBuffer),
};

int length = device.Execute(action, TransactionTimeoutMilliseconds);
Debug.Print(&quot;Byte count&quot; + length.ToString());

Then poll for measurement process to finish

conversionInProgress = true
do
{
   byte[] writeBuffer = { RegisterIdStatus };
   byte[] readBuffer = new byte[1];

   I2CDevice.I2CTransaction[] action = new I2CDevice.I2CTransaction[] 
   { 
      I2CDevice.CreateWriteTransaction(writeBuffer4),
      I2CDevice.CreateReadTransaction(readBuffer4)
   };

   int length = device.Execute(action, TransactionTimeoutMilliseconds);
   Debug.Print(&quot;Byte count &quot; + length.ToString());
   foreach (byte Byte in readBuffer)
   {
      Debug.Print(Byte.ToString());
   }

   if ((readBuffer[RegisterIdStatus] &amp;&amp; STATUS_RDY_MASK) != STATUS_RDY_MASK)
   {
      conversionInProgress = false;
   }
} while (conversionInProgress);

Then finally read and convert the value

byte[] writeBuffer = { REG_DATA_H };
byte[] readBuffer = new byte[2];

I2CDevice.I2CTransaction[] action = new I2CDevice.I2CTransaction[] 
{ 
   I2CDevice.CreateWriteTransaction(writeBuffer),
   I2CDevice.CreateReadTransaction(readBuffer)
};

int length = device.Execute(action, TransactionTimeoutMilliseconds);
Debug.Print(&quot;Byte count &quot; + length.ToString());
foreach (byte Byte in readBuffer)
{
   Debug.Print(Byte.ToString());
}

int temp = readBuffer[0];

temp = temp &lt;&lt; 8;
temp = temp + readBuffer[1];
temp = temp &gt;&gt; 2;

double temperature = (temp / 32.0) - 50.0;

Debug.Print(&quot; Temp &quot; + temperature.ToString(&quot;F1&quot;));

Azure Event Hub Service Gateway V0.1

My Netduino and Arduino devices can’t do https so I had been looking at different approaches for uploading sensor data to a Microsoft Azure Event Hub. In a previous post I published the “simplest” possible useful program (a console application) which could upload data and this code builds on that.

In this proof of concept I have integrated the core of the console application code into an ASP.NET MVC WebAPI 2 project which acts as a service gateway. My Netduino clients now use a website hosted on my Essentials 2012 home server to forward the requests to a Microsoft Azure Event Hub .

For more detail about how to program the energy monitor shield see these posts about the Nokia 5110 display, nrf24L01 wireless link, and non invasive current sensor algorithm optimisations.

try
{
   using (HttpWebRequest request = (HttpWebRequest)WebRequest.Create( AzureGatewayUrl ))
   {
      string payload = @&quot;{&quot;&quot;DeviceId&quot;&quot;:&quot; + deviceId + @&quot;,&quot;&quot;Usage&quot;&quot;:&quot; + value + &quot;}&quot;;
      byte[] buffer = Encoding.UTF8.GetBytes(payload);
      request.Method = &quot;POST&quot;;
      request.ContentLength = buffer.Length;
      request.ContentType = &quot;text/csv&quot;;
      request.KeepAlive = false;
      request.Timeout = 5000;
      request.ReadWriteTimeout = 5000;

      using (Stream stream = request.GetRequestStream())
      {
         stream.Write(buffer, 0, buffer.Length);
      }
      using (var response = (HttpWebResponse)request.GetResponse())
      {
         Debug.Print(&quot;HTTP Status&quot; + response.StatusCode + &quot; : &quot; + response.StatusDescription);
      }
   }
}
catch (Exception ex)
{
   Debug.Print(ex.Message);
}
Netduino power consumption monitor

Netduino power consumption monitor

Azure Service Bus Explorer by  Paolo Salvatori is great for debugging and testing Service Bus applications like this.

ServiceBus Explorer Displaying event hub power consumption data

ServiceBus Explorer displaying power consumption data

Bill of materials (prices as at Feb 2015)

The Azure Event Hub Service GatewayV0.1 is pretty basic with, no security, doesn’t have a lot of logging. wouldn’t scale terribly well (Though most home systems wouldn’t have a lot of sensors) and is hosted in Internet Information Server(IIS),

In future posts I’ll fix these limitations and make the service gateway secure, easier to install, configure and operate. But, this proof of concept proves the approach is viable

// POST api/eventhub
 public void Post(HttpRequestMessage request)
      {
         try
         {
            string connectionString = ConfigurationManager.AppSettings["Microsoft.ServiceBus.ConnectionString"];
            string eventHubName = ConfigurationManager.AppSettings["Microsoft.ServiceBus.EventHub"];

            NamespaceManager namespaceManager = NamespaceManager.CreateFromConnectionString(connectionString);

            EventHubClient client = EventHubClient.Create(eventHubName);

            EventData data = new EventData(request.Content.ReadAsByteArrayAsync().Result);

            // Set user properties if needed
            data.Properties.Add("UploadedAtUTC", DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss"));
            data.Properties.Add("UploadedBy", "devMobileAzureEventHubGateway");

            client.Send(data);
         }
         catch (Exception ex)
         {
            Debug.WriteLine("Send failed " + ex.Message);
         }
      }