AdaFruit IO basic Netduino HTTP client

I use Netduino devices for teaching and my students often build projects which need a cloud based service like AdaFruit.IO to capture, store and display their sensor data.

My Proof of Concept (PoC) which uses a slightly modified version of the AdaFruit.IO basic desktop HTTP client code has been running on several Netduino 2 Plus, Netduino 3 Ethernet and Netduino 3 Wifi devices for the last couple of days and looks pretty robust.

The Netduino 3 Wifi device also supports https for improved security and privacy. They also make great field gateways as they can run off solar/battery power.

N2PN3WDashBoard

The devices have been uploading temperature and humidity measurements from a Silicon labs Si7005 sensor. (Outside sensor suffering from sunstrike)

N3WifiTemperatureAndHumiditySensor

program.cs

*

Copyright ® 2017 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.

http://www.devmobile.co.nz

*/
using System;
using System.Net;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using Microsoft.SPOT.Net.NetworkInformation;
using SecretLabs.NETMF.Hardware.Netduino;
using devMobile.NetMF.Sensor;
using devMobile.IoT.NetMF;

namespace devMobile.IoT.AdaFruitIO.NetMF.Client
{
   public class Program
   {
      private const string adaFruitIOApiBaseUrl = @"https://IO.adafruit.com/api/v2/";
      private const string group = "netduino3";
      private const string temperatureFeedKey = "t";
      private const string humidityFeedKey = "h";
      private const string adaFruitUserName = "YourUserName";
      private const string adaFruitIOApiKey = "YourAPIKey";
      private static readonly TimeSpan timerDueAfter = new TimeSpan(0, 0, 15);
      private static readonly TimeSpan timerPeriod = new TimeSpan(0, 0, 30);
      private static OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);
      private static SiliconLabsSI7005 sensor = new SiliconLabsSI7005();
      private static AdaFruitIoClient adaFruitIoClient = new AdaFruitIoClient(adaFruitUserName, adaFruitIOApiKey, adaFruitIOApiBaseUrl);

      public static void Main()
      {
         // Wait for Network address if DHCP
         NetworkInterface networkInterface = NetworkInterface.GetAllNetworkInterfaces()[0];
         if (networkInterface.IsDhcpEnabled)
         {
            Debug.Print(" Waiting for DHCP IP address");

            while (NetworkInterface.GetAllNetworkInterfaces()[0].IPAddress == IPAddress.Any.ToString())
            {
               Debug.Print(" .");
               led.Write(!led.Read());
               Thread.Sleep(250);
            }
            led.Write(false);
         }

         // Display network config for debugging
         Debug.Print("Network configuration");
         Debug.Print(" Network interface type : " + networkInterface.NetworkInterfaceType.ToString());
         Debug.Print(" MAC Address : " + BytesToHexString(networkInterface.PhysicalAddress));
         Debug.Print(" DHCP enabled : " + networkInterface.IsDhcpEnabled.ToString());
         Debug.Print(" Dynamic DNS enabled : " + networkInterface.IsDynamicDnsEnabled.ToString());
         Debug.Print(" IP Address : " + networkInterface.IPAddress.ToString());
         Debug.Print(" Subnet Mask : " + networkInterface.SubnetMask.ToString());
         Debug.Print(" Gateway : " + networkInterface.GatewayAddress.ToString());

         foreach (string dnsAddress in networkInterface.DnsAddresses)
         {
            Debug.Print(" DNS Server : " + dnsAddress.ToString());
         }

         Timer humidityAndtemperatureUpdates = new Timer(HumidityAndTemperatureTimerProc, null, timerDueAfter, timerPeriod);

         Thread.Sleep(Timeout.Infinite);
      }

      static private void HumidityAndTemperatureTimerProc(object state)
      {
         led.Write(true);

         try
         {
            double humidity = sensor.Humidity();

            Debug.Print(" Humidity " + humidity.ToString("F0") + "%");
            adaFruitIoClient.FeedUpdate(group, humidityFeedKey, humidity.ToString("F0"));
         }
         catch (Exception ex)
         {
            Debug.Print("Humidifty read+update failed " + ex.Message);

            return;
         }

         try
         {
            double temperature = sensor.Temperature();

            Debug.Print(" Temperature " + temperature.ToString("F1") + "°C");
            adaFruitIoClient.FeedUpdate(group, temperatureFeedKey, temperature.ToString("F1"));
         }
         catch (Exception ex)
         {
            Debug.Print("Temperature read+update failed " + ex.Message);

            return;
         }

         led.Write(false);
      }

      private static string BytesToHexString(byte[] bytes)
      {
         string hexString = string.Empty;

         // Create a character array for hexidecimal conversion.
         const string hexChars = "0123456789ABCDEF";

         // Loop through the bytes.
         for (byte b = 0; b < bytes.Length; b++)          {             if (b > 0)
               hexString += "-";

            // Grab the top 4 bits and append the hex equivalent to the return string.
            hexString += hexChars[bytes[b] >> 4];

            // Mask off the upper 4 bits to get the rest of it.
            hexString += hexChars[bytes[b] & 0x0F];
         }

         return hexString;
      }
   }
}

AdaFruit.IO client.cs, handles feed groups and individual feeds

/*

Copyright ® 2017 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.

http://www.devmobile.co.nz

*/
using System;
using System.IO;
using System.Net;
using System.Text;
using Microsoft.SPOT;

namespace devMobile.IoT.NetMF
{
   public class AdaFruitIoClient
   {
      private const string apiBaseUrlDefault = @"http://IO.adafruit.com/api/v2/";
      private string apiBaseUrl = "";
      private string userName = "";
      private string apiKey = "";
      private int httpRequestTimeoutmSec;
      private int httpRequestReadWriteTimeoutmSec;

      public AdaFruitIoClient(string userName, string apiKey, string apiBaseUrl = apiBaseUrlDefault, int httpRequestTimeoutmSec = 2500, int httpRequestReadWriteTimeoutmSec = 5000)
      {
         this.apiBaseUrl = apiBaseUrl;
         this.userName = userName;
         this.apiKey = apiKey;
         this.httpRequestReadWriteTimeoutmSec = httpRequestReadWriteTimeoutmSec;
         this.httpRequestTimeoutmSec = httpRequestTimeoutmSec;
      }

      public void FeedUpdate(string group, string feedKey, string value)
      {
         string feedUrl;

         if (group.Trim() == string.Empty)
         {
            feedUrl = apiBaseUrl + userName + @"/feeds/" + feedKey + @"/data";
         }
         else
         {
            feedUrl = apiBaseUrl + userName + @"/feeds/" + group.Trim() + "." + feedKey + @"/data";
         }

         HttpWebRequest request = (HttpWebRequest)WebRequest.Create(feedUrl);
         {
            string payload = @"{""value"": """ + value + @"""}";
            byte[] buffer = Encoding.UTF8.GetBytes(payload);

            DateTime httpRequestedStartedAtUtc = DateTime.UtcNow;

            request.Method = "POST";
            request.ContentLength = buffer.Length;
            request.ContentType = @"application/json";
            request.Headers.Add("X-AIO-Key", apiKey);
            request.KeepAlive = false;
            request.Timeout = this.httpRequestTimeoutmSec;
            request.ReadWriteTimeout = this.httpRequestReadWriteTimeoutmSec;

            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());
         }
      }
   }
}

Bill of materials for PoC

AdaFruit IO basic desktop HTTP client

AdaFruit IO meets my basic criteria as it has support for HTTP/S clients (it also has an MQTT interface which I will look at in a future post) and the API is well documented.

My first Proof of Concept (PoC) was to build a desktop client which used the HttpWebRequest (for ease of porting to NetMF) classes to upload data.

The program uploaded one of three simulated values to AdaFruit.IO every 10 seconds.

I found the username, group, and feed keys to be case sensitive so pay close attention to the values displayed in the webby UI or copy n paste.

program.cs

 class Program
   {
      static void Main(string[] args)
      {
         string adaFruitIOApiBaseUrl = "https://IO.adafruit.com/api/v2/";
         string adaFruitIOUserName = "YourUserName"; // This is mixed case & case sensitive
         string adaFruitIOApiKey = "YourAPIKey";
         // The feed group and feed key are forced to lower case by UI
         const string feedGroup = "";
         //const string feedGroup = "devduinov2-dot-2";
         const string temperatureKey = "t";
         const double temperatureBase = 20.0;
         const double temperatureRange = 10.0;
         const string humidityKey = "h";
         const double humidityBase = 70.0;
         const double humidityRange = 20.0;
         const string batteryVoltageKey = "v";
         const double batteryVoltageBase = 3.00;
         const double batteryVoltageRange = -1.00;
         TimeSpan dataUpdateDelay = new TimeSpan(0, 0, 10);
         Random random = new Random();

         while (true)
         {
            double temperature = temperatureBase + random.NextDouble() * temperatureRange;
            Console.WriteLine("Temperature {0}°C", temperature.ToString("F1"));
            AdaFruitIoFeedUpdate(adaFruitIOApiBaseUrl, adaFruitIOUserName, adaFruitIOApiKey, feedGroup, temperatureKey, temperature.ToString("F1"));

            Thread.Sleep(dataUpdateDelay);

            double humidity = humidityBase + random.NextDouble() * humidityRange;
            Console.WriteLine("Humidity {0}%", humidity.ToString("F0"));
            AdaFruitIoFeedUpdate(adaFruitIOApiBaseUrl, adaFruitIOUserName, adaFruitIOApiKey, feedGroup, humidityKey, humidity.ToString("F0"));

            Thread.Sleep(dataUpdateDelay);

            double batteryVoltage = batteryVoltageBase + random.NextDouble() * batteryVoltageRange;
            Console.WriteLine("Battery voltage {0}V", batteryVoltage.ToString("F2"));
            AdaFruitIoFeedUpdate(adaFruitIOApiBaseUrl, adaFruitIOUserName, adaFruitIOApiKey, feedGroup, batteryVoltageKey, batteryVoltage.ToString("F2"));

            Thread.Sleep(dataUpdateDelay);
         }
      }

client.cs

      public void AdaFruitIoFeedUpdate(string apiBaseUrl, string userName, string apiKey, string group, string feedKey, string value, int httpRequestTimeoutmSec = 2500, int httpRequestReadWriteTimeoutmSec = 5000)
      {
         string feedUrl;

         if (group.Trim() == string.Empty)
         {
            feedUrl = apiBaseUrl + userName + @"/feeds/" + feedKey + @"/data";
         }
         else
         {
            feedUrl = apiBaseUrl + userName + @"/feeds/" + group.Trim() + "." + feedKey + @"/data";
         }

         Console.WriteLine(" Feed URL :{0}", feedUrl);

         try
         {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(feedUrl);
            {
               string payload = @"{""value"": """ + value + @"""}";

               byte[] buffer = Encoding.UTF8.GetBytes(payload);

               DateTime httpRequestedStartedAtUtc = DateTime.UtcNow;

               request.Method = "POST";
               request.ContentLength = buffer.Length;
               request.ContentType = @"application/json";
               request.Headers.Add("X-AIO-Key", apiKey);
               request.KeepAlive = false;
               request.Timeout = httpRequestTimeoutmSec;
               request.ReadWriteTimeout = httpRequestReadWriteTimeoutmSec;

               using (Stream stream = request.GetRequestStream())
               {
                  stream.Write(buffer, 0, buffer.Length);
               }

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

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

This approach seemed to work pretty reliably

DesktopHTTPRequest

Azure Event Hub Updates from a NetMF Device

I had read about how Azure Event Hubs supported both Advanced Message Queuing Protocol(AMQP) & Hypertext Transfer Protocol (HTTP) access and was keen to see how easy the REST API was to use from a .Net Microframework (NetMF) device.

My initial concept was an exercise monitoring system with a Global Positioning System (GPS) unit and a pulse oximeter connected to a FEZ Spider device. My posting GPS Tracker Azure Service Bus has more info about GPS Drivers  and Azure Service Bus connectivity.

FEZ Spider, GPS and PulseOximeter

Fez spider and sensors for exercise monitoring device

The software was inspired by the Service Bus Event Hubs Getting started, Scale Out Event Processing with Event Hubs,Service Bus Event Hubs Large Scale Secure Publishing and OBD Recorder for .Net Micro Framework with ServiceBus, AMQP (for IoT) samples. I created an Event Hub and associated device access keys and fired up Service Bus Explorer so I could monitor and tweak the configuration.

I started by porting the REST API SendMessage implementation of Service Bus Event Hubs Large Scale Secure Publishing sample to NetMF. My approach was to get the application into my local source control and then cut ‘n’ paste the code into a NetMF project and see what breaks. I then modified the code over several iterations so it ran on both the desktop and NetMF clients.

The next step was to download the HTTPS certificates and add them to the project as resources so the requests could be secured. See this post for more detail.

For the connection to be secured you need to set the local time (so the certificate valid to/from can be checked) and load the certificates so they can be attached to the HTTP requests

void ProgramStarted()
{
   ...
   Microsoft.SPOT.Hardware.Utility.SetLocalTime(NtpClient.GetNetworkTime());
   caCerts = new X509Certificate[] { new X509Certificate(Resources.GetBytes(Resources.BinaryResources.Baltimore)) };

I used the Network Time Protocol (NTP) library from the OBD Recorder for .Net Micro Framework sample to get the current time.

The Service Bus Event Hubs Large Scale Secure Publishing uses an asynchronous HTTP request which is not available on the NetMF platform. So I had to replace it with a synchronous version.

static void EventHubSendMessage(string eventHubAddressHttps, string token, string messageBody)
{
   try
   {
      HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(eventHubAddressHttps + "/messages" + "?timeout=60" + ApiVersion);
      {
         ...
         request.Headers.Add("Authorization", token);
         request.Headers.Add("ContentType", "application/atom+xml;type=entry;charset=utf-8");
         byte[] buffer = Encoding.UTF8.GetBytes(messageBody);
         request.ContentLength = buffer.Length;

         // request body
         using (Stream stream = request.GetRequestStream())
         {
            stream.Write(buffer, 0, buffer.Length);
         }
         using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
         {
            Debug.Print("HTTP Status:" + response.StatusCode + " : " + response.StatusDescription);
         }
      }
   }
   catch (WebException we)
   {
      Debug.Print(we.Message);
   }
}

The code to generate the SAS Token also required some modification as string.format, timespan, and SHA256 functionality are not natively available on the .NetMF platform. The GetExpiry, and SHA256 implementations were part of the OBD Recorder for .Net Micro Framework sample.

static string CreateSasToken(string uri, string keyName, string key)
{
   // Set token lifetime to 20 minutes. When supplying a device with a token, you might want to use a longer expiration time.
   uint tokenExpirationTime = GetExpiry(20 * 60);

   string stringToSign = HttpUtility.UrlEncode(uri) + "\n" + tokenExpirationTime;
   var hmac = SHA.computeHMAC_SHA256(Encoding.UTF8.GetBytes(key), Encoding.UTF8.GetBytes(stringToSign));

   string signature = Convert.ToBase64String(hmac);
   signature = Base64NetMf42ToRfc4648(signature);

   string token = "SharedAccessSignature sr=" + HttpUtility.UrlEncode(uri) + "&sig=" + HttpUtility.UrlEncode(signature) + "&se=" + tokenExpirationTime.ToString() + "&skn=" + keyName;
   return token;
}

static uint GetExpiry(uint tokenLifetimeInSeconds)
{
   const long ticksPerSecond = 1000000000 / 100; // 1 tick = 100 nano seconds</code>

   DateTime origin = new DateTime(1970, 1, 1, 0, 0, 0, 0);
   TimeSpan diff = DateTime.Now.ToUniversalTime() - origin;

   return ((uint)(diff.Ticks / ticksPerSecond)) + tokenLifetimeInSeconds;
}

private static string Base64NetMf42ToRfc4648(string base64netMf)
{
   var base64Rfc = string.Empty;
   for (var i = 0; i < base64netMf.Length; i++)
   {
      if (base64netMf[i] == '!')
      {
         base64Rfc += '+';
      }
      else if (base64netMf[i] == '*')
      {
         base64Rfc += '/';
      }
      else
      {
         base64Rfc += base64netMf[i];
      }
   }
return base64Rfc;
}

The HttpUtility class came from the OBD Recorder for .Net Micro Framework sample. The Base64NetMf42ToRfc4648 functionality is still necessary on NetMF 4.3.

After a couple of hours I had data upload working.(No GPS data as the device was running on my desk where GPS coverage is poor)

ServiceBusExplorerEventHub

HTTPS with NetMF calling an Azure Service Bus endpoint

Back in Q1 of 2013 I posted a sample application which called an Azure Service Bus end point just to confirm that the certificate configuration etc. was good.

Since I published that sample the Azure Root certificate has been migrated so I have created a new project which uses the Baltimore Cyber Trust Root certificate.

The sample Azure ServiceBus client uses a wired LAN connection (original one used wifi module) and to run it locally you will have to update the Date information around line 24.