Wireless field gateway protocol V2

I have now built a couple of nRF2L01P field gateways (for AdaFriut.IO & Azure IoT Hubs) which run as a background tasks on Windows 10 IoT Core on RaspberyPI). I have also written several clients which run on Arduino, devDuino, Netduino, and Seeeduino devices.

I have tried to keep the protocol simple (telemetry only) to deploy and it will be used in high school student projects in the next couple of weeks.

To make the payload smaller the first byte of the message now specifies the message type in the top nibble and the length of the device unique identifier in the bottom nibble.

0 = Echo

The message is displayed by the field gateway as text & hexadecimal.

1 = Device identifier + Comma separated values (CSV) payload

[0] – Set to 0001, XXXX   Device identifier length

[1]..[1+Device identifier length] – Unique device identifier bytes e.g. Mac address

[1+Device identifier length+1 ]..[31] – CSV payload e.g.  SensorID value, SensorID value

 

Xively Personal is being retired

This is going to cause me a problem especially my Netduino based nRF24 Xively Field gateway which gets used in quite a few of my student projects. I’m looking for a replacement Internet of Things service which has http/s and/or mqtt, amqp support, C & C#  client libraries (which I can get to work on Windows 10 IoT Core & NetMF) would be a bonus.

From the Xively email

”After careful consideration, LogMeIn has made the decision to retire Xively Personal from its current line of products effective January 15, 2018 at 12:00PM ET . Please note that LogMeIn will continue to offer our Xively Enterprise edition – there is no change to that edition and we will continue to support that platform as part of our IoT business.

Retiring a product is never an easy decision, and we recognize it does introduce potential challenges to active users. So we want to make sure you have all the information you need to make as seamless a transition as possible.

Access to your account:
Your Xively Personal account will remain active until January 15th. Please note that devices will not be accessible via the Xively Personal service once it is retired.

Transferring your products to another IoT service:
Should you choose to switch to another service, there are essentially two options.

1) Migrate to Xively Enterprise: The latest Enterprise version of Xively is built on a more modern and reliable architecture, which brings the benefits of pre-built hardware integrations, identity and device management features, MQTT messaging, and best-in-class security, but it may require some reconfiguring of your current devices. We do offer a 30 day free trial of Xively Enterprise should you want to try it out for yourself.

2) Migrate to another free service: If your use is primarily for experimenting and personal projects, there are several free IoT platform options on the market, such as Adafruit, Thingspeak, or SparkFun.”

One of the suggestions – Sparkfun Phant has been retired

Some possible alternatives in no particular order (this list may grow)

AdaFruit.IO – The internet of things for everyone

Microsoft IoT Central – Enterprise-grade IoT SaaS

ThingSpeak – The open IoT platform with MATLAB analytics

Blynk – Democratizing the Internet of Things

Cayenne – Simplify the Connected World

Thinger.io platform

SenseIoT – Internet of Things Data Hosting Platform

Temboo – Tools for Digital Transformation

Carriots by Altair

Nearbus – An IoT Open Project

ubidots – An application Builder for the Internet of Things

Microsoft IoT Central – Enterprise Grade IoT SaaS

Kii Cloud

Artik – End-to-end IoT Platform

goplusplatform – Connect your things with GO+

I’m initially looking for a platform which is the “least painful” transition from Xively.

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 pollution Monitor V0.1

As part of a project for Sensing City I had been helping with the evaluation of  PM2.5/PM10 sensors for monitoring atmospheric pollution levels. For my DIY IoT projects I use the SeeedStudio Grove system which has a couple of dust sensors. The Grove Dust Sensor which is based on a Shinyei Model PPD42 Particle Sensor looked like a cost effective option.

Seeedstudio Grove Dust Sensor

Seeedstudio Grove Dust Sensor

Bill of Materials for my engineering proof of concept (Prices as at June 2015)

I initially got the sensor running with one of my Arduino Uno R3  devices using the software from the seeedstudio wiki and the ratio values returned by my Netduino Plus 2 code (see below) look comparable. I have purchased a couple of extra dust sensors so I can run the Arduino & Netduino devices side by side. I am also trying to source a professional air quality monitor so I can see how reliable my results are

The thread ” (0x2) has exited with code 0 (0x0).

Ratio 0.012

Ratio 0.012

Ratio 0.020

Ratio 0.008

Ratio 0.031

Ratio 0.014

Ratio 0.028

Ratio 0.012

Ratio 0.013

Ratio 0.018

public class Program
{
private static long pulseStartTicks = 0;
private static long durationPulseTicksTotal = 0;
readonly static TimeSpan durationSample = new TimeSpan(0, 0, 0, 30);
readonly static TimeSpan durationWaitForBeforeFirstSample = new TimeSpan(0, 0, 0, 30);

public static void Main()
{
InterruptPort sensor = new InterruptPort(Pins.GPIO_PIN_D8, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeBoth);
sensor.OnInterrupt += sensor_OnInterrupt;

Timer sampleTimer = new Timer(SampleTimerProc, null, durationWaitForBeforeFirstSample, durationSample);

Thread.Sleep(Timeout.Infinite);
}

static void sensor_OnInterrupt(uint data1, uint data2, DateTime time)
{
if (data2 == 1)
{
long pulseDuration = time.Ticks - pulseStartTicks;

durationPulseTicksTotal += pulseDuration;
}
else
{
pulseStartTicks = time.Ticks;
}
}

static void SampleTimerProc(object status)
{
double ratio = durationPulseTicksTotal / (double)durationSample.Ticks ;
durationPulseTicksTotal = 0;

Debug.Print("Ratio " + ratio.ToString("F3"));
}
}

Next steps will be, adding handling for edges cases, converting the ratio into a particle concentration per litre or 0.1 cubic feet, selecting a weather proof enclosure, smoothing/filtering the raw measurements, and uploading the values to Xively for presentation and storage.

EVolocity 3 Axis G-Meter

A telemetry system could be used to monitor the progress of your electric vehicle and provide feedback to the team & driver about how efficiently/fast it is being driven. As part of a telemetry system lateral, longitudinal, and vertical acceleration could be monitored using a cheap ADXL345 mems accelerometer

Netduino based 3D GMeter

Netduino based 3D G-Meter

Bill of Materials for my engineering proof of concept (Prices as at May 2015)

The sample code reads the acceleration data from the ADXL345 using a driver originally created by Love Electronics. It then displays the magnitude of the scaled acceleration on 3 x LED Bars using code written by Famoury Toure

OutputPort Xcin = new OutputPort(Pins.GPIO_PIN_D0, false);
OutputPort Xdin = new OutputPort(Pins.GPIO_PIN_D1, false);
OutputPort Ycin = new OutputPort(Pins.GPIO_PIN_D3, false);
OutputPort Ydin = new OutputPort(Pins.GPIO_PIN_D4, false);
OutputPort Zcin = new OutputPort(Pins.GPIO_PIN_D5, false);
OutputPort Zdin = new OutputPort(Pins.GPIO_PIN_D6, false);

GroveLedBarGraph Xbar = new GroveLedBarGraph(Xcin, Xdin);
GroveLedBarGraph Ybar = new GroveLedBarGraph(Ycin, Ydin);
GroveLedBarGraph Zbar = new GroveLedBarGraph(Zcin, Zdin);

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

ADXL345 accel = new ADXL345(0x53);
accel.EnsureConnected();
accel.Range = 2;
accel.FullResolution = true;
accel.EnableMeasurements();
accel.SetDataRate(0x0F);

while (true)
{
   accel.ReadAllAxis();

   uint xValue = (uint)(((accel.ScaledXAxisG / 1.0 ) + 1.0) * 5.0) ;
   uint xbar = 1;
   xbar = xbar << (int)xValue;
   Xbar.setLED(xbar);

   uint yValue = (uint)(((accel.ScaledYAxisG / 1.0) + 1.0) * 5.0);
   uint ybar = 1;
   ybar = ybar << (int)yValue;
   Ybar.setLED(ybar);

   uint zValue = (uint)((-(accel.ScaledZAxisG / 1.0) + 2.0) * 5.0);
   uint zbar = 1;
   zbar = zbar << (int)zValue;
   Zbar.setLED(zbar);

   Thread.Sleep(20);
   }
}

St Margaret’s CodeClub information

If you want to follow along at home all the software is free (Visual Studio Express 2013) or open source (Netduino software & Hardware + NetMF) and can be downloaded from the following locations. The packages need to be sequentially installed in the order below.

If you want to purchase your own hardware, we use Netduino 2 Plus devices (we use them mainly for their integrated networking and MicroSD card) and Seeedstudio Grove sensors. (Prices as at 05/2015)

We are looking into Apple friendly options for later this term.