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

 

Wireless field gateway devDuino client V1

This client is a devDuino V2.2 device with an AdaFruit AM2315 temperature & humidity sensor. This sensor is powered by two AAA batteries and has an on-board support for unique device identification and encryption.

In this first iteration the focus was accessing the SHA204A crypto and authentication chip, the AM2315 sensor and message payload assembly. Reducing the power consumption, improving reliability etc. will be covered in future posts.

/*
Copyright ® 2018 Jan devMobile Software, All Rights Reserved

THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
PURPOSE.

You can do what you want with this code, acknowledgment would be nice.

http://www.devmobile.co.nz

*/
#include <RF24.h>
#include <Adafruit_AM2315.h>
#include <sha204_library.h>

// nRF24L01 ISM wireless module setup
RF24 radio(7,6);
const int nRFPayloadSize = 32 ;
char payload[nRFPayloadSize] = "";
const byte FieldGatewayAddress[5] = "Base1";
const byte FieldGatewayChannel = 10 ;
const rf24_pa_dbm_e RadioPALevel = RF24_PA_MAX;
const rf24_datarate_e RadioDataRate = RF24_250KBPS; 

// ATSHA204 secure authentication, validation with crypto and hashing (initially only used for unique serial number)
atsha204Class sha204(A2);
const int SerialNumberLength = 9 ;
uint8_t serialNumber[SerialNumberLength];

// AM2315 I2C Outdoors temperature and humdity sensor
Adafruit_AM2315 am2315;

const int LoopSleepDelay = 30000 ;

void setup()
{
  Serial.begin(9600);
  Serial.println("Setup called");

  // Retrieve the serial number then display it nicely
  sha204.getSerialNumber(serialNumber);

  Serial.print("SNo:");
  for (int i=0; i<SerialNumberLength; i++)
  {
    // Add a leading zero
    if ( serialNumber[i] < 16)
    {
      Serial.print("0");
    }
    Serial.print(serialNumber[i], HEX);
    Serial.print(" ");
  }
  Serial.println(); 

  // Configure the AM2315 temperature & humidity sensor
  Serial.println("AM2315 setup");
  am2315.begin();

  // Configure the nRF24 module
  Serial.println("nRF24 setup");
  radio.begin();
  radio.setPALevel(RadioPALevel);
  radio.setDataRate(RadioDataRate) ;
  radio.setChannel(FieldGatewayChannel);
  radio.enableDynamicPayloads();
  radio.openWritingPipe(FieldGatewayAddress);

  delay(1000);

  Serial.println("Setup done");
}

void loop()
{
  float temperature ;
  float humidity ;
  float batteryVoltage ;

  Serial.println("Loop called");
  memset( payload, 0, sizeof( payload));

  // prepare the payload header
  int payloadLength = 0 ;
  payload[0] = 1 ; // Sensor device unique ID header with CSV payload
  payloadLength += 1;

  // Copy the ATSHA204 device serial number into the payload
  payload[1] = SerialNumberLength ;
  payloadLength += 1;
  memcpy( &payload[payloadLength], serialNumber, SerialNumberLength);
  payloadLength += SerialNumberLength ;

  // Read the temperature, humidity & battery voltage values then display nicely
  am2315.readTemperatureAndHumidity(temperature, humidity);
  Serial.print("T:");
  Serial.print( temperature, 1 ) ;
  Serial.print( "C" ) ;

  Serial.print(" H:");
  Serial.print( humidity, 0 ) ;
  Serial.print( "%" ) ;

  batteryVoltage = readVcc() / 1000.0 ;
  Serial.print(" B:");
  Serial.print( batteryVoltage, 2 ) ;
  Serial.println( "V" ) ;

  // Copy the temperature into the payload
  payload[ payloadLength] = 'T';
  payloadLength += 1 ;
  dtostrf(temperature, 6, 1, &payload[payloadLength]);
  payloadLength += 6;
  payload[ payloadLength] = ',';
  payloadLength += 1 ;

  // Copy the humidity into the payload
  payload[ payloadLength] = 'H';
  payloadLength += 1 ;
  dtostrf(humidity, 4, 0, &payload[payloadLength]);
  payloadLength += 4;
  payload[ payloadLength] = ',';
  payloadLength += 1 ;

  // Copy the battery voltage into the payload
  payload[ payloadLength] = 'V';
  payloadLength += 1 ;

  dtostrf(batteryVoltage, 5, 2, &payload[payloadLength]);
  payloadLength += 5;

  // Powerup the nRF24 chipset then send the payload to base station
  Serial.print( "Payload length:");
  Serial.println( payloadLength );

  radio.powerUp();
  delay(500);

  Serial.println( "nRF24 write" ) ;
  boolean result = radio.write(payload, payloadLength);
  if (result)
    Serial.println("Write Ok...");
  else
    Serial.println("Write failed.");

 Serial.println( "nRF24 power down" ) ;
 radio.powerDown();

 delay(LoopSleepDelay);
}

Arduino monitor output

devDuinoAM2315V1Output

Prototype hardware

devDuinoAM2315V1Bill of materials (prices as at Jan 2018)

  • devDuino V2.2 USD18
  • AdaFruit AM2315 USD30
  • Grove – 5cm buckled cable USD1.90
  • Grove – Screw Terminal USD2.90
  • 10K resistors x 2

RaspberyPI UWP application diagnostic output

Interrupt Triggered: RisingEdge
Interrupt Triggered: FallingEdge
09:39:03 Address 01-23-32-66-C6-FE-0B-8D-EE Length 9 Payload T  25.0,H  48,V 3.31 Length 20
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-T Value 25.0
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-H Value 48
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-V Value 3.31
Interrupt Triggered: RisingEdge
Interrupt Triggered: FallingEdge
09:39:33 Address 01-23-32-66-C6-FE-0B-8D-EE Length 9 Payload T  24.9,H  48,V 3.30 Length 20
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-T Value 24.9
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-H Value 48
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-V Value 3.30
Interrupt Triggered: RisingEdge
Interrupt Triggered: FallingEdge
09:40:04 Address 01-23-32-66-C6-FE-0B-8D-EE Length 9 Payload T  24.9,H  48,V 3.31 Length 20
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-T Value 24.9
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-H Value 48
 Sensor 01-23-32-66-C6-FE-0B-8D-EE-V Value 3.31
Interrupt Triggered: RisingEdge

Wireless field gateway protocol V1

I’m going to build a number of nRF2L01P field gateways (Netduino Ethernet & Wifi running .NetMF, Raspberry PI running Windows 10 IoT Core, RedBearLab 3200  etc.), clients which run on a variety of hardware (Arduino, devDuino, Netduino, Seeeduino etc.) which, then upload data to a selection of IoT Cloud services (AdaFruit.IO, ThingSpeak, Microsoft IoT Central etc.)

The nRF24L01P is widely supported with messages up to 32 bytes long, low power consumption and 250kbps, 1Mbps and 2Mbps data rates.

The aim is to keep the protocol simple (telemetry only initially) to implement and debug as the client side code will be utilised by high school student projects.

The first byte of the message specifies the message type

0 = Echo

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

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

[0] – Set to 1

[1] – Device identifier length

[2]..[2+Device identifier length] – Unique device identifier bytes e.g. Mac address

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

Overtime I will support more message types and wireless protocols.

 

nRF24 Windows 10 IoT Core Background Task

First step is to build a basic Windows 10 IoT Core background task which can receive and display messages sent from a variety of devices across an nRF24L01 wireless link.

If you create a new “Windows IoT Core” “Background Application” project then copy this code into StartupTasks.cs the namespace has to be changed in the C# file, project properties\library\Default namespace and “Package.appxmanifest”\declarations\Entry Point.

/*

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.Diagnostics;
using System.Text;
using Radios.RF24;
using Windows.ApplicationModel.Background;

namespace devmobile.IoTCore.nRF24BackgroundTask
{
    public sealed class StartupTask : IBackgroundTask
    {
      private const byte ChipEnablePin = 25;
      private const byte ChipSelectPin = 0;
      private const byte nRF24InterruptPin = 17;
      private const string BaseStationAddress = "Base1";
      private const byte nRF24Channel = 10;
      private RF24 Radio = new RF24();
      private BackgroundTaskDeferral deferral;

      public void Run(IBackgroundTaskInstance taskInstance)
        {
         Radio.OnDataReceived += Radio_OnDataReceived;
         Radio.OnTransmitFailed += Radio_OnTransmitFailed;
         Radio.OnTransmitSuccess += Radio_OnTransmitSuccess;

         Radio.Initialize(ChipEnablePin, ChipSelectPin, nRF24InterruptPin);
         Radio.Address = Encoding.UTF8.GetBytes(BaseStationAddress);
         Radio.Channel = nRF24Channel;
         Radio.PowerLevel = PowerLevel.High;
         Radio.DataRate = DataRate.DR250Kbps;
         Radio.IsEnabled = true;

         Debug.WriteLine("Address: " + Encoding.UTF8.GetString(Radio.Address));
         Debug.WriteLine("PA: " + Radio.PowerLevel);
         Debug.WriteLine("IsAutoAcknowledge: " + Radio.IsAutoAcknowledge);
         Debug.WriteLine("Channel: " + Radio.Channel);
         Debug.WriteLine("DataRate: " + Radio.DataRate);
         Debug.WriteLine("IsDynamicAcknowledge: " + Radio.IsDyanmicAcknowledge);
         Debug.WriteLine("IsDynamicPayload: " + Radio.IsDynamicPayload);
         Debug.WriteLine("IsEnabled: " + Radio.IsEnabled);
         Debug.WriteLine("Frequency: " + Radio.Frequency);
         Debug.WriteLine("IsInitialized: " + Radio.IsInitialized);
         Debug.WriteLine("IsPowered: " + Radio.IsPowered);

         deferral = taskInstance.GetDeferral();

         Debug.WriteLine("Run completed");
      }

      private void Radio_OnDataReceived(byte[] data)
      {
         // Display as Unicode
         string unicodeText = Encoding.UTF8.GetString(data);
         Debug.WriteLine("Unicode - Payload Length {0} Unicode Length {1} Unicode text {2}", data.Length, unicodeText.Length, unicodeText);

         // display as hex
         Debug.WriteLine("Hex - Length {0} Payload {1}", data.Length, BitConverter.ToString(data));
      }

      private void Radio_OnTransmitSuccess()
      {
         Debug.WriteLine("Transmit Succeeded!");
      }

      private void Radio_OnTransmitFailed()
      {
         Debug.WriteLine("Transmit Failed!");
      }
   }
}

This was displayed in the output window of Visual Studio

Address: Base1
PA: 15
IsAutoAcknowledge: True
Channel: 10
DataRate: DR250Kbps
IsDynamicAcknowledge: False
IsDynamicPayload: True
IsEnabled: True
Frequency: 2410
IsInitialized: True
IsPowered: True
Run completed

Interrupt Triggered: FallingEdge
Unicode – Payload Length 19 Unicode Length 19 Unicode text T  23.8,H  73,V 3.26
Hex – Length 19 Payload 54-20-32-33-2E-38-2C-48-20-20-37-33-2C-56-20-33-2E-32-36
Interrupt Triggered: RisingEdge

Note the odd formatting of the Temperature and humidity values which is due to the way dtostrf function in the Atmel AVR library works.

Also noticed the techfooninja nRF24 library has configurable output power level which I will try to retrofit onto the Gralin NetMF library.

Next, several simple Arduino, devDuino V2.2, Seeeduino V4.2 and Netduino 2/3 clients (plus possibly some others)

nRF24 Windows 10 IoT Core reboot

My first live deployment of the nRF24L01 Windows 10 IoT Core field gateway is now scheduled for mid Q1 2018 so time for a reboot. After digging out my Raspbery PI 2/3 devices and the nRF24L01+ shield (with modifications detailed here) I have a basic plan with some milestones.

My aim is to be able to wirelessly acquire data from several dozen Arduino, devduino, seeeduino, and Netduino devices, Then, using a field gateway on a Raspberry PI running Windows 10 IoT Core upload it to Microsoft IoT Central

First bit of code – Bleepy a simple background application to test the piezo beeper on the RPI NRF24 Shield

namespace devmobile.IoTCore.Bleepy
{
   public sealed class StartupTask : IBackgroundTask
   {
      private BackgroundTaskDeferral deferral;
      private const int ledPinNumber = 4;
      private GpioPin ledGpioPin;
      private ThreadPoolTimer timer;

      public void Run(IBackgroundTaskInstance taskInstance)
      {
         var gpioController = GpioController.GetDefault();
         if (gpioController == null)
         {
            Debug.WriteLine("GpioController.GetDefault failed");
            return;
         }

         ledGpioPin = gpioController.OpenPin(ledPinNumber);
         if (ledGpioPin == null)
         {
            Debug.WriteLine("gpioController.OpenPin failed");
            return;
         }

         ledGpioPin.SetDriveMode(GpioPinDriveMode.Output);

         this.timer = ThreadPoolTimer.CreatePeriodicTimer(Timer_Tick, TimeSpan.FromMilliseconds(500));

         deferral = taskInstance.GetDeferral();

         Debug.WriteLine("Rum completed");
      }

      private void Timer_Tick(ThreadPoolTimer timer)
      {
         GpioPinValue currentPinValue = ledGpioPin.Read();

         if (currentPinValue == GpioPinValue.High)
         {
            ledGpioPin.Write(GpioPinValue.Low);
         }
         else
         {
            ledGpioPin.Write(GpioPinValue.High);
         }
      }
   }
}

Note the blob of blu tack over the piezo beeper to mute noise
nRF24ShieldMuted

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)

Netduino 3 Wifi xively nRF24L01 Gateway data stream live

The gateway is now live, I’m regularly updating the Netduino 3 wifi code and the client arduino, devDuino + netduino devices so there maybe short periods of downtime and/or missing data points.

The stream is available here and is currently just temperature and humidity readings from two bedrooms updating roughly once a minute.

I live in New Zealand which is currently UTC + 12.