Azure IOT Hub nRF24L01 Windows 10 IoT Core Field Gateway with BorosRF2

A couple of BorosRF2 Dual nRF24L01 Hats arrived earlier in the week. After some testing with my nRF24L01 Test application I have added compile-time configuration options for the two nRF24L01 sockets to my Azure IoT Hub nRF24L01 Field Gateway.

Boros RF2 with Dual nRF24L01 devices
public sealed class StartupTask : IBackgroundTask
{
   private const string ConfigurationFilename = "config.json";

   private const byte MessageHeaderPosition = 0;
   private const byte MessageHeaderLength = 1;

   // nRF24 Hardware interface configuration
#if CEECH_NRF24L01P_SHIELD
   private const byte RF24ModuleChipEnablePin = 25;
   private const byte RF24ModuleChipSelectPin = 0;
   private const byte RF24ModuleInterruptPin = 17;
#endif

#if BOROS_RF2_SHIELD_RADIO_0
   private const byte RF24ModuleChipEnablePin = 24;
   private const byte RF24ModuleChipSelectPin = 0;
   private const byte RF24ModuleInterruptPin = 27;
#endif

#if BOROS_RF2_SHIELD_RADIO_1
   private const byte RF24ModuleChipEnablePin = 25;
   private const byte RF24ModuleChipSelectPin = 1;
   private const byte RF24ModuleInterruptPin = 22;
#endif

private readonly LoggingChannel logging = new LoggingChannel("devMobile Azure IotHub nRF24L01 Field Gateway", null, new Guid("4bd2826e-54a1-4ba9-bf63-92b73ea1ac4a"));
private readonly RF24 rf24 = new RF24();

This version supports one nRF24L01 device socket active at a time.

Enabling both nRF24L01 device sockets broke outbound message routing in a prototype branch with cloud to device(C2D) messaging support. This functionality is part of an Over The Air(OTA) device provisioning implementation I’m working o.

Adafruit.IO nRF24L01 Windows 10 IoT Core Field Gateway with BorosRF2

A couple of BorosRF2 Dual nRF24L01 Hats arrived earlier in the week. After some testing with my nRF24L01 Test application I have added compile-time configuration options for the two nRF24L01 sockets to my Adafruit.IO nRF24L01 Field Gateway.

Boros RF2 with Dual nRF24L01 devices
public sealed class StartupTask : IBackgroundTask
{
   private const string ConfigurationFilename = "config.json";

   private const byte MessageHeaderPosition = 0;
   private const byte MessageHeaderLength = 1;

   // nRF24 Hardware interface configuration
#if CEECH_NRF24L01P_SHIELD
   private const byte RF24ModuleChipEnablePin = 25;
   private const byte RF24ModuleChipSelectPin = 0;
   private const byte RF24ModuleInterruptPin = 17;
#endif

#if BOROS_RF2_SHIELD_RADIO_0
   private const byte RF24ModuleChipEnablePin = 24;
   private const byte RF24ModuleChipSelectPin = 0;
   private const byte RF24ModuleInterruptPin = 27;
#endif

#if BOROS_RF2_SHIELD_RADIO_1
   private const byte RF24ModuleChipEnablePin = 25;
   private const byte RF24ModuleChipSelectPin = 1;
   private const byte RF24ModuleInterruptPin = 22;
#endif

private readonly LoggingChannel loggingChannel = new LoggingChannel("devMobile AdaFruit.IO nRF24L01 Field Gateway", null, new Guid("4bd2826e-54a1-4ba9-bf63-92b73ea1ac4a"));
private readonly RF24 rf24 = new RF24();

For this initial version only one nRF24L01 device socket active at a time is supported.

Windows 10 IoT Core BorosRf2 – Dual nRF24L01 pHat/Hat

I have a couple of nRF24L01P Raspberry PI projects (primarily my Adafruit.IO and Azure IoT Hubs/Central Windows 10 IoT Core telemetry field gateways) and recently Boros Lab a vendor of suitable Raspberry PI Hats opened a store on Tindie.com.

I ordered a couple of BorosRf2 – Dual nRF24L01 pHat/Hat + RTC for Pis (mine were without the Real-time clock(RTC)) for testing. The vendor’s github repository had details of the GPIO pins used so it was relatively quick and easy to modify my Windows 10 IoT nRF24L01 test harness to work with a single port on the hat.

Single port configuration

By setting a conditional compile option (CEECH_NRF24L01P_SHIELD, BOROS_RF2_SHIELD_RADIO_0 or BOROS_RF2_SHIELD_RADIO_1) my test application could be configured to support the Boros or Ceech (with a modification detailed here) shields.

namespace devmobile.IoTCore.nRF24L01BackGroundTask
{
	public sealed class StartupTask : IBackgroundTask
	{
		// nRF24 Hardware interface configuration
#if CEECH_NRF24L01P_SHIELD
      private const byte ChipEnablePin = 25;
      private const byte ChipSelectPin = 0;
      private const byte InterruptPin = 17;
#endif
#if BOROS_RF2_SHIELD_RADIO_0
      private const byte ChipEnablePin = 24;
      private const byte ChipSelectPin = 0;
      private const byte InterruptPin = 27;
#endif
#if BOROS_RF2_SHIELD_RADIO_1
      private const byte ChipEnablePin = 25;
      private const byte ChipSelectPin = 1;
      private const byte InterruptPin = 22;
#endif
      private const string BaseStationAddress = "Node1";
      private const byte nRF24Channel = 20;
      private RF24 Radio = new RF24();
      private BackgroundTaskDeferral deferral;
      private ThreadPoolTimer timer;

Both vendors’ shields worked well with my test application, the ceech shield (USD9.90 April 2019) is a little bit cheaper, but the Boros shield (USD15.90 April 2019 ) doesn’t require any modification and has a socket for a second nRF24 device.

Easy Sensors Wireless field gateway Arduino Nano client

After not much development on my nrf24L01 AdaFruit.IO and Azure IOT Hub field gateways for a while some new nRF24L01 devices arrived in the post last week.

This sample client is an Arduino Nano clone with an Arduino Nano radio shield for NRF24L01+.

I use the shield’s onboard SHA204A crypto and authentication chip, and a Seeedstudio Temperature & Humidity sensor with the data uploaded to adafruit.io.

/*
  Copyright ® 2018 September 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 <sha204_library.h>
#include <TH02_dev.h>

// RF24 radio( ChipeEnable , ChipSelect )
RF24 radio(9, 10);
const byte FieldGatewayChannel = 15 ;
const byte FieldGatewayAddress[] = {"Base1"};
const rf24_datarate_e RadioDataRate = RF24_250KBPS;
const rf24_pa_dbm_e RadioPALevel = RF24_PA_HIGH;

// Payload configuration
const int PayloadSizeMaximum = 32 ;
char payload[PayloadSizeMaximum] = "";
const byte DeviceIdPlusCsvSensorReadings = 1 ;
const byte SensorReadingSeperator = ',' ;

// ATSHA204 secure authentication, validation with crypto and hashing (only using for unique serial number)
atsha204Class sha204(A3);
const int DeviceSerialNumberLength = 9 ;
uint8_t deviceSerialNumber[DeviceSerialNumberLength] = {""};
const int LoopSleepDelaySeconds = 10 ;

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

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

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

  Serial.println();

  // Configure the Seeedstudio TH02 temperature & humidity sensor
  Serial.println("TH02 setup");
  TH02.begin();
  delay(100);

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

  Serial.println("Setup done");
}

void loop()
{
  int payloadLength = 0 ;
  float temperature ;
  float humidity ;

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

  // prepare the payload header with PayloadMessageType (top nibble) and DeviceID length (bottom nibble)
  payload[0] = (DeviceIdPlusCsvSensorReadings << 4) | sizeof(deviceSerialNumber) ;
  payloadLength += 1;

  // Copy the device serial number into the payload
  memcpy( &payload[payloadLength], deviceSerialNumber, sizeof( deviceSerialNumber));
  payloadLength += sizeof( deviceSerialNumber) ;

  // Read the temperature, humidity & battery voltage values then display nicely
  temperature = TH02.ReadTemperature();
  Serial.print("T:");
  Serial.print( temperature, 1 ) ;
  Serial.print( "C" ) ;

  humidity = TH02.ReadHumidity();
  Serial.print(" H:");
  Serial.print( humidity, 0 ) ;
  Serial.println( "%" ) ;

  // 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;

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

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

  Serial.println("Loop done");
  delay(LoopSleepDelaySeconds * 1000l);
}

Arduino monitor output

NanoArduinoNrf24

Prototype hardware

ArduinoNanonRF24

Bill of materials (prices as at Sep 2018)

  • Arduino Nano clone USD4.70
  • Easy Sensors Arduino Nano Radio Shield for nRF24L01 USD13
  • Seeedstudio Temperature and Humidity Sensor Pro USD11.50
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Adafruit.IO temperature display when I moved the sensor outside.

NanoNrf24

Wireless field gateway Netduino client V2

This revised client is a Netduino V2Plus/V3 Ethernet/V3 Wifi device with a Silicon Labs SI7005 temperature & humidity sensor. These devices when used as sensor nodes can be battery powered and I use the Mac Address as the unique device identifier.

In this version of the protocol the message type & device identifier are nibbles packed into the first bye of the message. This saved a byte but limits the number of message types and device identifier length

//---------------------------------------------------------------------------------
// Copyright (c) 2018, devMobile Software
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//---------------------------------------------------------------------------------
using System;
using System.Net;
using System.Text;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using Microsoft.SPOT.Net.NetworkInformation;
using devMobile.NetMF.Sensor;
using Gralin.NETMF.Nordic;
using SecretLabs.NETMF.Hardware.Netduino;

namespace devMobile.IoT.FIeldGateway.Netduino.Client
{
   class Client
   {
      private const byte nRF24Channel = 10;
      private const NRFDataRate nRF24DataRate = NRFDataRate.DR250kbps;
      private readonly byte[] nRF24ClientAddress = Encoding.UTF8.GetBytes("T&H01");
      private readonly byte[] nRF24BaseStationAddress = Encoding.UTF8.GetBytes("Base1");
      private static byte[] deviceIdentifier;
      private readonly OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);
      private readonly NRF24L01Plus radio;
      private readonly SiliconLabsSI7005 sensor = new SiliconLabsSI7005();

      public Client()
      {
         radio = new NRF24L01Plus();
      }

      public void Run()
      {
         // Configure the nRF24 hardware
         radio.OnDataReceived += OnReceive;
         radio.OnTransmitFailed += OnSendFailure;
         radio.OnTransmitSuccess += OnSendSuccess;

         radio.Initialize(SPI.SPI_module.SPI1, Pins.GPIO_PIN_D7, Pins.GPIO_PIN_D3, Pins.GPIO_PIN_D2);
         radio.Configure(nRF24ClientAddress, nRF24Channel, nRF24DataRate);
         radio.Enable();

         // Setup the device unique identifer, in this case the hardware MacAddress
         deviceIdentifier = NetworkInterface.GetAllNetworkInterfaces()[0].PhysicalAddress;
         Debug.Print(" Device Identifier : " + BytesToHexString(deviceIdentifier));

         Timer humidityAndtemperatureUpdates = new Timer(HumidityAndTemperatureTimerProc, null, 15000, 15000);

         Thread.Sleep(Timeout.Infinite);
      }

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

         double humidity = sensor.Humidity();
         double temperature = sensor.Temperature();

         Debug.Print("H:" + humidity.ToString("F1") + " T:" + temperature.ToString("F1"));
         string values = "T " + temperature.ToString("F1") + ",H " + humidity.ToString("F0");

         // Stuff the single byte header ( payload type nibble & deviceIdentifierLength nibble ) + deviceIdentifier into first byte of payload
         byte[] payload = new byte[ 1 + deviceIdentifier.Length + values.Length];
         payload[0] =  (byte)((1 <> 4];

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

         return hexString;
      }
   }
}

Bill of materials (prices as at March 2018)

Azure IoT Hub nRF24L01 Windows 10 IoT Core Field Gateway

This project is now live on Hackster.IO and github.com with sample *duino, Devduino and Netduino clients. While building the AdaFruit.IO field gateway, Azure IOT Hub field gateways and sample clients I changed the structure of the message payload and spent a bit of time removing non-core functionality and code.

The diagnostics logging code was refactored several times and after reading this reference on docs.Microsoft.com I settled on the published approach.

I considered using the built in Universal Windows Platform (UWP) application data class but this would have made configuration in the field hard for most of the targeted users school students & IT departments.

I have the application running at my house and it has proved pretty robust, last week I though it had crashed because the telemetry data stopped for about 20 minutes. I had a look at the Device portal and it was because Windows 10 IoT core had downloaded some updates, applied them and then rebooted automatically (as configured).

I put a socket on the Raspberry PI nRF24L01 Shield rather than soldering the module to the board so that I could compare the performance of the Low and High power modules. The antenna end of the high power module tends to droop so I put a small piece of plastic foam underneath to prop them up.

I had code to generate an empty JSON configuration but I removed that as it added complexity compared to putting a sample in the github repository.

I considered using a binary format (the nRF24L01 max message length is 32 bytes) but the code required to make it sufficiently flexible rapidly got out of hand and as most of my devices didn’t have a lot of sensors (battery/solar powered *duinos) and it wasn’t a major hassle to send another message so I removed it.

I need to tidy up the project and remove the unused Visual Assets and have a look at the automated update support.

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