Arduino LoRa Payload Addressing Client

This is a demo Arduino client (based on one of the examples from Arduino-LoRa) that uploads telemetry data to my Windows 10 IoT Core on Raspberry PI field gateway proof of concept(PoC).

Bill of materials (Prices Sep 2018)

ArduinoUnoR3DraginoLoRa

The code is pretty basic, it shows how to pack the payload and set the necessary RFM9X/SX127X LoRa module configuration, has no power conservation, advanced wireless configuration etc.

/*
  Adapted from LoRa Duplex communication with Sync Word

  Sends temperature & humidity data from Seeedstudio 

  https://www.seeedstudio.com/Grove-Temperature-Humidity-Sensor-High-Accuracy-Min-p-1921.html

  To my Windows 10 IoT Core RFM 9X library

  https://blog.devmobile.co.nz/2018/09/03/rfm9x-iotcore-payload-addressing/

*/
#include
#include
#include
const int csPin = 10;          // LoRa radio chip select
const int resetPin = 9;       // LoRa radio reset
const int irqPin = 2;         // change for your board; must be a hardware interrupt pin

// Field gateway configuration
const byte FieldGatewayAddress[] = "LoRaIoT1";
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int PayloadSizeMaximum = 64 ;
char payload[PayloadSizeMaximum] = "";
const byte SensorReadingSeperator = ',' ;

// Manual serial number configuration
char DeviceId[] = {"Arduino1"};

const int LoopSleepDelaySeconds = 60;

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

  Serial.println("LoRa Setup");

  // override the default CS, reset, and IRQ pins (optional)
  LoRa.setPins(csPin, resetPin, irqPin);// set CS, reset, IRQ pin

  if (!LoRa.begin(FieldGatewayFrequency))
  {
    Serial.println("LoRa init failed. Check your connections.");
    while (true);
  }

  // Need to do this so field gateways pays attention to messsages from this device
  LoRa.enableCrc();
  LoRa.setSyncWord(FieldGatewaySyncWord);  

  //LoRa.dumpRegisters(Serial);
  Serial.println("LoRa Setup done.");

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

  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 "To" Address length (top nibble) and "From" address length (bottom nibble)
  payload[0] = (strlen(FieldGatewayAddress) << 4) | strlen( DeviceId ) ;
  payloadLength += 1;

  // Copy the "To" address into payload
  memcpy(&payload[payloadLength], FieldGatewayAddress, strlen(FieldGatewayAddress));
  payloadLength += strlen(FieldGatewayAddress) ;

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], DeviceId, strlen(DeviceId));
  payloadLength += strlen(DeviceId) ;

  // Read the temperature and humidity values then display nicely
  temperature = TH02.ReadTemperature();
  humidity = TH02.ReadHumidity();

  Serial.print("T:");
  Serial.print( temperature, 1 ) ;
  Serial.print( "C" ) ;

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

  // Copy the temperature into the payload
  payload[ payloadLength] = 't';
  payloadLength += 1 ;
  payload[ payloadLength] = ' ';
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(temperature, -1, 1, &payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += sizeof(SensorReadingSeperator) ;

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

  // display info about payload then send it (No ACK) with LoRa unlike nRF24L01
  Serial.print( "RFM9X/SX127X Payload length:");
  Serial.print( payloadLength );
  Serial.println( " bytes" );

  LoRa.beginPacket();
  LoRa.write( payload, payloadLength );
  LoRa.endPacket();      

  Serial.println("Loop done");

  delay(LoopSleepDelaySeconds * 1000l);
}

In the debug output window the messages from the device looked like this

Register 0x40 – Value 0X00 – Bits 00000000
Register 0x41 – Value 0X00 – Bits 00000000
Register 0x42 – Value 0X12 – Bits 00010010

19:15:21-RX From Arduino1 PacketSnr 9.3 Packet RSSI -49dBm RSSI -105dBm = 11 byte message "t 18.8,h 91"

19:15:30-TX 25 byte message Hello from LoRaIoT1 ! 255
19:15:30-TX Done
19:15:31-RX From Arduino1 PacketSnr 9.3 Packet RSSI -49dBm RSSI -103dBm = 11 byte message "t 18.8,h 91"

19:15:41-RX From Arduino1 PacketSnr 9.3 Packet RSSI -48dBm RSSI -106dBm = 11 byte message "t 18.8,h 91"

There must be a nicer way of building the payload, a topic for a future post maybe.

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.

 

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

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)

NetMF MP3 Player Part 3

Building on the file listing code from the previous post in the next class we built a basic multi threaded music player using an enhanced version of the Vs1053B driver based on the softelectrotech.and bluecone code.

The code uses five interrupt ports (I used 5 buttons on the 4 analog ports on the Seeedstudio V2 Base shield and D5 to make it easier to fit the Mp3 shield)

As the Vs1053 driver is now running asynchronously it fires an event when the current track has finished playing

   public class Program
   {
      static string[] MusicFiles;
      static Vs1053B player = new Vs1053B(Pins.GPIO_PIN_D2, Pins.GPIO_PIN_D6, Pins.GPIO_PIN_D7, Pins.GPIO_PIN_D8);
      static byte volume = 200;
      static int trackNumber = 1;
      static public string TrackFilename { get { return MusicFiles[trackNumber - 1]; } }

      public static void Main()
      {
         MusicFiles = Directory.GetFiles(@"\SD");

         foreach( string file in MusicFiles)
         {
            Debug.Print(file);
         }

         InterruptPort playPause = new InterruptPort(Pins.GPIO_PIN_D5, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);
         playPause.OnInterrupt += playPause_OnInterrupt;

         InterruptPort volumeUp = new InterruptPort(Pins.GPIO_PIN_A0, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);
         volumeUp.OnInterrupt += volumeUp_OnInterrupt;

         InterruptPort volumeDown = new InterruptPort(Pins.GPIO_PIN_A1, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);
         volumeDown.OnInterrupt += volumeDown_OnInterrupt;

         InterruptPort previousTrack = new InterruptPort(Pins.GPIO_PIN_A2, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);
         previousTrack.OnInterrupt += previousTrack_OnInterrupt;

         InterruptPort nextTrack = new InterruptPort(Pins.GPIO_PIN_A3, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);
         nextTrack.OnInterrupt += nextTrack_OnInterrupt;

         player.SetVolume(volume);
         player.Filename = TrackFilename;
         player.onMusicFinished += player_onMusicFinished;

         player.Play();

         Thread.Sleep(Timeout.Infinite);
      }

      static void player_onMusicFinished()
      {
         trackNumber += 1;

         if (trackNumber > MusicFiles.Length)
         {
            trackNumber = 1;
         }
         Debug.Print("player_onMusicFinished " + trackNumber + " of " + MusicFiles.Length);

         player.Filename = TrackFilename;
      }

      static void previousTrack_OnInterrupt(uint data1, uint data2, DateTime time)
      {
         trackNumber -= 1;

         if (trackNumber  MusicFiles.Length)
         {
            trackNumber = 1;
         }
         Debug.Print("nextTrack_OnInterrupt " + trackNumber + " of " + MusicFiles.Length);

         player.CancelPlayback();
         player.Filename = TrackFilename;
      }

      static void playPause_OnInterrupt(uint data1, uint data2, DateTime time)
      {
         Debug.Print("playPause_OnInterrupt ");
         if (player.IsPaused())
         {
            player.Resume();
         }
         else
         {
            player.Pause();
         }
      }

      static void volumeDown_OnInterrupt(uint data1, uint data2, DateTime time)
      {
         Debug.Print("volumeDown_OnInterrupt " + volume);
         if (volume > 0)
         {
            volume -= 1;
         }
         player.SetVolume(volume);
      }

      static void volumeUp_OnInterrupt(uint data1, uint data2, DateTime time)
      {
         Debug.Print("volumeUp_OnInterrupt " + volume);
         if (volume < 255)
         {
            volume += 1;
         }
         player.SetVolume(volume);
      }
   }

Next steps are to ignore contact bounce on the buttons and play MP3 files in a more consistent order
musicplayerv2

Netduino with Mp3 Shield and 5 button UI

Netduino Mp3 player with 5 button UI

Netduino + SeeedStudio Grove LCD RGB Backlight

For the last year I have been teaching introductory programing classes using Netduino devices and Seeedstudio sensors which were sponsored by Microsoft New Zealand. The kits are based on a Grove Starter Kit for Arduino/Genuino 101 which contain a Grove LCD RGB Backlight display.

Seeedstudio have published an Arduino driver for the display and it looks like Sirsnork used this as the basis for his Netduino NetMF Port. In class a few people have commented that they have had difficulty getting the driver to work on a Netduino 2 or Netduino Plus 2 device.

I think the two main issues are the lack of termination resistors on the Grove RGB Backlight. Possibly the missing R9 & R10 in the picture below?

SeeedStudioRGBLCDBack

I have found the easiest way to work around this issue is to have another I2C device (In this case it’s a Grove 3 Axis Accelerometer ±16G)

SeeedStudioNetduinoAndRGBLCD

The other is the need to strobe the Serial Data Line (SDA) of the I2C port on later Netduino devices to get it to work

using System;
using System.Threading;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;

namespace SeeedStudio.Grove.RGBLCD
{
   public class Program
   {
      public static void Main()
      {
         using (OutputPort i2cPort = new OutputPort(Pins.GPIO_PIN_SDA, true))
         {
            i2cPort.Write(false);
         }

.....

With the I2C bus terminated and the SDA port strobe I have found the Netduino and display work as expected.

NetMF Electric Longboard Part 2

In part 1 I got the wireless WiiChuck working with a plug n play setup using a SeeedStudio Grove base shield, Wii Chuck adaptor, modified 5CM cable and FEZ Lemur. The FEZ Lemur is limited to a 5VDC supply which wasn’t going to work so well with the 6VDC output of my HobbyKing HK150 ESC without some extra electronics.

GHI Electronics also sell the FEZ Panda III which has a 6VDC-9VDC voltage range and more processing power which would be useful for my next project a dual motor longboard with traction control and anti lock braking .

I also figured vibration could be a problem for the plug n play setup so I built a custom shield for my wireless Wii Chuck dual motor longboard control using an Arduino protoshield, and a Wii-Nunchuck breakout board. The shield provides a solid mount for the wireless Wii chuck dongle and power for the NetMF board from the output of the ESC.

 

FEZ Panda III Protoshield for longboard with RC Servo for testing

FEZ Panda II Protoshield for longboard RC Servo test

I tested the shield wiring using a Radio Control (RC) Servo so the scope of disaster was greatly reduced. (The red jumper wire is supplying 3v3 to the servo for testing)

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using Toolbox.NETMF.Hardware;

public class Program
{
   private const int NunchukYMinimum = 0;
   private const int NunchukYMaximum = 255;
   private const int PWMPeriodMicroseconds = 20000;
   private const int DurationMinimum = 1250;
   private const int DurationMaximum = 1750;

   public static void Main()
   {
      WiiNunchuk Nunchuk = new WiiNunchuk();
      PWM pwm = new PWM(GHI.Pins.FEZPandaIII.PwmOutput.D6, PWMPeriodMicroseconds, DurationMinimum, PWM.ScaleFactor.Microseconds, false);

      pwm.Start();

      while (true)
      {
         // Reads all values
         Nunchuk.Read();

         Debug.Print(Nunchuk.AnalogStickX.ToString() + " " + Nunchuk.AnalogStickY.ToString());

         uint duration = (uint)map(Nunchuk.AnalogStickY, NunchukYMinimum, NunchukYMaximum, DurationMinimum, DurationMaximum);

         Debug.Print("Duration " + duration.ToString());
         pwm.Duration = duration;

         Thread.Sleep(100);
      }
   }

   private static long map(long x, long inputMinimum, long inputMaximum, long outputMinimum, long outputMaximum)
   {
      return (x - inputMinimum) * (outputMaximum - outputMinimum) / (inputMaximum - inputMinimum) + outputMinimum;
   }
}

I then connected the setup to my longboard ESC and it worked. (need a right angle connection for FEZ Panda III power)

Longboard with FEZ Panda III board based controller

Longboard with FEZ Panda III board based controller

The proof of concept software worked, the next step is to add throttle mapping and failure mode handling e.g. loss of communications with the Wiichuck.