TMP36 Temperature Sensor

Before I got on a side-track on the MQTT project, I'd wanted to interface with a temperature sensor. The one I had originally chosen turned out to be a one-wire digital sensor.  This is probably a great sensor, but there are, as I understand now, some issues with the Netduino and one-wire sensors.  So, that sensor got sidelined until this support is fixed up and in non-beta firmware (or until I buy a FEZ Cobra - which would address several issues I'm facing - albeit with a significantly higher price tag.)

So, off I went to find a analog temperature sensor.  There are numerous options - I even briefly thought about drafting one of my MSP430's for this.  :)

But I settled for a TMP36 from Futurlec.  This (I mean 'these' - never only buy 1 of anything :) ) arrived on Friday after a trip from Hong Kong along with a bunch of random odds and ends that I'm tired of going to Radio Shack to get - 2 at a time (I'm ok with 100%+ markup to get it in town - but throw 10-20 into a bag, not 2).

Between the datasheet (http://www.analog.com/static/imported-files/data_sheets/TMP35_36_37.pdf) and some help from the AdaFruit blog (http://www.ladyada.net/learn/sensors/tmp36.html) we got it working pretty well.

The cap is actually a normal orange ceramic disk - not sure why Fritzing doesn't have those.  It was added per the datasheet (0.1uF) for RFI purposes - but, in my non-scientific testing, it didn't make any difference if it was there or not (at least in my environment - which I'd figure is a mess RFI-wise).

I have several temperature sensors that I want to play with, so we made a class to hold those:

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

namespace Temperature_Sensors
{

    public static class TMP36
    {

        // port is analog port
        // sample is the number of samples to take
        // interval is the time (ms) to wait between samples
        // voltage is input voltage * 1000, default is 3.3v
        public static float getVoltage(AnalogInput port, int sample = 10, int interval = 100, int voltage = 3300)
        {
            int reading = 0;
            for (int i = 0; i < sample; i++)
            {
                Thread.Sleep(interval);
                // Read the value on the AIO port
                reading += port.Read();
            }
            reading /= sample;
            Debug.Print("Reading: " + reading + "");
            // Voltage at pin in milliVolts = (reading from ADC) * (3300/1024) http://www.ladyada.net/learn/sensors/tmp36.html
            return (reading * (voltage / 1024F));
        }

        public static float getCTemp(AnalogInput port, int sample = 10, int interval = 100, int voltage = 3300)
        {
            // Temp in °C = [(Vout in mV) - 500] / 10 http://www.ladyada.net/learn/sensors/tmp36.html
            return ((getVoltage(port, sample, interval, voltage) - 500F) / 10F);
        }

        public static float getFTemp(AnalogInput port, int sample = 10, int interval = 100, int voltage = 3300)
        {
            // Convert to °F 
            return ((getCTemp(port, sample, interval, voltage) * (9F / 5F)) + 32F);
        }
    }
}

And here is a program to drive this - with a timer being used to periodically collect the temperature:

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.NetduinoPlus;
using Temperature_Sensors;

namespace myTempSensor
{
    public class Program
    {
        static AnalogInput analogInput;

        static void checkTemp(object o)
        {
            float fTemp = TMP36.getFTemp(analogInput, 10, 100, 3300);
            Debug.Print("Temp: " + fTemp + "");
        }

        public static void Main()
        {

            analogInput = new AnalogInput(Pins.GPIO_PIN_A0);
            Timer tempTimer = new Timer(new TimerCallback(checkTemp), null, 1000, 10000);

            // go to sleep until the timer wakes us (saves power)
            Thread.Sleep(Timeout.Infinite);
        }
    }
}

Right now we're not doing anything with this data - but soon we'll smoosh this up against the MQTT stuff and start getting this published - probably to the test.mosquitto.org server.

<aside>
Speaking of which - we might have to take another break and write some visualization stuff - Roger of Mosquitto fame has issued a challenge (http://mosquitto.org/2012/01/challenge-web-based-mqtt-graphing/) for visualization of some energy data that is being fed to his server.  This might be fun.  I'm thinking of using the Node.js client then feeding that data into the Google charts API.
</aside>

Anyway, I haven't got this sensor to be particularly accurate yet.  Although, forcing my math to floating point math REALLY helped.  :)  I may just try a thermistor.  Not sure, I'm sure that a digital sensor is probably the right plan...  I think my main problem at this point is the accuracy of the sensor (+-2C), mixed with the stated "non-high precision" of the Netduino ADC's.  So, this combination seems to be about as accurate as that of my other "high precision" thermometer.  :)

Since the accuracy is odd - I added the ability to collect a bunch of readings and average them.  Not sure it really helped as much as I would have expected either, but it's there.

I think next up is going to be a Syslog library for the Netduino - which will require an NTP library since I don't have an RTC board handy and you need time for logs.  (FEZ Cobra has one though I think....Which might be a better approach than buying a mini-board...  I don't know...  I could do SSL with the Cobra too...)

And we'll keep working on the MQTT stuff.  Still need a couple message handlers and to redo some stuff related to the fixed headers.

Also, kind of seriously thinking about writing an MQTT-S gateway (forwarder?) and client for the Netduino Plus - then getting some sort of comm stuff to talk between a few things around here.  I'm kind of taking that "no publicly available implementation" bit as a challenge...  :)

Half-Baked MQTT Publisher for Netduino Plus

UPDATE:  This has been moved to GitHub: https://github.com/danielan/NetduinoMQTT

I received a Netduino Plus for Christmas this year. So, I needed a project to put this to work. After working my way through the O'Reilly/Make book, "Getting Started with the Internet of Things" book, I decided to implement a MQTT publisher for my Netduino Plus.

Now, MQTT is a really cool protocol that can be used for all sorts of things and supports all sorts of neat features.  This isn't that sort of program.  :)

All this does, in a weak way, is connect to a message broker, publish a message without QoS and then disconnect.  This is NOT how you should do it.  This doesn't work for long topics, long messages, etc.  It doesn't retry if there is a problem, etc.

This is intended only for my use - ultimately publishing a temperature from a sensor over and over - but I'm back to work tomorrow, so this will probably be idle for some time.

I hope this helps - but don't use it expecting it to be useful without more work. 

So, enough disclaimers... :)

MQTT

I learned of MQTT from this post at AdaFruit: http://www.adafruit.com/blog/2011/11/08/ibm-open-sources-potential-internet-of-things-protocol/

And the learned more from this Series on "ReadWriteWeb":
http://www.readwriteweb.com/hack/2011/11/ibms-andy-piper-negotiating-th.php
http://www.readwriteweb.com/hack/2011/11/ibms-andy-piper-part-2-how-mqt.php
http://www.readwriteweb.com/hack/2011/11/ibms-andy-piper-part-3-the-tax.php

There's also a web site at: http://mqtt.org/

And the quite useful official specification is over here: http://public.dhe.ibm.com/software/dw/webservices/ws-mqtt/mqtt-v3r1.html

Demoing MQTT

To use MQTT you need a "Broker" - I used "Really Small Message Broker" from here: https://www.ibm.com/developerworks/community/groups/service/html/communityview?communityUuid=d5bedadd-e46f-4c97-af89-22d65ffee070

To demo this, download rsmb from there and unzip it.  Then open 4 "cmd" windows and make your working directory in the folder "windows" (assuming Windows) in the rsmb directory you just extracted.

In one cmd window run: broker.exe

In the next cmd window run: stdinpub.exe test
In another cmd window run: stdoutsub.exe test --clientid one
In the last cmd window run: stdoutsub.exe test --clientid two

"test" is the name of our topic. The client ids are necessary because, I assume, there is a bug in the windows stdoutsub.exe binary - the names are supposed to be unique by default*, but aren't.

* "Help" for stdoutsub.exe: "--clientid <clientid> (default is hostname+timestamp)"  But in reality they seem to default to "stdout-subscriber" - I'll see if I can find someone to report this to.

Now, if you type something into the stdinpub.exe window - you should see it show up in the two stdoutsub.exe windows.  This is, simplistically, what MQTT is for (lightweight publisher/subscriber model comms).

(These windows will also be useful to see if our program is working.)

The Code

There's a library available for MQTT on all sorts of languages and software, but I couldn't find anything for the Netduino Plus (although maybe the .NET one would work?)

It would probably be a good idea to read through the standard first.  I used hex for flags and numbers where they made more sense.  I started to do constants, but didn't get finished yet...

(Note - the flags are easier to decipher if you remember that for hex you use 4 bits per hex digit.)

While keeping in mind that this is not appropriate for actual use....

Here is the code for the "library".

using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using Microsoft.SPOT;
using Socket = System.Net.Sockets.Socket;

namespace Netduino_MQTT_Client_Library
{
    static class Constants
    {
        public const int MQTTVERSION = 3;
    }

    public static class MQTTClient
    {
        // From Sample Code (SockClient.cs) Copyright Microsoft
        public static Socket ConnectSocket(String server, Int32 port)
        {
            // Get server's IP address.
            IPHostEntry hostEntry = Dns.GetHostEntry(server);

            // Create socket and connect to the server's IP address and port
            Socket socket = new Socket(AddressFamily.InterNetwork,
                SocketType.Stream, ProtocolType.Tcp);
            socket.Connect(new IPEndPoint(hostEntry.AddressList[0], port));
            return socket;
        }
        // End of Microsoft Copyright sample code

        public static void ConnectMQTT(Socket mySocket, String clientID)
        {

            int index=0;
            byte[] buffer = null;
            buffer = new byte[16 + clientID.Length];
            // Fixed Header (2.1)
            buffer[index++] = 0x10; // Fixed header flags
            buffer[index++] = (byte)(14 + clientID.Length); // Remaining Length
            // End Fixed Header
            // Connect (3.1) 
            // Protocol Name
            buffer[index++] = 0;       // String (MQIsdp) Length MSB
            buffer[index++] = 6;       // Length LSB
            buffer[index++] = (byte)'M';  // M
            buffer[index++] = (byte)'Q';  // Q
            buffer[index++] = (byte)'I';  // I
            buffer[index++] = (byte)'s';  // s
            buffer[index++] = (byte)'d';  // d
            buffer[index++] = (byte)'p';  // p
            // Protocol Version
            buffer[index++] = Constants.MQTTVERSION;
            // Connect Flags
            buffer[index++] = 0x02;
            //Keep alive (20 seconds)
            buffer[index++] = 0;     // Keep Alive MSB
            buffer[index++] = 20;    // Keep Alive LSB
            // ClientID
            buffer[index++] = 0;                        // Length MSB
            buffer[index++] = (byte)clientID.Length;    // Length LSB
            for (var i = 0; i < clientID.Length; i++) 
            {
                buffer[index++] = (byte)clientID[i]; 
            }
            mySocket.Send(buffer, index, 0);

        }

        public static void PublishMQTT(Socket mySocket, String topic, String message)
        {

            int index = 0;
            byte[] buffer = null;
            buffer = new byte[4 + topic.Length + message.Length];
            // Fixed header
            //      Publish (3.3) fixed header flags
            buffer[index++] = 0x30;
            //      Remaining Length (variable header + payload)
            buffer[index++] = (byte)(2 + topic.Length + message.Length);
            // End of fixed header 
            // Variable header (topic)
            buffer[index++] = 0;                   // Length MSB
            buffer[index++] = (byte)topic.Length;  // Length LSB
            // End of variable header
            for (var i = 0; i < topic.Length; i++)
            {
                buffer[index++] = (byte)topic[i];
            }
            // Message (Length is accounted for in the fixed header)
            for (var i = 0; i < message.Length; i++)
            {
                buffer[index++] = (byte)message[i];
            }
            mySocket.Send(buffer, buffer.Length, 0);
        }

        public static void DisconnectMQTT(Socket mySocket)
        {
            byte[] buffer = null;
            buffer = new byte[2];
            buffer[0] = 0xe0;
            buffer[1] = 0x00;
            mySocket.Send(buffer, buffer.Length, 0);
        }
    }
}

Here is the code to use this library (Don't forget to change to your IP (where broker.exe is running)).

using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.NetduinoPlus;
using Netduino_MQTT_Client_Library;

namespace NetduinoMQTT
{
    public class Program
    {
        public static void Main()
        {
            // This is where you would do your work
            Socket mySocket = MQTTClient.ConnectSocket("192.168.1.1",1883);
            MQTTClient.ConnectMQTT(mySocket,"tester123");
            MQTTClient.PublishMQTT(mySocket, "test", "testme12");
            Thread.Sleep(1000);
            MQTTClient.DisconnectMQTT(mySocket);
        }
    }
}

Deploy this to your Netduino Plus and you should see the message, "testme12" appear in your stdoutsub.exe windows (and some connection messages in your broker.exe window).


To Do

If you wanted to use this for anything, probably at a minimum you should account for connect failures, longer topics, longer messages, maybe QoS, maybe authentication, maybe use the SSL version, etc.  Since it is a "library" it would be good to support the whole subscription thing, etc.

Conclusion

So, that's it!  VERY simplistic MQTT publishing from a Netduino Plus to RSMB.  When I get around to setting up my temperature sensor maybe I'll make this a bit more robust and re-visit this.

I hope you enjoyed this post.

Netduino "Robot"

Over the past month or so my son and I built a "Robot" with our Netduino.

Parts:

• Magician Chassis Kit: http://www.sparkfun.com/products/10825
• Netduino: http://www.sparkfun.com/products/10107 
• Motor driver breakout TB6612FNG: http://www.sparkfun.com/products/9457
• Arduino Stackable Headers: http://www.sparkfun.com/products/9279
• Mini self-adhesive breadboard: http://www.sparkfun.com/products/8800
• Male to Male Jumper Wires: http://www.sparkfun.com/products/8431
• 4xAA Battery holder: http://www.sparkfun.com/products/9835
• 9 volt battery holder: http://www.sparkfun.com/products/10512
• Infrared Proximity Sensor (Sharp GP2Y0A21YK): http://www.sparkfun.com/products/242
• Infrared Sensor Jumper Wire: http://www.sparkfun.com/products/8733
• RadioShack female barrel connector RS# 274-1563

Physical Assembly:

First, we mounted the 8 pin headers upside down in the motor driver breakout like this:

We did this so that we could easily mount this into the breadboard and see the pin descriptions.  We didn't insert it all of the way into the breadboard - rumor has it that these get hot - although ours does not seem to.

Next, we assembled the robot chassis.  Some of the parts have tight tolerances, but everything fit together fine.

We attached the battery holders to the lower platform and the Netduino and breadboard onto the top platform.  Then we mounted the IR sensor to the "front" (the end with the 2 wheels).

Do NOT mount the IR sensor like it is in the picture above.  Our first day we managed to drive it under a kitchen cabinet and it cracked the circuit board of the IR sensor.  :(  When our replacement arrives, I think we will mount it on the lower deck so it is safer.

Wiring:

We wired it like this:

IR sensor yellow wire to the Netduino AIN0
IR sensor black to ground on Netduino
IR sensor red to Netduino 5V

9 volt power to Netduino
6 volt power black to ground on Netduino (via the RadioShack connector and some hookup wire)
6 volt power red to motor driver VM (same as above)

Netduino to TB6612FNG breakout
DIO0 = Standby (This needs to be high (true))
DIO1 = AIN1
DIO2 = AIN2
DIO5 = PWMA
DIO6 = PWMB
DIO8 = BIN1
DIO9 = BIN2
Ground to ground

TB6612FNG breakout to motors
AO1 = Red motor lead (Right)
AO2 = Black motor lead (Right)
BO2 = Black motor lead (Left)
BO1 = Red motor lead (Left)

Code:

Now it was time to code a little bit.  As usual, the path was paved by the great authors in the communities at Netduino.com (http://forums.netduino.com/index.php?/forum/4-netduino/).

We used the library provided from this post: http://forums.netduino.com/index.php?/topic/493-netduino-tankbot/page__view__findpost__p__3665 from user ajcg1973.

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;
// make sure you include the library - ours was (messily) inline

namespace IRRobot
{
    public class Program
    {
        static AnalogInput analogInput = new AnalogInput(Pins.GPIO_PIN_A0);
        public static void Main()
        {

            OutputPort stby = new OutputPort(Pins.GPIO_PIN_D0, true);
            AjbMotorTB6612FNG motors = new AjbMotorTB6612FNG(Pins.GPIO_PIN_D5, Pins.GPIO_PIN_D1, Pins.GPIO_PIN_D2, Pins.GPIO_PIN_D6, Pins.GPIO_PIN_D8, Pins.GPIO_PIN_D9);
            motors.Motor1Direction = AjbMotorTB6612FNG.MotorDirection.Forward;
            motors.Motor1Speed = 50;  // Set the motor to 50% speed
            motors.Motor2Direction = AjbMotorTB6612FNG.MotorDirection.Forward;
            motors.Motor2Speed = 50;  // Set the motor to 50% speed
            while (true)
            {
                Thread.Sleep(250); // pause to gather analog sample
                int analogValue = 1024 - analogInput.Read();
                Debug.Print(analogValue.ToString());
                if (analogValue < 550)
                {
                    motors.Motor1Direction = AjbMotorTB6612FNG.MotorDirection.Reverse;
                    motors.Motor1Speed = 30;  // Set the motor to 30% speed
                    motors.Motor2Direction = AjbMotorTB6612FNG.MotorDirection.Forward;
                    motors.Motor2Speed = 30;  // Set the motor to 30% speed
                    Thread.Sleep(1000);
                    motors.Motor1Direction = AjbMotorTB6612FNG.MotorDirection.Forward;
                    motors.Motor1Speed = 50;  // Set the motor to 50% speed
                    motors.Motor2Direction = AjbMotorTB6612FNG.MotorDirection.Forward;
                    motors.Motor2Speed = 50;  // Set the motor to 50% speed
                }

            }

        }

    }
}

This still needs some tweaking.  Or a whole re-write.  :)  But it shows how to drive the motors using ajcg1973's library and how to read the IR sensor.  We flipped forward and reverse in the library - this might mean we are driving backwards.  :)

You might want to watch the IR output values for a bit to get a feel for what it can see - ours is a bit far sighted so it runs into things some times. :) 

Conclusion:

This was a fun project.  The kids loved the little robot as it scooted across the floor avoiding obstacles.  We'll probably enhance our software and try some different sensors over the next few weeks.

We hope that you enjoyed this post.

References:

Original library code: http://forums.netduino.com/index.php?/topic/493-netduino-tankbot/page__view__findpost__p__3665
We got wiring help from this thread at the Netduino forum: http://forums.netduino.com/index.php?/topic/2396-control-dc-motor-with-dual-motor-driver/

A Netduino Keyboard Simulator

I realized that I haven't posted anything here in awhile...  So, to remedy this, here's my post on a Netduino keyboard simulator.

What this project does is to turn your Netduino into a "Human Interface Device" or HID.  I originally got the idea for this when I needed a fun project for a Halloween blog post at work.  A friend had sent me a link to a similar (but much more focused and useful) project: http://www.irongeek.com/i.php?page=security/programmable-hid-usb-keystroke-dongle

So, in their footsteps, and with some help from a library from the Netduino forums, we built a generic "virtual keyboard."

So, yeah - like hardware based macro keys I guess. :)

Gathering the Parts:

• FTDI Basic Breakout - 3.3V - http://www.sparkfun.com/products/9873 (These are a bit expensive IMO - but nice to have around for a variety of projects)
• 6 Pin Right Angle Male SMD Header - http://www.sparkfun.com/products/9015 (this is just to stick the FTDI breakout into the breadboard - not required at all)
• USB Mini-B Cable - 6 Foot - http://www.sparkfun.com/products/598 (You probably have 10 of these around your house already)
• Netduino - http://www.sparkfun.com/products/10107

I use SparkFun (and they are great) - but you can probably get all of these parts from a variety of vendors.

Development Environment:

If you don't already have your Netduino dev environment setup, you can go here: http://netduino.com/downloads/ and follow the "getting started" guide to setup your development environment.

Netduino Serial Hardware Setup:

First, connect the ground of the FTDI to the Netduino ground.
Next, hook the FTDI rx pin to the Netduino dio1.
Finally hook the FTDI tx pin to Netduino dio0.

You will also want to hook up an external power source.

Connect a USB to the FTDI.

Connect a USB to the Netduino.

Netduino Serial Setup Software:

(Check your firmware version with MFDeploy - mine didn't need re-flashed.)

Once you get your parts, and your dev environment is all setup - you will need to switch your Netduino to use serial programming (because the debug info is sent over that channel and it will interfere with the USB stuff you are trying to do).

Follow these instructions to do this: http://forums.netduino.com/index.php?showtopic=945

Here's a video from Omar on the Netduino Forum that covers this too:

http://www.youtube.com/user/VCSandARM#p/u/4/-yNC1nU1Nv4

Our Program:

Once you have this setup and tested, you'll want to move on to write your program.  You'll want to download keyboard.cs from this thread (use the last one on the page): http://forums.netduino.com/index.php?/topic/2274-netduino-usb-hid-keyboard-updated-code/

Then create a new "solution" in Visual Studio, target it to your serial interfaced Netduino and add the keyboard.cs to the solution (instructions from Omar in the link above).

Finally, we add our little bit of code for this:

using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using SecretLabs.NETMF.Hardware;
using SecretLabs.NETMF.Hardware.Netduino;
using System.IO.Ports;
using Netduino_USB_HID_Library;

namespace Netduino_Touch_Keyboard
{
    public class Program
    {
        public static void Main()
        {

            string setupResult = Keyboard.SetUp();

            Debug.Print(setupResult);

            if (setupResult != "Success")
                return;

            OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);
            led.Write(true);
            Thread.Sleep(1000);
            led.Write(false);
            Thread.Sleep(1000);
            // setup our interrupt port (on-board button)
            // InterruptEdgeLow = Interrupt on button press only (not button up)
            InterruptPort button = new InterruptPort(Pins.ONBOARD_SW1, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLow);

            // assign our interrupt handler
            button.OnInterrupt += new NativeEventHandler(button_OnInterrupt);

            // go to sleep until the interrupt wakes us (saves power)
            Thread.Sleep(Timeout.Infinite);

        }

        // the interrupt handler
        static void button_OnInterrupt(uint data1, uint data2, DateTime time)
        {
            Keyboard.HoldDown(Keyboard.Modifiers.LeftGUI);
            Keyboard.SendChar('r');
            Keyboard.AllUp();
            Keyboard.SendString("notepad.exe");
            Thread.Sleep(2000);
            Keyboard.SendString("\n");
            Thread.Sleep(2000);
            Keyboard.SendString("Hello World!");
        }
    }
}

Compile and deploy this to the Netduino.

Then unplug (if it was already plugged into the USB) and re-plug the USB to the Netduino. This is needed because the app takes a bit to start the first time and the USB driver will fail if you plug it in too quickly - this isn't a problem in "production" since it will be externally powered and running already.

Now press the on-board button.

It should, open up a copy of notepad.exe then write "Hello World!" into it.

References:
Netduino USB HID Code and Example:
http://forums.netduino.com/index.php?/topic/2274-netduino-usb-hid-keyboard-updated-code/
Official thread on beta HID support:
http://forums.netduino.com/index.php?/topic/1514-driverless-pc-netduino-communication-using-usb/
Keyboard class from here:
http://forums.netduino.com/index.php?/topic/2372-netduino-usb-hid-touch-screen-keyboard/

How to annoy your wife with a Netduino...

So, I stopped by a Radio Shack tonight to pick up some parts and decided to buy the Netduino some toys.

Amongst some other pieces, I picked up a 12 VDC Piezoelectric Buzzer (RS# 273-0059).  You can find cheaper ones online - just make sure that the low-end of the voltage range for yours is around 3 volts (http://www.netduino.com/netduino/specs.htm).

You can drive this pretty easily by simply plugging this buzzer in between the ground pin (GND) and one of the digital I/O ports (I used 13 - it's right next to the ground pin).  Somewhat annoyingly, it will immediately begin buzzing when you power-up the Netduino - this does not endear you to your sleeping wife.  :)

The plan was to make the last project into something useful.  As you may know - the FCC requires that amatuer radio operators identify periodically during operation (Sec 97.119 - http://www.w5yi.org/page.php?id=124).  With a couple quick modifications - you can make your Netduino provide your ID whenever you press the button.  This might actually be useful. I don't operate on CW often, but you can ID with CW wherever CW is authorized - So, everywhere but 60 meter right (not an issue for me)?

You can do this with a couple tiny modifications from the previous project:

First, change your OutputPort from:

// setup our output port (on-board LED)
static OutputPort led = new OutputPort(Pins.ONBOARD_LED, false);

to

// setup our output port (piezo buzzer (RS # 273-0059) between D13 and ground)
static OutputPort piezo = new OutputPort(Pins.GPIO_PIN_D13, false);

Then change your write operations from:

led.Write(true|false);

to

piezo.Write(true|false);

Then switch the MESSAGE constant to your call sign.   Hit the "Start debug" button and then press your button and you should get your call sign in CW over the buzzer at about 14 wpm (based on the UNIT constant being left at 100).

(I also ran across this free eBook on the .NET Micro Framework tonight - I haven't read through it yet - but it looks interesting - check it out:  Beginner's Guide to C# and .NET Micro Framework)