I think you guys need a facebook page...

Here's another little sample that I put together called BlinkyTimer.

This basically does the same thing as the Blinky tutorial, but it uses a Timer object with a callback method to turn the LED on and off.

Here's the code. If you think of any cool variations, please share.

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

namespace BlinkyTimer
{
    public class Program
    {
        const int blinkPeriod = 250;
        static bool ledState;
        static OutputPort led;

        public static void Main()
        {
            // Set the initial state of the LED to off (false).
            ledState = false;

            led = new OutputPort(Pins.ONBOARD_LED, ledState);

            // Create a System.Threading.Timer instance and pass it the timer callback method.
            Timer blinkTimer = new Timer(
                new TimerCallback(BlinkTimerCallback),
                null,
                blinkPeriod,
                blinkPeriod);

            Thread.Sleep(Timeout.Infinite);
        }

        public static void BlinkTimerCallback(Object obj)
        {
            // Invert the previous state of the LED.
            ledState = !ledState;

            // Set the LED to its new state.
            led.Write(ledState);
        }

    }
}

Thanks Chris! And thanks for moving it to the new forum.

One quick note: you don't need to put the infinite sleep inside a loop. It will only execute once...so they while(true) is redundant...

Yeah, I keep meaning to fix that. It was in a sample program from the book "Embedded Programming with the Microsoft .NET Micro Framework", but I agree it seems redundant. It might also make the code a little smaller by removing the while loop(?).

I just updated it for you. Please let me know if you'd like me to change it back.

You beat me to it. Thanks again, Chris!

(And get some sleep, OK?)

Hi Netduino fans,

Here's a fun little project that builds on my previous PwmSample and PwmGamma programs.

The Pwm2Color sample controls a 2-color LED (or 2 individual LEDs, if you wish). It uses 2 pushbutton switches as input; one button controls the intensity of the Red LED, and the other button controls the Green LED.

The buttons gradually ramp the LED intensity up and back down, using Gamma correction to make the ramps more linear.

By using a 2-color LED (which is just 2 LED substrates in the same package), you can mix the red and green components in different proportions, creating intermediate shades of yellow and orange.

Please see the comments in the code for a description of the circuit. I'll try to post up a schematic later if there's interest.

I've made a few tweaks since the PwmGamma sample, and tried to streamline the code a bit:

• The code now makes use of the InterruptPort's glitchFilter parameter, so please make sure you are running Netduino firmware 4.1.0.2 or later.
  
• Since I'm now using the glitch filter, there's no need to disable and re-enable the interrupts in the interrupt callback method.
  
• Note that the same interrupt callback is used to handle the interrupts from both buttons. The interrupt callback uses the data1 parameter to determine which button generated the interrupt.
  
• The Channel class is used to encapsulate the PWM port (for the LED), the InterruptPort (for the corresponding pushbutton), and the state variables. This makes the code much simpler, since it can just iterate over Channel objects. It also makes it much easier to extend the sample to use a 3-color LED (literally a 2-line code change).

Here's the code. Have fun!

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

namespace Pwm2Color
{
    // The Channel class encapsulates the PWM port for an LED, the InterruptPort
    // for the corresponding pushbutton switch, and some state variables.
    public class Channel
    {
        public bool ButtonState { get; set; }
        public int PwmIndex { get; set; }
        public int PwmIncrement { get; set; }

        public PWM Led 
        {
            get { return _Led; }
        }
        private PWM _Led;

        public InterruptPort Button 
        {
            get { return _Button; }
        }
        private InterruptPort _Button;

        public Channel(Cpu.Pin LedPin, Cpu.Pin ButtonPin)
        {
            ButtonState = false;
            PwmIndex = 0;
            PwmIncrement = 1;
            _Led = new PWM(LedPin);
            _Button = new InterruptPort(
                ButtonPin,
                true,
                Port.ResistorMode.Disabled,
                Port.InterruptMode.InterruptEdgeBoth
            );
        }
    }


    public class Program
    {
        const int pwmPeriod = 50;
        const uint MaxDutyCyle = 100;

        // Lookup table for the LED brightness.  The table contains the 
        // gamma-corrected values (for gamma = 2.5).  This approximates
        // a linear increase in the perceived brightness.
        //
        // Declaring it as a byte array makes the assembly a little smaller,
        // and the byte values automatically get promoted to uint when
        // setting the PWM duty cycle.
        static byte[] gammaTable = {
             0,  0,  0,  0,  1,  1,  1,  2,  2,   3,
             4,  5,  6,  7,  9, 10, 12, 14, 16,  18,
            20, 22, 25, 28, 31, 34, 37, 41, 45,  49,
            53, 57, 62, 67, 72, 77, 82, 88, 94, 100,
        };

        static Channel[] channels;

        public static void Main()
        {
            // NOTE: You will need to connect 2 LEDs and an additional pushbutton switch 
            // to the Netduino board.  The circuit is as follows:
            //
            // 1. Connect a 100-ohm resistor between the anode of the Green LED and Digital Pin 5.
            // 2. Connect a 100-ohm resistor between the anode of the Red LED and Digital Pin 6.
            // 3. Connect the LED cathode(s) to GND on the Power header.
            // 4. Connect a 1K pull-up resistor between 3V3 on the Power header and Digital Pin 1.
            // 5. Connect one side of the SPST pushbutton switch to Digital Pin 1. (This switch 
            //    controls the Red LED).
            // 6. Connect the other side of the SPST pushbutton switch to GND on the Power header.
            //
            // I used a 2-color LED which has red and green LEDs in the same package.
            // Electrically, it's the same as 2 separate LEDs, so the circuit is virtually the same.
            // If you use a 2-color LED, be sure to get the common-cathode variety.
            // With a 2-color LED, you can "mix" the colors in varying proportions.
            // When both red and green are on, the resulting color is yellow or orange.
            //
            // It should be almost trivial to modify this program to handle a 3-color LED. ;)

            // Allocate the array to hold 2 Channel references.
            channels = new Channel[2];

            // Create each Channel and add it to the channels[] array.
            channels[0] = new Channel(Pins.GPIO_PIN_D5, Pins.ONBOARD_SW1);  // Green channel
            channels[1] = new Channel(Pins.GPIO_PIN_D6, Pins.GPIO_PIN_D1);  // Red channel

            // Bind the interrupt handler to the pin's interrupt event.
            // The same interrupt handler is used for all the channels.
            // The data1 parameter in the handler will determine which button
            // generated the interrupt.
            foreach (Channel ch in channels)
            {
                ch.Button.OnInterrupt += new NativeEventHandler(SwitchInterruptHandler);
            }

            // Create a System.Threading.Timer instance and pass it the timer callback method.
            Timer pwmTimer = new Timer(
                new TimerCallback(PwmTimerCallback),
                null,
                pwmPeriod,
                pwmPeriod);

            Thread.Sleep(Timeout.Infinite);
        }

        public static void PwmTimerCallback(Object obj)
        {
            // Only change the LED brightness when the corresponding button is pushed (true).
            foreach (Channel ch in channels)
            {
                if (true == ch.ButtonState)
                {
                    // Set the pin's new duty cycle.
                    ch.Led.SetDutyCycle(gammaTable[ch.PwmIndex]);
                    ch.PwmIndex += ch.PwmIncrement;

                    Debug.Print(gammaTable[ch.PwmIndex].ToString());

                    if (((gammaTable.Length - 1) == ch.PwmIndex) || (0 == ch.PwmIndex))
                    {
                        // The duty cycle has hit the min or max value.
                        // Start ramping in the other direction.
                        ch.PwmIncrement = -ch.PwmIncrement;
                    }
                }
            }
        }

        // port:  The pin number of the port that generated the interrupt
        // state: The logic state of the port
        // time:  Time of the event
        public static void SwitchInterruptHandler(UInt32 port, UInt32 state, DateTime time)
        {
            foreach (Channel ch in channels)
            {
                if (port == (UInt32)ch.Button.Id)
                {
                    ch.ButtonState = (0 == state);
                }
            }
        }

    }
}

I'm in the same boat. This book has been fan-freakin-tastic: Make: Electronics

Stacy

+1 on Make: Electronics. Very fun and easy read, with clear explanations and experiments that demonstrate the principles well.

Some of the old Radio Shack books by Forest M. Mims are also quite good. I believe you can still get his classic "Getting Started in Electronics", as well as reprints that combine several of the small "Engineer's Mini Notebook" titles in one book.

Hi folks,

Some the little sample projects that I've been sharing over on the Project Showcase are getting large enough that it would be helpful to post a schematic along with the code. I expect the circuits will only get bigger as time goes on.

I've been out of the electronics hobby for a while, so I'm curious what kind of schematic capture software is hobbyist-friendly. Basically, this means free (or cheap), and easy to learn.

It looks like Eagle supports schematic capture as well as PCB layout, and has a limited freeware version.

I've also heard some recommendations for KiCad (open-source).

Are there any others I should look into? I'm on the Windows platform, BTW.

Did you look at Fritzing? It's what I use to document schematics for my projects.
And CW2 already created Fritzing part for Netduino.

Thanks, Szymon. I'll take a look at Fritzing - it looks interesting.

Yep, generally PC fans are available in the following flavors:

2 wires: Constant speed
3 wires: Constant speed w/ tachometer output
4 wires: Variable speed w/ tachometer output and speed input (PWM)

I recently saw an article on the Make: blog where a guy had connected a 3-wire fan to an Arduino and it displayed the fan's speed on 7-segment displays. I think that would be a good re-make with the Netduino.

http://blog.makezine...th_arduino.html

And if you have any questions about the PwmSample, please feel free to post them here or in the Project Showcase forum (I posted the sample code). Let us know when you get the Cylon / Knight Rider circuit working (and share the code if you don't mind).

Nice! I'm glad I brought a Netduino with me on vacation so I can play with this

You mean you actually take vacation?

As a follow-up to the PwmSample, CW2 suggested extending it to address the non-linear response of the LED.

After a bit of research, I found that this is referred to as "gamma correction", and even found an application note that discusses using gamma correction with PWM:

http://www.maxim-ic....dex.mvp/id/3667

So, here's an update to PwmSample that uses a pre-computed LUT (lookup table) for the PWM output values. These are the gamma-corrected values (for gamma = 2.5) that produce a brightness ramp that looks linear (more or less) to our eye.

Here's the code:

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

namespace PwmGamma
{
    public class Program
    {
        const int pwmPeriod = 50;

        // Lookup table for the LED brightness.  The table contains the 
        // gamma-corrected values (for gamma = 2.5).  This approximates
        // a linear increase in the perceived brightness.
        static uint[] gammaTable = {
             0,  0,  0,  0,  1,  1,  1,  2,  2,   3,
             4,  5,  6,  7,  9, 10, 12, 14, 16,  18,
            20, 22, 25, 28, 31, 34, 37, 41, 45,  49,
            53, 57, 62, 67, 72, 77, 82, 88, 94, 100,
        };

        static bool buttonState;
        static int pwmIndex;
        static int pwmIncrement;
        static InterruptPort button;
        static PWM led;

        public static void Main()
        {
            pwmIndex = 0;
            pwmIncrement = 1;
            buttonState = false;

            // NOTE: You will need to connect an LED to Digital Pin 5 on the Netduino board.
            // Use a 100-ohm (brown-black-brown) resistor between the LED anode (+) and Digital Pin 5.
            // Connect the LED cathode (-) to one of the GND pins on the Power header.
            //
            // You can use any other PWM-enabled pin (5, 6, 9 or 10), but also remember to change
            // the Pin parameter in the PWM constructor below.

            led = new PWM(Pins.GPIO_PIN_D5);

            button = new InterruptPort(
                Pins.ONBOARD_SW1,
                false,
                Port.ResistorMode.Disabled,
                Port.InterruptMode.InterruptEdgeBoth);

            // Bind the interrupt handler to the pin's interrupt event.
            button.OnInterrupt += new NativeEventHandler(SwitchInterruptHandler);

            // Create a System.Threading.Timer instance and pass it the timer callback method.
            Timer pwmTimer = new Timer(
                new TimerCallback(PwmTimerCallback),
                null,
                pwmPeriod,
                pwmPeriod);

            Thread.Sleep(Timeout.Infinite);
        }

        public static void PwmTimerCallback(Object obj)
        {
            // Only change the LED brightness when the button is pushed (true).
            if (true == buttonState)
            {
                // Set the pin's new duty cycle.
                led.SetDutyCycle(gammaTable[pwmIndex]);
                pwmIndex += pwmIncrement;

                Debug.Print(gammaTable[pwmIndex].ToString());

                if (((gammaTable.Length - 1) == pwmIndex) || (0 == pwmIndex))
                {
                    // The duty cycle has hit the min or max value.
                    // Start ramping in the other direction.
                    pwmIncrement = -pwmIncrement;
                }
            }
        }

        public static void SwitchInterruptHandler(UInt32 data1, UInt32 data2, DateTime time)
        {
            button.DisableInterrupt();

            buttonState = (0 == data2);

            button.EnableInterrupt();
        }

    }
}

ummmm didnt think about that.... I dont really know. I guess what I'm asking is what can I do to get a battery with high amps and at least 9V... cuz they sell them for RC model airplanes, but those are crazy expensive

Well, you could put two of the 6V batteries in series to get 12V.

With a regulator, it's fairly easy to *decrease* the voltage. But, in general, it's not easy to increase the voltage of a DC source.

Increasing the voltage generally involves converting DC to AC (or a DC square wave), passing it through a step-up transformer, and converting back to DC.

But if you do that, then the current will decrease proportionally with the voltage increase (actually, you'll lose even more current due to losses in the transformer, etc.).

I think we'd need to see the rest of the code in order to find the problem. Can you post the complete source code?

On second thought...

fileLocation += fStream.Read(buffer, fileLocation, System.Math.Min(128, (int)(fInfo.Length - fileLocation)));

fileLocation is 128 on your second loop--too high of an offset in your 128-byte buffer array. Did you want to pass 0 as your second parameter?

Chris

Also, it looks like you can just use 128 for the 3rd parameter to FileStream.Read()...if it reads less than 128 bytes, then it should be OK (the method will return the actual number of bytes it read).

Shouldn't the SW1 button act like all the other GPIO's?

If you start out by using the SW1 for input, but later on decides to use another pin for the button, it wouldn't be good to require further code changes.

The way the button is wired (Pull-Up scenario) is pretty common, and having all GPIO's "inverted" wouldn't be fun is you ask me.

I'd say that a LOW signal on a pin should be FALSE, and a HIGH signal should be TRUE - Including the SW1 input.

Just my 5 cents...

/Thomas

You can make a good case for either option. I think the real problem is that a Port is fairly generic, while connecting a switch to an input port is a specific use case.

A couple of suggestions:

1. Define a new switch-specific enumeration, so that ON corresponds to boolean false, and OFF corresponds to boolean true.

2. Derive a Switch class from the InputPort class, and give the Switch class semantics that make sense for a switch (reading the state as being On/Off, Open/Closed, etc.).

Option 1 is probably simpler, while option 2 may be a "next version" type of thing.

Thanks,
-David

Gaah, never mind. I just found that the Event Handlers tutorial has been posted in the Projects section.

I'll take a look at that...

Hmm, I seem to have the same issue with the AdvancedButtonApp tutorial. Works as expected under the debugger, but not when I just deploy the solution to the Netduino.

Is there some kind of timing issue that's causing this? Has anybody else got this working outside the debugger?

Hmm, I seem to have the same issue with the AdvancedButtonApp tutorial. Works as expected under the debugger, but not when I just deploy the solution to the Netduino.

Is there some kind of timing issue that's causing this? Has anybody else got this working outside the debugger?

D'oh! Dumb mistake - I was just selecting the "Deploy Solution" menu option from the Build menu. I needed to select "Start Without Debugging" from the Debug menu to get the solution to actually run.

Now both programs work as expected.

Move along, nothing to see here...

I decided to try modifying the ButtonApp sample to use interrupts instead of polling the state of the pushbutton switch.

Gaah, never mind. I just found that the Event Handlers tutorial has been posted in the Projects section.

I'll take a look at that...

Hi,

I decided to try modifying the ButtonApp sample to use interrupts instead of polling the state of the pushbutton switch.

I found an example in the book "Embedded Programming with the Microsoft .NET Micro Framework", and kinda mashed up my own ToggleButton app.

The basic idea is to have the pushbutton switch "toggle" the LED on and off with each successive press (i.e., the first time the button is pushed and released, the LED turns on, and the next time the button is pushed, the LED turns off, etc.).

Here's the code that I came up with. There's probably some unnecessary code in here, since I was trying various ways to make it work.

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

namespace ToggleButton
{
    public class Program
    {
        static InterruptPort button;
        static OutputPort led;
        static bool ledState;

        public static void Main()
        {
            // Set the initial state of the LED to off (false).
            ledState = true;

            led = new OutputPort(Pins.ONBOARD_LED, ledState);
            button = new InterruptPort(Pins.ONBOARD_SW1, false, Port.ResistorMode.Disabled, Port.InterruptMode.InterruptEdgeLevelLow);

            // Bind the interrupt handler to the pin's interrupt event.
            button.OnInterrupt += SwitchInterruptHandler;
            button.EnableInterrupt();

            while (true)
            {
                Thread.Sleep(Timeout.Infinite);
            }
        }

        public static void SwitchInterruptHandler(UInt32 data1, UInt32 data2, DateTime time)
        {
            Debug.Print("+SwitchInterruptHandler");
            button.DisableInterrupt();

            // Invert the previous state of the LED.
            ledState = !ledState;

            // Set the LED to its new state.
            led.Write(ledState);

            button.EnableInterrupt();
            button.ClearInterrupt();
            Debug.Print("-SwitchInterruptHandler");
        }

    }
}

The problem is that the code seems to run fine under the debugger, but doesn't work as expected when it's not running in the debugger.

Can anybody spot what I'm doing wrong here?

Thanks,
-David

This is a timely topic . It would nice to make this a sticky thread for future reference (and a place to point somebody to when they ask where to find things).

I'll add a couple more:

• Evil Mad Science Shop: This is the companion store for the Evil Mad Scientist Laboratories blog. A smaller but more eclectic shop. They mainly sell kits of their own design, and also have some good deals on components (like RGB LEDs). Also check out the EggBot.
  
• Adafruit Industries: The companion store for the LadyAda.net blog (aka Limor Fried). Like Evil Mad Science, the store carries a lot of kits designed by LadyAda, as well as lots of Arduino boards and shields. There's some overlap with MakerShed and SparkFun, but a lot of cool stuff.

Perhaps we could "dedicate" bug fixes to our community members?

Or maybe you could award Fabulous Prizes^TM to the top bug finders (like a Netduino board or a trip to Hawaii).

Hi Chris,

Yeah, I know how delegates and events work. I've been coding professional for 10+ years. I found out why my InterruptPort wasn't working!! It was the glitchFilter, I set it to true. I remember reading it somewhere that if you set the glitchFilter to true, that will automatically handle switch debouncing for you. Could you clarify the use of this parameter for me as I am confused now. And thanks for the quick reply. You guys are doing great job helping the Netduino community to get started.

xc2rx

Hi xc2rx,

I found the same thing that you did with the glitchFilter parameter. (BTW, I'm the guy who posted the ToggleButton sample that Chris referred to).

In the ToggleButton sample, if I set the InterruptPort's glitchFilter parameter to true, it seems that the interrupts don't fire (or the event associated with the interrupt doesn't fire - not sure which one).

@Chris - is there a way we can investigate this further?

Quick update... We found the problem. A single line of code in the GPIO debouncer code was causing the glitch in the glitchfilter.

We have implemented the GlitchFilter fix in the v4.1.0.2 (4.1.0 patch 2) update along with the AnalogInput bugfix. The updated firmware will be posted by tomorrow.

Chris

Cool, I'll be sure to try it out (tomorrow).

You'll probably need three resistors--one for each of the Red, Green, and Blue elements.

Chris

1K is probably too high a resistance if you're driving LEDs from the Netduino output pins (3.3v).

Something like 100 ohms is probably more appropriate for Red or Green LEDs. I think Blue LEDs generally have a higher forward voltage, so you may need an even smaller resistor (or maybe no resistor at all). Best bet is to buy a resistor assortment, and save yourself some frustration.

Also, you'll probably want a potentiometer to attach that knob to .

If you're just getting started in electronics, I'd highly recommend the Make: Electronics book. It's a great hands-on introduction to basic electronics. It doesn't cover Arduino/Netduino specifically, but it's a good learning guide.