Tag Archives: Panda II

Leaving the FEZ comfort zone – say hello to the breadboard

I’ve been very busy over the last weeks, but now I’ve taken some time to get deeper into the “core electronics part”, which simply means that I got a breadboard and some electronic components like resistors, transistors, LEDs and a lot of wires.

The first step was to get a normal LED on the breadboard blinking by connecting it directly to the Digital IO ports on the FEZ Panda board. Sounds easy but I did not want to break anything so after carefully reading some postings about the topic I connected die Digital IO port to a 220 Ohm resistor which was connected to the LED and then back to Ground. Using the OutputPort class on the given IO port the LED was blinking. That easy :)

As it was not as complicated as I thought it would be, I remembered the 2×24 LCD panel that I got from a friend. I wasn’t sure how it exactly works, but as I found out it has a HD44780 controller on-board that accepts 4-bit commands using additional wires for signals and power. And there is even a very useful C# class at the GHI Electronics website, nearly ready to use.

And guess what? After connecting the wires and including the pre-defined class I got the LCD working! Awesome!

I actually had to de-wire everything to put it back in the boxes for storage, but it’s not as hard as I thought to put everything together, so manybe I’ll use the LCD in some of the next projects.

And the next part of equipment is waiting: I just soldered the needed connectors to a 4×7 segment LED element, so stay tuned ;)

Netduino Scripted Lights

Playing around with a FEZ Panda II is a lot of fun, especially when it comes to LED lights (and when it’s getting dark outside). Sure, you can make them simply blink, or maybe progam a more complex light-switching pattern, but you always end up with a lot of code to address the LEDs and wait some time between changing their state.

To make it easier to work with an LED, I’ve written a small wrapper class some time ago as described in this posting, but I really wanted to come around having to write a lot of (non-reusable) code just to make some LEDs blink.

My current solution: a very simple, char-based scripting module to control the LEDs. This is how it works:

  • You define some simple script like "R2 r2" or "GH4 YZ4 a2"
  • Based on the ILights interface, you create an instance of LEDLights
  • An outer loop defines how often the sequence should be executed
  • The inner loop iterates over the sequence and passes each char to the mini engine
  • The lights start blinking, or whatever you told them to do

Actually, some of these steps could be encapsulated and the pin configuration for the LEDs is currently hard-coded, but for the beginning I wanted to keep the things as easy as possible.

See it in action

How does the script work?

In short: an uppercase letter switches the LED on, a lowercase letter switches it off, and a numerical letter pauses between two actions. I recently got some additional LEDs so I added support for 6 LEDs (please look up the pin configuration in the source code).

  • r / R : red LED no. 1
  • s / S : red LED no. 2
  • y / Y : yellow LED no. 1
  • z / Z : yellow LED no. 2
  • g / G : green LED no. 1
  • h / H : green LED no. 2
  • a / A : all LEDs at once
  • 1, 2, 3, …, 9 : pause for 500ms, 1000ms, 1500ms, …, 4500ms

All other characters are currently ignored, so you can add spaces to separate the parts of the script which makes it easier to read the script sequence.

Some examples

R2 r2 – the red LEDs is switched on, then waits for 1000ms, then ┬áthe LED is switched off and the script waits again for 1000ms

R1Y1G4 r1y1g4 – the red, yellow and green LED is switched with short delay, then switched off again

zY2 yZ2 – the two yellow LEDs blink alternately

Tipps, tricks and ideas

When defining a sequence make sure that you add pauses, because otherwise the LEDs fill flicker based on the Netduino’s maximum speed.
It’s easy to forget the pause at the end of the script, which makes the sequence look strange when it gets repeated.
Of course, you can switch off an LED at the beginning of the script, even if it was not switched off before. This is very useful if the sequence has a complex overall pattern and an LED must stay switched on at the end of the script.

Some ideas to extend this project:

  • Store more than one sequence in the program and add an IR-receiver or simply a button to switch the sequences
  • Read the sequences from an SD card
  • Connect the Netduino to the network and add either a webserver to the program to enter the sequence or fetch it from a website (or even from Twitter)

Source Code

For the LED class please look at this posting.

public interface ILights
{
    void LightCommand(char c);
}

public class LEDLights : ILights
{
    private int baseDelay = 500;

    private LED led_R = new LED(GHIElectronics.NETMF.FEZ.FEZ_Pin.Digital.Di1);
    private LED led_Y = new LED(GHIElectronics.NETMF.FEZ.FEZ_Pin.Digital.Di0);
    private LED led_G = new LED(GHIElectronics.NETMF.FEZ.FEZ_Pin.Digital.Di8);
    private LED led_S = new LED(GHIElectronics.NETMF.FEZ.FEZ_Pin.Digital.Di5);
    private LED led_Z = new LED(GHIElectronics.NETMF.FEZ.FEZ_Pin.Digital.Di3);
    private LED led_H = new LED(GHIElectronics.NETMF.FEZ.FEZ_Pin.Digital.Di2);

    public void LightCommand(char c)
    {
        switch (c)
        {
            case 'r': led_R.Off(); break;
            case 'R': led_R.On(); break;
            case 'y': led_Y.Off(); break;
            case 'Y': led_Y.On(); break;
            case 'g': led_G.Off(); break;
            case 'G': led_G.On(); break;
            case 's': led_S.Off(); break;
            case 'S': led_S.On(); break;
            case 'z': led_Z.Off(); break;
            case 'Z': led_Z.On(); break;
            case 'h': led_H.Off(); break;
            case 'H': led_H.On(); break;
            case 'a': led_R.Off(); led_Y.Off(); led_G.Off(); led_S.Off(); led_Z.Off(); led_H.Off(); break;
            case 'A': led_R.On(); led_Y.On(); led_G.On(); led_S.On(); led_Z.On(); led_H.On(); break;
            case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': Sleep(c); break;
        }
    }

    protected void Sleep(char c)
    {
        int num = c - '1' + 1;
        int delay = num * baseDelay;
        Thread.Sleep(delay);
    }
}

public class Program
{
    public static void Main()
    {
        string sequence = "R2 r2;
        // process sequence
        ILights lights = new LEDLights();
        // switch off all lights at the beginning
        lights.LightCommand('a');
        // outer loop
        bool looping = true;
        while (looping)
        {
            for (int i = 0; i < sequence.Length; i++)
            {
                char c = sequence[i];
                lights.LightCommand(c);
            }
        }
    }
}

Networking with the FEZ Panda II

First of all: using the ethernet connection with the FEZ Panda II works well if you follow the steps from GHIElectronic’s eBook “FEZ Internet of Things”. You just set up MAC, IP, netmask, gateway and DNS server settings and you are ready to go.

But, there is actually a drawback: although the FEZ Panda II uses the .NET Microframework 4.x (NETMF), it does not fully support the System.Net namespace due to resource limitations of the device!

This means that all code using System.Net from the NETMF will not work, giving you a System.NotSupportedException. One disadvantage of this is, that most 3rd party NETMF projects using networking will not work as well.

The workaround to this problem is to use the network classes provided by GHIElectronics. In detail, it helps to add the following references to your project:

  • GHIElectronics.NETMF.Net
  • GHIElectronics.NETMF.W5100
  • GHIElectronics.NETMF.W5100.Http

Those references provide all the classes used to successfully establish network connections via TCP or UDP. As said above, the examples in the eBook are very useful, so I’ll not go into detail here ;)

Now that I basically got the network connection working I’m going to think about some example usages and over the course of the next weeks I’ll share my observations (and maybe some code too) here.