Category: IT

Tutorials, guides & stuff I stumbled upon.

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Wire and control ledstrips with the esp8266

I am trying to correctly wire an rgb adressable ledstrip. In a successive blog post, I will make it smart as my goal is to control the lights via Home Assistant, depending on triggers.

Hardware required is the cheap WS2811. This ledstrip works on 12V and you can control every 3 leds (as one). I will wire it with both a Raspberry Pi Zero and an Esp8266. If you’re interested, read on!

Continue reading “Wire and control ledstrips with the esp8266”
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Create a connected temperature sensor with a Raspberry PI

Since the Raspberry PI was introduced in 2012, it’s so much easier to build the Internet of Things! Connecting sensors and exposing the values they read, so much fun!

Time to get our hands dirty! In the coming months, I will stuff my house with sensors to gather data. Motion, temperature, barometric pressure and any other sensors I may come across?

Continue reading “Create a connected temperature sensor with a Raspberry PI”

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Raspbian cheat sheet

My own cheat sheet for commands I often use. It’s a work in progress.

See CPU Temperature
/opt/vc/bin/vcgencmd measure_temp
List hard disks
sudo blkid
Reboot
sudo reboot -n
Shutdown
sudo shutdown -h now
Upgrade your installed packages
sudo apt-get update
sudo apt-get upgrade
See available disk space
df -h
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The singleton

While I agree that a Singleton shouldn’t be used to often, I do want to share my favourite way to implement the singleton pattern for reference.

public class Example
{
    private static Example instance;

    private Example()
    {
        // this class cannot get instantiated
    }

    public static Example getInstance()
    {
        if (instance == null)
        {
            instance = new Example();
        }

        return instance;
    }
}
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Compare objects in java

If you want to compare if plain old java objects have the same properties, it is easiest to override the equals method.  This way, if you initialise objects on different places, you can be certain when comparing that they are the same.

We will show you how to do it with this simple class:

public class Insect
{
    private int legs;
    private int eyes;
    private int colour;
    private String sortName;
}

Override equals

@Override
public boolean equals(Object o)
{
    if (this == o)
    {
        return true;
    }

    if (o == null || this.getClass() != o.getClass())
    {
        return false;
    }

    final Insect that = (Insect) o;

    if (this.legs != that.legs)
    {
        return false;
    }

    if (this.eyes != that.eyes)
    {
        return false;
    }

    if (this.colour != that.colour)
    {
        return false;
    }

    if (this.sortName != null ? (this.sortName != that.sortName) : (that.sortName != null))
    {
        return false;
    }

    return true;
}

Override hashCode()

@Override
public int hashCode()
{
    int hash = super.hashCode();
    hash = 14 * hash + this.legs;
    hash = 14 * hash + this.eyes;
    hash = 14 * hash + this.colour;
    hash = 14 * hash + (this.sortName != null ? this.sortName.hashCode() : 0);
    return hash;
}
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How to use the Microsoft Azure Storage SDK

After visiting Microsoft Cloud Camp in Brussels last week I wanted to dive into android developing by using Microsoft Azure.

I wanted to store images on a storage account, and since I didn’t use Gradle or Maven, I had some issues getting it to work. In the end, this is quick guide how I did it.

On github you can find the Microsoft Azure Storage SDK for Android. I checked out the project information on the maven-repository. I had to download the com.fasterxml.jackson.core since that was a dependency I wasn’t yet using.

On the repository URL I found the azure-storage-android-0.3.1.aar file. You need to download it and open it with a ZIP client. The classes.jar file is the library you need to put in your libs folder. I renamed it to azure-storage-android-0.3.1.jar. I also put the azure-storage-android-0.3.1-sources.jar in the libs folder.

For uploading an image to a storage account, this is a code example. Remember to execute it in an Async Task!

The image object is returned after pushing it to an Azure Mobile Service and contains the sasQueryString to authorize the upload.

String FileRef = FILEPATH + FILENAME of the file.
String BaseUrl = "http://storageaccountX.blob.core.windows.net";
CloudBlobClient blobClient = new CloudBlobClient(new URI(BaseUrl);
String blobName = image.ResourceName;
URI uri = new URI(blobClient.getEndpoint().toString() + "/" + "containername" + "/" + blobName + "?" + image.SasQueryString);
CloudBlockBlob sasBlob = new CloudBlockBlob(uri, blobClient);
File fileReference = new File(FileRef);
sasBlob.upload(new FileInputStream(fileReference), fileReference.length());