Blinking an LED with Raspberry Pi 2 and C# Mono

This should work with either a Raspberry Pi B+ or a Raspberry Pi 2.  The B+ and 2 identical, save for the faster processor and increased RAM on the Pi 2.  I’m assuming you’ve gone through the setup and can boot to a command prompt or the GUI, and are using the Raspbian distro.  For most of this post, you’ll need the command line to install the different libraries, although Monodevelop is a graphical IDE.  We have to use an older version of Monodevelop (3.x), but it’s all good enough.

I have a CanaKit Raspberry Pi 2 Ultimate Starter Kit, which includes a nice breadboard and pinout connector, but greatly lacks for manuals.  This made it really tough for me to get started.  As I found out later, the pinouts are the same as other connectors, so their examples will work also.  The CanaKit does have the nice extra sets of 3.3V and 5V pinouts, which should come in handy for some uses.  Overall it’s a great kit, and I’m glad I bought it, and I hope this post helps others in the same situation.

The flashing LED is the Hello, world of GPIO (General Purpose Input Output), but it’s still pretty exciting the first time the light flashes.  Here’s how I got the LED to flash with C# and Mono.

Step 1: Install Mono and Monodevelop

At the command line, issue the following commands

sudo apt-get update

sudo apt-get upgrade

sudo apt-get install mono-complete

sudo apt-get install monodevelop

Update is used to update all of the package sources for Raspbian, and upgrade brings all your installed packages to their latest versions.  The  first install command installs just the mono runtime, and the second one installs the actual IDE.  You can develop Mono without Monodevelop, but the IDE makes life easier.  Collectively these commands install a lot of stuff, so this all could take several minutes to run. Apt-get is an application/package manager, and is part of the inspiration for nuget and chocolatey.

Once this is done, open Monodevelop and make sure it starts.

Step 2: add nuget to Monodevelop

Nuget, if you don’t know already, is a package manager for .NET.  It makes adding and maintaining dependencies much easier.  The dependencies we need are hosted on nuget.org.  The API which Monodevelop will use to search and retrieve packages is HTTPS, so we need to update the certificate store.

mozroots –import “sync

Next, install the nuget add-in by following the instructions at https://github.com/mrward/monodevelop-nuget-addin for Monodevelop 3.0.  This will now allow you to add nuget references for solutions.

Step 3: Write the program

Start by opening Monodevelop and creating a new project.  If you’re familiar with Visual Studio, this will seem very familiar.  Name your project whatever you want.

In order to access the GPIO pins of the Raspberry Pi in C#, we’ll use the Raspberry.IO.GeneralPurpose library.  We’ll reference this package from nuget by right-clicking the References node, and choosing Manage Nuget Packages (see below; if you don’t see this option, something went wrong in Step 2, look back and make sure you followed the installation completely).

image

In the Manage Packages window, search for Raspberry, select Raspberry.IO.GeneralPurpose and click Add.

image

The code sample we’ll use is based on the example at https://github.com/raspberry-sharp/raspberry-sharp-io/wiki/Raspberry.IO.GeneralPurpose.  Since there are two ways to number the GPIO pins (physical numbering, and CPU address), and since only some pins are actual i/o, it can be a little confusing when coding and wiring.  Sticking to the physical pins numbering is probably easiest, and your connector board should  have shipped with a decoder card which shows the pins.  If not, most boards have the same numbering, so anyone’s should do.  For more details, see Appendex 1 at http://www.raspberrypi.org/documentation/usage/gpio/.  Raspberry.IO.GeneralPurpose limits us to addressing only the i/o pins, so that can be a useful guide, too.

Below is the complete main.cs for our project.  If you’re copying and pasting, don’t forget to change the namespace to match your solution.

using System;
using Raspberry.IO.GeneralPurpose;
using Raspberry.IO.GeneralPurpose.Behaviors;

namespace blinky
{
	class MainClass
	{
		public static void Main (string[] args)
		{

		// Here we create a variable to address a specific pin for output
		// There are two different ways of numbering pins--the physical numbering, and the CPU number
		// "P1Pinxx" refers to the physical numbering, and ranges from P1Pin01-P1Pin40
		var led1 = ConnectorPin.P1Pin07.Output();

		// Here we create a connection to the pin we instantiated above
		var connection = new GpioConnection(led1);

		for (var i = 0; i<100; i++) {
			// Toggle() switches the high/low (on/off) status of the pin
			connection.Toggle(led1);
			System.Threading.Thread.Sleep(250);
		}

		connection.Close();

	}
	}
}

Step 4: Wire the breadboard

Do this part with your I turned off and power disconnected!  Also, touch some metal and try to get rid of any static electricity you’ve built up.  Here’s what you’ll need:

  • LED
  • 220-ish Ohm resistor
  • Two jumper wires, preferably different colors

The resistor is needed as a precaution, so we don’t accidentally burn out a pin.  A Raspberry Pi is capable of producing output currents greater than its inputs can handle.  Normally, a bunch of things like LEDs and other peripherals wired together will use enough current that it won’t matter, but for this simple task it’s better to be safe than sorry.  My kit has 220 Ohm resistors, yours may have different ones, just as long as you have something in the same range.  For a great explanation and refresher on resistors, watch https://www.youtube.com/watch?v=UApKArED3JU.   The while video is 3:23 but explains what I’ve just said even better and shows you how to calculate and read a resistor.  My Canakit also included a nice decoder card for reading resistor codes.  If you don’t have a card, check out http://en.wikipedia.org/wiki/Electronic_color_code.

The jumper wires are so you can move the stuff to a different part of the breadboard.  You can probably bend and twist the LED and resistor so you can directly wire the components, but using jumpers allows you to spread out a little more on another part of the board.  If you want a little background about a breadboards, here’s a 6 minute video: https://www.youtube.com/watch?v=q_Q5s9AhCR0.

Here’s a photo of my board, and the wiring steps.  Do this while the board is not connected to the Pi.

  1. The red wire runs from Pin 7 (GPIO 4) to an empty row on the breadboard
  2. The resistor connects the red row to another empty row.  Make sure to orient the resistor correctly.
  3. The long end of the LED is in the same row as the output end of the resistor.  The short end of the LED is in yet another empty row.
  4. The white wire connects the end of the LED to Pin 6 (GPIO GND), but you can use any GND.

20150316_201106643_iOS

Step 5: Run the program!

Connect the breadboard to the Pi, boot up to a command prompt, and change directories until you’re in the same folder as your .EXE (remember Linux paths are case sensitive).  Access to the GPIO pins requires superuser level, so you’ll need to run the binaries from the command line, using sudo:

sudo ./blinky.exe

You should be good to go!

 

References

A book I found to be very helpful is Make: Getting Started with Raspberry Pi.  Highly recommended if you don’t have a book already.

I owe a huge debt of gratitude to the authors of the blog posts listed below, in addition to any links above.  I am very lucky people more knowledgeable than I am are paving the way for my curiosity.

http://www.maketecheasier.com/write-c-sharp-programs-raspberry-pi/

http://logicalgenetics.com/raspberry-pi-and-mono-hello-world/

http://blogs.msdn.com/b/brunoterkaly/archive/2014/06/11/mono-how-to-install-on-a-raspberry-pi.aspx

https://github.com/mrward/monodevelop-nuget-addin

https://monomvc.wordpress.com/2012/03/06/nuget-on-mono/

NoSQL Datastores of Interest to the .NET Developer

The world of NoSQL is vast, and this is in no way a comprehensive list of NoSQL datastores (just see http://en.wikipedia.org/wiki/NoSQL for how vast the NoSQL universe is).  After spending a lot of time researching, this is just a list of ones that have officially supported C# libraries, or are written in .NET.  I thought it would be a little easier to start learning the ins-and-outs of the different types of datastores without having to learn new languages also.  Pretty much every NoSQL datastore has some sort of REST-ful API, which you can work with regardless of your language choice.  Don’t let the presence or absence of a system on this list make your decision for your application choices–this is more a list of systems I think would be fairly simple and interesting to experiment with.  I have not yet worked with all of these datastores, but as I do I’ll add posts to this blog.

Every category of NoSQL is designed to solve a particular problem, and each option in each category has its ups and downs.  There are many options, so you really need to know what you want to do.  Do you need an embedded solution, or a scalable cluster?  Are you trying to discover relations between populations, store profile data in a flexible schema, or cache the results of API requests?  What types of indexing are supported?  Can you live with eventual consistency?

I tried to note some easy and low cost ways to get started with each datastore.  If there isn’t direct DBaaS support, you can always deploy Azure or AWS VMs, and even the Google Cloud Platform has some hosting options.  Try not to install everything on your local machine, but have fun!

Category Datastore .NET Support Notes
Graph neo4j http://neo4j.com/developer/dotnet/ Neo4j is perhaps the best known graph database.  Although the clients are community supported, they are maintained by two amazing developers.  It’s easy to get started, especially since GrapheneDB offers a free Hobby account.  There is also a simplified Azure VM deployment.
Titan none This is on the list as œsomething to watch.  Datastax (Cassandra) recently acquired the company behind Titan, and Datastax has a good history of .NET support.
OrientDB https://github.com/orientechnologies/OrientDB-NET.binary There are also community supported clients.  OrientDB is a hybrid datastore, supporting both document and graph features.
VelocityGraph Written in C# An open source hybrid (graph/document) datastore, written in C# which can be embedded or distributed.  There is a paid model for the distributed version also.
Document MongoDB Official and community clients listed at http://docs.mongodb.org/ecosystem/drivers/csharp/ One of the best known and most used document datastores, MongoDB is backed by 10gen, and mongolab.com offers a free sandbox account to get started.  MongoDB and Mongolab are available via Azure Marketplace, so you can spend free Azure credits if you have them.
Azure DocumentDB It’s Microsoft, no worries.
https://msdn.microsoft.com/en-us/library/dn781482.aspx
This is still in Preview at the time of writing, but it looks very promising.  Being Azure, if you have Azure credits you can spend them on this.  It’s another DBaaS, so you won’t need to mess with VMs.
Amazon DynamoDB http://aws.amazon.com/sdk-for-net/ Another high performance DBaaS datastore, DynamoDB supports both document and key-value modes.  This is included in AWS’s free tier for a year.
OrientDB https://github.com/orientechnologies/OrientDB-NET.binary There are also community supported clients.  OrientDB is a hybrid datastore, supporting both document and graph features.
VelocityGraph Written in C# An open source hybrid (graph/document) datastore, written in C# which can be embedded or distributed.  There is a paid model for the distributed version also.
CouchDB https://couchdb.apache.org/ Another popular datastore, this is the open source project from Apache.  This is supported by Couchbase (see below)
Couchbase http://docs.couchbase.com/couchbase-sdk-net-1.2/ A next generation of CouchDB, in a way (see http://www.couchbase.com/couchbase-vs-couchdb).  Has both open source and commercial licenses.  Popular as an in-memory cache by some big name companies.  There is an Azure VM image in the Azure VM Depot.
RavenDB Written in .NET Open source and commercial licenses.  Has a embedded and scalable server options.  A RavenHQ hosted plan is available through the Azure Marketplace.
NinjaDB Pro Written in .NET Commercial, embeddable document datastore which is also compatible with Xamarin.  Supports either document or relational modes.  There is also a version for WinRT.
NDatabase Written in .NET An open-source in-memory object database.
Big Table Cassandra Official driver from Datastax,
https://github.com/datastax/csharp-driver
Datastax is the company supporting Planet Cassandra and largely supporting the Apache Cassandra project.  Datastax provides the commercial licensing for Cassandra.  Cassandra is very similar to HBase, but because of Datastax’s backing is the better choice, IMO.  Cassandra can be run on Azure (DataStax Guidance for Azure), and there is an older VM available from the Azure VM Depot.  As part of their wonderful “Succinctly” e-book series, Syncfusion also has Cassandra Succinctly.
Apache HBase community SDKs are just wrappers for the REST API.  Most of the .NET SDKs you’ll find are for HDInsight and aren’t guaranteed to work with Apache HBase. I really just put this here for comparison purposes.  HBase can be a real pain.  Seriously, look at Cassandra or HDInsight instead.
HDInsight It’s Microsoft, no worries HDInsight covers a lot of the Hadoop ecosystem, the HBase specific bits are introduced at http://azure.microsoft.com/en-us/documentation/articles/hdinsight-hbase-overview/.
Key-Value Couchbase http://docs.couchbase.com/couchbase-sdk-net-1.2/ A next generation of CouchDB, in a way (see http://www.couchbase.com/couchbase-vs-couchdb).  Has both open source and commercial licenses.  Popular as an in-memory cache by some big name companies.  There is an Azure VM image in the Azure VM Depot.
Redis There are a number of community supported clients, listed at http://redis.io/clients#c.  Two of the more popular ones are from ServiceStack and StackExchange. A very popular choice as a cache layer.  Durable persistence isn’t the strong suit, and multiple-node sharding is only in beta.  You can add Redis to Azure from the Azure Marketplace.
Azure Tables It’s Microsoft, no worries Perhaps one of the top choices, especially if the rest of your application is on Azure.  Crazy scalable and very performant.  Table storage was one of the original features of Azure, and is very well vetted by now.
Amazon DynamoDB http://aws.amazon.com/sdk-for-net/ Another high performance DBaaS datastore, DynamoDB supports both document and key-value modes.  This is included in AWS’s œfree tier for a year.
Riak https://github.com/basho-labs/riak-dotnet-client/wiki An open-source distributed datastore.  There is also a commercial offering.  An Azure VM image is available via the Azure VM Depot.

Hosting Without Limits: A Review of 1&1 Internet’s Unlimited Package

Back in the days before the ‘tubes, when all items were analog and knowledge printed, “unlimited” used to mean there were no limits. Cable companies and cell phone providers have tortured the definition to be one of fine print, term limits, caps and rate increases. When I was asked to review 1&1 Internet’s Unlimited Package (tagline: “Hosting without limits”), I entered into it with a high amount of trepidation; worried I might be reviewing “Crazy Eddie’s House of Electrons (and fine print)”. Happily, that was not the case, and I was pleasantly surprised at the ease of use, features, and price.

Earlier in my career, I developed a number of websites for small businesses and individuals. Along the way, I found myself wondering how “normal” (i.e., non-technical) people could manage. The truth was, between the complexities of hosting and the knowledge needed to build a site, they just didn’t, and that’s why they called me. Even pre-built applications meant matching requirements to the offerings of a particular host. As IT professionals, we take a lot of work upon ourselves because it’s just easier to do it ourselves than it is to explain how to do something.

Some hosting companies strive to improve the hosting experience, and over the past 27 years, 1&1 has become one of the most successful and popular hosting companies in the world by offering simple, inexpensive ($0.99/month for three months, then $8.99/month thereafter) and feature-rich hosting plans. In fact, 1&1 has over 13.5 million customer contracts and the group has more than 19 million domains registered. After working off and on for a month with my trial account, I can say this may be the hosting I could help set up for my parents or in-laws, and they could manage most things themselves.

According to the company, 1&1 has over 7,000 employees and 70,000 servers in seven data centers around the word. Beyond website hosting, 1&1 also offers domain registrations, email hosting and GeoTrust SSL certificates. This company is far more than you first imagine.

1&1’s hosting plans are all-inclusive (with unlimited space, unlimited bandwidth and unlimited sites—check that out, really unlimited!) and also include a free domain name registration. These plans can be either Windows or Linux, with MS SQL Server and MySQL as database options. Linux hosting supports PH, Perl, Python, Ruby and Zend, while Windows hosting supports PHP, .NET and Perl. These are just some of the features that appeal to the more technical user.

From the moment you sign up and first log in, you can tell right away that 1&1 is also reaching out to the less technical users. Each time you log in, a helpful tip about some aspect of your plan is displayed. 1&1 has built a custom control panel, which gives you full control over all of your services in a very simple way. If a company pays this much attention to how you interact with its services, it’s a good sign they’re paying attention to the other details of their business.

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All new accounts are given a temporary URL so that you can begin development right away. You can upload your own code via FTP or SSH (WebDeploy does not appear to be an option), choose an application from the 1&1 App Center, or you can build a custom website using the 1&1 Website Builder and 1&1 Mobile Website Builder tools.

If you want an easy way to get a site online, and don’t mind starting from one of over 50 highly customizable layouts, the website builder tools are a great option. These tools are aimed at the Wix and SquareSpace crowd and provide an easy way to build a multi-page static website without having to know HTML, CSS or JavaScript (although you can edit these if you want to). The process is very simple: choose a page layout, select a color scheme, font and background, then add content. Create as many pages as you need, ad tweak the HTML or CSS as needed. If you find you need help with the website builders, there is a Contact button right on the menu. Live chat and phone help is available 24/7. I found the Website Builder to be simple, intuitive and complete. Again, “here you go older generation and former clients, I’ll help get you started, but you can make this happen.”

If you need a more dynamic site, or a blog, CMS or shopping cart, the 1&1 App Center features over 140 of the most popular applications, including WordPress, Joomla, Drupal and phpBB. The 1&1 App Center is a great example of how much effort 1&1 has put into simplifying the hosting experience. Every application has a detailed information page (see below), and installation requires only a couple clicks and minimal information.

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Applications can be installed in “Safe Mode”, which is a default install of the application for which 1&1 handles all the updates and patches, or you can install an application in “Free Mode”, which gives you more flexibility, but you’re responsible for updates and patches. The Safe Mode installer is simpler than the Free Mode installer (shown below for Joomla), but if you plan on adding themes or plugins to your application, you’ll need to use Free mode. You can change a site from Safe Mode to Free Mode, but you cannot change from Free Mode to Safe Mode.

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Regardless of how you built your site, once it’s online, it’s replicated across multiple data centers. This geo-redundancy provides failover protection, but not load balancing. Also, since the replication is nearly instant, whatever you do to destroy your main site will affect the failover before you can dial support. Fortunately, 1&1 also has daily backups of your site and data. To aid performance and security, 1&1 offers a CDN with CloudFlare traffic monitoring and Railgun™ caching, plus storage and global distribution of large libraries.

Getting yourself online is just the start. To monitor your site’s traffic, 1&1 has their own site analytics package which reports on referring sites, search engine terms and more. Additionally, there are tools to create sitemaps for Google Analytics. To keep your customers engaged, 1&1 also offers email marketing tools. Considering the cost of most email marketing services, this makes the hosting fee even more of a bargain.

For a heck of a lot of sites, I think 1&1 would be a great solution, even for the more technical crowd. It’s obvious the services and control panel are very well thought out, the services offered are feature-rich and a great value. It was pretty hard to find something to criticize, mainly that this didn’t exist 15 years ago. More advanced sites may miss uptime monitoring tools or load balancing, but anything with those needs is probably looking at a different place in the market. Although simple enough for non-technical user, there are enough features to interest a more technical crowd, especially if you have multiple domains and are paying more than $8.99/month total.