The .NET Micro Framework is a free and open source version of the .NET Framework, created by Microsoft, and supported by both Microsoft and the community. The current production version is 4.1 and supports C# development. The latest beta, version 4.2, adds support for Visual Basic as well as several Microsoft-contributed and community-contributed features.

The .NET Micro Framework, Apache 2.0 licensed, is a great open source success story at Microsoft. It's also a great way to either learn programming, or to leverage your current .NET skills to go places you may not have previously considered.

In a nutshell, .NET MF is a CLR and set of libraries that runs on tiny low-cost microcontrollers which have limited resources. Many of these have memory measured in KB, as opposed to GB, and processing speeds well under 100Mhz. Over 1.5 million devices, commercial and hobby, are currently running the .NET Micro Framework. This includes things like vending machines, and the various components we'll talk about in this post.

You code for the .NET MF using either a free or retail version of Visual Studio, and an SDK and drivers provided by the microcontroller or board manufacturer. As each unique microcontroller requires the .NET MF to be ported to it by those vendors, they are the source for all the software you'll need. Since it's open source, you could also port it to any processor of your choice if you have the skill and time.

There are many ways to get started with the .NET MF, and there are hundreds of boards available, ranging from tiny $30 chip-sized designs all the way to full boards that resemble hand-held game devices. In this post, I'll focus just on the Arduino-form-factor devices, as those are the most popular.

Don't Feel Guilty

At MADExpo this week, we had a number of Micro Framework sessions, and I had my robots and other stuff in the expo hall (Chris Walker from Secret Labs/Netduino was also there, and we had freebies from both Chris and GHI/FEZ). We also had sessions on using the Kinect SDK. One thing that several attendees said was that they feel guilty attending a fun session or two like that when their employer let them go to this two day event.

I say: Don't Feel Guilty.

When you code for the .NET Micro Framework, you're continuing to hone your .NET development skills. Perhaps more importantly, you're leaning to code tight code that has to run on low power devices with very little memory. As developers with gigs of RAM available, we can get a bit lazy and write very inefficient code. Devices like this help bring those skills back to us by forcing these constraints. And, as I mentioned, it's all .NET and C#/VB.

Finally, stuff like this keeps you excited about development, and motivated. Sometimes you need to mix it up a little to keep from burning out.

Suggested Boards and Kits

Arduino is an open source device and software (now a set of devices) which have an ingenious physical layout which allows stacking "shields" (add on boards) on top of each other to build a circuit. A huge ecosystem has built up around Arduino, and a large number of shields have been produced.

Several .NET Micro Framework board manufacturers have created .NET MF-based boards which are physically compatible with the Arduino shields (in most cases; there are some voltage differences which trip you up once in a while as the Arduino uses 5v logic and the .NET MF boards and most modern microcontrollers use 3.3v logic). This allows immediate access to an enormous number of components and add-on boards right from the start.

There are a number of players in the .NET Micro Framework space, but the two most important ones in the Arduino-compatible market are GHI and Netduino.

Secret Labs Netduino, Netduino Plus

The Netduino and Netduino Plus are fully open source (hardware and software) boards created by Chris Walker at Secret Labs. The Netduino is the board that personally got me started with the .NET Micro Framework, which then led me do doing things like parsing MIDI messages with the .NET Micro Framework. The boards themselves are very inexpensive and come in three versions. The Netduino+ is the flagship and includes onboard Ethernet and SD card support. You'll typically find this for $60 retail. The Netduino - which was the first board released - is just like the plus, but lacks ethernet and SD, and retails for around $35. The Netduino Mini is a super tiny version, sized to that of a Basic Stamp, and suitable for very small projects or projects with tight space requirements. All the Netduino boards use an Atmel microcontroller.

Netduino has a very active community and a growing number of examples available on the web.

GHI Electronics FEZ Domino, Panda, Panda II, and Mini

GHI Electronics manufactures a range of .NET MF boards including several Arduino-compatible ones. The most commonly seen ones are the Panda and Panda II. The Panda is a nice $35 board, similar in capabilities to the Netduino. The Panda II for only $40 adds in SD card support, analog audio playback, and a 40 pin header which provides access to a lot of extra IOs. While neither of these boards include on-board ethernet, they do offer a shield which adds that and their e-block ports for $35. If selecting between the Panda and Panda II, I'd personally pick the Panda II every time unless the extra space taken up by the 40 pin header would get in the way. GHI also has the more expensive FEZ Domino and a slim and trim FEZ Mini for $40.

You can get started using either Netduino or FEZ boards directly, and do things like blink an onboard LED or similar. However, many will prefer to get started with an all-in-one kit of one sort or another.

General and Sensor-Oriented Kits

The general electronics and sensor kits are a great way to get started with the Micro Framework. With these kits, you can do things like light up LEDs, take readings from sensors, send information across the network or internet (like tweeting every time you push a button), display information on LCD panels and more.

MakerSHED Ultimate Microcontroller Pack

For $120, MakerSHED has the "Ultimate Microcontroller Pack". This kit lets you pick the controller you want (Arduino, Netduino or Netduino Plus - which gives you ethernet support), and includes jumper wires, discrete components, switches, LCD panel, several motors, tilt sensors, LEDs and more. This kit will appeal more to the people who want to tinker with the electronics side as much as the code side. I essentially work with something like this, but I've built the parts up over time from various sources.

FEZ Ultimate Kit

If you want to have sensors and other bits that are plug and play, albeit with special (but easily obtainable) connectors, then I recommend the FEZ Ultimate Kit. For grins, I picked one of these up (also, in the interest of full disclosure, FEZ gave me a coupon that covered a large portion of the cost). Total retail cost of the kit is $150. I'll have a full review and walkthrough in an upcoming post. This is a great kit for people who don't necessarily want to whip out a soldering iron or a prototyping board and simply want to get started coding.

Robot Kits

One of the most exciting ways to get started with the .NET Micro Framework is to build a robot. It's very exciting to write code which makes your robot roll around in your hall, room, or office. Once you add in interesting things like distance sensors, suddenly you're able to make the robot perform basic collision avoidance, maybe turning around and trying again. Or maybe you'd rather add on a downward-facing color sensor and create a line-following robot. The possibilities are endless.

There are lots of different ways to get started with .NET MF-based robots. Let's start with the easiest: the all-in-one kit.

FEZ Mini Robot Kit

GHI sells an all-in-one robot kit which makes use of their FEZ Mini board. This has everything you need to get started without having to source drive systems and whatnot from different vendors. It would make an excellent first robot, and should be really easy to assemble. Note that, like most mouse-type robots, it's pretty small, probably a bit smaller than a CD, so make sure you realize the scale before get it shipped to you. One thing that's nice about this kit is that it's .NET all the way down. Most beginning robot kits use other microcontrollers (Basic Stamp or even Arduino).

Building a Robot From Chassis Kits

Most robots are built from different components from various vendors. While many advanced builders will create their own chassis by bolting or welding metal, many will start with a chassis kit and build up from there.

One of my favorite robot sites, Robotshop.com, has a number of different robot kits from the tiny $20 kits to the computer-on-wheels $15k beasts. When piecing together your own kit, you'll need to get:

• A chassis of some sort to hold everything together
• A set of drive wheels (typically 2 or 4)
• For two wheeled robots, a set of ball castors or similar for the front and back (see above) unless you're going to get a gyroscope and create a balancing robot as your first build :)
• For three wheeled robots, a third wheel or castor
• A motor for each drive wheel. Make sure the shaft is the right size for the wheels
• A motor controller (or set of controllers) that can control as many motors as you have
• Rechargeable batteries, or a holder for regular batteries, with the correct voltage to drive the microcontroller and motors

Luckily, the base robot kits typically include the wheels, castors, chassis and motors, so you know those are already properly mated. Here are (by picture) some of the more interesting kits that include all the right parts. All you then need to get are the motor controllers (covered below) and your Netduino or FEZ board. If the chassis kit says it is made for Arduino, that simply means that it'll work with boards of that form factor, including Netduino and FEZ Panda.

Chassis kits under $35

These kits are great starter kits if you don't want to go the route of an all-in-one kit like the FEZ mentioned above. I tried to pick kits here that look like they'd support the Netduino and FEZ boards, but you may still need to be creative with stacking the shields or controllers up a bit high, as these are usually pretty small. I left out the ones that were obviously too small. When in doubt, check for Arduino compatibility, as that typically means they are sized correctly and have compatible mounting holes (note that I also left out robots that have an Arduino-compatible board built directly into the body, as that will be of no use to you in learning the .NET Micro Framework).

Chassis kits $36 to $65

Kits in this range tend to be a good compromise. They're not typically 4wd (which is fine), but they're large enough for you to mount components and boards without having to create the Tower of Pisa robot shield stack.

Chassis kits $66 to $100

Kits in this range tend to be a bit larger, with more room for additional sensors. Some are also 4wd, although keep in mind that the additional two motors typically means you'll need additional motor controllers, or higher capacity controllers.

The 4wd DF Robot chassis kit above is one of the ones I own, and is the one seen in this video on YouTube. In Fairness, the wheels are truly awful (don't like to sit straight on the motors, treads tend to twist a bit too) if you're expecting something with any precision. In fact, I'm not sure I'd get any of the three kits shown here that use those yellow wheels. Of course, for the price, you can't really get better; you're well into the next price range when the wheels, hubs, and motors are kick up a notch or two.

Chassis kits well over $100, but still somewhat in the realm of sanity, kind-of… Ok, under $500

Now you start getting into kits with some quality and ruggedness. Of course, you're in big dollar-wise and these also tend to be more complex, so I recommend starting small before jumping here. Also, I recommend shopping around on price for these, as there can be significant difference between the various retail sites, especially when you consider sales. These are where you'll find the kits with good wheels and motors, though. In truth, I like the very inexpensive mouse-sized kits, and the kits in this section. The mid-range tends to have the worst of both.

Motor Controllers

When you purchase a chassis kit, you need to get motor controllers as well. These provide the interface between your microcontroller running .NET MF, and the motors themselves. You don't want to hook motors directly to the microcontroller as it typically can't handle the voltage or amps required to drive a regular motor. In addition, you want a level of isolation between your motor and microcontroller so stalling your motor doesn't blow up your microcontroller. There are also issues with EMF noise etc. Just trust me here: get a motor controller. :)

Almost all motors used in the chassis kits are brushed DC motors. Most of them are also low-power (although in the > $100 kit range, you'll need to verify that yourself, as some of those are battlebot-ready medium to high amp motors). When selecting a motor controller, you need to match up:

• Number of motors with what you have (you can use more than one controller, if you have enough logic signal ports available)
• Controller logic interface mode (must be something you can support from your microcontroller. Examples include I2C, PWM, and Serial)
• Motor voltage and amp requirements
• Controller logic voltage levels

I mention the last one as some are expecting 12v control signals, making use from a .NET MF (or Arduino board) much more complicated. In addition, some require 5v signals as that is what the Arduino puts out. All the .NET MF boards use 3.3v logic which often, but not always, works with the 5v boards.

The boards I found to be compatible with most of the smaller robots are the DFRobot 2A Dual Motor Controllers. I have two of them powering my robot in the video above. I'll have more info in my article on building that robot. The 2A motor shield from DFRobot may also work, but I'm unsure if the 5v/3.3v difference will mess it up (likely). I haven't bought one to try.

If you have a smaller robot, I recommend the DC Motor Shield from GHI. This is compatible with the Netduino and FEZ boards, supports the right signal levels, and has enough power for small robot motors. For the smaller robots, this also has the huge advantage of being a shield, which allows you to stack it above your microcontroller thus taking up far less room than the separate DFRobot controllers.

My recommendation for getting started with .NET MF Robotics

If I was looking for the easiest way to build my first robot, I'd probably go with the GHI FEZ Mini Robot kit. With that kit, you don't need to worry about pairing up the various components, and you get a robot that you can build and start coding for in an afternoon.

Get Started

So pick out the board or kit you find interesting, and go build something today. This can be fun to do by yourself, or as a family activity with your spouse or kids. Once you start designing and coding for these little microcontrollers, you'll find you suddenly have tons of ideas on where you can take them (home automation and security, monitoring, small electronics projects, synthesizers, robots, video games, fun gadgets, automated fish tanks, self-propelled lawn equipment, computer room water and temperature alerts and more).