Everything for Electronics
Posted in: Developing Perspectives (October 2012)

Full Power to the Shields

By Bryan Bergeron

Today, thanks largely to the microcontroller market, many daughterboards — better known as shields — are plug-and-play devices. They provide an efficient, costeffective means of transforming a generic microcontroller into a servo controller, RF transceiver, sensor array, or what have you.

The Arduino exemplifies what a standard shield can do for experimenters. Not only are there hundreds of shields available for the Arduino, but the pin configuration of the Arduino shields (Uno and Mega) has been duplicated for other microcontrollers.

For example, Parallax offers the StampDuino, a BASIC Stamp development board designed to be compatible with most Arduino shields. Parallax also offers a sort of reverse shield — the Board of Education for the Arduino. Whereas most shields are the same size as the Arduino and sit above the microcontroller, the Board of Education is significantly larger than the Arduino and accepts the Arduino from above. Digilent — my go-to company for high performance Arduino compatible microcontrollers — also has one of the best assortments of shields on the market. I’ve used their Basic I/O shield — a real life saver when you have more important things to do than figure out how to connect motors, servos, and I2C devices to your microcontroller.

Digilent also offers 60+ minishields — Pmods™ — based on sixand 12-pin connectors, supporting everything from Wi-Fi and organic LED displays to a Bluetooth. I’ve used the audio input mini-shield which is a real time saver.

Together with the added processing power of the chipKIT microcontroller, the mini-shield and processor hold up to just about anything my PC with sound card can handle. The Pmods — while not a standard shield configuration — are designed to work with their Arduino compatible shields.

SparkFun — the source of countless red shipping boxes in my workroom — offers some of the coolest shields available, especially if you’re into kits. I’ve built several of their MIDI and joystick shields for various projects. SparkFun also offers the Netduino which — at first glance — could pass for an Arduino Uno but uses the .NET Micro Framework. The hardware is compatible with most Arduino shields.

There are exceptions, of course. Because of size and weight limitations, there are a number of Arduino compatible boards on the market that can’t accept shields. For example, I’m working on an ArduPilot Mega 2.0 from 3DRobotics which is essentially a Mega-compatible shield chocked full of SMT sensors for making flying, diving, and walking robots.

The open source board is expensive ($199), but crams an amazing amount of sensor technology into a very small, lightweight package. A regular sized Mega would be too heavy and too large for a small flying vehicle. I’ll be reviewing this shield with a DIY quadcopter in an upcoming issue of SERVO.

I’m all for shields. Look what the Arduino has done for the add-on industry and for experimenters. There is a downside, of course. There’s a lot of unused space on the latest generation of Arduino compatible shields.

While ASICS and SMT components continually reduce component count and the space requirement, shield size has remained constant. So, even though it’s possible to shrink the form factor with no loss in functionality, the standard size and pinout dictate otherwise.

At some point, the standard Arduino will evolve to a new size, and you’ll have to buy new shields or some sort of adapter — perhaps akin to the Pmod mini-shields. But that’s the price for progress. For now, full power to the shields. NV