Monday, November 12, 2012

Arduino Prototyping, a beginner's thoughts

After eliminating the Netduino, I've chosen the Arduino platform for my prototyping. Here is the form factor for the Arduino Uno board. As you can see, for the most part the connectors expose the micro controller's i/o pins.
Arduino prototyping can be accomplished at the component level, and/or at a subsystem level. By component I mean a simple potentiometer or LED, and by subsystem I mean an entire assembly that does wireless networking for example. These higher level sub-assemblies are most often referred to as Arduino shields. These plug directly into and on top of the Arduino board, and then expose the pins for another shield or component. For example, here is the WiFi Shield:
Note that some shields are not complex subsystems but rather bus or pin extensions. I'm not going to discuss higher level shields at this point because I don't think I need them right now.

Prototyping can be accomplished by either a bread board of jumpered components, or with some inexpensive plugin modules similar in concept to Gadgeteer or GoBus, or probably a combination of both.

I originally started down the path of breadboards and components but discovered a module based component system from SeeedStudio called Grove that will help me prototype. The plugin components are called twigs, and they plug into a SeeedStudio Grove base board shown here:
This board plugs directly into the Arduino form factor and does little more than expose the analog (left side ports) and the digital i/o (center ports). Then by using a 4 wire connector, an inexpensive (compared to Gadgeteer or GoBus) component can be plugged into the board such as this Grove touch sensor and LED connected to some digital ports:

What could be simpler? As an added bonus, the built in micro controller I2C bus and SPI bus are exposed as a connector, but more on that later.

So my first order was a SeeedStudio version of the Arduino Duemilanove called Seeeduino V3.0 (Atmega 328P). As of this date it is in transit.
In addition to being one of the most inexpensive boards in its class, I also chose it because it is designed to run in either a 5 volt or 3.3 volt mode via a voltage select switch. The Atmega 328P chip is rated from 1.8v to 5.5 volts. This may be particularly useful if I can run my project on 4 AA rechargeable batteries for a reliable total of about 4.6 volts. Running at 5v requires a minimum of 7 volts in, which means 6 AA's at 1.2 volts for a solid 7.2 volts. In one forum I was told that most batteries only output about 1.2 to 1.3 volts throughout their life.

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