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Al Williams

Dr. Dobb's Bloggers

Is it Embedded?

December 25, 2009

Over the holidays you talk to a lot of relatives and old friends that you don't see very often. That's always a good thing as you either see people you wish you saw more often, or you are reminded of why you don't see them more often. Either way, its a winner. At one holiday dinner one of my family members mentioned she had heard I was blogging and wanted to know what I was talking about, When I replied "embedded systems" I got mostly blank stares. Luckily, no one really cared and the conversation rapidly shifted to the latest gossip about someone who wasn't there.


But it did get me thinking. How would you define "embedded systems" to a "civilian" (that is, someone who isn't in the business)? Is "embedded" getting to be a meaningless label like minicomputer? One problem is that even we don't always agree on what makes an embedded system. I spent most of my career working on what I think of as highly embedded systems. A little bitty MPU buried in something like an automotive control computer, a mouse, or an amusement park ride (for some strange reason, I have a lot of designs in theme parks). But today, I work on things they tell me are embedded systems, but I think of them more as multi-blade Linux servers on wheels. In my past life, anything running Linux or with a conventional user interface wasn't much of an embedded system.

Yet clearly, many embedded systems today are basically PCs doing some dedicated task. More and more systems have human-machine interfaces now than ever. But there are still hoards of CPUs anonymously toiling in supporting roles that ordinary people never perceive. I think we need more categories. When I design a tiny sensor that has to run off a button cell battery for 3 months, I am doing a whole different design than if I am building a GPS navigation system, for example. Or an MP3 player. Or a network router. I could argue that all of those are embedded systems, but the reality is each has very different trade spaces.

I always think the user interface is one differentiator between systems. On the other hand, I also think we will soon reach a time where user interface becomes a separate issue for embedded systems but that's another blog for another day. Systems that interact with humans seem to have fundamentally different issues than those that don't in most cases. Some of the developers I know who write Linux or VxWorks code all day might not fare as well working with a "raw" PIC, AVR, or TI microcontroller. By the same token, I always find it a little difficult to shift gears and start writing Linux code after I've been immersed in programming an ARM7 CPU with a minimal homebrew operating system.

The key, however, is not identifying systems after they are designed -- that's easy. I can build a taxonomy and sort existing systems into it with ease. The important thing is to be able to identify the type of system ahead of time. How many projects fail, I wonder, because they were over or under designed? Inputs to that design trade would be things like cost, power consumption, user interface capability, networking capability, and amount of data to store. 

I've often thought that the term "architect" applies to many of us even if we use a different title. Architects have to fuse engineering and art. I'm not sure selecting the basic "shape" of an embedded system in the design phase isn't one of the places where most of us do more art than engineering. Then using the broad framework we impose on ourselves by that choice, we do the engineering to complete the design.

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