Some media analysts have admitted to being confused by the fact that companies engaged in the personal computer business, such as Dell and Microsoft, have recently published less-than-stellar financial results and gloomy guidance for the future, while other companies, such as Intel and Apple, are fairly jumping with glee over future prospects. This seeming paradox evaporates, however, as soon as one realizes that the vast majority of computers aren't PCs, anymore.
I talked about one aspect of this phenomenon in this blog's last entry ("The PC as Dodo"). In today's entry, I'll talk about a second trend: embedded systems technology. I've mentioned embedded systems before in this blog, but today I want to get a little deeper into the guts of the things to show how this trend affects so many technology companies so differently.
Embedded systems, as Figure 1 shows, generally embody a control loop where a microcontroller reads signals from sensors attached to some equipment out in the real world (IRL). Based on those sensor readings, the microcontroller calculates some changes it wants to make IRL to control the equipment. The equipment responds to these changing signals, which changes the sensor readings.
Figure 1: Embedded systems include a control loop governed by a microcontroller.
What makes the system a control loop, rather than the proverbial snake swallowing its tail, is the fact that there is a control input, called a set point to which the controller compares the sensor inputs. The controller bases its output signals on how the actual readings from the sensors compare to the set point. In actual fact, there may be several sensors and several set points, and the controller likely will take into account how the sensor inputs are changing with time as well as their instantaneous values. People can select how they want the system to behave by changing the set points.
The classic embedded system that everyone uses as an example is a digital thermostat. This system has one sensor (a temperature sensor sampling the room air), one IRL equipment unit (a heater or air conditioner), and one controller (the digital thermostat). You control the temperature you want to have in the room by changing the temperature set point. Almost any digital thermostat worth its price will also include a time sensor (a clock) that allows you to program different temperature set points depending on the time of day.
What makes this technology important is the fact that embedded systems are now used to control just about every device we have. In the past, I've commented that microcontrollers now run just about every device more complicated than a lead pencil. That may be an exaggeration, but not much of one. To paraphrase the announcer from the old "Chickenman" radio show: "They're everywhere! They're everywhere!"
(If you don't know about Chickenman, you missed one of the great campy entertainment experiences of the mid-1960s. Episodes from the original series and two resurrections are still available for purchase on the Internet.)
Figure 2: Microcontrollers include a microprocessor, memory and I/O circuits on a single chip.
The heart of an embedded system is that little microcontroller. Figure 2 shows what's inside a typical microcontroller. It's a monolithic integrated circuit (IC) that has a microprocessor, multiple types of memory, including read-only memory (ROM), random-access memory (RAM) similar to what you see in a PC, along with a programmable read-only memory that holds the software that the microprocessor needs to run, along with several types of input/output circuits to take care of reading sensors, driving actuators, and communicating with the outside world. Many microcontrollers even have microscopic radio sets to communicate wirelessly with other systems.
What sets these things apart is that, unlike the components of a personal computer, all of this circuitry is crammed into one tiny chip. As anyone who's seen a PC with the covers off knows, the PC architecture has its circuitry spread around on a number of ICs. That takes up a lot of space, adds weight, and makes the whole thing bulky. One characteristic that embedded systems, from experimental nanobots to cellphones to television set-top boxes, share is the need to have their controllers as tiny and as light as possible.
Now, the semiconductor companies that make chips for PCs also make chips for embedded systems. The companies that use these chips in their products are more-or-less traditional industrial companies that make dishwashers, microwave ovens, cars, cellphones, etc.
The software these microcontrollers run is not the same as the software PCs run, either. Instead of operating systems like Windows Vista, or Apple Mac OS, they run things like LynxOS, QNX, and VxWorks that most people have never heard of.
In the world of computer technology, embedded systems are where the action is. PCs, for all their historical significance and public share of mind, are a small part of the market with lackluster (at best) growth prospects.
So, companies involved in the embedded system business, such as Intel and Apple, report spectacular profits and predict stellar growth prospects. Companies whose businesses depend on the PC industry complain of shrinking markets and poor future prospects.
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