Challenges in Embedded Computing System Design

CHALLENGES IN EMBEDDED COMPUTING SYSTEM DESIGN

The following external constraints are one important source of difficulty in embedded system Design.

^ü How much hardware do we need?

We have a great deal of control over the amount of computing power we apply to our problem. We cannot only select the type of microprocessor used, but also select the amount of memory, the peripheral devices, and more. If too little hardware and the system fails to meet its deadlines, too much hardware and it becomes too expensive.

^ü How do we meet deadlines?

It is entirely possible that increasing the CPU clock rate may not make enough difference to execution time, since the program’s speed may be limited by the memory system.

^ü How do we minimize power consumption?

In battery-powered applications, power consumption is extremely important. Even in non- battery applications, excessive power consumption can increase heat dissipation. One way to make a digital system consume less power is to make it run more slowly, but naively slowing down the system can obviously lead to missed deadlines.

^ü How do we design for upgradability?

The hardware platform may be used over several product generations or for several different versions of a product in the same generation, with few or no changes.

^ü Does it really work?

Reliability is always important when selling products—customers rightly expect that products they buy will work.

The sources that make the design so difficult are:

■  Complex testing: Exercising an embedded system is generally more difficult than typing in some data. The timing of data is often important, meaning that we cannot separate the testing of an embedded computer from the machine in which it is embedded.

Limited observability and controllability: Embedded computing systems usually do not come with keyboards and screens. This makes it more difficult to see what is going on and to affect the system’s operation. We may be forced to watch the values of electrical signals on the microprocessor bus, for example, to know what is going on inside the system. Moreover, in real-time applications we may not be able to easily stop the system to see what is going on inside.

■ Restricted development environments: The development environments for embedded systems (the tools used to develop software and hardware) are often much more limited than those available for PCs and workstations.