Page 362 - Programming Microcontrollers in C

Chapter 7

Advanced Topics in Programming

Embedded Systems (M68HC12)

During the past few years, we have seen an unbelievable
proliferation of embedded systems products. Devices that could only
be imagined ten years ago are commonplace today and their very
existence demonstrates the importance of C programming for small
microcontrollers. Let’s take a look at one such application and see
how easily you can develop rather complicated applications on
microcontrollers.
Throughout this text, much emphasis has been placed on the
construction of small functions and then integrating these functions
into a working package. This approach is about the only way that
you can really hope to create a complicated piece of firmware in a
sensible time. My early projects would always start with careful design
of the whole project, partitioning of the project into sensible modules,
design of each module, writing the code for each module, integration
of the whole project and then, after cleaning up syntax errors, I’d
begin to test the whole program. What a disaster! These programs
would never work and there would be no hope of ever getting the
package to run as a unit.
As I gained experience, I found that the top-down approach I
used was probably satisfactory if I tempered the integration of the
system. Today, I start with a careful design for the whole system.
This design is partitioned into constituent components. At that point,
another look at the design is in order to see if the existing components
can be further reduced into sensible components. At that point, the
lowest-level components are coded. Often these functions are so
simple that they work when first tested. Whenever there is a required

347