Essential Embedded Software Skills

I spend a lot of time trying to grapple with what makes embedded systems different than desktop computer systems in terms of skills and development processes.  Often the answer to this question on  discussion groups ends up being something like "everything has to be super-optimized," or "you need to meet real-time deadlines." But those are technical measures that seem to me to be more symptoms of particular embedded system projects rather than root cause of the differences.  And, such answers tend to be a bit one-dimensional.

After some thought, perhaps the distinctive attributes of embedded systems can be summarized in the following way:

Interaction with the physical world:
Embedded systems generally have a primary goal of interacting with the physical world using sensors  and actuators. This in turn encompasses various topics depending on the application, including:
  - Real time responsiveness (scheduling, concurrency management, timekeeping)
  - Analog & digital interfacing
  - Control approaches
  - Signal processing
  - Coordination via networked and Cloud services
  - Reliability, safety, system robustness

Special-purpose computing platform:
Most embedded systems don't use a general purpose computing platform (a desktop comptuer, laptop, tablet, smart phone, etc.).  Rather, they use a customized hardware platform that is permanently embedded into the product. (Even those that do use somewhat standardized hardware often have specialized I/O devices attached.)  This in turn encompasses various topics depending on the application, including:
  - Software optimization (squeezing to fit into a cost-constrained platform)
  - Close-to-hardware programming (interrupts, device interfacing)
  - Hardware specialization (application-specific hardware, DSP platforms)
  - Specialized network protocols
  - Special-purpose human interaction devices
  - Hardware-dependent testing approaches
  - Customized operating system (or custom non-OS task manager)
  - Power management

Domain-centric development:
Outside the consumer electronics area, in my experience it is rare to meet a deeply embedded system developer with a primary college degree in computer engineering or computer science.  Generally they have a degree more relevant to their product domain. Yet, nonetheless, here they are writing significant amounts of code for a living. Those trained in software development are also missing somewhat different pieces. Regardless of background, developers usually need to understand the following areas:
  - General software process and technical practice literacy (for domain experts) / Domain expertise (for software experts)

  - Life-cycle support for long-lived, hard-to-update products

  - Distributed and federated system architecture design
  - Domain-optimized development (e.g., model-based design for control systems)
  - Domain-specific aspects of security

Looking at this list, it becomes clear that skills such as knowing how to write super-optimized code are merely pieces of a larger puzzle. In general, you need to be at least literate in all the topics above to be a well-rounded embedded system developer.  Sure, not everyone and not every project needs deep expertise in everything. But if you're planning on a career in embedded systems you'll likely hit just about everything on the list -- I know that I certainly have. (And, if you're a hiring manager, now you have a shopping list for skills for your senior developers.)