EC-20.8 Reliability and Functional Safety in a Product That Ships
You can carry out a structured hazard analysis on a small embedded product, choose defences appropriate to the severity you find, and explain what a functional safety standard asks of the development process rather than of the code.
Before:EC-11. Data Communications and Computer NetworksEC-16. Ethics, Safety, Sustainability and Standards
A device that can hurt somebody is held to a different standard from one that cannot, and the difference is mostly about evidence rather than cleverness. This topic is the argument a shipped product has to be able to make: here is what could go wrong, here is how likely and how bad each one is, here is what the design does about it, and here is the record showing all of that was done before release rather than after the first accident.
Work through these
Failure modes and effects: listing what can break, one part at a time
Walking through a design part by part and asking what happens if this one fails open, shorted or stuck finds hazards that no amount of testing would. The output is a table, and the table is the deliverable.
NPTEL: Real-Time Systems (IIT Kharagpur) · CourseSeverity, likelihood and detectability, and what they combine into
A rare failure with a severe consequence and no warning is more dangerous than a common one that is obvious and harmless. Scoring the three separately is what stops the assessment from becoming a single unexamined opinion.
Watchdogs, safe states and graceful degradation
A watchdog resets a system that has stopped making progress, which helps only if the state it resets into is safe. Deciding what the safe state is for your product is a design decision that has to be made explicitly.
NPTEL: Embedded System Design with ARM (IIT Kharagpur) · CourseRedundancy, diversity and the common-cause failure that defeats both
Two identical units fail identically when the cause is a design fault or a shared supply, so duplication alone buys less than it appears to. Diversity in implementation or in supply is what turns redundancy into real protection.
What a functional safety standard actually requires
These standards mostly govern process: what analysis was done, what evidence exists, who reviewed it and how changes are controlled. A team meeting one for the first time is usually surprised by how little of it is about code.
NPTEL: Real-Time Systems (IIT Kharagpur) · CourseReliability figures, and what a mean time between failures does not tell you
A large figure for mean time between failures says nothing about wear-out and assumes a constant failure rate the product may not have. Quoting it without the assumptions behind it is one of the more common pieces of engineering dishonesty.
NPTEL: Design for Internet of Things (IISc Bangalore) · Course
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