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The HAL Pattern

Abstract a peripheral behind an interface so app logic survives an MCU swap and runs in a PC unit test, using runtime virtuals or zero-overhead compile-time polymorphism.

25 min read

In this lesson:

the HAL pattern, separate what hardware does from how a chip does it
runtime polymorphism (virtual interface), flexible, testable, small cost
compile-time polymorphism (templates / CRTP), zero overhead, type fixed early
the testability payoff: run firmware logic in a PC unit test with a fake
choosing between the two, and not over-abstracting

This is the capstone: it combines classes, RAII, references, const, and templates into the pattern that makes firmware portable and testable.

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