163. Abstraction

Question.3

A GPIO HAL abstracts away platform-specific register access:

// Application code (portable)
void blink(IGPIO& led) {
   led.write(HIGH);
   delay(500);
   led.write(LOW);
   delay(500);
}

On STM32, write accesses BSRR registers. On AVR, it accesses PORTB. On Linux, it writes to /sys/class/gpio. The application code is:

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Identical for all platforms -- the HAL abstraction hides platform-specific register access behind a common interface
Different for each platform
Identical but slower on embedded platforms
Only portable between ARM platforms

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