performance - Arduino: faster alternatives to digitalread() and digitalwrite()?

What are the fastest alternatives to calling the Arduino functions digitalread() and digitalwrite()? AVR-specific or chip-specific solutions are acceptable.

Answer

Access the digital ports directly!

The 3 methods I tested were

• digitalWrite(pin, LOW); digitalWrite(pin, HIGH);


• CLR(PORTB, 0) ; SET(PORTB, 0);



• PORTB |= _BV(0); PORTB &= ~(_BV(0));

[...]

As you can see, digitalWrite takes around 56 cycles to complete, while direct Port addressing takes 2 cycles. That’s a big difference in time for programs that have lot’s of IO operations!