Trouble speeding up arduino

Question

I'm trying to speed up my Arduino code by direct writing to registers. I wrote a short test script, but it doesn't seem to do much. If I use the 'digitalWrite()' function I can see an output on the oscilloscope, but using this code it just stays 0. I used this link as a reference. I can't quite grasp what I missed.

byte *outputRegister;
byte bitMask;

void setup() {
  pinMode(8,OUTPUT);
  outputRegister = portOutputRegister(8);
  bitMask = digitalPinToBitMask(8);
}

void loop() {
  *outputRegister |= bitMask;
  delay(1);
  *outputRegister &= ~bitMask;
  delay(1);
}

EDIT: The portOutRegister should return the port where the output pins are set. The digitalPinToBitmask function returns a bitmask (something like 0b00000001 for the first pin on the respective port). With some further testing, I concluded that the digitalWrite function doesn't seem to actually change the values in these registers, which does nothing more than confuse me.

Hard to say without see portOutputRegister and digitalPinToBitMask code — Duloren
compare the result of portOutRegister to your expected value: Arduino Pin 8 on an atmega328 (uno/nano) is PORTB — datafiddler

Dave_Z. Dave_Z. · Accepted Answer · 2019-09-19T21:05:00

Arduino, if its Model = Uno, then it is ATmega-328 AVR, the best way to solve critical timing issues and achieve better execution times and code optimizations you should program via direct register modifications. That being said, use AVR-GCC, include and then do bit twiddling. Your code is not readable and hard to understand. IMO you should either write in C++ inside Arduino IDE >> slower but easier option, or start programming outside IDE inC and directly the AVR, >> orders of magnitude performance increase. Get to know the AVR Freaks Forum.

Trouble speeding up arduino

1 Answers