[solved/understood] int main() versus setup()/loop() - Serial.begin/print bug?

Projects Programming
1

Hi,
The following code only prints "st" on a Nano clone and nothing more.

int main(void) {
  Serial.begin(9600);
  Serial.print("start ...");
  Serial.println("init");
  while(1);
  return 0;
}

This code prints "start ...init"

void setup() {
  Serial.begin(9600);
  Serial.print("start ...");
  Serial.println("init");
}
void loop() {}

Why does the main-version not print the text correctly?

Tested on IDE 1.6.9 and 1.8.2.
Thanks & best

2

Why? I don't know, but here's a clue.
Try this:

int main(void) {
  init();
  Serial.begin(9600);
  Serial.print("start ...");
  Serial.println("init");
  while(1);
  return 0;
}

The answer probably lies in the source code of that function.

3

Because if you use main() things like interrupts are not setup() for you. If you use loop() and setup() init() and initVariant() is called before setup()

From main.cpp

int main(void)
{
 init();

 initVariant();

#if defined(USBCON)
 USBDevice.attach();
#endif
 
 setup();
    
 for (;;) {
 loop();
 if (serialEventRun) serialEventRun();
 }
        
 return 0;
}
4

Thanks for the answers.
I wasn't aware of relevant settings done in init(). Now I'm aware :slight_smile:

Best