I'm trying to send some data to my arduino mega 2560 using serial communication.

I'm using the exemple that I found here without success.

Every site I read say that I can send data to the arduino board like writing to any file on ubuntu.

But I alway get Segmentation fault

Here is my code

#include <stdio.h>
#include <string.h>

char arduinoPort[] = "/dev/ttyACM0";

int main() {

  char buffer[] = {'1'};

  FILE *usb_port;

  usb_port = fopen(arduinoPort, "rwb");

  fwrite(buffer, sizeof(char), sizeof(buffer), usb_port);


  return 0;
  • why are you not using the arduino IDE?
    – jsotola
    Jul 3, 2019 at 4:20
  • 1
    @jsotola, because they write for PC
    – Juraj
    Jul 3, 2019 at 5:28

1 Answer 1


Your program works flawlessly on my Ubuntu 18.04. I would guess that you have a problem with your setup (flaky USB port, permission problems...) rather than the program itself. Still, I would recommend you add some error checking: right after the fopen() call,

if (!usb_port) {
    return 1;

I would expect you see something like

/dev/ttyACM0: No such file or directory


/dev/ttyACM0: Permission denied

that could help you pin down the real problem.

  • 1
    Thank you so much. It wasn't working because i opened the serial monitor and because the message i could see it. When serial monitor is opened the serial is busy. Jul 3, 2019 at 12:00

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