Serial communication between PC and Arduino using C

Question

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);
 fclose(usb_port);
 return 0;
}

• jsotola: why are you not using the arduino IDE?
• Juraj: @jsotola, because they write for PC

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) {
 perror(arduinoPort);
 return 1;
}

I would expect you see something like

/dev/ttyACM0: No such file or directory

or

/dev/ttyACM0: Permission denied

that could help you pin down the real problem.

• Shinforinpola: 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.