[Linux][RS232] Can not write to arduino unless serial monitor is open

Projects Programming
1

I have a C program that is writing to /dev/ttyACM0 file (RS232).

The system is working only if the Serial Monitor is opened :{

My question is:

Is there additional serial port configuration needed to communicate to the Arduino ?

I use Serial.readString() on the Arduino side, I never had such issue using readBytes() nore read(), ...

2

Additional details:

The Arduino seems to reset each time I configure (C program side) the RS232 line.
The LED behaves the same as when I push the reset button.
When I send the datas to the arduino, the RX blinks but the TX stays led.

When I open the "serial monitor" the behaviour is:

The LED doesn't blink and the TX blinks ((as I send a message to the serial port thru
Serial.println() for debugging)) and when the C program does the write() operation the RX blinks but TX still blinks.

The C programs uses the function as describes below:

int ConfigureArduino(char *pFichier,speed_t vitesse)
{
int portdesc;
struct termios options;

portdesc=open(pFichier, O_RDWR | O_NOCTTY | O_NONBLOCK);
if(portdesc>0)
{
fcntl(portdesc,F_SETFL,0);

tcgetattr(portdesc, &options);
cfsetispeed(&options, vitesse);
cfsetospeed(&options, vitesse);
options.c_cflag |= (CLOCAL | CREAD);
options.c_oflag &= ~(IXON | IXOFF | IXANY);
options.c_cflag &= ~CRTSCTS;

tcsetattr(portdesc, TCSANOW, &options);

int Terminal_flag;
//Terminal_flag |= (TIOCM_DTR | TIOCM_RTS);
Terminal_flag &= ~(TIOCM_DTR | TIOCM_RTS);

ioctl(portdesc,TIOCMBIS,&Terminal_flag);

}
return portdesc;
}

3

Which Arduino? A number if models (328P based and 2560 based) do reset when you open the serial connection to them.

4

You probably need to set DTR or RTS or both. When you open the Serial Monitor it does that.

...R