Inconsistency reading from serial port in C LINUX

I have an inconsistency problem while I read in my serial port using Linux and C.

The code that I use to configure the serial port is this:

serial = open("/dev/ttymxc1", O_RDWR | O_NOCTTY | O_SYNC); //Open in non blocking read/write mode if (serial == -1) { //ERROR - CAN'T OPEN SERIAL PORT printf("Error - Unable to open UART. Ensure it is not in use by another application\n"); } struct termios tty; memset (&tty, 0, sizeof tty); if (tcgetattr (serial, &tty) != 0) { printf("error from tcgetattr"); return -1; } cfsetospeed (&tty, B115200); tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8; // 8-bit chars // disable IGNBRK for mismatched speed tests; otherwise receive break // as \000 chars //tty.c_iflag &= ~IGNBRK; // disable break processing tty.c_lflag = 0; // no signaling chars, no echo, // no canonical processing tty.c_oflag = 0; // no remapping, no delays tty.c_cc[VMIN] = 0; // read doesn't block tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls, // enable reading tty.c_cflag &= ~(PARENB | PARODD); // shut off parity tty.c_cflag |= 0; tty.c_cflag &= ~CSTOPB; tty.c_cflag &= ~CRTSCTS; if (tcsetattr (serial, TCSANOW, &tty) != 0) { printf("error from tcsetattr"); return -1; } 

Then I poll the UART (from the same thread which has configured the serial port) with the following code:

while(1) { if (serial != -1) { //memset(rx, 0, sizeof(rx)); int rx_length = read(serial, &rx, MAX_TXRX_BUF); //Filestream, buffer to store in, number of bytes to read (max) if(rx_length > 0){ //Bytes received //rx[rx_length] = '\0'; printf("1) %i bytes read : %s\n", rx_length, rx); //forward_data(rx, rx_length); printf("2) %i bytes read : %s\n", rx_length, rx); //tcflush(serial, TCIOFLUSH); } // else: NO DATA } else{ fprintf(stderr, "TEST: %s SERIAL FAIL\n", __func__); releaseUart(); } } 

The problem is that this print:

printf("1) %i bytes read : %s\n", rx_length, rx); 

always WORKS and print the correct data read from serial. While the second print:

printf("2) %i bytes read : %s\n", rx_length, rx); 

which is immediately below the first one, sometimes works and other items it just prints an unknown character.

Below I show you the ouput but in the case in which it works and in the case in which it does not work:

Correct:

1) 2 bytes read : gv 2) 2 bytes read gv 

Wrong:

1) 2 bytes read : gv 2) 2 bytes read: � 

Why even if the two prints are one below the other sometimes I get these kind of inconsistencies in printing the SAME buffer?

Thanks in advance very much for your help.

Best regards, Marco