serial - alex-aleyan/linux_wiki GitHub Wiki

#!/bin/bash
DEVICE=/dev/ttyUSB0

while true; do
    read -p "> " userString
    if [[ $userString = *[!\ ]* ]]; then
      echo -e -n "$userString\r" > $DEVICE
    else
      echo -e -n ' \r' > $DEVICE                                                
    fi  
done

root@localhost:tty_programming[<1313>]# cat tty1_write.c
#include <stdio.h>   /* Standard input/output definitions */                                                
#include <string.h>  /* String function definitions */
#include <unistd.h>  /* UNIX standard function definitions */
#include <fcntl.h>   /* File control definitions */
#include <errno.h>   /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */

/*
	*  *  * 'open_port()' - Open serial port 1.
	*   *   *
	*    *    * Returns the file descriptor on success or -1 on error.
	*     *     */

int open_port(char *port)
{
int fd; /* File descriptor for the port */

// O_NOCTTY flag tells UNIX the program is not to be the CONTROLLING TERMINAL!
// O_NDELAY flag tells UNIX the program d.n. care what the state the DCD SIGNAL LINE is in.
fd = open( port, O_RDWR | O_NOCTTY | O_NDELAY | O_SYNC);

  if (fd == -1)
		{
				/*
				*     *     * Could not open the port.
				*         *         */
				perror("open_port: Unable to open /dev/ttyf1 - ");
		}
		else fcntl(fd, F_SETFL, 0);

return (fd);
}

int set_tty_attribs(int fd, unsigned int speed)
{
		struct termios tty_options;

		if (tcgetattr(fd, &tty_options) < 0) {
				printf("Error from tcgetattr: %s\n", strerror(errno));
				return -1;
		}
		
		cfsetospeed(&tty_options, (speed_t) speed);
		//cfsetospeed(&tty_options, B115200);
		cfsetispeed(&tty_options, (speed_t) speed);
		//cfsetispeed(&tty_options, B115200);
		
		// ignore modem controls; insures the program does not become the owner of 
		// the port, subject to sporatic job control and hangup signals.
		tty_options.c_cflag |= (CLOCAL | CREAD); 

		tty_options.c_cflag &= ~CSIZE;
		tty_options.c_cflag |= CS8;

		//tty_options.c_cflag &= ~PARENB;
  //tty_options.c_cflag &= ~CSTOPB;

		//tty_options.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON);
		//tty_options.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
		//tty_options.c_oflag &= ~OPOST;

//		tty_options.c_cc[VMIN] = 1;
//		tty_options.c_cc[VTIME] = 1;

		if (tcsetattr(fd, TCSANOW, &tty_options) != 0) {
				printf("Error from tcsetattr: %s\n", strerror(errno));
				return -1;
		}

		return 0;
}

void set_mincount(int fd, int mcount)
{
		struct termios tty;

		if (tcgetattr(fd, &tty) < 0) {
				printf("Error tcgetattr: %s\n", strerror(errno));
				return -1;
		}

		tty.c_cc[VMIN] = mcount ? 1 : 0;
		tty.c_cc[VTIME] = 5;        /* half second timer */

		if (tcsetattr(fd, TCSANOW, &tty) < 0) printf("Error tcsetattr: %s\n", strerror(errno));
}

#define CNUM 23
int main(int argc, char **argv)
{
		char *portname = "/dev/ttyUSB0";
		int fd;
		int msgLen;
		unsigned char buf[512];

		if (argc >= 2) memcpy(buf, argv[1], strlen(argv[1])+1);
		//printf("After memcpy dest = %s\n", buf);
		
		fd = open_port( portname );

		set_tty_attribs(fd, B9600);

 	msgLen = write( fd, buf, strlen(buf)+1);
 	if (msgLen != CNUM) {
				printf("Error from write: %d, %d\n", msgLen, errno);
		}
		
		tcdrain(fd);

return 0;
}

cat /dev/ttyUSB0

#!/bin/bash
DEVICE='/dev/ttyUSB0'
BAUDRATE=9600

stty -F $DEVICE $BAUDRATE
cat $DEVICE

sudo screen /dev/ttyUSB0 115200

root@localhost:tty_programming[<1376>]# cat tty1_read.c
#include <stdio.h>   /* Standard input/output definitions */                                                
#include <string.h>  /* String function definitions */
#include <unistd.h>  /* UNIX standard function definitions */
#include <fcntl.h>   /* File control definitions */
#include <errno.h>   /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */

/*
	*  *  * 'open_port()' - Open serial port 1.
	*   *   *
	*    *    * Returns the file descriptor on success or -1 on error.
	*     *     */

int open_port(char *port)
{
int fd; /* File descriptor for the port */

// O_NOCTTY flag tells UNIX the program is not to be the CONTROLLING TERMINAL!
// O_NDELAY flag tells UNIX the program d.n. care what the state the DCD SIGNAL LINE is in.
fd = open( port, O_RDWR | O_NOCTTY | O_NDELAY | O_SYNC);

  if (fd == -1)
		{
				/*
				*     *     * Could not open the port.
				*         *         */
				perror("open_port: Unable to open /dev/ttyf1 - ");
		}
		else fcntl(fd, F_SETFL, 0);

return (fd);
}

int set_tty_attribs(int fd, unsigned int speed)
{
		struct termios tty_options;

		if (tcgetattr(fd, &tty_options) < 0) {
				printf("Error from tcgetattr: %s\n", strerror(errno));
				return -1;
		}
		
		cfsetospeed(&tty_options, (speed_t) speed);
		//cfsetospeed(&tty_options, B115200);
		cfsetispeed(&tty_options, (speed_t) speed);
		//cfsetispeed(&tty_options, B115200);
		
		// ignore modem controls; insures the program does not become the owner of 
		// the port, subject to sporatic job control and hangup signals.
		tty_options.c_cflag |= (CLOCAL | CREAD); 

		tty_options.c_cflag &= ~CSIZE;
		tty_options.c_cflag |= CS8;

		//tty_options.c_cflag &= ~PARENB;
  //tty_options.c_cflag &= ~CSTOPB;

		//tty_options.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON);
		//tty_options.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
		//tty_options.c_oflag &= ~OPOST;

//		tty_options.c_cc[VMIN] = 1;
//		tty_options.c_cc[VTIME] = 1;

		if (tcsetattr(fd, TCSANOW, &tty_options) != 0) {
				printf("Error from tcsetattr: %s\n", strerror(errno));
				return -1;
		}

		return 0;
}

void set_mincount(int fd, int mcount)
{
		struct termios tty;

		if (tcgetattr(fd, &tty) < 0) {
				printf("Error tcgetattr: %s\n", strerror(errno));
				return -1;
		}

		tty.c_cc[VMIN] = mcount ? 1 : 0;
		tty.c_cc[VTIME] = 5;        /* half second timer */

		if (tcsetattr(fd, TCSANOW, &tty) < 0) printf("Error tcsetattr: %s\n", strerror(errno));
}

#define CNUM 23
int main(int argc, char **argv)
{
		char *portname = "/dev/ttyUSB0";
		int fd;
		int msgLen;

		
		fd = open_port( portname );
		set_tty_attribs( fd, B9600 );

		
		tcdrain(fd);

		//simple noncanonical input 
		do {
				unsigned char buf[512];
				int rdlen;

				rdlen = read(fd, buf, sizeof(buf) - 1); 
				if (rdlen > 0) {
#ifdef DISPLAY_STRING
								buf[rdlen] = 0;
								//printf("Read %d: \"%s\"\n", rdlen, &buf[0]);
								printf("%s\n", buf);
#else //display hex                                                              
								unsigned char   *p; 
								printf("Read %d:", rdlen);
								for (p = buf; rdlen-- > 0; p++)
										printf(" 0x%x", *p);
										printf("\n");
#endif
				}
				else if (rdlen < 0) {
						printf("Error from read: %d: %s\n", rdlen, strerror(errno));
				}
				// repeat read to get full message 
		}
		while (1);
		
		//fcntl(fd, F_SETFL, 0);
return 0;
}

- Using custom bash script (make sure to copy your .Xauthority file to roots home directory) 

#!/bin/bash
DEVICE='/dev/ttyUSB0'
BAUDRATE=9600

echo $PWD

stty -F $DEVICE $BAUDRATE
gnome-terminal --title=RS232-TX -e "$PWD/serialWrite.sh" &
gnome-terminal --title=RS232-RX -e "$PWD/serialRead.sh" &