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Beaglebone Black RS485 Echo
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| #include <stdlib.h> | |
| #include <stdio.h> | |
| #include <sys/types.h> | |
| #include <sys/stat.h> | |
| #include <fcntl.h> | |
| #include <errno.h> | |
| #include <string.h> | |
| #include <linux/serial.h> | |
| #include <termios.h> | |
| #include <unistd.h> | |
| #include <sys/ioctl.h> | |
| #include <poll.h> | |
| #include <unistd.h> | |
| #include <getopt.h> | |
| #include <time.h> | |
| /* RS485 ioctls: */ | |
| #define TIOCGRS485 0x542E | |
| #define TIOCSRS485 0x542F | |
| int main( int argc, char **argv ) | |
| { | |
| char buf[80]; | |
| if( argc < 2 ) { | |
| printf("Usage: %s [port name]\n", argv[0]); | |
| exit(0); | |
| } | |
| char *port = argv[1]; | |
| int fd = open(port, O_RDWR); | |
| if (fd < 0) { | |
| /* Error handling. See errno. */ | |
| fprintf( stderr, "Error opening port \"%s\" (%d): %s\n", port, errno, strerror( errno )); | |
| exit(-1); | |
| } | |
| struct serial_rs485 rs485conf; | |
| if (ioctl (fd, TIOCGRS485, &rs485conf) < 0) { | |
| printf("Error: TIOCGRS485 ioctl not supported.\n"); | |
| } | |
| struct termios newtio; | |
| bzero(&newtio, sizeof(newtio)); /* clear struct for new port settings */ | |
| /* man termios get more info on below settings */ | |
| newtio.c_cflag = B115200 | CS8 | CLOCAL | CREAD; | |
| newtio.c_iflag = 0; | |
| newtio.c_oflag = 0; | |
| newtio.c_lflag = 0; | |
| // block for up till 128 characters | |
| newtio.c_cc[VMIN] = 128; | |
| // 0.5 seconds read timeout | |
| newtio.c_cc[VTIME] = 5; | |
| /* now clean the modem line and activate the settings for the port */ | |
| tcflush(fd, TCIOFLUSH); | |
| tcsetattr(fd, TCSANOW, &newtio); | |
| rs485conf.delay_rts_after_send = 0; | |
| rs485conf.delay_rts_before_send = 0; | |
| rs485conf.flags = 0; | |
| rs485conf.flags |= SER_RS485_ENABLED; | |
| /* If sending HI LEVEL */ | |
| rs485conf.flags &= ~(SER_RS485_RTS_ON_SEND); | |
| /* If recv LO LEVEL */ | |
| rs485conf.flags |= SER_RS485_RTS_AFTER_SEND; | |
| rs485conf.flags |= SER_RS485_RX_DURING_TX; | |
| if (ioctl (fd, TIOCSRS485, &rs485conf) < 0) { | |
| printf("Error: TIOCSRS485 ioctl not supported.\n"); | |
| } | |
| int bytes_read = 0; /* Number of bytes read by the read() system call */ | |
| while(1 == 1) | |
| { | |
| bytes_read = read(fd, &buf, 32); | |
| if (bytes_read != 0) | |
| { | |
| write(fd, buf, bytes_read); | |
| } | |
| } | |
| /* Close the device when finished: */ | |
| if (close (fd) < 0) { | |
| fprintf( stderr, "Error closing port (%d): %s\n", errno, strerror( errno )); | |
| } | |
| exit(0); | |
| } |
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