Simple RS485 stress

rs485_test.c

#include <linux/serial.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <termios.h>
#include <errno.h>

int main(int argc, char *argv[])
{
  struct serial_rs485 rs485;
  int fd;
  struct termios tio;
  const char *port_name = "/dev/ttymxc2";

  if (argc >= 2)
  	port_name = argv[1];
  printf("Opening %s\n", port_name);
  fd = open(port_name, O_RDWR | O_NONBLOCK | O_NOCTTY);
  if (fd < 0) {
  	perror("open");
  	return -1;
  }
  rs485.flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
  ioctl(fd, TIOCSRS485, &rs485);
  if (tcgetattr(fd, &tio) == -1) {
  	perror("tcgetattr");
  	return -1;
  }
  // cfmakeraw(&tio);
  tio.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
              | INLCR | IGNCR | ICRNL | IXON);
  tio.c_oflag &= ~OPOST;
  tio.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
  tio.c_cflag &= ~(CSIZE | PARENB);
  tio.c_cflag |= CS8;
  tio.c_cflag = B115200 | CS8 | CLOCAL | CREAD;
  tio.c_iflag = IGNPAR | ICRNL;
  tio.c_oflag = 0;
  tio.c_lflag = ICANON;
  tio.c_cc[VMIN] = 1;
  tio.c_cc[VTIME] = 0;
  if (tcflush(fd, TCIFLUSH) == -1) {
    fprintf(stderr, "tcflush failed: %d %s\n", errno, strerror(errno));
  }
  if (tcsetattr(fd, TCSANOW, &tio) == -1) {
    printf("tcsetattr failed: %d\n", errno);
  }
  const char* data = "foo\r\n";
  char buf[10];
  int i = 1, ret;
  unsigned int read_count = 0, write_count = 0;
  while (i++) {
    if ((ret = write(fd, data, 5)) == -1) {
      fprintf(stderr, "write failed: %d %s\n", errno, strerror(errno));
    }
    else {
    	write_count += ret;
    }
    while ((ret = read(fd, buf, 10)) != -1) {
    	read_count += ret;
    }
    usleep(100 * 1000);

    if (i % 10 == 0) {
    	printf("data: read=%d write=%d\n", read_count, write_count);
    }
  }
  close(fd);
  return 0;
}