Question

我试图在linux中编写一个与serialport交互的C程序。该程序有2个线程，一个主要写入和一个监听线程。我的问题在于监听线程。我希望read函数在单个字节到达后立即读取原始数据。

无论我尝试使用termios结构，我只能读取数据，直到收到换行符（\ n或\ r）。我使用连接了Rx和Tx的USB-Serial棒进行测试。提前谢谢。

#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 */
#include <stdlib.h>   
#include <pthread.h>

#define RESET_HIGH  RESET_HIGH
#define RESET_LOW   RESET_LOW
#define SLEEP_TPE   usleep(5200)  //min 5100usec = 5.1msec
#define FALSE 0
#define TRUE 1

#define BAUDRATE    B115200

//function declaration
void *read_port(void);

//variable declaration
volatile int LISTENING=TRUE;
int fd;
unsigned char rx_buffer[255];


int main(int argc, char const *argv[]){
  int error;
  struct termios oldtty,newtty;
  pthread_t txthread;

  printf("-------->ZM5304 FLASHING PROGRAM<--------\n");
  fd = open_port("/dev/ttyUSB0"); //  "/dev/ttymxc3"  "/dev/ttyUSB0"


  //save current port settings
  error = tcgetattr(fd, &oldtty);
  if(error==-1){
    close(fd);
    perror("unable to read portsettings\n");
    return(1);
  }

  //clear new struct
  memset(&newtty, 0, sizeof(newtty));


  newtty.c_cflag |= CS8 | CSTOPB;  //8bit, 2 stopbits
  newtty.c_cflag &= ~CRTSCTS;  //disable hardware flowcontrol
  //newtty.c_lflag |= ICANON;        //cannonical
  newtty.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG); //raw input
  newtty.c_oflag &= ~OPOST;
  newtty.c_cc[VMIN] = 1;
  newtty.c_cc[VTIME] = 0; //read() blocking
  //cfmakeraw(&newtty);

  cfsetispeed(&newtty, BAUDRATE);
  cfsetospeed(&newtty, BAUDRATE);

  //apply portsettings
  printf("Applying portsettings\n");
  error = tcsetattr(fd, TCSANOW, &newtty);
    if(error==-1){
      close(fd);
      printf("unable to adjust portsettings - %s\n", error);
      return(1);
    }

  //SETUP LISTENING THREAD
  error = pthread_create(&txthread, NULL, read_port, (void *)NULL);
  if(error){
    printf("Error - pthread_create() return code: %d\n", error);
    return(2);
  }


  sleep(1);
  write(fd, "A",1);
  sleep(1);
  write(fd, "B",1);
  sleep(1);
  write(fd, "C\n",2);
  sleep(1);
  write(fd, "Talking Serial\n",15);
  sleep(1);
  write(fd, "q\n",2);
  sleep(1);


  close(fd);
  printf("-------->END OF PROGRAM<--------\n");
  pthread_exit(NULL);
  return 0;
}

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

  printf("Opening serialport: %s\n", path);
  fd = open(path, O_RDWR | O_NOCTTY | O_NDELAY);
  if (fd == -1){  //Could not open the port.
    fprintf(stderr, "Error - Unable to open %s - %s\n", path, strerror(errno));
    exit(1);
  }
  return (fd);
}

void *read_port(){
  printf("Reading Tx\n");
  int len;
  while(LISTENING){
    len = read(fd,rx_buffer,255);
    rx_buffer[len]=0;   /* set end of string, so we can printf */
    if(len>0){printf("%s", rx_buffer);}
    if(rx_buffer[0]=='q'){LISTENING=FALSE;}
  }
  printf("Stop listening\n");
}

Linux termios.h：传入的字节只能在\ n之后读取

0 个答案: