imx6ul usb转串口调试（代码）-蒲公英云

这里需要注意的是，当usb转串口模块插到usb上面/dev下面才能有设备，拔了设备就没了，所以操作的时候要注意。

#include <stdio.h>        //标准输入输出,如printf、scanf以及文件操作
#include <stdlib.h>        //标准库头文件，定义了五种类型、一些宏和通用工具函数
#include <unistd.h>        //定义 read write close lseek 等Unix标准函数
#include <sys/types.h>    //定义数据类型，如 ssiz e_t off_t 等
#include <sys/stat.h>    //文件状态
#include <fcntl.h>        //文件控制定义
#include <termios.h>    //终端I/O
#include <errno.h>        //与全局变量 errno 相关的定义
#include <getopt.h>        //处理命令行参数
#include <string.h>        //字符串操作
#include <time.h>        //时间
#include <sys/select.h>    //select函数
#include <sys/ioctl.h>
#include <net/if.h>
#include <pthread.h>
int usb2uartfd;
int setOpt(int fd, int nSpeed, int nBits, int nParity, int nStop)
{
    struct termios newtio, oldtio;
    // 保存测试现有串口参数设置，在这里如果串口号等出错，会有相关的出错信息
    if (tcgetattr(fd, &oldtio) != 0)
    {
        perror("SetupSerial 1");
        return -1;
    }
    bzero(&newtio, sizeof(newtio));        //新termios参数清零
    newtio.c_cflag |= CLOCAL | CREAD;    //CLOCAL--忽略 modem 控制线,本地连线, 不具数据机控制功能, CREAD--使能接收标志
    // 设置数据位数
    newtio.c_cflag &= ~CSIZE;    //清数据位标志
    switch (nBits)
    {
        case 7:
            newtio.c_cflag |= CS7;
        break;
        case 8:
            newtio.c_cflag |= CS8;
        break;
        default:
            fprintf(stderr, "Unsupported data size\n");
            return -1;
    }
    // 设置校验位
    switch (nParity)
    {
        case 'o':
        case 'O':                     //奇校验
            newtio.c_cflag |= PARENB;
            newtio.c_cflag |= PARODD;
            newtio.c_iflag |= (INPCK | ISTRIP);
            break;
        case 'e':
        case 'E':                     //偶校验
            newtio.c_iflag |= (INPCK | ISTRIP);
            newtio.c_cflag |= PARENB;
            newtio.c_cflag &= ~PARODD;
            break;
        case 'n':
        case 'N':                    //无校验
            newtio.c_cflag &= ~PARENB;
            break;
        default:
            fprintf(stderr, "Unsupported parity\n");
            return -1;
    }
    // 设置停止位
    switch (nStop)
    {
        case 1:
            newtio.c_cflag &= ~CSTOPB;
        break;
        case 2:
            newtio.c_cflag |= CSTOPB;
        break;
        default:
            fprintf(stderr,"Unsupported stop bits\n");
            return -1;
    }
    // 设置波特率 2400/4800/9600/19200/38400/57600/115200/230400
    switch (nSpeed)
    {
        case 2400:
            cfsetispeed(&newtio, B2400);
            cfsetospeed(&newtio, B2400);
            break;
        case 4800:
            cfsetispeed(&newtio, B4800);
            cfsetospeed(&newtio, B4800);
            break;
        case 9600:
            cfsetispeed(&newtio, B9600);
            cfsetospeed(&newtio, B9600);
            break;
        case 19200:
            cfsetispeed(&newtio, B19200);
            cfsetospeed(&newtio, B19200);
            break;
        case 38400:
            cfsetispeed(&newtio, B38400);
            cfsetospeed(&newtio, B38400);
            break;
        case 57600:
            cfsetispeed(&newtio, B57600);
            cfsetospeed(&newtio, B57600);
            break;
        case 115200:
            cfsetispeed(&newtio, B115200);
            cfsetospeed(&newtio, B115200);
            break;
        case 230400:
            cfsetispeed(&newtio, B230400);
            cfsetospeed(&newtio, B230400);
            break;
        default:
            printf("\tSorry, Unsupported baud rate, set default 9600!\n\n");
            cfsetispeed(&newtio, B9600);
            cfsetospeed(&newtio, B9600);
            break;
    }
    // 设置read读取最小字节数和超时时间
    newtio.c_cc[VTIME] = 1;     // 读取一个字符等待1*(1/10)s
    newtio.c_cc[VMIN] = 1;        // 读取字符的最少个数为1
    tcflush(fd,TCIFLUSH);         //清空缓冲区
    if (tcsetattr(fd, TCSANOW, &newtio) != 0)    //激活新设置
    {
        perror("SetupSerial 3");
        return -1;
    }
    printf("Serial set done!\n");
    return 0;
}
void usb2uartfdCreate()
{
    int ret = 0;
    usb2uartfd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY);
    if(usb2uartfd < 0)
    {
        printf("usb uart open failed ret = %d\r\n",usb2uartfd);
        usb2uartfd = -1;
        return;
    }
    ret = fcntl(usb2uartfd, F_SETFL, 0);
    if(ret < 0)
    {
        printf("fcntl failed ret = %d\r\n",ret);
        close(usb2uartfd);
        usb2uartfd = -1;
        return;
    }
    if (isatty(usb2uartfd) == 0)
    {
        printf("standard input is not a terminal device\r\n");
        close(usb2uartfd);
        usb2uartfd = -1;
        return;    
    }
    if (setOpt(usb2uartfd, 115200, 8, 'N', 1)== -1)    //设置8位数据位、1位停止位、无校验
    {
        printf("Set opt Error\r\n");
        close(usb2uartfd);
        usb2uartfd = -1;
        return ;                
    }
    tcflush(usb2uartfd, TCIOFLUSH);    //清掉串口缓存
    fcntl(usb2uartfd, F_SETFL, 0);    //串口阻塞
    printf("uart fd create ok\r\n");
}
void *uartrecv(void *arg)
{
    unsigned int maxfd = 0;
    unsigned int ret = 0;
    struct timeval waittime;
    fd_set rfd;
    char buf[128];
    while(1)
    {
        FD_ZERO(&rfd);
        if(usb2uartfd == -1)
            return NULL;
        FD_SET(usb2uartfd,&rfd);
        if(maxfd < usb2uartfd)
        {
            maxfd = usb2uartfd;
        }
        waittime.tv_sec = 1;
        waittime.tv_usec = 0;
        ret = select(maxfd + 1,&rfd,NULL,NULL,&waittime);
        if(0 >= ret)
        {
            continue;
        }
        if(FD_ISSET(usb2uartfd,&rfd))
        {
            memset(buf,0,sizeof(buf));
            read(usb2uartfd,buf,sizeof(buf) - 1);
            printf("usb uart recv buf = %s\r\n",buf);
        }
    }
}
void main()
{
    char buf[128];
    pthread_t ntid;
    usb2uartfdCreate();
    pthread_create(&ntid, NULL, uartrecv, NULL);
    while(1)
    {
        if(usb2uartfd != -1)
        {
            memset(buf,0,sizeof(buf));
            sprintf(buf,"this is usb uart send date");
            write(usb2uartfd,buf,strlen(buf));
            tcflush(usb2uartfd,TCOFLUSH);
        }
        sleep(5);
    }
}