Question

我正在使用嵌入式Linux中的串口，因为你知道我可以在互联网上找到很多来源。但是我对函数tcsetattr有一点问题，我试图设置ubit端口使用stopbit disable和enable（如果CSTOPB位置1，则使用两个停止位。否则，只使用一个停止位），但是我无法在tcsetattr中保存选项结构。

以下代码是示例：

#include <stdio.h>
#include <glib.h>
#include <termios.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/timeb.h>

static int uart_fd = 0;

void set_uart_fd(int fd) {
    uart_fd = fd;
}

int get_uart_fd() {
    return uart_fd;
}

void close_uart() {
    printf("Uart was closed \n");
    close(get_uart_fd());
}

void open_uart(){
   int flags = O_RDONLY;
   int fd;

   flags = O_RDWR | O_NOCTTY | O_NDELAY;
   fd = open("/dev/ttyUSB2", flags);

   if (fd < 0) {
        printf("Unable to open device \n");
   }
   set_uart_fd(fd);
}

void configuration_uart(speed_t baudrate,int data_bit, int stop_bit, int parity, int hardware_flow) {

    int status = 0,rc = 0;
    struct termios options;
    int uart = get_uart_fd();


    fcntl(uart, F_SETFL, 0);

    if ((rc = tcgetattr(uart,&options)) < 0){
        printf("failed to get attr\n");
    }
    printf("Bits get: %d \n",options.c_cflag);

    sleep(1);
    options.c_cflag &= ~PARENB; 
    options.c_cflag &= ~CSTOPB; 
    options.c_cflag &= ~CSIZE; 
    options.c_cflag |= CS8; 
    options.c_cflag &= ~CRTSCTS; 

    options.c_cc[VMIN] = 1; 
    options.c_cc[VTIME] = 0; 
    options.c_cflag |= CLOCAL | CREAD;

    if (data_bit == 7) {
        options.c_cflag &= ~CS8;
        options.c_cflag |= CS7;
    }

    if (stop_bit == 1) {
        printf("Stop Bit enable to two stop bits\n");
        options.c_cflag |= CSTOPB;
    }

    if (parity == 1) {
        options.c_cflag |= PARODD;
    } else if (parity == 2){
        options.c_cflag |= PARENB;
    }

    if (hardware_flow == 1) {
        options.c_cflag |= CRTSCTS;
    }

    cfsetispeed(&options, baudrate);
    cfsetospeed(&options, baudrate);

    printf("Bits set: %d \n",options.c_cflag);
    if ((rc = tcsetattr(uart, TCSANOW, &options)) < 0) { 
        printf("UART error in tcsetattr \n");
    }

    if ((rc = tcgetattr(uart,&options)) < 0){
    printf("failed to get attr\n");
    }
    printf("Bits end: %d \n",options.c_cflag);

}

int main(int argc,char** argv)
{
    speed_t baudrate =B115200;
    int data_bit=8;
    int parity=0;
    int stop_bit=0;
    int hardware_flow=0;

    open_uart();
    printf("Start Serial Port Configuration \n");
    configuration_uart(baudrate,data_bit,stop_bit,parity,hardware_flow);
    printf("New Configuration \n");
    stop_bit=1;
    configuration_uart(baudrate,data_bit,stop_bit,parity,hardware_flow);
    close_uart();
}

我可以在停止位设置为0的情况下运行代码，代码运行没有问题。但是当我将停止位更改为1时，tcsetattr不会设置options.c_cflag变量中的值。此变量显示相同的值。

以下输出来自代码：

Start Serial Port Configuration 
Bits get: 3261 
Bits set: 7346 
Bits end: 7346 
New Configuration 
Bits get: 7346 
Stop Bit enable to two stop bits
Bits set: 7410 
Bits end: 7346 
Uart was closed

感谢您的帮助

tcsetattr不能与嵌入式linux中的串口一起使用

0 个答案: