字符串写入到串行端口在C ++中的Linux [英] Writing STRINGS to serial port in C++ linux

问题描述

我知道这个问题是分散在互联网上，不过，没有什么是让我完全还没有。我想将数据写入到C ++（Linux版）的一个螺旋桨板上的串行端口。从控制台输入取程序时工作正常，但是当我写字符串它总是返回：错误 - 无效的命令从设备。我尝试创建字符的数组十六进制值，然后它的工作。这里有一个工作code，下文。但是我怎么能够只提供命令的字符串变量，并将其发送到串行端口？也许，你怎么把它转换成十六进制值，如果它是唯一的方法？谢谢大家。

I know this question is scattered all over the internet, but still, nothing is getting me completely there yet. I want to write data to a serial port in C++ (linux) for a a Propeller board. Program works fine when taking input from the console, but when I write strings to it always return: ERROR - Invalid command from the device. I tried creating array of char with Hex values then it worked. here's a working code, below. But how will i be able to just provide a string variable of command and send it to the serial port? perhaps, how do you I convert it to hex values if it's the only way? Thanks everyone

请注意：该循环使用从控制台的用户输入。我需要的是一个字符串变量发送到串行端口的方式。

note: the loop is to use user input from console. What i need is a way to send a string variable to the serial port.

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>

int main(int argc,char** argv){
    struct termios tio;
    struct termios stdio;
    int tty_fd;
    fd_set rdset;

    unsigned char c='D';

    printf("Please start with %s /dev/ttyS1 (for example)\n",argv[0]);
    memset(&stdio,0,sizeof(stdio));
    stdio.c_iflag=0;
    stdio.c_oflag=0;
    stdio.c_cflag=0;
    stdio.c_lflag=0;
    stdio.c_cc[VMIN]=1;
    stdio.c_cc[VTIME]=0;
    tcsetattr(STDOUT_FILENO,TCSANOW,&stdio);
    tcsetattr(STDOUT_FILENO,TCSAFLUSH,&stdio);
    fcntl(STDIN_FILENO, F_SETFL, O_NONBLOCK);       // make the reads non-blocking

    memset(&tio,0,sizeof(tio));
    tio.c_iflag=0;
    tio.c_oflag=0;
    tio.c_cflag=CS8|CREAD|CLOCAL;           // 8n1, see termios.h for more information
    tio.c_lflag=0;
    tio.c_cc[VMIN]=1;
    tio.c_cc[VTIME]=5;

    tty_fd=open(argv[1], O_RDWR | O_NONBLOCK);      
    cfsetospeed(&tio,B115200);            // 115200 baud
    cfsetispeed(&tio,B115200);            // 115200 baud

    tcsetattr(tty_fd,TCSANOW,&tio);

    //char str[] = {'V','E','R','\r'};
    //the above str[] doesn't work although it's exactly the same as the following
    char str[] = {0x56, 0x45, 0x52, 0x0D}; 
    write(tty_fd,str,strlen(str));
    if (read(tty_fd,&c,1)>0)
        write(STDOUT_FILENO,&c,1);

    while (c!='q')
    {
            if (read(tty_fd,&c,1)>0)        write(STDOUT_FILENO,&c,1); // if new data is available on the serial port, print it out
            if (read(STDIN_FILENO,&c,1)>0) 
                if(c!='q')
                    write(tty_fd,&c,1);        // if new data is available on the console, send it to the serial port
    }

    close(tty_fd);

}

推荐答案

我很高兴能解决我自己的解决方案，但还没有失望，没有更快看到的小事。 字符默认情况下是签署在C ++中，这使得它保持的范围从-128到127。然而，我们期待ASCII值而0到255因此，它作为宣称它是无符号字符海峡[] 和其他一切应该工作一样简单。我傻，我傻。

I'm happy to solve my own solution but yet disappointed to not have seen the trivial matter much sooner. char by default are signed in c++, which makes it holding the range -128 to 127. However, we are expecting the ASCII values which are 0 to 255. Hence it's as simple as declaring it to be unsigned char str[] and everything else should work. Silly me, Silly me.

不过，谢谢大家对我的帮助！

Still, Thank you everyone for helping me!!!

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