在 C++ linux 中将字符串写入串口 [英] Writing STRINGS to serial port in C++ linux

问题描述

我知道这个问题散布在整个互联网上，但仍然没有什么能让我完全做到这一点.我想将数据写入 C++ (linux) 中的串行端口，用于 Propeller 板.从控制台获取输入时程序工作正常，但是当我向它写入字符串时，总是返回: ERROR - Invalid command 从设备.我尝试使用十六进制值创建 char 数组，然后它起作用了.这是一个工作代码，如下.但是我如何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，如果这是唯一的方法，我如何将其转换为十六进制值?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

注意:循环是使用来自控制台的用户输入.我需要的是一种将字符串变量发送到串口的方法.

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)
",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','
'};
    //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

我很高兴自己解决了问题，但对没有早点看到这个小事感到失望.默认情况下，char 在 c++ 中是 signed，这使得它的范围为 -128 到 127.但是，我们期望 ASCII 值是 0 到 255.因此它是简单的声明它是 unsigned char str[] 其他一切都应该工作.傻我，傻我.

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.

还是谢谢大家帮助我！！！

Still, Thank you everyone for helping me!!!

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