串口二进制传输改回车

Question

过去一周我一直在尝试用 C 语言实现一个原始的串行文件传输协议，但我遇到了一个非常奇怪的问题，我似乎无法在线找到解决方案。 我设法通过串行端口传输二进制数据并接收它，但在此过程中，所有“0D”字节都转换为“0A”。 以下是我的代码。

#include <stdlib.h>
#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 <signal.h>
#include <sys/ioctl.h>
#include <termios.h>

//eventually plan to set up a proper communication protocol
#define ACK 0x01 
#define NAK 0x00

int setAttribs (int fd, int speed, int parity);
unsigned char* readFile(char* filename, int* file_size);

int main(void){

    //set up ports
    int fd = 0, r = 0, i = 0;
    fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY | O_NDELAY);//sending port
    if(fd<0){
            perror("open port ttyUSB0 failed");
            return -1;
    }
    setAttribs(fd,1500000,0);

    int rd =0, file_size=0, bytes=0;
    rd = open("/dev/ttyUSB1", O_RDWR | O_NOCTTY | O_NDELAY);//receiving port
    setAttribs(rd,1500000,0);

    //create file to which the binary data will be written
    FILE *newFile;
    newFile = fopen("t.bin","wb");
    if(newFile<0){
            printf("open file failed\n");
            return -1;
    }

    //This character array will hold the file to be transferred
    unsigned char* data = '\0';
    data = readFile("t.odt", &file_size);

    ioctl(rd, TCFLSH, &bytes);//port flush which does not seem to work      
    do{

            //write data in 1024 byte chunks
            write(fd,data+i,1024);

            //wait for write to finish
            usleep(8500);

            //buffer to hold received bytes
            unsigned char buffer[1024];

            //ensure buffer is empty
            memset(buffer,0,1024);

            //read in 1024 byte chunks
            read(rd, buffer, 1024);

            //printing bytes in the buffer to check for errors
            for(r=0;r<1024;r++){
                    if(r%16==0)
                            printf("\n");
                    printf("%02X ", buffer[r]);
            }

            //write to file in 1024 byte chunks
            fwrite(buffer, 1,1024,newFile);

            //increase counter
            i+=1024;

    }while(i<8197);//its an 8088 byte file  
    printf("Done!\n");
    return 0;
}

unsigned char* readFile(char* filename, int* file_size){

    unsigned char *buffer = NULL;
    int string_size, i;
    FILE *handler = fopen(filename, "rb");

    if (handler)
    {
            // Seek the last byte of the file
            fseek(handler, 0, SEEK_END);
            // Offset from the first to the last byte, or in other words, filesize
            string_size = ftell(handler);
            printf("File length: %d\n",string_size);
            *file_size = string_size;
            // go back to the start of the file
            rewind(handler);

            // Allocate a string that can hold it all
            buffer = (unsigned char*) malloc(sizeof(unsigned char) * (string_size + 1) );

            // Read it all in one operation
            for(i=0;i<string_size;i++){
                    fread(buffer+i, sizeof(unsigned char),1, handler);
                    if(i%16==0)
                            printf("\n");
                    printf("%02X ",*(buffer+i));
            }
            // fread doesn't set it so put a \0 in the last position
            // and buffer is now officially a string
            //      buffer[string_size] = '\0';
            printf("Finished read\n");

            // Always remember to close the file
            fclose(handler);
    }
 return buffer;
}
int setAttribs (int fd, int speed, int parity)
{
    struct termios tty;
    memset (&tty, 0, sizeof tty);
    if (tcgetattr (fd, &tty) != 0)
    {
            fputs("error %d from tcgetattr", stderr);

    }
    cfsetospeed (&tty, speed);
    cfsetispeed (&tty, speed);

    tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
    // disable IGNBRK for mismatched speed tests; otherwise receive break
    // as \000 chars
    tty.c_iflag &= ~IGNBRK;         // disable break processing
    tty.c_lflag = 0;                // no signaling chars, no echo,
    // no canonical processing
    tty.c_oflag = 0;                // no remapping, no delays
    tty.c_cc[VMIN]  = 0;            // read doesn't block
    tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout

    tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl

    tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
    // enable reading
    tty.c_cflag &= ~(PARENB | PARODD);      // shut off parity
    tty.c_cflag |= parity;
    tty.c_cflag &= ~CSTOPB;
    tty.c_cflag &= ~CRTSCTS;

    if (tcsetattr (fd, TCSANOW, &tty) != 0)
    {
            fputs("error %d from tcsetattr", stderr);

    }
    return 1;
}
                                                                                                                                                                                                                                         

它所做的只是在一个端口上写入 USB 串行转换器，然后在另一个端口上读取。 我只是用一个 8088 字节（Hello World）的 ODT 文件测试它，并尝试了不同的波特率和写入块大小。 经过反复试验，我发现这种配置（1500000 bps 和 1024 字节块）既快又相对更可靠。 唯一的错误如下所示。

传输字节数：70 6E 67 89 50 4E 47 0D 0A 1A 0A 00 00 00 0D 49

接收字节数：70 6E 67 89 50 4E 47 0A 0A 1A 0A 00 00 00 0A 49

如您所见，所有“0D”字节都更改为“0A”。 我尝试了更低的波特率和更小的块大小，但问题仍然存在。 据我了解，它们分别是回车和换行值，换行作为Linux中异步通信的控制值； 但我不明白为什么这会影响回车值。 串口通信中回车有什么特殊意义吗？ 在这种情况下，有没有办法发送“0D”字节？

TL;DR：原始串行通信导致“0D”字节被“0A”替换。 知道为什么吗？ 有什么办法解决吗？

Answer 1

非常感谢它起作用了！！ 我从来不知道有 ICRNL 选项可以将换行符转换为回车符。 一旦我设置了那个和其他人

tty.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR | IGNCR | ICRNL | IXON); //tty is the name of the struct termios

它是金色的。