rs485通讯协议代码详解

RS485通讯协议是一种常用的串行通讯协议，常用于工业自动化、仪器仪表等领域。下面是一个简单的RS485通讯协议代码示例：

1. 定义通讯参数

#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyS1"
#define _POSIX_SOURCE 1 /* POSIX compliant source */
#define FALSE 0
#define TRUE 1

2. 打开串口

int fd; /* file descriptor for the port */
int open_port(void)
{
    fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY | O_NDELAY);
    if (fd == -1)
    {
        /* Could not open the port. */
        perror("open_port: Unable to open /dev/ttyS1 - ");
    }
    else
        fcntl(fd, F_SETFL, 0);
    return (fd);
}

3. 配置串口参数

void configure_port(int fd)
{
    struct termios oldtio, newtio;
    tcgetattr(fd, &oldtio); /* save current port settings */

    bzero(&newtio, sizeof(newtio));
    newtio.c_cflag = BAUDRATE | CS8 | CLOCAL | CREAD;
    newtio.c_iflag = IGNPAR;
    newtio.c_oflag = 0;

    /* set input mode (non-canonical, no echo,...) */
    newtio.c_lflag = 0;

    newtio.c_cc[VTIME] = 0; /* inter-character timer unused */
    newtio.c_cc[VMIN] = 1;  /* blocking read until 1 character arrives */

    tcflush(fd, TCIFLUSH);
    tcsetattr(fd, TCSANOW, &newtio);
}

4. 发送数据

void send_data(int fd, char *data)
{
    int len = strlen(data);
    int n = write(fd, data, len);
    if (n < 0)
        fputs("write() of bytes failed!\n", stderr);
}

5. 接收数据

void receive_data(int fd, char *buffer, int size)
{
    int n = read(fd, buffer, size);
    if (n < 0)
        fputs("read failed!\n", stderr);
    else
        buffer[n] = '\0';
}

以上是一个简单的RS485通讯协议代码示例，可以根据实际情况进行修改和完善。