modbus rtu主站从站源码

以下是一个简单的Modbus RTU主站和从站的示例代码：

主站代码：

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

#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyS0"
#define _POSIX_SOURCE 1 /* POSIX compliant source */
#define FALSE 0
#define TRUE 1

int fd; /* File descriptor for the port */
struct termios oldtio, newtio;

unsigned char query[8] = {0x01, 0x03, 0x00, 0x00, 0x00, 0x01, 0x85, 0xDB};
unsigned char response[256];
int query_length = 8;
int response_length = 0;

void open_port(void)
{
  fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY | O_NDELAY);
  if (fd < 0)
  {
    perror("open_port: Unable to open /dev/ttyS0 - ");
    exit(1);
  }
}

void set_options(void)
{
  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;
  newtio.c_lflag = 0; /* No local echo */
  newtio.c_cc[VTIME] = 0; /* Wait indefinitely */
  newtio.c_cc[VMIN] = 1; /* Wait for at least one character */
  tcflush(fd, TCIFLUSH);
  tcsetattr(fd, TCSANOW, &newtio);
}

void send_query(void)
{
  int n = write(fd, query, query_length);
  if (n < 0)
  {
    perror("write() failed - ");
    exit(1);
  }
}

void read_response(void)
{
  int n = read(fd, response, 256);
  if (n < 0)
  {
    perror("read() failed - ");
    exit(1);
  }
  response_length = n;
}

void print_response(void)
{
  printf("Response: ");
  for (int i = 0; i < response_length; i++)
  {
    printf("%02X ", response[i]);
  }
  printf("\n");
}

void close_port(void)
{
  tcsetattr(fd, TCSANOW, &oldtio);
  close(fd);
}

int main(void)
{
  open_port();
  set_options();

  send_query();
  sleep(1); /* Wait for response */
  read_response();
  print_response();

  close_port();
  return 0;
}

从站代码：

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

#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyS0"
#define _POSIX_SOURCE 1 /* POSIX compliant source */
#define FALSE 0
#define TRUE 1

int fd; /* File descriptor for the port */
struct termios oldtio, newtio;

unsigned char query[8] = {0x01, 0x03, 0x00, 0x00, 0x00, 0x01, 0x85, 0xDB};
unsigned char response[256];
int query_length = 8;
int response_length = 0;

void open_port(void)
{
  fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY | O_NDELAY);
  if (fd < 0)
  {
    perror("open_port: Unable to open /dev/ttyS0 - ");
    exit(1);
  }
}

void set_options(void)
{
  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;
  newtio.c_lflag = 0; /* No local echo */
  newtio.c_cc[VTIME] = 0; /* Wait indefinitely */
  newtio.c_cc[VMIN] = 1; /* Wait for at least one character */
  tcflush(fd, TCIFLUSH);
  tcsetattr(fd, TCSANOW, &newtio);
}

void read_query(void)
{
  int n = read(fd, query, 256);
  if (n < 0)
  {
    perror("read() failed - ");
    exit(1);
  }
  query_length = n;
}

void process_query(void)
{
  /* Process the query */
  /* In this example, we simply echo the query back as the response */
  response_length = query_length;
  memcpy(response, query, response_length);
}

void send_response(void)
{
  int n = write(fd, response, response_length);
  if (n < 0)
  {
    perror("write() failed - ");
    exit(1);
  }
}

void close_port(void)
{
  tcsetattr(fd, TCSANOW, &oldtio);
  close(fd);
}

int main(void)
{
  open_port();
  set_options();

  while (1)
  {
    read_query();
    process_query();
    send_response();
  }

  close_port();
  return 0;
}

这些代码只是示例，需要根据你的具体需求进行修改。请注意，这些代码仅适用于Linux操作系统，如果你使用其他操作系统，请根据其API进行修改。