Kommunikation mit Seriellem Gerät

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


using namespace std;


char *buffer;
char* szData;
int write_size=0,read_size=0;


int main()


{
  int rs232ali=open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NONBLOCK);
  if (rs232ali == -1 ) { perror("open_port: Unable to open /dev/ttyS0"); }
  else { printf("Port RS232 has been sucessfully opened and %d is the value of open()\n",rs232ali); }
  szData="MR\n";
  cout<<"folgender Befehl wird gesendet: "<<szData<<endl;


 
  write_size=write( rs232ali, szData, sizeof(szData));
  if(write_size==-1) { printf( "Error writing: %s\n", strerror( errno ) );}
  else {  cout<<"Bytes written: write_size="<<write_size<<endl;}


  for(int e=0;e<1e7;e++){} //wait some time
  cout << "rs232ali = "<<rs232ali << endl;

  //read_size=read("/dev/ttyS0",buffer,10);
  read_size=read(rs232ali,buffer,10);
  if(read_size==-1) { printf( "Error reading: %s\nBuffer= %s\n", strerror( errno ),buffer);}
  else {cout<<"Bytes read: read_size="<<read_size<<endl;printf("Position Achse1 = %d\n",buffer);}
 
  close(rs232ali);
}

#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 <termios.h> /* POSIX terminal control definitions */


int writeport(int rs232, char *chars);
int readport(int rs232, char *result);
int getbaud(int rs232);
int initport(int rs232);
int rs232;
int wtm=900000; //set wait time between write and read


int main(int argc, char **argv) {
	rs232 = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NONBLOCK);
	if (rs232 == -1) {
		perror("open_port: Unable to open /dev/ttyS0: ");
		return 1;
	} else {
		perror("Open Port /dev/ttyS0: ");
		// fcntl(rs232, F_SETFL, 0);
		}
	int old_baud=getbaud(rs232);
	initport(rs232);
	printf("baud=%d\n", old_baud);
	if(getbaud(rs232)==old_baud){}
	else printf("new baud=%d\n", getbaud(rs232));
	char sCmd[254];
	for(int i=0;i<254;i++){sCmd[i]=0x00;}
/*	sCmd[0] = 0x4D;
	sCmd[1] = 0x52;
	sCmd[2] = 0x3B;
	sCmd[3] = 0x4D;
	sCmd[4] = 0x4F;
	sCmd[5] = 0x3B;*/
	sCmd[0] = 0x31;
	sCmd[1] = 0x54;
	sCmd[2] = 0x50;

	if (!writeport(rs232, sCmd)) {
		printf("write failed!\n");
		close(rs232);
		return 1;
	}


	printf("written: %s\n", sCmd);
	printf("wait %i ms\n",wtm/1000);
	usleep(wtm);
	char sResult[254];
	fcntl(rs232, F_SETFL, FNDELAY); // don't block serial read
	if (!readport(rs232,sResult)) {
		printf("READING of SERIAL PORT FAILED\n");
		close(rs232);
		return 1;
	}
	printf("readport = %s\n", sResult);
	close(rs232);
	return 0;
}


int initport(int rs232) {
	struct termios options;
	// Get the current options for the port...
	tcgetattr(rs232, &options);
	// Set the baud rates to 19200...
	cfsetispeed(&options, B19200);		/*sets the input baud rate stored in the structure pointed to by termios_p to speed.*/
	cfsetospeed(&options, B19200);		/*shall set the output baud rate stored in the structure pointed to by termios_p to speed.*/
	// Enable the receiver and set local mode...
	options.c_cflag |= (CLOCAL | CREAD);	/* Enable receiver, set local */


	options.c_cflag &= ~PARENB;	/* Clear parity enable */
	options.c_cflag &= ~CSTOPB;	/*That clears the bits which cause a 2 bit wide stop bit.*/
	options.c_cflag &= ~CSIZE;	/*This clears all of the bits which determine data length. */
	options.c_cflag |= CS7;		/*This sets bits to enable 7 bit data. */


	// Set the new options for the port...
	tcsetattr(rs232, TCSANOW, &options);	/*TCSANOW: sets terminal attributes immediately.*/
	return 1;
}




int writeport(int rs232, char *chars) {
	int len = strlen(chars); //len is the length of the string chars.
	chars[len] = 0x0D; // stick a <CR> after the command
	chars[len+1] = 0x00; // terminate the string properly
	int n = write(rs232, chars, strlen(chars));
	if (n < 0) {
		return 0;
	}
	return 1;                                                                       	                                
}


int readport(int rs232, char *result) {
	int bytes_read = read(rs232, result, 254);
	result[bytes_read-1] = 0x00;
	if (bytes_read == -1) {
		/*if (errno == EAGAIN) {
			printf("SERIAL EAGAIN ERROR\n");
			return 0;
		} else {*/
			printf("FATAL READ ERROR Nr. %d: %s\n", errno, strerror(errno));
			return 0;
		}
	//}                    
	return 1;
}


int getbaud(int rs232) {
	struct termios termAttr;
	int inputSpeed = -1;
	speed_t baudRate;
	tcgetattr(rs232, &termAttr);
	/* Get the input speed.                              */
	baudRate = cfgetispeed(&termAttr);
	switch (baudRate) {
		case B0:      inputSpeed = 0; break;
		case B50:     inputSpeed = 50; break;
		case B110:    inputSpeed = 110; break;
		case B134:    inputSpeed = 134; break;
		case B150:    inputSpeed = 150; break;
		case B200:    inputSpeed = 200; break;
		case B300:    inputSpeed = 300; break;
		case B600:    inputSpeed = 600; break;
		case B1200:   inputSpeed = 1200; break;
		case B1800:   inputSpeed = 1800; break;
		case B2400:   inputSpeed = 2400; break;
		case B4800:   inputSpeed = 4800; break;
		case B9600:   inputSpeed = 9600; break;
		case B19200:  inputSpeed = 19200; break;
		case B38400:  inputSpeed = 38400; break;
		case B57600:  inputSpeed = 57600; break;
	}
	return inputSpeed;
}