Use the POSIX serial i/o ioctl stuff. Makes it portable. Have not worried
about flow control, but at the bottom is some snippets of C code I wrote 6
years or so ago to do IXO/TAPI alpha paging. The concept is similar. These
snippets just open the serial port ("modem"), send, and get data to/from
the port. There is a lot more to do, e.g., checking for locks to see if
device is in use, setting a lock, etc. [Note all the ifdef's for BSD, since
BSD was not POSIX compliant].
- rick
On Tue, 10 Sep 2002, [iso-8859-1] cana rich wrote:
>
> To ansmer yours questions, i would like to make a C or C++ program which
>communicate via the serial port COM1 to a device. The device is a screen plasma. I
>would like the program to remote the sreen : switch on, switch off, change channel ...
> The serial communication setting is :
> Baud : 4800 BPS
> Data length : 8 bits
> Parity : none
> Stop bit : 1 bit
> Flow control RTS/CTS
> Communication code : ASCII code
> Reception time out : 4 seconds
> To do it, I need to send ASCII code. For exemple, to switch off the screen i must
>send the "%A0001" code.
> I need to receive the acknoledgment to know if it has been well done. (code for good
>receive : "@S")
> Thanks for your help.
> Canarich
-------------------------------------------------------------------
char *modem = "/dev/ttyS1";
/* ***********************************************************
Function: initmodem
Purpose: Initialize modem device.
Returns: File descriptor for device.
************************************************************** */
int
initmodem(char *dev)
{
struct termios modemioctl;
int modem, ioctlres;
errno = 0;
#ifdef DEBUG
printf("Initializing modem\n");
#endif
modem = open(dev, O_RDWR, 0);
if (errno || modem < 1) {
stop_and_exit(modem, NOTOPEN, 7);
}
errno = 0;
#ifdef DEBUG
printf("Modem fd is %d\n",modem);
#endif
#ifdef BSD
ioctlres = tcgetattr(modem,&modemioctl);
#else
ioctlres = ioctl(modem,TCGETS,&modemioctl);
#endif
if (errno || ioctlres < 0) {
stop_and_exit(modem, NOINIT, 8);
}
modemioctl.c_iflag |= IGNBRK; /* ignore breaks */
modemioctl.c_iflag &= ~INPCK; /* ignore parity errors */
modemioctl.c_iflag |= ISTRIP; /* strip 8th bit */
modemioctl.c_iflag &= ~INLCR; /* no CR to NL xltn */
modemioctl.c_iflag &= ~ICRNL; /* no CR to NL xltn */
modemioctl.c_iflag &= ~IGNCR; /* do not ignore CR */
modemioctl.c_oflag &= ~OPOST;
#ifdef BSD
cfsetspeed(&modemioctl, (speed_t) BAUDRATE);
#else
modemioctl.c_cflag &= ~CBAUD; /* set baud rate */
modemioctl.c_cflag |= BAUDRATE;
#endif
modemioctl.c_cflag &= ~CSIZE;
modemioctl.c_cflag |= CS7; /* 7 bit */
modemioctl.c_cflag &= ~CSTOPB; /* 1 stop bit */
modemioctl.c_cflag |= PARENB;
modemioctl.c_cflag &= ~PARODD; /* even parity */
#ifdef BSD
cfsetspeed(&modemioctl, (speed_t) BAUDRATE);
#else
modemioctl.c_cflag &= ~CBAUD; /* set baud rate */
modemioctl.c_cflag |= BAUDRATE;
#endif
modemioctl.c_cflag &= ~CSIZE;
modemioctl.c_cflag |= CS7; /* 7 bit */
modemioctl.c_cflag &= ~CSTOPB; /* 1 stop bit */
modemioctl.c_cflag |= PARENB;
modemioctl.c_cflag &= ~PARODD; /* even parity */
modemioctl.c_cflag |= HUPCL; /* hang up */
modemioctl.c_cflag |= CRTSCTS; /* hardware handshaking */
modemioctl.c_cc[VMIN] = 0; /* read() as few as 0 bytes */
modemioctl.c_cc[VTIME] = 50; /* 5 second timeout */
modemioctl.c_lflag &= ~ISIG; /* no signals */
modemioctl.c_lflag &= ~ICANON; /* no signals */
modemioctl.c_lflag &= ~ECHO; /* no echo */
#ifdef BSD
ioctlres = tcsetattr(modem,TCSANOW, &modemioctl);
#else
ioctlres = ioctl(modem, TCSETS, &modemioctl);
#endif
#ifdef DEBUG
printf("Modem initialization complete. fd is: %d\n",modem);
printf("Error value is: %d\n",errno);
#endif
if (errno || ioctlres < 0) {
stop_and_exit(modem, NOINIT, 8);
}
return (modem);
}
/* ***********************************************************
Function: senddata
Purpose: Send data, CR terminated, to the modem device.
Returns: Number of bytes written.
************************************************************** */
int
senddata(int modem, char *str)
{
int numsent;
char packet[MAXSIZE+2];
sprintf(packet,"%s\r",str);
numsent = write(modem, packet, strlen(packet));
return(numsent);
}
/* ***********************************************************
Function: getdata()
Purpose: Reads input from the modem device, ignoring CR and LF.
Returns: Length of the string read.
************************************************************** */
int
getdata(int modem, char *str)
{
char c;
char *packet;
int numread;
packet = str;
while(read(modem,&c,1) == 1)
{
#ifdef DEBUG
if ( isprint(c) )
printf("%c ",c);
else
printf("%x ",c);
#endif
switch(c) {
case LF : break;
case CR : break;
default : *packet = c;
++packet;
break;
}
}
*packet = EOS;
#ifdef DEBUG
printf("\n");
#endif
return(strlen(str));
}
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