modem_open()

Open a serial port

Synopsis:

#include <sys/modem.h>

int modem_open( char* device, 
                speed_t baud );

Arguments:

device
The path name of the serial port that you want to open.
baud
Zero, or the baud rate that you want to use.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

This function is in libc.a, but not in libc.so (in order to save space).

Description:

The modem_open() function opens a serial port identified by device. The device is set to raw mode by changing the control flags using tcgetattr() and tcsetattr() as follows:

termio.c_cflag = CS8|IHFLOW|OHFLOW|CREAD|HUPCL;
termio.c_iflag = BRKINT;
termio.c_lflag = IEXTEN;
termio.c_oflag = 0;

Any pending input or output characters are discarded.

If baud is nonzero, then the baud rate is changed to that value.

Returns:

An open file descriptor, or -1 on failure ( errno is set).

Errors:

EACCES
Search permission is denied on a component of the path prefix, or the file doesn't exist.
EBADFSYS
While attempting to open the named file, either the file itself or a component of the path prefix was found to be corrupted. A system failure — from which no automatic recovery is possible — occurred while the file was being written to, or while the directory was being updated. You'll need to invoke appropriate systems-administration procedures to correct this situation before proceeding.
EBUSY
The file named by device is a block special device that's already open for writing, or device names a file that's on a filesystem mounted on a block special device that's already open for writing, or device is in use.
EINTR
The open operation was interrupted by a signal.
EISDIR
The named device is a directory.
ELOOP
Too many levels of symbolic links or prefixes.
EMFILE
Too many file descriptors are currently in use by this process.
ENAMETOOLONG
The length of the device string exceeds PATH_MAX, or a pathname component is longer than NAME_MAX.
ENFILE
Too many files are currently open in the system.
ENOENT
The named device doesn't exist, or the path argument points to an empty string.
ENOSYS
The modem_open() function isn't implemented for the filesystem specified in device.
ENOTDIR
A component of the path prefix isn't a directory.
ENXIO
No process has the file open for reading.

Examples:

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <sys/modem.h>
#include <stdio.h>
#include <errno.h>

/*
 curstate curflags newstate newflags newtimeout 
 newquiet retvalue pattern response
*/

struct modem_script table[] ={
  {1, 0,            1, 0,              2,  5, 0,
   NULL,              "ATZ\\r\\P0a"},
  {1, 0,            2, 0,              30, 5, 0,
   "*ok*",            "ATDT5910934"},
  {2, MODEM_BAUD,   3, MODEM_LASTLINE, 10, 5, 0,
   "*connect*",       NULL},
  {3, 0,            4, 0,              8,  5, 0,
   "*login:*",        "guest"},
  {4, MODEM_NOECHO, 5, 0,              15, 5, 0,
   "*password:*",     "xxxx"},
  {5, 0,            0, 0,              0,  0, 0,
   "*$ *",            NULL},
  {0, 0,            0, 0,              0,  0, 1,
   "*no carrier*",    NULL},
  {0, 0,            0, 0,              0,  0, 2,
   "*no answer*",     NULL},
  {0, 0,            0, 0,              0,  0, 3,
   "*no dialtone*",   NULL},
  {0, 0,            0, 0,              0,  0, 4,
   "*busy*",          NULL},
  { NULL }
};

void io(char* progress, char* in, char* out) {

    if(progress)
        printf("progress: %s\n", progress);    

    if(in)
        printf("input: %s\n", in);    

    if(out)
        printf("output: %s\n", out);    
}


int main(int argc, char* argv[]) {
    int        fd, status;
    speed_t    baud = -1;

    if((fd = modem_open(argv[1], 0)) == -1) {
        fprintf(stderr, "Unable to open %s: %s\n",
                argv[1], strerror(errno));
        exit(1);
    }

    status = modem_script( fd, table, &baud, 
                           &io, NULL );
    printf("status=%d  baud=%d\n", status, baud);
    exit(status);
}

Classification:

QNX Neutrino

Safety:  
Cancellation point Yes
Interrupt handler No
Signal handler Yes
Thread Yes

Last modified: 2013-12-23

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