poll() is not reccomended. On many systems it can't work on devices at all.
serial devices have their own read timeouts, in any case, you could perhaps use those. See man termios.
Of course, you'd have to set them up using the termios calls you're not sure are working yet. Seriously, it would be really useful to know if those worked at all.
Understand that, since we don't have your device handy to test with, it's really hard for us to tell at a distance. I'd really hoped you were having trouble with your setup instead.
From man termios:
Code:
Canonical and non-canonical mode
The setting of the ICANON canon flag in c_lflag determines whether the
terminal is operating in canonical mode (ICANON set) or non-canonical
mode (ICANON unset). By default, ICANON set.
In canonical mode:
* Input is made available line by line. An input line is available
when one of the line delimiters is typed (NL, EOL, EOL2; or EOF at
the start of line). Except in the case of EOF, the line delimiter is
included in the buffer returned by read(2).
* Line editing is enabled (ERASE, KILL; and if the IEXTEN flag is set:
WERASE, REPRINT, LNEXT). A read(2) returns at most one line of
input; if the read(2) requested fewer bytes than are available in the
current line of input, then only as many bytes as requested are read,
and the remaining characters will be available for a future read(2).
In non-canonical mode input is available immediately (without the user
having to type a line-delimiter character), and line editing is dis-
abled. The settings of MIN (c_cc[VMIN]) and TIME (c_cc[VTIME]) deter-
mine the circumstances in which a read(2) completes; there are four
distinct cases:
* MIN == 0; TIME == 0: If data is available, read(2) returns immedi-
ately, with the lesser of the number of bytes available, or the num-
ber of bytes requested. If no data is available, read(2) returns 0.
* MIN > 0; TIME == 0: read(2) blocks until the lesser of MIN bytes or
the number of bytes requested are available, and returns the lesser
of these two values.
* MIN == 0; TIME > 0: TIME specifies the limit for a timer in tenths of
a second. The timer is started when read(2) is called. read(2)
returns either when at least one byte of data is available, or when
the timer expires. If the timer expires without any input becoming
available, read(2) returns 0.
* MIN > 0; TIME > 0: TIME specifies the limit for a timer in tenths of
a second. Once an initial byte of input becomes available, the timer
is restarted after each further byte is received. read(2) returns
either when the lesser of the number of bytes requested or MIN byte
have been read, or when the inter-byte timeout expires. Because the
timer is only started after the initial byte becomes available, at
least one byte will be read.
So you'd want to add these to your setup:
Code:
bool cClassSerialLIB::OpenPort(bool bloccante)
{
// make sure port is closed
ClosePort();
//ttymxc4
QByteArray Porta_byte_array = Porta.toLatin1();
const char* Porta_char=Porta_byte_array.data();
fd = open(Porta_char/*"/dev/ttymxc4"*/, O_RDWR |
O_NOCTTY | /* tells UNIX that this program doesn't want to be the "controlling terminal" for that port*/
O_NDELAY); /* tells UNIX that this program doesn't care what state the DCD signal line is in */
if (fd < 0)
{
qDebug("errore in apertura %d %s\n", errno, strerror(errno));
return false;
}
else
{
qDebug("ok %d",fd);
struct termios options;
/* The FNDELAY option causes the read function to return 0 if no
characters are available on the port. To restore normal (blocking) behavior,
call fcntl() without the FNDELAY option: */
if(bloccante)
{
printf("bloccante\n");
fcntl(fd, F_SETFL, 0);
}
else
{
printf("NON bloccante");
fcntl(fd, F_SETFL, FNDELAY);
}
//cfmakeraw(&options); //ABILITARLO NEL CASO DI ERRORE!
tcgetattr(fd, &options);
//set port speed 115200
cfsetispeed(&options, B115200);
cfsetospeed(&options, B115200);
options.c_cflag |= (CLOCAL | CREAD);
//set 8n1
options.c_cflag &= ~PARENB; /* Enable parity bit */
options.c_cflag &= ~CSTOPB; /* 2 stop bits (1 otherwise) */
options.c_cflag &= ~CSIZE; /* Mask the character size bits */
options.c_cflag |= CS8; /* Select 8 data bits */
options.c_iflag &= ~IXON; //RIMUOVE X0N/XOFF control
options.c_iflag &= ~IXOFF;
options.c_iflag &= ~IGNCR;
//set raw input
options.c_lflag &= ~(ICANON | /*Enable canonical input (else raw)*/
ECHO | /*Enable echoing of input characters*/
ECHOE | /*Echo erase character as BS-SP-BS*/
ISIG); /*Enable SIGINTR, SIGSUSP, SIGDSUSP, and SIGQUIT signals*/
options.c_cc[VMIN]=0;
options.c_cc[VTIME]=5; // For half-second timeout
tcsetattr(fd, TCSANOW, &options); /*Make changes now without waiting for data to complete*/
}
return true;
}
...and then read() will timeout by itself in the manner described above.
What do do with it depends on what you need.
Does the device write entire lines, or just a stream without newlines?
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