Re: RS232 Redirector Program in C using Linux

Steffen wrote:
On 21 Jan., 16:42, William Pursell <bill.purs...@xxxxxxxxx> wrote:

On Jan 21, 5:42 am, Steffen <steffen.ku...@xxxxxxxxx> wrote:


I need some help with a c program I am writing.

I can't answer your immediate questions, but I do
have a thought: you don't need to use
signals. You might be happier if you use
select/poll/epoll instead. That might simplify
the design and make it easier to track down
the error, if it doesn't eliminate the error
completely.


Really, Is this better than using the receive interrupt? ... Can some
body give me a skeleton how to do this with polling?

Have a look at the select() or poll() manual page.
In essence the difference is that rather than have signal processing cause you to read *both* fds (you must read both as you don't know which one caused the SIGIO), you create a set of fds and wait for data to be available on one of those, much like:

/*
* Setup fd1 and fd2 for the two serial ports
*/
while (keep_running) {
fd_set infds;
int nfds;

FD_CLR(&infds);
FD_SET(fd1, &infds);
FD_SET(fd2, &infds);
nfds = (fd1 > fd2) ? fd1+1 : fd2+1;

if (select(nfds, &infds, NULL, NULL, NULL) == -1) {
perror("select");
break;
}
if (FD_ISSET(fd1, &infds))
copy(fd1, fd2);
if (FD_ISSET(fd2, &infds))
copy(fd2, fd1);
}

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