RE: ISO Example for reading/writing uart/rs-232

[Chris Galas]

Hi,

I'm still having trouble with getting the read callback to fire. I've verified 
(via Realterm) that when I write my values to the file descriptor, byes are 
received on the port. So I know traffic is going back and forth, but I can't 
seem to get libev to detect a read on the file descriptor. Thanks.

#define EV_COMPAT3 0

#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <ev.h>
#include <errno.h>

    ev_io iow;
    ev_io ior;

void somecallbackwrite(ev_loop *loop, ev_io *iowatch, int revents)
{
    char buffer[10];
    char c;
    int i;
    int count;

    memset(&buffer, 0, sizeof(buffer));

    buffer[0] = 0x55;
    buffer[1] = 0xAA;
    buffer[2] = 0xFF;
    buffer[3] = 0x02;

    printf("somecallbackwrite\n");
    i = write(iowatch->fd, &buffer, 4);
    printf("write(%d) = %d\n", iowatch->fd, i);

    ev_io_stop(loop, iowatch); // stop the write watcher
    ev_io_start(loop, &ior); // start the read watcher

}

void somecallbackread(ev_loop *loop, ev_io *iowatch, int revents)
{
    char buffer[10];
    char c;
    int i = 1;
    int count;

    while (i > 0) {
        i = read(iowatch->fd, &c, 1);
        count += i;
    }
    printf("write(%d) = %d\n", iowatch->fd, i);

    ev_io_stop(loop, iowatch); // stop the read watcher
    ev_io_start(loop, &iow); // start the write watcher
}

main()
{
    ev_loop *mainloop;
    int fd;

    fd = open("/dev/ttyUSB1", O_RDWR | O_NOCTTY | O_NONBLOCK);

    if (fd >= 0) {
        mainloop = ev_default_loop(EVFLAG_AUTO);
        ev_io_init(&iow, somecallbackwrite, fd, EV_WRITE);
        ev_io_init(&ior, somecallbackread, fd, EV_READ);
        ev_io_start(mainloop, &iow);
        ev_io_start(mainloop, &ior);
        ev_run(mainloop, 0);
        close(fd);
    } else {
        printf("errno = %d\n", errno);
    }
}

-----Original Message-----
From: libev [mailto:libev-bounces+chrisg=nytec....@lists.schmorp.de] On Behalf 
Of Thilo Schulz
Sent: Monday, December 14, 2015 4:52 PM
To: libev@lists.schmorp.de
Subject: Re: ISO Example for reading/writing uart/rs-232

Hi,

wrote last source off the top of my head and the declaration of fd got lost 
while reshuffeling. This should work for real.

#define EV_COMPAT3 0

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <ev.h>

void somecallback(ev_loop *loop, ev_io *iowatch, int revents) {
        write(iowatch->fd, "booya", 5);
        ev_io_stop(loop, iowatch);
}

main()
{
        ev_io iow;
        ev_loop *mainloop;
        int fd;

        fd = open("/dev/ttyS0", O_RDWR | O_NOCTTY | O_NONBLOCK);

        if(fd >= 0)
        {
                mainloop = ev_default_loop(EVFLAG_AUTO);
                ev_io_init(&iow, somecallback, fd, EV_WRITE);
                ev_io_start(mainloop, &iow);
                ev_run(mainloop, 0);
                close(fd);
        }
}


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