Function read_device

src/microham.c:737–881

This thread reads from the microHam device and puts data on the sockets it also issues periodic heartbeat messages it also reads the sockets if data is available

// it also reads the sockets if data is available
//
static void *read_device(void *p)
{
    unsigned char frame[4];
    int framepos = 0;
    unsigned char buf[2];
    fd_set fds;
    struct timeval tv;

    // the bytes from the microHam decive come in "frames"
    // a frame is a four-byte sequence. The first byte has the MSB unset,
    // then come three bytes with the MSB set
    // What comes here is an "infinite" loop. However this thread
    // terminates if the device is closed.
    for (;;)
    {
        int ret;
        int maxdev;

        //
        // setting uh_is_initialized to zero in the main thread
        // tells this one that it is all over now
        //
        if (!uh_is_initialized)
        {
            return NULL;
        }


#if defined(HAVE_SOCKETPAIR) && defined(HAVE_SELECT)

        //
        // This is the right place to ensure that a heartbeat is sent
        // to the microham device regularly (15 sec delay is the maximum
        // allowed, let us use 5 secs to be on the safe side).
        //
        if ((time(NULL) - lastbeat) > 5)
        {
            heartbeat();
        }

#endif

        //
        // Wait for something to arrive, either from the microham device
        // or from the sockets used for I/O from hamlib.
        // If nothing arrives within 100 msec, restart the "infinite loop".
        //
        FD_ZERO(&fds);
        FD_SET(uh_device_fd, &fds);
        FD_SET(uh_radio_pair[0], &fds);
        FD_SET(uh_ptt_pair[0], &fds);
        FD_SET(uh_wkey_pair[0], &fds);

        // determine max of these fd's for use in select()
        maxdev = uh_device_fd;

        if (uh_radio_pair[0] > maxdev)
        {