此程序是(我相信)select()(在Debian for ARM上)的直接應用程序。 XBEEDEVICE指向一個串行端口。串行端口存在,並且ic連接到設備。即使緩衝區中有數據,select()也會超時
問題是,即使有數據收到,select()也會返回0。我暫時註釋掉了最後的'else',程序打印出TIMEOUT,然後是遠程設備返回的字符串。
int main(int argc, char **argv) {
int fd, c, res, n;
struct termios oldtio, newtio;
char buf[255] = {0};
fd_set input;
struct timeval timeout;
// define timeout
timeout.tv_sec = 5;
timeout.tv_usec = 0;
fd = open(XBEEDEVICE, O_RDWR | O_NOCTTY);
if(fd < 0){
perror(XBEEDEVICE);
return(-1);
}
tcgetattr(fd, &oldtio); /* save current port settings */
bzero(&newtio, sizeof(newtio));
newtio.c_cflag = CRTSCTS | CS8 | CLOCAL | CREAD;
newtio.c_iflag = IGNPAR;
newtio.c_oflag = 0;
/* set input mode (non-canonical, no echo,...) */
newtio.c_lflag = 0;
newtio.c_cc[VTIME] = 0; /* inter-character timer unused */
newtio.c_cc[VMIN] = 2; /* blocking read until 2 chars received */
tcflush(fd, TCIFLUSH);
tcsetattr(fd, TCSANOW, &newtio);
// Sending +++ within 1 second sets the XBee into command mode
printf(" Sending +++\n");
write(fd, "+++", 3);
n = select(fd, &input, NULL, NULL, &timeout);
if(n < 0)
printf("select() failed\n");
else if(n == 0)
printf("TIMEOUT\n");
//else{
res = read(fd, buf, 250);
buf[res] = 0;
printf("Received: %s\n", buf);
//}
tcsetattr(fd, TCSANOW, &oldtio);
return(0);
}
您應該爲您的問題添加更多標籤。 Stackoverflow有一個很好的系統來通知人們他們最喜歡的標籤,所以如果你添加更多相關標籤,他人會更容易找到你的問題... – 2013-02-13 03:23:21