return 0;
        }
 
-       usleep(1000);
-
        if (done) {
                err = libusb_interrupt_transfer(usbdev->usb_devh, EP_OUT, send_data, 0, &cnt, USB_TIMEOUT);
                if (err) {
                        fprintf(stderr, "Can't send data: %s\n", usb_strerror(err));
                        return 0;
                }
-
-               usleep(1000);
        }
 
        return 1;
        if (err != 0) {
                fprintf(stderr, "Can't submit transfer: %s\n", usb_strerror(err));
                libusb_free_transfer(transfer);
-               free(data_buf);
                return NULL;
        }
 
 
        dev->n_pfd = dev->n_usb_pfd;
 
+       quit = 0;
+
        return dev;
 }
 
                n = poll(dev->pfd, dev->n_pfd, tv.tv_sec * 1000);
                if (n < 0) {
                        perror("poll");
+                       errno = 0;
                        return -1;
                } else if (n == 0) {
                        usb_event = 1;
                                                usb_event = 1;
                                                break;
                                        } else {
+                                               errno = 0;
                                                return dev->pfd[fd_n].fd;
                                        }
                                }
                }
        }
 
-       if (quit)
+       errno = 0;
+       if (quit) {
+               fprintf(stderr, "closing device-connection due to error %d\n", quit);
                errno = quit;
+       }
 
        return -1;
 }