revert null frame to zero length

diff --git a/hmcfgusb.c b/hmcfgusb.c
index 0857a4b..6df2bca 100644 (file)
--- a/hmcfgusb.c
+++ b/hmcfgusb.c
@@ -150,7 +150,7 @@ int hmcfgusb_send_null_frame(struct hmcfgusb_dev *usbdev, int silent)
 
        memset(out, 0, sizeof(out));
 
-       err = libusb_interrupt_transfer(usbdev->usb_devh, EP_OUT, out, sizeof(out), &cnt, USB_TIMEOUT);
+       err = libusb_interrupt_transfer(usbdev->usb_devh, EP_OUT, out, 0, &cnt, USB_TIMEOUT);
        if (err && (!silent)) {
                fprintf(stderr, "Can't send null frame: %s\n", usb_strerror(err));
                return 0;