more upgrade

src/usb_prop.c

@@ -228,7 +228,7 @@ gnuk_setup (uint8_t req, uint8_t req_no,
 	      if (addr < &_regnual_start || addr + len > &__heap_end__)
 		return USB_UNSUPPORT;
 
-	      if (index == 0)
+	      if (index == 0 && len != 256)
 		memset (addr, 0, 256);
 	      usb_lld_set_data_to_recv (addr, len);
 	      return USB_SUCCESS;