I want to use a USB modem-like device on my DS411slim. It is a ADS-B receiver and there is a tutorial available http://translate.google.de/translate?hl ... technology (translated from Russian). I tested the module that is offered there for download and I also compiled the necessary CDC-ACM module from the sources provided by Synology. Both have the same size and I can load either module and my USB device also gets recognized. However, if I want to access it (e.g. cat /dev/ttyACM0) I always get a "Input/Output error". The device works under windows, Mac OS and Ubuntu so I think I can rule out a device specific issue. The question is: are there any known limitations of the USB ports of the DS411slim?