11 Replies Latest reply on Dec 23, 2010 2:31 PM by

    USB Stops




      We are using lots of MINI-ITX boards D945GCLF/LF2 and the common problem is usb communication interruption. We tested the same configuration with some ATX boards no problem happened. What is the main differences? May be earth ground connection or usb communication line filters etc..


      USB communication works well for ex. 2 hours or 5 hours, sometimes 1 day, but suddenly one of the device stop communication. I'm sure this problem isnot related with the device, which I connect to usb port. Because I tried different devices but same problem happened, but I tried same configuration with ATX board problem solved.


      I need to use MINI-ITX boards what do you suggest?

        • 1. Re: USB Stops

          I would guess it depends on what USB devices you are using , ?? In your BIOS do you have the USB set to normal or Legacy.

          • 2. Re: USB Stops

            I have tried different usb devices (Ex. some usb-rs232 with different IC, (FTDI and Profilic)), If you are asking USB Legacy,it is enabled. OS is Windows XP.


            For example:

            1 usb-RS232 with FTDI chipset created COM5 on OS.

            After 3 hours or 12 hours or ...  no COM5

            OR after some hours I see COM5 in device manager but it doesn't respond.


            Same things also with profilic chipset.

            • 3. Re: USB Stops

              I would suguest that you look at the downloads for your board and see if there is a up-date for the chipset.

              • 4. Re: USB Stops

                Hello , sounds like a power management issue , maybe in sometime when after device inactivity period this enter in sleep mode  and never wake up again until you unplug and plug again or restart the pc . I only guess . Regards

                • 5. Re: USB Stops

                  I'm sure that it is not related with device or something like sleep or wake-up. Because I have 30 computers with same configuration and same devices connected some of them works for 1-2 months without any problem. It looks like signal ground to earth ground connection problem or maybe USB filtering function .... Because most of the time which I power on a relay or motor brake or something else near to the system, USB connection fails. But this never happens with ATX boards.


                  Yesterday I connected a USB-RS232 to directly ATX board, then I used it for hours without problem. Then I used a USB HUB between PC and USB-RS232, and I powered on a relay 2-3 times, usb communication failed. I tested the same situation several times, same things.


                  I broked the usb hubs box and check the connections in it. Signal ground is directly connected to Chasis.


                  Maybe the same problem is in ITX boards. Maybe a different problem but I couldn't find out why?

                  • 6. Re: USB Stops



                    Just sharing some ideas. Motors produces noise in the power line when switched on and off. Some relays also exhibit the same behavior. Maybe you have to look at the filtering of your power lines on these devices to avoid affecting your computer system.

                    • 7. Re: USB Stops

                      I dont know what happen. But my response is posted as an RSS feed. There is no button in this thread to do that. Anyway, here's what I am stating.


                      Just sharing my idea. Motors and some Relays  produce power line noises. So that one possibility to your problem might to provide a filter to the power line side of those devices. Without the filter, your computer system will be affected by the power disturbance due to the switching on and off of these devices.

                      • 8. Re: USB Stops

                        Actually I have tested one of the system with Line filter before the Power supply, but no change.

                        Another one I have tested by different power supply (DC-DC power supply) and I supplied power from battery, but no change.

                        If I disconnected earth ground from the chasis, system works better but still same situation goes on.

                        But If I change ITX board with ATX board everything go well..

                        • 9. Re: USB Stops

                          Signal ground is directly connecting with chasis (earth ground) on ITX boards. I think there must be a capacitor or resistor or something else between these grounds. This situation may affect USB communication?. Or may be there is no filter on USB line? Or both of them ?


                          If this is the reason what can I do to solve usb communication problem?

                          • 10. Re: USB Stops

                            Have you tried any add on cards for USB , Koutech makes a real good card with a NEC chipset says it can control 127 devices. Part # IO-PU520 , they are $15.00, it's woth a try??

                            • 11. Re: USB Stops


                              I just read about your problem. I had the same sort of problems using my own developed USB-ports (FTDI-Chips). It has nothing to do with sleep and suspend modes of the USB port. After I directly connected chassis ground with system ground it works perfect. All other tries only costs time.

                              Best regards