3 Replies Latest reply on Oct 31, 2018 10:54 PM by YangyangC_06

    HX2VL Self powered

      I recently bought the CY4608 HX2VL USB Hub development kit and trying to get it to work in self-powered mode. The documentation on the page does not match the Rev. 4.0 board I received in the kit. I would assume that when it is "Self-powered" it would be getting it's power via the USB B jack and I did measure 5V at each USB downstream port. When I plug a simple USB thumb drive into any of the 4 ports, I hear it enumerate on the PC but does not show up in explorer. The only way I can get it to work is to plug in the external power supply which is not what I wanted.


      I just want to evaluate the chip to determine if I want to use it as a hub for a board I am designing. I also do not need the EEPROM and it seems this is not necessary for simple hub operation but I would like to confirm this is the case.


      Thank you in advance is anyone has any insight into this board.

        • 1. Re: HX2VL Self powered

          Hi Joshua,


          You can pull up the pin selfpwr to HIGH. In this condition, you may get your drive work without a external power adapter.

          • 2. Re: HX2VL Self powered

            yyca, thank you for the response. After looking into this, if I were to pull the "SELF_PWR" pin high by manually setting it to 5V it would of shorted out the supply because it uses the switch inside the DC barrel jack to pull this pin to ground when the barrel plug is not inserted. So just by inserting the plug from the AC adapter (without plugging it in), it removed this pull down and the hub starting working as self-powered.

            • 3. Re: HX2VL Self powered

              Hi Joshua,


              I will explain the function of pin self_pwr here.

              This pin is used to indicate whether a HUB is bus power or self power. If it is pulled down to GROUND, it indicates the HUB is bus powered and it is connected to HIGH to indicted self powered.



              For the bus powered hub, according to USB spec v2.0, the device which is connected to its DS port could sink no more than 100 mA current  in default state(it is a terminology defined in USB2.0 spec). In the enumeration process, communication between the host and device will occur. Device will report all of its information including power consuming requirment. If the device state it needs more than 100mA current, the device could not  enumerate on PC side. A warning message will pop up.


              For a self powered hub, external pwoer jack will provide 5V at DS port. Thus the device on DS port could sink current from external power source instead of USB bus.

              In this way, a device which need more power will work normally.