• Resolved

USB hub on cape board for Beaglebone Black

Hi , 

We are designing a board which can be stacked on to Beaglebone black like a cape. We want to have two host ports on that board, so we are interfacing the USB1 Host port available on Beaglebone Black to upstream of a USB HUB , which is on the Cape board. 

The Host port from Beaglebone Black is connected to cape board by a mini USB-B connector, which then goes to the USB HUB. On the Downstream of USB HUB, one of the ports is always occupied ( non removable) and the other is removable. 

So the issue that we are facing is that  hotplug for non removable device is not working, i.e. when all the connections are intact and it just switches off and on, or we make the connections at the USB host after Beaglebone Black has booted up. 

We tried to probe the USB_VBUS for the downstream port for non removable device and saw that after the device is turned off, the VBUS signal dies of after 10s and then when the device is turned on or host connections are done again, VBUS does not get active , it stays low.  After this the removable device port is also not working, basically the USB HUB is not working .

I have attached a snip of the USB HUB portion of my schematic, where we intend to use just the four signals that come from the USB host port, USB1_VBUS, USB1_DP , USB1_DM and GND. 

Can you please help us in determining what might be the issue with VBUS ? why does it go to sleep and never come back. Mind you the USB HUB works hotplug for the removable port when the other device is on or not present at boot. 

I went through lots of reference for AM335X and the problem seems to me with the USB1_VBUS signal ? 

How do i design the USB hub to work with just those signals (VBUS, DP and DM) . I have used TPS2052 in downstream

Please help us in resolving this issue. 

  • Hi Nitesh,
     
    What is the USB hub you are using? Have you tried supplying VBUS_DET from the VDD_5V on P9 of the BB Black, instead of USB1_VBUS?

     

    Best Regards
    Biser
  • In reply to Biser Gatchev-XID:

    Hi Biser sir, 

    I am using USB2412 , same as that used in Beaglebone. 

    No sir, I did not check by supplying VDD_5V to VBUS_DET.  You think that it should solve the problem ?

  • In reply to Nitesh Singh:

    Hi Nitesh,
     
    It probably will. According to the USB2412 datasheet: VBUS_DET detects the state of upstream VBUS power. The USB2412 hub monitors VBUS_DET  to determine when to assert the internal D+ pull-up resistor which signals a connect event. On the other hand AM335X USB in Host mode waits for a connect event in order to switch on VBUS. As you see they are both waiting for the other one to act first, so nothing happens.

     

    Best Regards
    Biser
  • In reply to Biser Gatchev-XID:

    Hi Sir, 

    I tested with what you said, applying VDD_5V to VBUS_DET of usb hub USB2412 . Hotplug is now working but I observed  that on 'lsusb' , Beaglebone Black still shows the devices are present even when they have been removed.

    And , so i have made the following change in my schematic, applying USB1_VBUS to a buffer whose output is pulled up to VDD_5V and connected to VBUS_DET. So that, 

    when USB1_VBUS : 0  VBUS_DET=0

              USB1_VBUS : 1  VBUS_DET=1

      and USB1_VBUS: X  VBUS_DET=1

    Is this circuit fine and you think that the USB host port will work with hotplug ?

    Here is the snap of the schematic :

  • In reply to Nitesh Singh:

    You can give it a try and see how it behaves.

     

    Best Regards
    Biser
  • In reply to Biser Gatchev-XID:

    Sir, 

    We have a board designed with the former configuration and i explained to you the issues faced. 

    Now i wanted to be certain about it for the second board but i will test it someway to ascertain that it will work. 

    Thank you sir for your help .

    Best regards,

    Nitesh

  • In reply to Nitesh Singh:

    Why don't you test it with wire rigging on your old board first? In my opinion it should work. I'm not sure why the host port is still seeing devices after they have been detached, but I don't know much about software.

     

    Best Regards
    Biser