• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 13 subscribers
  • Views 769 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISOUSB211: No USB communication

Hielke Bakker
Prodigy 70 points
Part Number: ISOUSB211

Tool/software:

We are using the ISOUSB211 in a design. We are only using the ISOUSB211 for the isolation of the DD+ and DD- lines. Therefore, it does not have an isolated power supply and shares the same ground.

The upstream-facing port will be connected through a USB connector to the PC. The downstream port has a USB switch behind it. Upon insertion of the USB cable, the switch first connects to a battery charging IC. After determining the charger type, it switches to a processor module (i.MX6ull) for data communication.

The problem I'm facing is that the isolator does not allow any USB communication through. I understand it's an isolator, but this isolation seems excessive.

Here's what I've verified: All power supplies (VBUS, V3V3, and 1V8) are present on both sides of the ISOUSB211. Additionally, both VxOk are high on both sides.

I also purchased the development kit (ISOUSB211DPEVM) and recreated the same configuration on it. The configuration works fine on the development kit.

I bypassed the ISOUSB211 to rule out any issues with the USB switch, etc. In this case, it works fine, indicating that the ISOUSB211 is not functioning correctly.

I'm at a loss. Any advice on how to proceed? It seems like it should work, but it doesn't.

I've also noticed that the ISOUSB211 has functions like Connect and speed and disconnect detection. Could these functions be causing problems due to the switching of the USB lines?

Any help would be appreciated.

  • 0
    TI__Guru 55815 points

    Hi Hielke,

    Thank you for reaching out.

    Can you please share the whole schematic including battery charger and processor along with the part numbers?
    Connect, speed and disconnect detect are the handshaking features of USB interface, these are going to happen between devices to establish and terminate communication. A proper handshake is necessary between host and peripheral is necessary for a successful communication.

    I am not sure why your solution is not working, but if you share the larger schematic with part number then I can review to see if there are any concerns.
    The schematic will also help me understand if the ISOUSB, USB switch, battery charger and processor are powered by USB bus or by the battery. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 70 points

    Dear Koteshwar Rao,

    How can I share the schematic with you? The complete schematic is not something I can share in this forum. Can I send you a private email/message?

    Thanks

  • 0 in reply to Hielke Bakker
    TI__Guru 55815 points

    Hi Hielke,

    I have sent you a friend request in E2E. Once you accept the friend request, you will be able to private message me the schematic. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Hielke Bakker
    TI__Guru 55815 points

    Hi Hielke,

    Thank you for sharing the schematic.
    I reviewed the schematic and I couldn't find any obvious issues in it. When a USB device is connected, they go through a handshake to recognize each other and align on speed. If the connection is dynamically changed through a switch, the handshake gets broken in-between. I am not sure if such switching would allow for any communication.

    USB requires that a peripheral once connected stays there till the communication is ended. If disconnected and then reconnected, it will go through a new set of handshaking. But in your case, switching the connection dynamically doesn't make ISOUSB recognize this as a new connection and will fail to initiate a new connect sequence.

    Hielke Bakker said:
    I also purchased the development kit (ISOUSB211DPEVM) and recreated the same configuration on it. The configuration works fine on the development kit.

    Did you connect the ISOUSB211DPEVM in place of ISOUSB211 on your PCB and all other connections remained the same?
    i.e., did you simply exchange UD± and DD± pins of ISOUSB211 on your PCB ot ISOUSB211DPEVM?
    Did this is work and establish connection to the charger and the processor?


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 70 points

    Thanks for your reply.

    About the development kit, I did not connect it to our PCB. What I did was recreate the power supply setup, because I thought that the different power (shared ground) setup I used could be the problem.

    What I will do is remove the USB switch from our board and wire the USB lines directly to the iMX6 module. If your assumption is correct, it should work. If not, we can investigate what else could be the problem.

    I will keep you informed.

  • 0 in reply to Hielke Bakker
    TI__Guru 55815 points

    Hi Hielke,

    Thanks for sharing details of EVM testing. The device has two separate sections, side1 and side2, that are independently powered. Whether two separate power supplies are used or one supply used, the device doesn't see any difference in operation. Therefore, I do not expect the power supply connection to be of any issue.

    Yes, wiring ISOUSB to iMX6 module directly and then powering from USB port would be a good step to debug the issue. I expect this connection to work fine. I will wait for your update, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 70 points

    I want to let you know that I solved the problem. It had nothing to do with the ISOUSB211. The ISOUSB211 worked fine, and the switching of the USB lines also works.

    The problem was the buck-boost converter that generates the 5V_USB from the input power. The voltage sagged when the USB-communication was started, probably resetting the ISOUSB211.

    The reason for the voltage sag was that before the buck-boost converter, there was a fuse with a cold resistance of 7 ohms. The voltage drop across this resistor was too great for the converter to handle.

    To fix it, I needed to either decrease the cold resistance of the fuse (another fuse) or add more capacitance to the input of the buck-boost converter.

    So again, the switching of the USB lines works fine, and the ISOUSB211 was not to blame.

    Thanks for your help.

  • 0 in reply to Hielke Bakker
    TI__Guru 55815 points

    Hi Hielke,

    Thank you for sharing the update and glad to know that you were able to identify the issue and that it is not related to ISOUSB211. I will go ahead and mark this closed, thanks.


    Regards,
    Koteshwar Rao