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TUSB2046B: Connection Status: "0x06 (Not enough bandwidth)" for downstream device. How is bandwidth managed by the hub and what is the limit?

Arthur Lancelyn Green
Prodigy 30 points

Part Number: TUSB2046B

We are using TUSB2046B in a design. When we connect three FT260 devices (USB to I2C/UART/HID), all three are detected and work fine. When we add a fourth, that device fails to connect, with connection status 0x06 (Not enough bandwidth). The design is self powered and available power is not the issue. It looks like the FT260 cannot negotiate enough bandwidth (Windows says it is asking for 11%, but it's not clear what this is a proportion of).

What is the bandwidth limitation of the TUSB2046B and can it be adjusted? Is there a limit to the number of connected devices (each FT260 appears as two HID devices, so total of 8 on the four ports)?

Thanks for any help,

Arthur

Screenshot of information for the failed device in USBTreeView:

  • 0
    TI__Guru 60870 points
    Hi Arthur,

    There is no limitation on the number of devices that can be connected to the TUSB2046B. The likely issue is that the TUSB2046B is a full speed hub limited to 12 Mbps, and it seems the host controller is not able to budget enough bandwidth for 4 FT260 devices through a single full speed connection (host to hub). There is no way to adjust this bandwidth in the TUSB2046B.

    Regards,
    JMMN