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HD3SS3220: USB3.0 Hub Connection Issues

Pang
Expert 2415 points
Part Number: HD3SS3220
Other Parts Discussed in Thread: TUSB8020B

Hi Ti,

           

If we are going to use this part from TI, would the TX/RX be swapped on both sides or one side? Why it is swapped on HUB but not on MUX or splitter? We've checked that if we connect module USB to hub, then we should connect TX to TX, RX to RX, and the other side of the hub which connect to MCU should connect to TX to RX, RX to TX.

The above is just said that you should swapped two side of HUB, just need to swap the side that connect to MCU side. Is this correct?

  • 0
    TI__Guru**** 176811 points
    HD3SS3220 is not a USB hub, it is a CC controller, are you referring to the right part?

    For HD3SS3220, please refer to Figure 11 and 12 for the TX/RX connection.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Expert 2415 points

    Yes it is a CC controller with 1:2 Mux to give us extra ports on the connector. In either case, we are using TI part as hub, we need advise from TI to be sure. Please help to verify the data lines swapping on both ends inside the red circle.

  • 0 in reply to Pang
    TI__Guru**** 176811 points
    Please refer to TUSB8020B hub datasheet. You can't swap between TX and RX since TX is defined as output only, and RX is defined as input only.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Expert 2415 points
    Hi David,

    I am not swapping the TX with RX, i am connecting the TX from CPU to RX of hub and RX of CPU to TX of the HUB, and same on the out put side. Can you help to confirm?
    Because from what i understand, i don't need to swap the input side, i just have to do the salve side that connects to the module.
  • 0 in reply to Pang
    TI__Guru**** 176811 points
    The TUSB8020B SSTX is defined as output and SSRX is defined as input for both upstream and downstream. Please take a look at the TX/RX pin definition of CPU and the module. TUSB8020B SSTX needs to be connected to the input of CPU and the module through the AC coupling caps. And TUSB8020B SSRX needs to be connected to the output of CPU and the module, with the AC coupling caps on the output side. Cap on SSRX is optional with recommended value of 330nF.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Expert 2415 points

    Can you help to verify as this is my latest block.

  • 0 in reply to Pang
    TI__Guru**** 176811 points
    Your direction on the TUSB8020B UFP is incorrect. The TX is output, the arrow needs to be pointed toward the CPU. The RX is input, the arrow needs to be pointed toward TUSB8020B.

    You also drawn the TUSB8020B as a mux representation, but TUSB8020B is a hub, not a mux.

    I don't know the I/O definition of CPU TX/RX and LTE TX/RX, so please double check the I/O definition of these signal to make sure which one is output and which one is input.

    The interface also needs to be AC coupled.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Expert 2415 points

    Yes i know the direction was different by mistake. All i need to know is the connection of CPU to HUB and LTE..... Just look at the TX and RX from input and output as below picture.

  • 0 in reply to Pang
    TI__Guru**** 176811 points
    I don't know the TX and RX definition for the CPU and LTE1/2. please don't look at TX and think it is an output and look at RX and think it is an input. It is better to check the CPU and LTE1/2 datasheet to make sure which one is being defined as output and which one is being defined as an input.

    If we assume CPU TX is an output, then it needs to be connected to hub RX, and CPU RX needs to be connected to hub TX. The connection between hub and LTE1/2 is OK assume TX is an output and RX is an input for LTE1/2.

    But this is just a assumption, it is better to check the datasheet for each device to make sure.

    Thanks
    David
  • 0 in reply to David (ASIC) Liu
    Expert 2415 points

    Hi David,

    If we are going to follow your suggestion, how would it work if we swap on both sides of the hub, please see my comments in red in the picture. Appreciate for your help to confirm.

                    if we follow TI suggestion, how would it work if we swap on both sides of the hub, please see me comments in red in the picture. confirm this with TI

  • 0 in reply to Pang
    TI__Guru**** 176811 points
    The hub is not a USB extender. The hub RX will recover the SuperSpeed data sent by the CPU TX (assuming CPU TX in this case is the transmitter) and re-send the data out on its TX.

    Thanks
    David