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TUSB211A-Q1: Wired Carplay connection failed with iPhoneXR

Owen Chang
Prodigy 10 points
Part Number: TUSB211A-Q1
Other Parts Discussed in Thread: TUSB216-Q1, TUSB211A

Tool/software:

We have successfully used the TUSB211A-Q1 to meet the USB-IF eye diagram specification with a 150-cm actual vehicle cable.

 

However, despite ensuring that the eye diagram meets the USB-IF specification, we are still unable to pass the ATS test required for CarPlay certification. The test setup is as follows: After passing through the actual vehicle cable, a Beagle of TotalPhase are used to establish the CarPlay connection with iPhone, and the ATS on a Mac will capture packets for analysis. During this test, iPhone 12 and above show no error messages in the ATS, whereas the iPhone XR, while able to initiate CarPlay normally, displays numerous error messages in the ATS. We have tried adjusting the BOOST level, but there was no improvement. We also tried replacing the TUSB216-Q1 and adjusting RX-SEN. Although there are fewer ATS Error when RX-SEN is high, it still does not meet the CarPlay criteria.

Further analysis of the CarPlay connection packets revealed that the packets sent from the iPhone to the CPU exhibit significant attenuation and distortion during compensation by the TUSB211A-Q1. However, when we disconnect the Vcc of the TUSB211A-Q1, we observe better signal performance. It is worth noting that the attenuation and distortion caused by the TUSB211A-Q1 do not appear in the packets transmitted from the CPU to the iPhone.

  • 0
    TI__Guru*** 146785 points

    Hi  Owen:

      Did you try with lower EQ setting for TUSB211A_Q1 for I-phone XR? 

      Can you help to take waveform with I-phone 12 as well?

    Best

    Brian

  • 0
    Prodigy 10 points

    Hi Brian,

    We have attempted to optimize the EQ settings, but it is fail when the EQ is set above level 1. It can be pass only when the EQ is set to level 0.
    I can provide a comparison between the iPhone XR and iPhone 14 Pro Max that we conducted previously. Please refer to the details below. (EQ Boost level 2)

    Best,

    Owen

  • 0 in reply to Owen Chang
    TI__Guru*** 146785 points

    Hi Owen:

       When EQ is 0, can it pass HS eye-diagram?

        Can you provide a comparison between the iPhone XR and iPhone 14 Pro Max?

    Best

    Brian

  • 0
    Prodigy 10 points

    Hi Brian,

    Our machine does not meet the USB-IF eye diagram criteria at EQ level 0 after a 150 cm actual vehicle cable.

    I'm not sure what kind of comparison you're looking for, but I can only provide a CarPlay packet comparison at TUBS211A-Q1 OFF between the iPhone XR and iPhone 14 Pro Max.

    Best,

    Owen

  • 0 in reply to Owen Chang
    TI__Mastermind 38955 points

    Hi Owen,

    Sorry for the late response on my end, I was OoO for the new year.

    Owen Chang said:

    We have successfully used the TUSB211A-Q1 to meet the USB-IF eye diagram specification with a 150-cm actual vehicle cable.

     

    Looking at this eye diagram, I believe the redriver may not be activating in certain cases. Could you monitor the ENA_HS and CD pins and let me know what you are seeing? If these pins are low, it is possible the redriver is not actually activating.

    Additionally, looking at these waveform, it does look like the IPhone XR is either being boosted not as much, or has a lower drive strength than the 14ProMax, and when it has a lower level of boost or when it is not enabled, it tends to pass. My guess is that the signal is being boosted too much, so I would recommend testing different cable lengths as well. If you can see a pass with a longer cable, that would indicate that the signal is being boosted too much.

    Thanks,

    Ryan

  • 0
    Prodigy 10 points

    Hi Ryan,

    We have confirmed that both the ENA_HS and CD pins remain high during the compliance test and CarPlay communication. Additionally, I can provide the eye diagram of our head unit without TUSB211A-Q1 compensation for your reference.

     

    I tried extending the vehicle cable to 2 meters, but there still are numerous errors in the ATS software.

    Best,
    Owen

  • 0 in reply to Owen Chang
    TI__Mastermind 38955 points

    Hi Owen,

    Would it be possible to capture eye diagrams at each boost setting to see how the eyes compare? It definitely looks like the eye needs to be boosted, so its odd that the test can pass when the redriver is disabled but not when it is enabled.

    I would test each boost level with different cable lengths at different cable lengths like you did previously, just to see if there is any combination that works, Additionally, eye diagrams of each would help, but it's not required.

    If after testing each level there are no improvements to the functionality, then it may be that the redriver boosts the signal too much, causing over-compensation in regards to the levels required by apple carplay.

    Thanks,

    Ryan

  • 0
    Prodigy 10 points

    I don't have the eye comparison for every boost level, but I think the signal integrity from the head unit to the iPhone is sufficient. Below are the CarPlay packets we captured from the USB-C connector. As you can see, only the IN Packet, which is from the iPhone to the head unit, shows distortion when the conditioner is ON. The DATA Packet, which is from the head unit to the iPhone, exhibits better signal integrity when the conditioner is ON. The behavior of the DATA Packet aligns with the USB-IF eye diagram results.

    My concern is that, while the TUSB211A-Q1 compensation might help our head unit meet the eye diagram criteria, it could introduce signal distortion when packets are transmitted from the iPhone to the head unit

    Best,

    Owen

  • 0 in reply to Owen Chang
    TI__Mastermind 38955 points

    Hi Owen,

    I believe there shouldn't be any reason the TUSB211A-Q1 causes any packet distortion, at least to a large degree. If possible, could we try different types of cables between the head unit and the IPhone? There should be a cable that came with the ATS box/system, but also different Type-C cables could be good to try. For the connection, with the IPhone XR, are you using a USB-C to lightning adapter, or a USB-C to lightning cord? If the adapter, its possible this is also affecting the signal integrity.

    For the ATS testing, we've found in the past that the ATS box tends to attenuate the signal to a large degree, causing the signal to degrade more than normal. As such, sometimes it may require a specific setup via trying different cables or settings.

    It sounds like you also tested the TUSB216-Q1 and might have had slightly better results when using RX_SEN. If you want, you could also try with that again. Right now, however, I think looking at the cables and/or adapters being used and seeing if changing those helps to improve the results would be good to test, as those are variables we can easily change.

    Thanks,

    Ryan