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TPS65987EVM: DP alt mode with Samsung Galaxy S8

Laurence Symonds
Intellectual 545 points

Part Number: TPS65987EVM

Hi

I have a TPS65987EVM that I'm trying to use as a DP sink. I have the 10G-EXPANSION sink board attached.

I have DP outputting from a Macbook Pro fine but cannot get DP coming from the Samsung Galaxy S8. I've looked through the forum and have seen that a number of users have had issues with Samsung devices but without much resolve.

The S8 will output DP fine using a Kingston USB-C to HDMI adapter.

I have a Cypress CY4500 analyser that I have used to probe both connection events that I've uploaded. I've tried changing as many settings in the customisation tool that I can see to try and replicate the messages from the adapter. I read the thread below and also tried the initiate ufp swap.

https://e2e.ti.com/support/interface/f/138/p/825152/3065998?tisearch=e2e-sitesearch&keymatch=tps65987%2520samsung%2520galaxy#3065998

Any ideas would be greatly appreciated.

Thanks

TPS65987evm settings.zipUSB PD captures.zip

  • 0
    TI__Mastermind 36756 points

    Hi Laurence,

    The Samsung S8 has a known RCP issue with the TPS65987. When the TPS65987 becomes the power source of VBUS, the Samsung S8 will back feed VBUS with 9V. This is non-compliant to the USB Type-C/PD spec. As a workaround, you can configure the OVP in the TPS65987D to trip at 10V or greater by adjusting the OVP setting in the Port Configuration register (0x28).

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Intellectual 545 points

    Hi Eric

    Thanks for the reply. Sorry for the delay but my EVM somehow got corrupted and it took me a day to get it back to working.

    I have the over voltage protection trip point set at 24V and the over voltage usage is set to disconnect if vbus is above that trip point. This has not enabled the EVM to receive DP from the S8. I haven't detected a higher voltage using an external voltmeter or the one built into the analyser, but I haven't tried with a scope so it may happen.

    I've looked over the PD messages and I've noticed a difference between the adapter, which does work OK and the EVM. The first message from the sink, after the goodcrc is a request. When the adapter makes this request it is 0x13025896, but the EVM is 0x17025896. The only difference is that the EVM has the capability mismatch flag raised.

    Do you know why the flag would be raised on one and not the other, when essentially they are requesting the same PD object? And is there any way to have control over that flag manually?

    The other message that is different is the DFP VDM giving details of the DP capabilities. The EVM advertises its UFP pin assignments as C & D and nothing supported for DFP, as per the TI recommendations. The adapter basically shows the opposite, with C & D available for DFP and nothing for the UFP. If I set the EVM to these settings, it doesn't display DP on other sources, like a laptop. This makes sense as I understand those setting being for a DP source, not  sink.

    After this message, with the EVM connected, the S8 responds the a get_sink_cap message, whereas the adapter is responded with another VDM message relating to DP.

    I'm guessing the reason the S8 doesn't engage further in the DP contract with the EVM is something to do with the power contract.

    Thanks

  • 0 in reply to Laurence Symonds
    TI__Mastermind 36756 points

    Hi Laurence,

    From the PD Spec: "A Sink unable to fully operate at the offered capabilities requests an offered capability but indicates a capability mismatch i.e. that it would prefer another power level". I would suggest modifying the Sink Capabilities of the TPS65987DEVM to match what the Samsung S8 is offering as a source. This should help you remove any issues with the power contract. 

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Intellectual 545 points

    Hi Eric

    Thanks for the quick response.

    I started by changing the EVM sink capabilities to match the adapter sink capabilities. This is how the 2 request messages are the same apart from the mismatch bit.

    I've now tried to go through and tweak the settings around the the other information that the source capabilities offered.

    For PDO1, the voltage is 5V, the operating current and max operating current is 1.5A, the peak current is 100%.

    I'm a little confused as to what else I can change to try and match the source capabilities and avoid the EVM raising the mismatch flag.

    The source capabilities message that the S8 sends is 0x36019096. I've attached the customisation project file.

    Thanks

    TPS65987evm settings 2.zip

  • 0 in reply to Laurence Symonds
    TI__Mastermind 36756 points

    Hi Laurence,

    The Samsung S8 will send some Source capability. Probably 5V with some current. I would suggest using a PD analyzer to read what that current is and then setting the Sink Current in the TPS65987EVM to match. Unfortunately, we don't have a Samsung S8 here for testing but we do not see any issues with the Samsung S10. However, I have heard of many issues with connecting to the Samsung S8, it appears these were fixed with the newer versions of the phone.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Intellectual 545 points

    Hi Eric

    Thanks for the response.

    I have a PD analyser. I am using the Cypress CY4500. I have attached 2 files in a zip from that analyser. I'm not sure if you already have the software for it or not. In case you don't, I have attached some screenshots of the messages in question.

    I understand that maybe the S10 has resolved these issues but what is keeping us going with the S8 is that other consumer products are able to work without issues with the S8. I have attached the PD analyser results from the TP65987EVM connected to the S8 as well as the adapter product connected to the S8. The adapter I have is a kingston nucleum, which uses a VIA tech VL101 PD controller.

    With the capability mismatch bit, do you know what parts of the PDO need to match? Is it the entire PDO, with every option bit being the identical, or is it just the voltage and current usage?

    Thanks

    0363.USB PD captures.zip

  • 0 in reply to Laurence Symonds
    TI__Mastermind 36756 points

    Hi Laurence,

    After looking at the PD logs, I don't think this issue is related to the capabilities mismatch bit. The power negotiation looks ok and the Cap. Mismatch bit should not cause adverse effects. After checking out the logs, I looked at the project file that you sent. It looks like in the Display Port Capabilities register, you had set the DP Receptacle Indication set at Plug. This should be set to Receptacle if you are using the TPS65987EVM.

    Thank you,
    Eric