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TDP142: Want to detect both source and sink recognize each other

Atsushi Hirai
Expert 3740 points
Part Number: TDP142

Hi team,

My customer is developing a display product and, using TDP142.

There is a MCU close to the TDP142 and, he want to detect it by MCU that both source(PC) and sink(his product) recognize each other.

Is there any way to recognize it by monitoring the pin state or register of TDP142?

Customer noticed Pin26(RSVD6) outputs similar signal as AUX_N. Could you tell me what signal is output from RSVD6-pin?

Best Regards,

  • 0
    TI__Guru*** 143595 points

    Hi,

    MCU can detect the following,

    1. Voltage on AUXN for powered-on source connection

    2. Voltage on AUXP for unpowered source connection

    3. HPD for sink connection

    Thanks

    David 

  • 0 in reply to David (ASIC) Liu
    TI__Expert 3740 points

    David-san,

    Thanks. Is it just connecting AUXN/P or HPD with MCU directly or through a logic buffer?

    Is it possible to know that the Sink and Source recognize each other by reading SET_POWER_STATE or LINE_COUNT_SET in the Displayport Control/Status Register at address 0x12?

    Regards,

  • 0 in reply to Atsushi Hirai
    TI__Guru*** 143595 points

    Hi,

    Thanks. Is it just connecting AUXN/P or HPD with MCU directly or through a logic buffer?

    It depends on the actual detection function that customer wants to accomplish with their MCU. Please note HPD has dual function, a connect/disconnect and an interrupt function. The difference between them is the HPD pulse duration. An HPD interrupt has a min 0.5ms and max 1ms duration.  

    Is it possible to know that the Sink and Source recognize each other by reading SET_POWER_STATE or LINE_COUNT_SET in the DisplayPort Control/Status Register at address 0x12?

    If the source is able to read the EDID and read/write the DPCD from the sink, and the sink is able to ACK the request from the source, then they are recognizing each other.

    Thanks

    David

  • 0 in reply to David (ASIC) Liu
    TI__Expert 3740 points

    David-san,

    Could you please give me a more direct answer?

    Did you mean that reading SET_POWER_STATE or LINE_COUNT_SET cannot know that source and sink recognize each other?

    Or, did you mean that these registers are updated by reading EDID, read/write DPCD and ACK so, the reading these registers can know it?

    Regerds,

  • +1 in reply to Atsushi Hirai
    TI__Guru*** 143595 points

    Hi,

    TDP142 register 0x12 SET_POWER_STATE or LINE_COUNT_SET bits are continuously updated based on the AUX monitoring. But depending on how AUX bus is being routed and possible AUX noise, you may get false reading. So I do not recommend using register 0x12 as an indication that source and sink recognizing each other.

    My previous response is that the MCU should read and decode the AUX traffic directly without using TDP142 register 0x12.

    Thanks

    David