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TPS65981: HPD and AMSEL are not asserted

navin Gautam
Prodigy 80 points

Part Number: TPS65981
Other Parts Discussed in Thread: TUSB546A-DCI

We are having issue with this chip (configured as DFP role) where the HPD and AMSEL events are not being asserted when we connect a USB C Alt mode DP device. The internal register 0x58 indicates that the PD controller is entered in DP mode. Here is the register read from device ( 0x58), The first byte 0x03 is the byte 1. 

0x03 0x01 0x00 0x00 0x00 0x08 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x05 0x10 0x00 0x00

This indicates DPModeActive = 1  and DP_SID_Detected =1. Which is DP device is detected. However as we already said, it does not assert HPD and AMSEL.

 

What else we need to do to make it work. 

  • 0
    TI__Expert 8400 points

    Naveen, You should look at PD trace logs. I am assuming you are DP source as well ( as in you are host trying to connect to a monitor to dock). In this case the far-end should be sending DP attention message which will then convert to HPD. Please check out DP Alt mode documentation for details.

    TPS6598x DisplayPort Alternate Mode (Rev. B)

  • +1 in reply to Ghouse Mohiuddin23
    Prodigy 80 points

    HI, 

    An update --------

    Looks like the PD controller is working at least in one direction of cable. Need to understand why it does not work in other direction. However, we are using TUSB546A-DCI as the crossover switch. The crossover switch requires CTL pin 0 to be toggles from 0 to 1 and back to 0 in order to take to Alt mode. How this can be achieved with the PD controller? I saw schematic using AMSEL for CTL0 but the AMSEL just goes to high. Which event I have to use to get this behavior? 

    Thanks