TPS65994AE: HPD_Tx not asserted when DP adapter is connected to USB-C port

Alex H

Part Number: TPS65994AE
Other Parts Discussed in Thread: TUSB1146,

I have a a TPS65994AERSL (PD controller) and TUSB1146 (USB3, DisplayPort crosspoint switch) on a custom carrier board. Port A on the PD controller is the one connected to the TUSB1146 for DisplayPort Alt modes.

I have USB 3.1 data working on this Port A. I am now trying to get DisplayPort working.

When I connect a Framework DisplayPort Expansion Card (USB VID: 32ac, PID: 0003) into Port A, I found that the Hot Plug Detect (HPD_Tx) pin on GPIO1 does not assert. It stays low. Yes I do have a DisplayPort monitor (Asus PB277) connected and turned on.

If I put the TI Application Customization Tool into Debug mode and look at the DisplayPort Status register (0x58) I see the following.

Why is "DP Status TX" still showing `HPD_Low` even though a DisplayPort adapter and monitor are connected?

Thank you!

7 months ago

0 Kevin Kosta 7 months ago

TI__Genius 14645 points

Hi,

Thanks for reaching out on E2E!

We will get back to you soon.

Thank you,

Kevin

0 Alex H 6 months ago

Prodigy 41 points

Is the HotPlug Detect pin functionality somehow related to Thunderbolt instead of DisplayPort?

I only want USB3 (gen2) and DisplayPort (1.4) in my application. I do not have a Thunderbolt-capable port on my board.

0 Kevin Kosta 6 months ago in reply to Alex H

TI__Genius 14645 points

Hi Alex,

HPD is related to DP Alt mode, not thunderbolt.

Do you have the PJT file that you can share with me?

Thank you,

Kevin

0 Alex H 6 months ago in reply to Kevin Kosta

Prodigy 41 points

Right, HPD should just be related to DisplayPort Alt mode. However, in practice I cannot seem to get DisplayPort working without having some Thunderbolt settings enabled.

Here are two PJTs, one with DisplayPort working (because I have some Thunderbolt settings enabled), and the other with DisplayPort broken. Have a look and let me know what I might be doing wrong.

tps65994ae_port1_dp_broken.pjt

tps65994ae_port1_dp_working.pjt

Thanks!

0 Kevin Kosta 6 months ago in reply to Alex H

TI__Genius 14645 points

Hi Alex,

Can you provide me with a PD for both cases?

Thank you,

Kevin

0 Alex H 6 months ago in reply to Kevin Kosta

Prodigy 41 points

What do you mean by "a PD", I don't understand.

0 Kevin Kosta 6 months ago in reply to Alex H

TI__Genius 14645 points

Hi Alex,

A USB-C Power Delivery log. Basically it decodes the CC line communication so that I can see the contract negotiation including alternate mode entry.

Thank you,

Kevin

0 Alex H 6 months ago in reply to Kevin Kosta

Prodigy 41 points

> A USB-C Power Delivery log.

Ah, I see.

I'm sorry for my delayed response. I found out that the "Thunderbolt Configuration (0x52)" register's default value for the "Data Status HPD Events" field was set to "HPD events are reported in DATA_STATUS.HpdLevel and HpdIrqSticky". This was the default value in a fresh project file ("TPS65994AE_v6_4_31.tpl").

It seems that changing this register's field to "HPD events are reported using the GPIO configured as HPD" has helped.

Does this sound correct to you, that I have to change this field in the Thunderbolt register to get a proper DisplayPort hot-plug detect signal on GPIO1?

If this doesn't sound right, yes, I'll try to recreate my debugging setup and get you those logs.

Thanks!

0 Kevin Kosta 6 months ago in reply to Alex H

TI__Genius 14645 points

Hi Alex,

This would be correct!

If changing this fixed the issue then this would be correct. We would want HPD events to be GPIO reported rather than I2C in the data status register.

Thank you,

Kevin

Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

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TPS65994AE: HPD_Tx not asserted when DP adapter is connected to USB-C port