TDP158: DP++ to HDMI no sound issue

Polly Chung1

Part Number: TDP158

Dear Team,

My customer took our TDP158EVM to test. It can have video, but no sound. Below is their configuration.

PCH with DDC MUX will output DP++ signal. And they connect this signal to TPD158 EVM (J2) by DP to DP cable. Then they connect TPD158 EVM (J4) to monitor by HDMI to HDMI cable. This configuration is no sound.

[PCH (DDC ouput DP++) --> MUX--> DP to DP cable --> TPD158 EVM (J2) -->TPD158 EVM (J4) --> HDMI to HDMI cable --> monitor]

But if they use DP to HDMI passive cable to connect PCH and monitor. It can have video and sound.

So I would like to know is there any setting of TDP158 that we should change to support DP++ to HDMI? Thank you.

Best Regards,

Polly Chung

over 6 years ago

0 David (ASIC) Liu over 6 years ago

TI__Guru**** 176811 points

Polly

Can they use a DP159 EVM and see if they can get the audio through the EVM?

Thanks
David

0 Polly Chung1 over 6 years ago in reply to David (ASIC) Liu

TI__Intellectual 2110 points

Dear David,

Thanks for your reply. May I know why you suggested to change to DP159 EVM? If you doubt that the signal quality is not good, I think it might not be big problem. Because they can have video and sound after changing DP to HDMI passive cable. Thanks again.

Regards,
Polly

0 David (ASIC) Liu over 6 years ago in reply to Polly Chung1

TI__Guru**** 176811 points

Polly

I think the issue here is that DP158 does not have a Adapter ID Buffer, and HDMI ID code will be read as 0x00h when Adapter ID Buffer is being read. HDMI ID code of 0x00h would indicate this to be a DVI interface, and audio is not supported over DVI. If switched to DP159, and when selected as HDMI, DP159 will have its Adapter ID buffer read as HDMI, and then audio will be supported.

Thanks
David

0 Polly Chung1 over 6 years ago in reply to David (ASIC) Liu

TI__Intellectual 2110 points

Dear David,

Customer tested DP159 EVM and it can have sound output now. But customer want to know if there is any possibility that TDP158 can adjust some register setting or other workaround to support DP++ to HDMI? Or DP159 is only way to support DP++ to HDMI? Thank you.

Regards,
Polly

0 David (ASIC) Liu over 6 years ago in reply to Polly Chung1

TI__Guru**** 176811 points

Polly

They have to use DP159 since DP158 does not include the Adapter ID Buffer.

Thanks
David

0 Polly Chung1 over 6 years ago in reply to David (ASIC) Liu

TI__Intellectual 2110 points

Dear David,

Now, I have some confusion about the descriptions of TDP158. It shows that TDP158 could support "DisplayPort Dual Mode Standard Version 1.1". Why cannot I use at DP++ to HDMI? Is there any misunderstanding? Thank you.

Regards,

Polly

0 David (ASIC) Liu over 6 years ago in reply to Polly Chung1

TI__Guru**** 176811 points

Polly

DP158 supports DP++ to HDMI, and DP++ can transmit DVI/HDMI as well as DP. In this particular case, then there is no Adapter ID buffer, the source will think this is DVI, which will be converted to HDMI.

Thanks
David

0 jenghau Chen over 6 years ago in reply to David (ASIC) Liu

Prodigy 10 points

Dear David:

Do you mean DP158 only support platform vBIOS set to HDMI only, and if I set vBIOS to DP++ that DP158 will make source identify this is DVI because DP158 doesn't have Adapter ID buffer?
If so, is this the limitation of DP158?

Thanks

Jenghau

0 David (ASIC) Liu over 6 years ago in reply to jenghau Chen

TI__Guru**** 176811 points

Jenghau

Yes, if using DP158, you have the force the source into HDMI since DVI does not carry audio.

Thanks
David

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TDP158: DP++ to HDMI no sound issue