DS90UB949A-Q1: HPD assertion : what conditions must be met ?

O'Mellin

TEam,

My customer has issues getting HPD to get asserted by 949 : what are the conditions to be met for HPD to be asserted by the 949?

I have 2 :

- get a 5V from the HDMI source

- serializer must detect the deserializer (or reg 5Ch bit 6 must be forced to 1)

-...

Olivier

over 4 years ago

0 Casey McCrea over 4 years ago

TI__Guru** 103215 points

Hello Olivier,

Those should be the only two steps needed but you could also try the manual steps described in this post:

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/807888/linux-ds90ub929-q1-ds90ub929-hdmi-hpd-signal-is-always-low

Best Regards,

Casey

0 O'Mellin over 4 years ago in reply to Casey McCrea

TI__Expert 6445 points

ok customer managed to get the HDMI link up with the serializer EVM simply with reg 5Ch bit 6. but on their HW they had to force bit 5 as well : does bit 5 relate to the stability of the HDMI clock or the stability of the FPDlink clock?

what do you think is happening here?

thanks

0 Casey McCrea over 4 years ago in reply to O'Mellin

TI__Guru** 103215 points

Hello Olivier,

That seems unusual. I just tried on my own 949 setup and only setting 0x5C[6] = 1 allows the PC to see HPD and start outputting to the display. What resolution are they doing? Are you sure that the PC can generate that specific resolution? Keep in mind that if they are testing a non-standard custom resolution, there is no guarantee that the PC can actually generate that timing over the HDMI interface. I have seen problems like that before

Best Regards,

Casey

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DS90UB949A-Q1: HPD assertion : what conditions must be met ?