DS90UB941AS-Q1: white display issue

chen zh

Intellectual 300 points

Part Number: DS90UB941AS-Q1

Dear TI:

We met white display issue. Please help check it. Thanks.

Envirement: Host DSI -> UB941 -> two UB948(split mode)

Display is ok in normal process:

1 Host DSI init

2. Power on UB941/UB948 and init UB941;

3. init UB948;

Display is NOK(white display) in this process:

1. Host DSI init

2. Power on UB941 and init UB941;

3. Power on UB948 and init UB948;

It seems need to negotiation with UB948 when init UB941, otherwise display will be NOK. Do we miss some operations? Thanks.

1. OK_UB941_reg

2. OK_UB948_reg

3. NOK_UB941_reg

4. NOK_UB948_reg

over 4 years ago

0 chen zh over 4 years ago

Intellectual 300 points

More info, pattern test is ok in this issue...

0 Solomon Ali over 4 years ago in reply to chen zh

TI__Intellectual 1905 points

Hi Arvin,

Let me look into it and I will try to get back to you by the end of this week.

Re: "More info, pattern test is ok in this issue..."

I just want to clarify this statement. Do you mean here that you are able to display test pattern with no issues and you are only having the issue when trying to display from the Host DSI?

Regards,

Solomon

0 chen zh over 4 years ago in reply to Solomon Ali

Intellectual 300 points

Hi Solomon:

Yes, so I wonder if some negotiation happen between Host and UB941, and it's related with if UB948 exist or not. Please help find out the cause. It maybe some configuration is missing.

0 Solomon Ali over 4 years ago in reply to chen zh

TI__Intellectual 1905 points

Hi Arvin,

In the datasheet, section 10.2, there are two recommended power-up and initialization sequences. Could you let us know which one you are currently using?

Also, there is a document called "DS90UB941AS-Q1 DSI Bringup Guide". On page 9, there is a debug flow chart. Could you to use that and let's know here where in that chart you observe an issue?

Here is the link for "DS90UB941AS-Q1 DSI Bringup Guide":
https://www.ti.com/lit/an/snla356/snla356.pdf?ts=1622159305890

Regards,
Solomon

0 chen zh over 4 years ago in reply to Solomon Ali

Intellectual 300 points

Hi Solomon:

Don't we find some issue from register configuration now?

0 Solomon Ali over 4 years ago in reply to chen zh

TI__Intellectual 1905 points

Hi Arvin,

I checked the provided register maps and couldn't find anything abnormal. So, could you help to provide feedback to my previous response above?

0 chen zh over 4 years ago in reply to Solomon Ali

Intellectual 300 points

Hi Solomon:

Sorry for my later answer. Based on your advise, we found that platform DSI driver didn't enable BLLP and this issue has been solved now. Thanks again

BRs,

Arvin

0 Solomon Ali over 4 years ago in reply to chen zh

TI__Intellectual 1905 points

Great, thanks for the update!

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DS90UB941AS-Q1: white display issue