DS90C385A: DS90C385A, TFP401

Christian Hartz

Prodigy 40 points

Part Number: DS90C385A
Other Parts Discussed in Thread: TFP401A, DS90C387

Hi,

I am using TFP401A and DS90C385A to drive a 10" IPS TFT panel. It works generally, I got a stable picture but

reading characters or icons is hard. I have tried different HDMI timings with no luck. Currently I guess the problem

doesn´t come from timing issues rather than pin mapping of the DS90C385A driver.

I created a rgb picture with eight values for each color to find out if there is a pinout mapping problem.

It seems I have connected the DS90C385A driver the wrong way. I used the slna014a.pdf to find out the right

mapping. The table from my display datasheet looks like a format 2 mapping.

Could someone give me an idea what i have made wrong?

All the best,

Chris

rgb values:

how they are displayed:

over 6 years ago

0 Ikechukwu Anyiam over 6 years ago

TI__Mastermind 35130 points

Hi Christian,

It appears that you did not map the bits correctly. Please cross-check Figure 11 in the DS90C385A datasheet with the input format from your display to map the bits to the correct channels.

Regards,
I.K.

0 Christian Hartz over 6 years ago in reply to Ikechukwu Anyiam

Prodigy 40 points

Hi I.K.,

thank you for the quick response. I can see clearly that the signals are not mapped correctly.

I am wondering a bit why the application note shows another mapping. It says:

"Specific part numbers like the DS90C387 and DS90C385 are used as examples in this document"

So I made the mapping according to the application note.

It will not be easy to change the mapping but I will try it.

Best regards,

Chris

0 Ikechukwu Anyiam over 6 years ago in reply to Christian Hartz

TI__Mastermind 35130 points

Hi Christian,

The mapping shown in the datasheet is only an example. You'll need to map it according to the input your display expects. The introduction in this app note lays out the steps: www.ti.com/.../snla014a.pdf

Regards,
I.K.

0 Christian Hartz over 6 years ago in reply to Ikechukwu Anyiam

Prodigy 40 points

Hi I.K.

I needed a while to change the pins physically. :)

Now the picture is displayed correctly. I am complete up to you that you have to match the signals carefully and
according to the datasheet.

But I don´t understand why the appnote suggests you to connect Txin27 to R0. (for example)
The information "Specific part numbers like the DS90C387 and DS90C385 are used as examples in this document"
implies that the tables are showing the right pin mapping for the DS90C385.

Obviously this is wrong. Just my two cents, would it be better to show the correct pin mapping in the application
note?

Best regards,
Chris

0 Ikechukwu Anyiam over 6 years ago in reply to Christian Hartz

TI__Mastermind 35130 points

Hi Chris,

I'm glad you were able to resolve your issue. But, the application note is not wrong, it's just an example.

JEIDA input format displays would use this format, where the LSB are mapped to the 4th LVDS lane (e.g. this display www.data-modul.com/.../LQ231U1LW32_specification_SD20931.pdf, see page 11). Your display is VESA format, where the MSB are mapped to the 4th LVDS lane. The introduction in the application note goes over this.

Regards,
I.K.

0 Christian Hartz over 6 years ago in reply to Ikechukwu Anyiam

Prodigy 40 points

Hi I.K.
thank you for the explanation. It seems I have misunderstood the application note.

Thank you for your excellent support!

Best regards,
Chris

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DS90C385A: DS90C385A, TFP401