AM335X: LCD problem

Mario Pucciarelli

Other Parts Discussed in Thread: TPS61081

Hi,

I've a custom board that I interface to the base board of the AM335X EVM, with some peripherals that I need and aren't on the original daughter board. In this board I've included also the circuitry for the lcd (as on the AM335X EVM lcd board).

Initially I've a problem on the lcd for blue and red colors that was swapped, so I change the video driver, recompile the kerner and now it's ok, so the pins and their configuration are correct.

Now I've this problem, I'm using two different lcd (taken from two original AM335x EVM kit); if I use the screen with code:

TFC-S9700RTWV43-01C

everything works fine, but if I use the screen with code:

TFC-S9700RTWV35TR-03B

the visualization isn't correct, the brightness seems too high.

What are the difference between the two display? Both they work properly instead with the AM335X EVM kit.

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

Hi,

I will ask the factory team about this.

0 Biser Gatchev-XID over 10 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Hi Mario,

Several questions from the factory team to narrow down the issue:

1. Is brightness the only difference? If this is so, are you using the same backlight driver circuit that was used on the AM335x EVM LCD board?

2. The ThreeFive web site shows the TFC-S9700RTWV43 doesn't have the touch screen panel while the TFC-S9700RTWV35TR has a touch screen panel. All of our displays should have the touch panel. If not, the display without a touch panel would appear brighter. Can you confirm that both displays have a touch panel?

3. Can you provide the EVM revision information from which you removed these displays?

0 Mario Pucciarelli over 10 years ago in reply to Biser Gatchev-XID

Prodigy 100 points

Hi Bisier,

I make two photos of the situation, in these the hardware is the same and also software is the same (i have used the same sd card).

The circuit is the same of the LCD Board of the kit, the only difference is the lcd, as you can see from the third image, and all of them have the touch panel. In the photo of the display, the lower one works fine.

For the revision, I have:

- BASE BOARD: v1.6A

- LCD BOARD: v1.3A (on my board I've the same control hardware)

LCD OK: www.dropbox.com/.../20160310_171915.jpg

LCD NOT OK: www.dropbox.com/.../20160310_165551.jpg

LCD PANEL: www.dropbox.com/.../20160310_172453.jpg

0 Biser Gatchev-XID over 10 years ago in reply to Mario Pucciarelli

TI__Guru**** 393215 points

I really can't say anything without comparing the datasheets of both displays. If you have them I would suggest you check if the backlights are identical. From these photos it seems that one backlight is overdriven.

0 Mario Pucciarelli over 10 years ago in reply to Biser Gatchev-XID

Prodigy 100 points

Hi, I have just checked the current flowing into the backlight of the display, and for both the value is the same, so it can't be overcurrent. Also datasheet seems the same, but I'm going to check better.

0 Biser Gatchev-XID over 10 years ago in reply to Mario Pucciarelli

TI__Guru**** 393215 points

Hi Mario,

Maybe I wasn't clear. The TPS61081 that drives the backlight is connected as a LED driver, so it will output a constant current. The question is are the backlights of the two displays identical regarding number of LEDs used and their configuration (rows/columns)?

0 Mario Pucciarelli over 10 years ago in reply to Biser Gatchev-XID

Prodigy 100 points

Hi Bisier,

the configuration is exactly the same, both the display have 3 columns and 9 row for the backlight, and from the datasheet also the current is the same (180mA).

0 Biser Gatchev-XID over 10 years ago in reply to Mario Pucciarelli

TI__Guru**** 393215 points

Then I have no idea what could be the issue.

0 yashavadan Dalsaniya over 9 years ago in reply to Mario Pucciarelli

Intellectual 550 points

Hi,

Does your problem resolved??

We are also facing same issue. We were early using old sdk having kerenl versuon 3.2 and in that lcd was working perfectly fine. After upgrading to sdk 3.00.00.04 having kernel 4.4.12 some times suddenly lcd become over bright. This issue is observed in all of the board. We have also varified backlight and it is working fine. It seems that there is an issue in framebuffer.
Please, help us thanks in advance.

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AM335X: LCD problem