AM335x Display interfacing.

sandeep reddy

Hi,

We are using AM335x Customized board with 3.5"(320x240) Display it is working fine with board, and recently we are working on 5" landscape(800x480) and 5" portrait(480x854) displays.

In 5" landscape(800x480) device is booting fine and its working by adding display parameters given by data sheet in kernel where as 5" portrait(480x854) display is not working, When we connect the display Device is not booting and no logs in DEBUG port.

AM335x will support portrait display like 5"(480x854) or not????

Regards,

Sandeep V

over 7 years ago

0 Biser Gatchev-XID over 7 years ago

TI__Guru**** 393215 points

Hi,

It will be supported if you set 480p horizontal and 854p vertical resolution. If you are trying display rotation, this is not supported by the AM335x LCD controller.

0 sandeep reddy over 7 years ago in reply to Biser Gatchev-XID

Prodigy 185 points

Hi Biser,

Thank you for reply,

We are not trying for display rotation, We set 480p horizontal and 854p vertical resolution in da8xx-fb.c and when we connect this portrait display to AM335x Device its not booting and no debug log in DEBUG PORT.

Regards,

Sandeep V

0 Biser Gatchev-XID over 7 years ago in reply to sandeep reddy

TI__Guru**** 393215 points

You need to check the LCD_DATA[15:0] signals at boot time. These are also the SYSBOOT signals and it may be that the display is pulling these lines to undesired levels at boot time.

0 sandeep reddy over 7 years ago in reply to Biser Gatchev-XID

Prodigy 185 points

Hi Biser,

I have checked the LCD_DATA[15:0] at boot time, In this signals DATA14,7,6,5,4,3,2 are getting pull down(880mv) when we connect the Portrait Display where is should be 2.36v at boot time on working Display. Portrait display is pulling these signals to down on boot time these SYSBOOT signals are getting low with portrait display. How to set High these signals in kernel.

Regards,
Sandeep V

0 Biser Gatchev-XID over 7 years ago in reply to sandeep reddy

TI__Guru**** 393215 points

What is the value of the SYSBOOT pullup resistors on these lines? You will probably need to decrease it in order to overcome the display pulldowns.

0 sandeep reddy over 7 years ago in reply to Biser Gatchev-XID

Prodigy 185 points

Hi Biaser,

Thank you for support i have checked the SYSBOOT Pull up resistors and i have decreased the Value of Pull-up resistors for that signals and now with display it is booting properly.
at those signals 100k Pull-up is there changed to 10k pull up and now voltage at SYSBOOT signals is High (3.2v).
Now i will go further to initialize the portrait display.

Regards,
Sandeep V

0 Biser Gatchev-XID over 7 years ago in reply to sandeep reddy

TI__Guru**** 393215 points

Yes, 10k is OK. Glad you have solved this. I will leave this thread open in case you have more questions. If not, please mark it as resolved and close it.

0 sandeep reddy over 7 years ago in reply to Biser Gatchev-XID

Prodigy 185 points

In Standard AM335x schematic it is given as 100k Pull-up and it is working for different Displays but when portrait is connected voltage is getting down why it is happening and now 10k pull-up is working for this portrait display can i know the reason for what purpose it is behaving like this?

Regards,
Sandeep V

0 Biser Gatchev-XID over 7 years ago in reply to sandeep reddy

TI__Guru**** 393215 points

Obviously your display has strong pulldowns on the data lines, which the 100k pullups cannot overcome.

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AM335x Display interfacing.