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Configuring AM3517 display subsystem (DSS)

mrunmoy samal
Prodigy 90 points
Other Parts Discussed in Thread: AM3517

Hi,

Environment:

AM3517 EVM (Logic PD with Sharp LCD provided with the evaluation board), u-boot, Windows 7

Background:

I am new to the world of omap processors. I come from the world of character LCDs.

While trying to debug an issue with the start up logo in u-boot, I had to go through the entire code to figure out what was going wrong. The problem was a clocking issue and now is solved (Thanks to TI's forums).

Now, that the display subsystem triggered an interest in me to add a progress bar to the u-boot while it fetches application code from external NAND into RAM.

I read through a bunch of documentations provided on ti's wiki.

  1. http://processors.wiki.ti.com/index.php/LCD_connectivity
  2. http://processors.wiki.ti.com/index.php/Display_Subsystem
  3. as well as the reference manual

I compared the u-boot code of DSS initialization and putting a static bitmap image and disabling the auto-refresh feature.I noticed that if I enable the auto refresh feature the logo becomes unrecognizable (pixelated).

The reference manual states that the DMA will try to auto refresh but from its own FIFO. But the FIFO is filled only once from the address specified in the DISPC_GFX_BAj registers. How can I continuously fill data into the DMA FIFO?

My Intention:

Leaving aside these complex operations, I went ahead and re-read the DSS documentation from the reference manual. But I am not able to figure out how to achieve simple things. This is what I would like to do with the LCD:-

  1. Put ASCII text at certain co ordinates on the LCD , like lcd_printf() ...
  2. Put Pixel, Get Pixel of a certain color at certain co ordinates on the LCD
  3. Put bitmaps onto the LCD (this one might be same as u-boot does it, but still I want to understand the physics behind it)

Is there any documentation which explains in real simple terms, how to initialize the DSS, and draw on the screen? with examples.

I do not want any OS code. I just want standalone code snippets to init the lcd, and then play with the pixels, like put a bmp and then modify the pixels at certain locations.

Any help will be highly appreciated.

TIA,

Mrunmoy