Pixels problem

[lpcware]

Content originally posted in LPCWare by DT1 on Fri Jan 31 14:56:54 MST 2014
Hi,

I currently using the MCB4357 dev board. I have a custom application using emWin. When I try to draw something on the screen, some pixels don't behave correctly. The pixels are always the same, but their behavior is not constant.

For example, let's say I have those pixels that are problematic:
- Pixel 1 (located at some x and some y)
- Pixel 2 (located at some x and some y)
- Pixel 3 (located at some x and some y)
- Pixel 4 (located at some x and some y)

- Execute action 1 (redrawn the whole screen)
- Pixels are ok
- Execute action 2 (draw a small bitmap image somewhere in the screen)
- Pixel 2 is black instead of white, others are ok.
- Execute action 3 (draw a small bitmap image at another place in the screen)
- Pixel 2 is ok
- Pixel 1, 3 and 4 are black instead of white.
etc.

If I redo the above, the same pixels will behave wrongly, but not necessarily in the same order. What I have in mind is a problem with the SDRAM or maybe one of the RGB trace, but my dev board is brand new and I have this problem on another MCB4357 too.

Any suggestion on where to look?
Thanks.

[lpcware]

Content originally posted in LPCWare by DT1 on Tue Feb 11 14:56:52 MST 2014
hum, I found the problem.It was not related to my buffers, but to the SDRAM configuration.

I used a file named SDRAM_Init.c originally taken from an example (can't recall if it was from a Keil example or a LPC one, but it was for the MCB4357 board I'm sure). That configuration was working fine on some MCB4357 boards (that I don't have anymore). After validating that the SDRAM chip had indeed changed between the boards, I used the initialization code made by Keil in the MCB4357 emWin demo and all my problems are gone.