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Topics - robincornelius

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TFTs / nhd-7.0-800480ef-atxv color issues
« on: September 22, 2015, 10:12:44 AM »
Hi, i'm having a few issues with one of your displays. We have it connected to a PIC32MZ via a epson S1d13517. The design is based on the microchip Pictail Plus S1D13517 reference board.

The summary of the problem is that colors seem quite wrong on the display, as if i've lost some bits, or swapped some bits somewhere. I have checked the datasheets for the display, the epson chip and the PIC32 and cannot find any possible bit swapping anywhere.

I have tried setting the entire screen to a single shade of red with one bit set in the RGB color eg RGB(1<<c,0,0) where c was 0-7 i then looked at the RGB signal on the ribbon and found for each increment of c i only saw corresponding R0-R7 signals on the ribbon as expected, so that seems to be working perfectly.

The problem can be seen with the attached picture where i have drawn a 16x16 grid of grey boxes each box is one possible grey shade, horizontal is the upper nibble of the color and vert is the lower nibble. I also attach another test with various other gradients and it can be seen that the "brightness" is out of order.

if i run the same code on the reference board driving the Truly display, everything looks as expected. There are of cause minor differences between the two setups. Currently the NHD display is in 24bit color mode so i could try all combinations of colors, i was in 16bit mode and the reference board is always in 16bit mode. I've tried various clock and pixel timing settings but they make no difference until i push them to far then i get corruption.

I'm at a bit of a loss to what is actually wrong with the setup, so seeking any ideas.

I've attached one photo and had to make it smaller to fit the forum allowed size but I've also put some slightly higher rez photos on imagebin:-

actual result:-
http://imagebin.ca/2GWtoKUf2J0K/messedupgreys.jpg

expected result:-
http://imagebin.ca/2GWtcmGVr1ii/goodgreys.jpg

some other gradients on the NHD display :-
http://imagebin.ca/2GQNVajvJ9ru/IMG_0498.JPG


Thanks in advance,


Robin

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