About the 5 Inch TFT LCD

Hello everybody !

First I'd like to say that I'm more than happy to have received my Mimas v2 this week ! I ordered it along with the LCD expansion board in order to explore (simple) graphics cards.

From the documentation, I undestand that it kind of works like VGA, which is fine for me, but there seem to be some undocumented functionalities. Indeed, there is this "6 PIN ZIF CONNECTOR" showing pins that read "SCL", "SDA", "INT" and "WAKE"... My (wild) guess is that the display supports Text Mode, but then I don't understand signals INT and WAKE.

Let me know what you think and of course if you have THE answer it would also fit

Thanks in advance !

 

Hi Tom,

This is great news, can't wait to know more about these mysterious serial-link-looking signals ! I'm also very interested in a sample code. Indeed, albeit its similarities with the VGA "standard", I am still unable to make it display anything... I'm now trying my design under Modelsim to check my timings, hopping to find a loophole in my code !

Regards.

 

Thanks a lot for all these details Tom, it is greatly appreciated here !

I took a look at both the datasheets and the sample code. From this datasheet I understand that the mysterious serial link is used to configure the LCD, which sounds interesting, especially for brightness diming and image correction. I'll give it a try one day or the other

As for why my code was not working, the UCF in your sample code gave me the answer: I mismatched pins' order... I took for granted that headers in the LCD expansion board where mirrored with regards to those in the Mimas but it's not the case:

_Mimas _ LCD board
_ P9 _______ P6
┌──────><──────┐
01 02──><──01 02
┌──────><──────┐
03 04──><──03 04
┌──────><──────┐
05 06──><──05 06
┌──────><──────┐
07 08──><──07 08
┌──────><──────┐
09 10──><──09 10
┌──────><──────┐
11 12──><──11 12​

Which is kind of misleading, but why not!

The rest of my design was correct in fact: timings provided in the datasheet seem to be allright, and I successfully address every pixel of the screen. The sample code you provided stick the signal DEN to '1' all the time, which lead to a shift in the displayed image:



This can be (partly) fixed by driving this signal from your entity vga_driver:

Code:

-- If in display range
if (nxt_HCount < HResolution and nxt_VCount < VResolution) then
  red_d   <= count_h(5 downto 4) & count_h(5 downto 0);
  green_d <= count_h(7 downto 0);
  blue_d  <= count_v(7 downto 0);
  D_EN    <= '1';
else
  red_d   <= (others => '1');
  green_d <= (others => '0');
  blue_d  <= (others => '0');
  D_EN    <= '0';
end if;

I would like to propose a different approach to drive the 5" TFT LCD display which has the following result (there is a 1px red border, top 2nd line and left 2nd column are green, bottom 2nd line and right second column are blue):



Every process is synchronous (with the main FPGA clock), and the entity can be modified to output current pixel coordinates to a module that would be responsible for driving pixel colors.

Thank you again for the datasheet. I guess I'll come back here when I get a chance to play with the serial link, to report on my findings

Cheers.

 

necsito ayuda (helpme please)