White flickering new 2.4" LCD screen issue

[Rovalo]

Hello Dmitri,

I have bought the full MD kit and some time later the PS add-on board, larger display and a MD housing.
I worked on the re-assembly in the new housing from time to time and now finished it.

The new 2.4" LCD replaces the original 1.8" LCD display.
I cannot remember when I connected the 2.4" LCD if I had to change wiring.
I do see different naming of some pins between the two LCD boards.

Before I switched on power I double checked the connections against the manual.
The only thing I could not find was the correct position of the jumper, it is now on MD board LCD connector pins 13/13.

When I switch on the power the display is flickering mainly white, so I switched off power immediately.

Can you please confirm the correct jumper position and how to trouble shoot this issue?
Thanks in advance.

[dmitri]

As per the instruction manual PDF:

For ILI9340/ILI9341 LCDs pins 11 and 12 of the LCD Connector must be connected with a jumper.

Btw, if the jumper on the LCD Connector is place for an incorrect LCD type, it won't damage the LCD or the board - it'll just display garbage on the LCD.

[Rovalo]

Thanks for the reply and I have to admit that I did not read the manual careful enough...

I set the jumper on pins 11/12 and now I have a normal screen.

I found similar info in this thread viewtopic.php?f=3&t=2935&hilit=tft+wiring&start=50 and there I read that the background LED was not connected to pin 3 but pin 15/16 or with a 100E pull-up resistor to +5V.
Is that also applicable to my MD board / LCD?

[dmitri]

The backlight LED is on the LCD_color connector pin 8. It is the same for 1.8" and 2.4" color LCDs.

[Rovalo]

I have LED (white wire) on MD LCD connector pin 3.
That probably explains why I cannot change contrast.

When I put the white LED wire on pin 8 with LCD contrast on 100% then the display is black.

How can I get contrast setting to work?

[dmitri]

Did changing brightness work with the 1.8" LCD? Was it connected to the LCD_color connector, including the backlight LED pin?
Maybe you set backlight/contrast too low?
Set it higher with MDMFX or by pressing Up button right after power up (i.e. not navigating anywhere in the menu).

[Rovalo]

Yes, with the 1.8" LCD I remember brightness worked fine.

White LED wire is still on pin 3.
I checked it better and the brightness does work but the adjustment window is much smaller then it was with the 1.8" LCD.

The brightness really changes from 0 (still readable, not black as with the 1.8" LCD) till 35.
Above 35 to 100 I see no change.

I have set it to 15 which seems to my taste.