Read pixel in LCDWIKI_GUI doesn't work

Other Hardware Displays
1

Hey. I have a lcd ST7796S/ILI9488. I use LCDWIKI_GUI, LCDWIKI_KBV libraries and everything worked 'til now. But when I try to read pixel color using method uint16_t LCDWIKI_GUI::Read_Pixel(int16_t x, int16_t y) I get same color, every time, no matter which color this pixel really has - even if I'm using example straight from LCDWIKI_KBV library. I checked it on two different Arduino Mega 2560, and two diffrents lcd's. What can be wrong?

2

Since you say LCDWIKI_KBV I presume that you have a Parallel display rather than SPI display.

Please note that LCDWIKI have never asked me for the use of KBV.
They don't seem to understand several things, but have never acknowledged or replied to me.

Please post a link to the actual Shield that you have bought.
Mcufriend Uno Shields are read-write
Mcufriend Mega Shields are write-only
Surenoo Mega Shields are write-only

ILI9488 and ST7796S are two completely different controllers.

David.

3

This is shield that I bought: Page Not Found - Aliexpress.com

4

Thanks for the link.

That shield is write-only. The LCD_RD pin does not work. It is in fact completely wrong. (at least on the 8-bit version of that board)

So readID(), readReg(), readPixel(), readGRAM() can never work.

Since you are using a Mega2560 Shield, I suggest that you enable the jumpers for 16-bit.
It is still write-only but it will be a little faster than the default 8-bit.

And most importantly, 16-bit is supported by several libraries. Even though ST7796S is only supported by MCUFRIEND_kbv

David.

5

Thanks for an answer :slight_smile: So as I understand - there is no possibility to read pixel. That's very sad, but I least now I know where the problem lies. Thanks also for a hin with enabling 16-bit jumpers!