3.5 inch TFT LCD Touch Screen not working on Arduino Mega2560

Other Hardware Displays
1

I recently purchased an Arduino MEGA2560 board and this 3.5'' TFT LCD Screen module from

https://www.amazon.de/gp/product/B07KK4NV3V/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&th=1

I have no problem making the screen display what I want. However, I couldn't make the touch screen work.

I followed the tutorial available at, which match the version of my device. But the Calibration doesn't work, when I touch it, it simply doesn't react
http://www.lcdwiki.com/3.5inch_Arduino_Display-UNO

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Investigating a bit further on, I also checked the tutorial here in this old forum post: My 3.5 inch TFT LCD Touch Screen is finally working!

And I noticed my problem happens in step 5 of that tutorial, when diagonizing the touchpins using the MCUFRIEND_kbv library, but I noticed the Serial just shows one touchpin connection found, when they expect two pairs of pins.

Typical 30k Analog pullup with corresponding pin
would read low when digital is written LOW
e.g. reads ~25 for 300R X direction
e.g. reads ~30 for 500R Y direction

Testing : (A1, D7) = 32

And finally running the calibration of the touch screen, from the same MCUFRIEND_kbv library, it gives me a Touch Calibration Failed.

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What could be happening? Is my touch screen broken? I actually don't need it for the project I'm working on, I just need the display that is working fine, but I paid for everything I want it all.

I'm also trying other libraries, like Wavesharehttps://www.waveshare.com/wiki/3.5inch_TFT_Touch_Shield, I can report it later if it works.

2

Thanks for providing the link to your shield.

Please make sure that you have installed MCUFRIEND_kbv via the IDE Library Manager.
If you have installed from a random site on the Internet or have multiple copies --- delete them. Start the IDE again. Run the Library Manager and install properly (it should be v2.9.9Release)

Run the Calibration sketch. Copy-paste the output from the Serial Terminal to your message.

I can tell you what the "problem" is.

David.

3

Yes I had installed MCUFRIEND_kbv via the IDE and it is the version is 2.9.9. I re-ran the Calibration Sketch from this library and I got this in the serial:

TouchScreen.h GFX Calibration
Making all control and bus pins INPUT_PULLUP
Typical 30k Analog pullup with corresponding pin
would read low when digital is written LOW
e.g. reads ~25 for 300R X direction
e.g. reads ~30 for 500R Y direction

Testing : (A1, D7) = 32
ID = 0x9486

Similar of what I had in the touchpins diagnostic test but with an id in the end.

4

From memory, it should report as BROKEN.

It looks as if the Touch panel has a vertical crack in the glass.
It diagnoses the YP, YM pins but does not find the XP, XM pins.

If you have a DMM : unplug the shield. measure resistance between A2 and D6 pin. (printed LCD_RS and LCD_D6)

Such is life. I think that I received three broken 3.5 inch Touch Panels before the Chinese shops started packing the delicate glass panels properly.

If you can take a photo of the cracked glass, Ebay, AliExpress, ... will refund your money.

David.

5

I don't have a multimeter to test it right now, but it seems broken from the output in the Serial and in the touch diagnostic. it doesn't seem to have any visible crack on the touch, but i'll try to return it anyway, because I don't want to keep a broken product.

Thanks for the help!

Thiago.

6

Go on. You can borrow a DMM. It is far more impressive to quote the resistance values.

If there is no visible crack you need to provide some evidence.

I have a 2.4 inch Shield with no visible crack but no XP, XM resistance.
The bonding between Touch glass, ribbon, pcb can fail. Or the ribbon metallisation can break.

David.

7

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