Brightness difference between TFT_320QVT_9341 and TFT_320QDT_9341

Other Hardware Displays
1

Hello to all.

I have two sets of Mega2560 + shield + tft displays. Arduino boards and shields are identical, but displays are not. One of them has TFT_320QVT_9341 printed on his back and the other has TFT_320QDT_9341.

Both displays are working fine with UTFT libraries and examples downloaded from Rinky-Dink Electronics. Codes using UTFT myGLCD(ILI9341_16,38,39,40,41) and UTFT myGLCD(CTE32_R2,38,39,40,41) works fine, no difference in performance.

The problem is that 320QVT is much more brighter than 320QDT. Although the pictures show a small difference, it is big. I have tried using setBrightness and setContrast, but they are useless.

I'd appreciate your help to understand the reasons for this difference and how to improve the 320QDT's brightness.

Thanks for your help.

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2

You have forgotten to unpeel the plastic film on both of your displays.

One is a lot brighter than the other. There will be a small value series resistor in the backlight circuit. Change it.

Untested. I do not own either of your displays or adapter shields.

There is little point in using a variable backlight. You either want it on (with a sensible brightness) or off.
I assume that you have two 40-pin adapter shields. You might find it easier to modify the adapter than the display i.e. add / change LED series resistor.

David.

3

Hello David,

Thank you very much for your time and help.

Yes, I haven't upeeled the plastic film on both displays, but also I haven't tested them until this morning. I tested both a few minutes ago, before reading your answer, using UTFT, URTouch, UTFT_tinyFAT and tinyFAT libraries from Rinky-Dink Electronics. The test results are:

For TFT_320QVT_9341: everything works fine with both UTFT myGLCD(ILI9341_16,38,39,40,41) and UTFT myGLCD(CTE32_R2,38,39,40,41); codes

For TFT_320QDT_9341: Display tests run ok with both UTFT myGLCD(ILI9341_16,38,39,40,41) and UTFT myGLCD(CTE32_R2,38,39,40,41); codes, but touch screen is horizontaly mirrored, which means touching a button located on the upper left corner activates a function located on the lower left corner.

About brightness, I do have two shields, which I assumed to be identical. I will check the resistors in the display and shield boards. If I understood correctly, for both displays, brightness is hardware controlled only, so there is no other way of doing it, excepy by changing resistors.

Another point, but I will open a new topic for that: I can read SD cards with both displays, using the same libraries mentioned above, but image rendering (screen updating) is taking too long.

Once again, Thank you for your help.

Rene

4

Looking at Google images of TFT_320QVT_9341 and TFT_320QDT_9341 pcbs.

R5 "looks" like the LED series resistor. You should be able to read the value or test with a DMM.
And it would not be too difficult to change R5.

Since the label says LED_A or LEDA, it is probably an anode.
Look at your adapter shield. What does it do with LED_A pin? e.g. is there another series resistor?

Sort out your hardware first.
UTFT is a widely used library. It is "Universal" but not fast. It has an "unusual" set of methods. If you are using a legacy UTFT project, stick with it.

If you want to go faster, there are several other libraries. With more intuitive graphics methods.
I would suggest Adafruit_GFX style methods are a better choice for any new project.
You will find that most "other" libraries use this style.

David.

5

How the problem is solved to prevent the touch screen from being reflected horizontally, which means that touching a button located in the upper left corner activates a function located in the lower left corner. What can be done to avoid changing the code? In a program I did with the TFT_320QVT_9341 screen, it was correct when I pressed exactly on the button press. Thank you!

6

Run the URTouch Calibration program. Edit the URTouchCD.h file e.g. with both sets of Calibration values but one set disabled by #if or comment block.

The alternative is to use the same calibration but to map the getX() and getY() values.
God gave you the map() function with the Arduino.

You will be stuck with editing library file or sketch file whenever you swap screens.

Hey-ho. There is nothing unusual in Touch Panels that are different in a new batch. That is why you have a Calibration program.

David.