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We have an issue with our TFT display. The display constantly flickers while displaying. What are common causes for flickering in this type of display? How can we resolve this issue?

It's a 3.5 inch local TFT display

We are using Arduino Mega for programming, with AdaFruit graphics and AdaFruit TFT LCD library. The driver IC used is 9341.

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  • \$\begingroup\$ May be related. \$\endgroup\$ – Unknown123 Apr 7 '19 at 5:10
  • \$\begingroup\$ Does it have a backlight? Newer panels use LEDs, older ones can use florescent tubes with high voltage power supplies. Put a scope on the backlight power supply. \$\endgroup\$ – Randy Nuss Apr 7 '19 at 13:23
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Flicker is almost always a timing issue. In theory it's possible it's a wiring issue in the LED, and unstable power can be unpredictable, so check you connections, solder joints, and power supply. Use the shortest cable possible between the screen and whatever it's connected to. If your hardware is good, try and slow down your timing/refresh rates/etc. The Mega doesn't have much in the way of RAM and can easily choke trying to push that many frames of that many pixels per second. It's also worth knowing how you are connecting to the screen, I2C, SPI, etc

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You can try tracking down the source of the flicker with the following:

  • If there's flickering when the LCD + backlight are on even when there's nothing being written to the display then you have a power supply or other electrical issue. Power on the LCD + backlight without data.
  • You may notice some flicker-like effects if you aren't updating the screen efficiently (ex: constantly re-drawing things that don't need to be updated). Do a couple of simple tests displaying only a single solid color, then do a test with red/green/blue regions. If there's no flickering with the test patterns then it's likely that you're rewriting sections of the frame multiple times and seeing the effects. If the flickering is present with the test patterns, you likely have a timing issue.
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I had the same problem with one of my TFT displays. However, when I checked the written driver that I downloaded, I realized that the problem was in the driver, where it set the display refresh rate to 20 in the init function. I changed the framerate to max and the flicker and beating was gone.

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Flickering can be caused by the backlight or by ‘tearing’ where the LCD controller is rendering the image to the display at the same time you are writing the image data. The ILI9341 drivers are generally well-behaved in my experience. Can you provide a video recording of the display in action?

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