ESP32-S3 best 3.5" touch-display solution (ILI9488 + FT6236?)

[Queequack]

I am creating a custom solution for a smart home control for each room. I need about 20 of these units.
In a first step I successfully started with ILI9488 IPS Display + FT6236 Touch (this one). Used setup and requirements see below.

Summary of the questions:

• SPI+DMA or 8 bit parallel?
• Is the ILI9488 + FT6236 the right choice for the LiliGo board with ESP32-S3?
• Is it possible to improve the resource utilisation of the ESP32-S3?
• How do I determine the correct buffer sizes?

Issues with the ILI9488:

Inverted colours: I first tested the display successfully with an ESP32-DevKit + SPI interface and with an ESP32-S3-DevKit + 8 bit parallel. I had to invert the display colours (tft.invertDisplay(true);), which I had not yet found out during the test with SPI. With 8-bit parallel and inversion the colours were correct. By the way: It took a while until I had assigned the correct width and height everywhere and was able to use the UI export from Squareline Studio correctly.

Pin assignment with LilyGo T-ETH-Lite: For the LilyGo board, the pin assignment from Setup70d_ILI9488_S3_Parallel.h had to be adapted slightly. Since there is no board support by PlatformIO yet, LilyGo uses the esp32s3box for their examples. I therefore had to comment out the board-specific pin-defines (here: [...].platformio\packages\framework-arduinoespressif32\variants\esp32s3box\pins_arduino.h).

Corrupt display: As soon as I added the Ethernet functionalities to the code, the display was corrupt and showed unattractively distorted graphics. I plan to run the visualisation only on one processor and the rest on the other processor (TEST PENDING). This may already have solved the problem.

Animations not running smoothly: I haven't tested many animations yet. But I am not particularly satisfied with the performance. Switching screens is jerky (swiping the screen). Before I try other displays, I try to optimise the setup.

SPI+DMA vs. 8 Bit Parallel: There will probably be very few displays with which you can use the QSPI interface of the ESP32-S3. However, I wonder whether I will achieve a better result with the SPI interface and DMA (TEST PENDING) than with the 8-bit parallel. This is because DMA is not possible with the ESP32-S3 with 8-bit parallel.

Buffer sizes: I also struggle a bit with the buffer sizes. For LVGL I initialise a display buffer of width x height / 10 (480 * 320 / 10).

Burn-in effect: The display only ran for a few minutes (undimmed). After that, a burn-in effect of white text on a black background was already visible. I have read that the ILI9488 is very bright, but after my first attempts on the breadboard I cannot quite confirm this. To be honest, the brightness also changes brighter/darker as soon as I touch the cables ;)

I am using the following setup:

• LilyGo T-ETH-Lite ESP32-S3 (16MB Flash, 8MB PSRAM) + T-ETH-Lite-POE-Shield (PoE is essential. With a printed housing this fits into my flush-mounted boxes)
• LVGL for the design of the UI with Squareline Studio (UI easy to export and reuse in my code)
• TFT_eSPI display driver
• Adafruit_FT6206 for the touch controller

Display + touch requirements:

• 3.5"
• Capacitive touch (single or more)
• Without carrier board/breakout board --> Only display + touch panel with FPC connectors (e.g. 40pin or 50pin (display) + 6pin I2C-touch)
• Display + touch panel best pre-assembled
• No more than 8 bit parallel, as I still need a few pins of the LilyGo T-ETH-Lite for other functions.
• Best compatibility with the ESP32-S3