4-inch LF40 square touchscreen display modules are designed for Luckfox Pico Ultra development board

Luckfox LF40-480480-ARK and LF40-720720-ARK are two new 4-inch square touchscreen display modules specially designed for the Luckfox Pico Ultra micro Arm Linux development board. Both displays feature IPS panels with wide viewing angles and capacitive touch input. The display modules connect to the Pico Ultra board via the RGB666 interface ensuring compatibility with the board. Both displays have a brightness of 400cd/m² and an operating temperature range of -20~70°C.

The main differences between the two boards are in the resolution, color gamut, and contrast ratio. The LF40-720720-ARK has a resolution of 720×720 pixels with a wider color gamut of 68% NTSC and a 1000:1 contrast ratio. The LF40-480480-ARK on the other hand features a 480×480 pixels display, with an unspecified color gamut and  380:1 contrast ratio.

Previously we have written about various products with rounded and semi-rounded displays like the Waveshare RP2040-LCD-0.99-B, the Waveshare ESP32-S3 1.69-inch touch display, the SB-Components Dual Roundy, and many more, but we have seen fewer products with square displays like the SB Components’ 2-inch Squary Display and this new Luckfox module adds one to that square display list.

 

Luckfox square touchscreen display modules specifications:

• Common specifications
  • Display Size – 4-inch
  • Display Panel – IPS
  • Touch Type – Capacitive
  • Touch Chip – GT911
  • Brightness – 400 cd/m²
  • Operation Temperature:  -20 to 70°C
  • Communication Interface – RGB666
• LF40-720720-ARK specifications
  • Resolution – 720×720
  • Viewing Angle – 170°
  • Contrast Ratio – 1000:1
  • Display Colour Gamut – 68% NTSC
  • Pixel Pitch – 0.0999×0.0999 mm (H×V)
  • Outline Dimension – 84.0×84.0 mm (H×V)
  • Display Area – 71.93×71.93 mm (H×V)
• LF40-480480-ARK specifications
  • Resolution – 480×480
  • Viewing Angle – 160°
  • Contrast Ratio – 380:1
  • Display Colour Gamut – Not Mentioned
  • Pixel Pitch – 0.1497×0.1462 mm (H×V)
  • Outline Dimension – 84.2×84.2 mm (H×V)
  • Display Area – 71.86×70.18 mm (H×V)

The displays are all well and good but upon checking the wiki page for both display modules, I found out that the company talks about a certain design issue that you need to fix yourself for the display to work with the Pico Ultra development board. The company mentions that you have to remove a resistor from the back of the board to work with the display module. They also mention that “for versions shipped after July 5, 2024, this resistor will not be soldered by default”. The wiki also provides an LVGL sample and goes into detail about the source code for the Linux driver.

The flex PCB that’s coming out of the display gets connected to an adapter board from which an FPC cable carries out the power and data signals from the SBC to the display, there’s also a 3.3V, GND, and a DIO pad for maybe for connecting external power but the company does not clearly mentions what the pads are for.

The Luckfox square IPS touch displays LF40-480480-ARK cost $24.13 on Aliexpress, $35.99 on Amazon, and $23.99 from Waveshare. The LF40-720720-ARK is priced at $30.61 on Aliexpress, $42.99 on Amazon, and $29.99 from Waveshare.

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