The preenfm3 uses a cheap color TFT display in 2.8" (or 2.4") inches based on ILI9341 chip with a 240x320 pixels resolution.

Chose your TFT

This one works very well with the preenfm3. It can be found under different brand such as HiLetgo on amazon france.

!! AliExpress TFT : Some TFT sold on aliexpress have wrong SD tracks and do not work. Verify the wiring to the SD card. The first connection should be on the second pin from the TOP. Wrong TFTs have a connection on the first pin !!

I really wanted to use a widely available and cheap display. In addition this one has a built-in SD card reader which made a perfect candidate.

These displays are actually a set of 3 (or 4) components :

• The TFT itself (that includes the ILI9341 chip).
• The red PCB with resistors, capacitors, and a 5v -> 3.3v adapter. There are several different ones available not all equals.
• The SD Card socket soldered on the PCB.
• Optionally the Touch glass on top of the TFT (in this case the PCB has an additional chip)

The touch layer is not used by the preenfm3, it decreases a bit the contrast, it adds a welcome protection, and it makes the TFT a bit thicker.

Here are the components that are worth looking for.

• U1 always here and is the 5v->3.3v convertor.
• J1 leave open by default for the preenfm3. It powers the TFT with 5v and U1 is used.
• Q1 transistor that makes use of VCC to power the TFT.
• U2 the touch screen chip. No touch screen : no chip.

A note on Q1
The TFT leds are controlled by the LED pin.
The STM32 has a GPIO connected to this pin to switch it on and off (and optionally adjust lightness).
So it's better if your TFT PCB has a Transistor so that the GPIO does not feed directly the leds but only switch on/off the current that comes from VCC.